5Eastern Pacific Coral Reef Provinces, Coral Community Structure and Composition: An Overview Peter W. Glynn, Juan J. Alvarado, Stuart Banks, Jorge Cortés, Joshua S. Feingold, Carlos Jiménez, James E. Maragos, Priscilla Martínez, Juan L. Maté, Diana A. Moanga, Sergio Navarrete, Héctor Reyes-Bonilla, Bernhard Riegl, Fernando Rivera, Bernardo Vargas-Ángel, Evie A. Wieters, and Fernando A. Zapata P.W. Glynn (&) Department of Marine Biology and Ecology, Rosenstiel School of Marine and Atmospheric Science, 4600 Rickenbacker Causeway, Miami, FL 33149, USA e-mail: pglynn@rsmas.miami.edu J.J. Alvarado Escuela de Biología/Museo de Biología, Centro de Investigación en Ciencias del Mar y Limnología (CIMAR), Universidad de Costa Rica, 11501-2060 San Pedro, San José, Costa Rica e-mail: juan.alvarado@ucr.ac.cr S. Banks Marine Ecosystem Research Programme, Charles Darwin Research Station, Galápagos, Ecuador; Conservation International, c/o Christian Lavoie, Av. Catalina Aldáz N34-181 y Portugal, Edificio Titanium II, Piso 4, of. 402, Quito, Ecuador e-mail: sbanksocean@gmail.com J. Cortés Centro de Investigación en Ciencias del Mar y Limnología (CIMAR), Escuela de Biología, Ciudad de la Investigación, Universidad de Costa Rica, 2060 San Pedro, San José, Costa Rica e-mail: jorge.cortes@ucr.ac.cr J.S. Feingold Department of Marine and Environmental Sciences, Halmos College of Natural Sciences and Oceanography, Nova Southeastern University, 3301 College Avenue, Fort Lauderdale, FL 33314-7796, USA e-mail: Joshua@nova.edu C. Jiménez Energy, Environment and Water Research Center (EEWRC), The Cyprus Institute (CyI), P.O. Box 274561645 Nicosia, Cyprus e-mail: c.jimenez@cyi.ac.cy J.E. Maragos Department of Geography, University of Hawaii at Manoa, Kilauea, P.O. Box 1338Honolulu, HI 96754, USA e-mail: jimmaragos@yahoo.com P. Martínez Instituto Nazca de Investigaciones Marinas, Avenida 12 de Octubre, # 1615, entre calle 20 y 21, Salinas, Ecuador e-mail: pmartinez@institutonazca.org J.L. Maté Smithsonian Tropical Research Institute, 0843-03092 Panama, Republic of Panama e-mail: matej@si.edu D.A. Moanga Department of Environmental Science, Policy, & Management, University of California, Berkeley, # 326 Mulford Hall, Berkeley, 94720, CA, USA e-mail: dianamng@berkeley.edu S. Navarrete Estación Costera de Investigaciones Marinas, Advanced Studies in Ecology and Biodiversity, Departamento de Ecología, Facultad de Ciencias Biológicas, Pontificia, Universidad Católica de Chile, Casilla 114-d, Alameda 340, Santiago, Chile e-mail: snavarrete@bio.puc H. Reyes-Bonilla Departamento Académico de Biología Marina, Universidad Autónoma de Baja California Sur, Carretera al sur km 5.5. col. El Mezquitito, 23080 La Paz, B.C.S, Mexico e-mail: hreyes@uabcs.mx B. Riegl Department of Marine and Environmental Sciences, Halmos College of Natural Sciences and Oceanography, Nova Southeastern University, 8000 North Ocean Drive, Dania, FL 33004, USA e-mail: rieglb@nova.edu F. Rivera Instituto Nazca de Investigaciones Marinas, Avenida 12 de Octubre # 1615, entre calle 20 y 21, Salinas, Ecuador e-mail: frivera@institutonazca.org B. Vargas-Ángel Pacific Islands Fisheries Science Center, Coral Reef Ecosystem Division, NOAA Inouye Regional Center, 1845 Wasp Blvd, Bldg #176, Honolulu, HI 96818, USA e-mail: bernardo.vargasangel@noaa.gov E.A. Wieters Estación Costera de Investigaciones Marinas, and Departamento de Ecología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, La Alameda 340, Santiago, Chile e-mail: ewieters@bio.puc F.A. Zapata Departamento de Biología, Universidad del Valle, Apartado Aéreo 25360, Cali, Colombia e-mail: fernando.zapata@correounivalle.edu.co By consensus, authors are arranged alphabetically after lead author P. W. Glynn © Springer Science+Business Media Dordrecht 2017 P.W. Glynn et al. (eds.), Coral Reefs of the Eastern Tropical Pacific, Coral Reefs of the World 8, DOI 10.1007/978-94-017-7499-4_5 107 Abstract Advances in our knowledge of eastern tropical Pacific (ETP) coral reef biogeography and ecology during the past two decades are briefly reviewed. Fifteen ETP subregions are recognized, including mainland and island localities from the Gulf of California (Mexico) to Rapa Nui (Easter Island, Chile). Updated species lists reveal a mean increase of 4.2 new species records per locality or an overall increase of 19.2 % in species richness during the past decade. The largest increases occurred in tropical mainland Mexico, and in equatorial Costa Rica and Colombia, due mainly to continuing surveys of these under-studied areas. Newly discovered coral communities are also now known from the southern Nicaraguan coastline. To date 47 zooxanthellate scleractinian species have been recorded in the ETP, of which 33 also occur in the central/south Pacific, and 8 are presumed to be ETP endemics. Usually no more than 20–25 zooxanthellate coral species are present at any given locality, with the principal reef-building genera being Pocillopora, Porites, Pavona, and Gardineroseris. This compares with 62–163 species at four of the nearest central/south Pacific localities. Hydrocorals in the genus Millepora also occur in the ETP and are reviewed in the context of their global distributions. Coral community associates engaged in corallivory, bioerosion, and competition for space are noted for several localities. Reef framework construction in the ETP typically occurs at shallow depths (2–8 m) in sheltered habitats or at greater depths (10–30 m) in more exposed areas such as oceanic island settings with high water column light penetration. Generally, eastern Pacific reefs do not reach sea level with the development of drying reef flats, and instead experience brief periods of exposure during extreme low tides or drops in sea level during La Niña events. High rates of mortality during El Niño disturbances have occurred in many ETP equatorial areas, especially in Panama and the Galápagos Islands during the 1980s and 1990s. Remarkably, however, no loss of resident, zooxanthellate scleractinian species has occurred at these sites, and many ETP coral reefs have demonstrated significant recovery from these disturbances during the past two decades. Keywords Species distributions � Biogeography � Eastern Pacific � Coral occurrences � Species richness 5.1 Introduction Geographic isolation, variable oceanographic conditions, and a peninsula-like shallow shelf spanning a relatively narrow latitudinal corridor, have all figured prominently in the formation and development of the eastern tropical Pacific coral reef region. The vast majority of eastern Pacific corals belong to species occurring in the central and south Pacific (e.g., Wells 1983; Cortés 1986; Grigg and Hey 1992; Veron 1995; Glynn and Ault 2000). Dana (1975) recognized this faunal affinity, and suggested the existence of genetic con- nectivity between the central Pacific Line Islands and the equatorial eastern Pacific by larval dispersal via the North Equatorial Counter Current (NECC). A few species are eastern Pacific endemics, and there is a near absence of Caribbean and western Atlantic species along western American shores. The narrowing and eventual closing of the Central American isthmus, 3.5-3.0 Ma (Coates and Obando 1996), brought about extinctions of once-shared transo- ceanic species, and the invasion of coral species from the west by long-distance dispersal (see Chap. 2, López-Pérez, and Chap. 16, Lessios and Baums; López-Pérez and Budd 2009). The occurrence of reef-building corals along coastal western America is highly skewed toward the northern hemisphere, with a strong presence of corals from the northern Gulf of California, Mexico (*30°N) to just a few degrees south of the equator along coastal Ecuador (2°S). Modern zooxanthellate coral communities have not been reported on continental shores south of the Gulf of Guaya- quil, Ecuador, which are under the influence of the cool, north-flowing Peru Coastal Current (Fig. 5.1). Five rela- tively isolated oceanic island groups, from the northern-most Revillagigedo Islands off Mexico to the Galápagos Islands lying astride the equator, also belong to the eastern Pacific coral reef region. Vibrant coral communities and incipient 108 P.W. Glynn et al. http://dx.doi.org/10.1007/978-94-017-7499-4_2 http://dx.doi.org/10.1007/978-94-017-7499-4_16 reef development also appear far to the south and west, about 4000 km from the Galápagos Islands and coastal Ecuador. Rapa Nui (Easter) and Salas y Gómez Islands, at 27°S and over 1000 km west of Chile, represent the most isolated ETP coral outpost (Glynn et al. 2003, 2007; Hubbard and Garcia 2003; see Chap. 6, Toth et al.). Fig. 5.1 Eastern Pacific coral and coral reef localities, Gulf of California, Mexico to Ecuador, and remote Rapa Nui (Easter) and Salas y Gómez Islands, Chile. Red diamonds identify oceanic localities supporting coral communities and coral reefs 5 Eastern Pacific Coral Reef Provinces, Coral Community Structure … 109 http://dx.doi.org/10.1007/978-94-017-7499-4_6 The most recent overview of the eastern tropical Pacific (ETP) coral reef region was published over 10 years ago, in Latin American Coral Reefs edited by Jorge Cortés (2003). This work comprised seven chapters dedicated to the ETP, describing coral communities and coral reefs from mainland Mexico to Ecuador, including offshore islands from the Revillagigedo Islands, Mexico to Rapa Nui, Chile. These summaries included historical sketches of coral reef research, site descriptions, species lists, natural and anthro- pogenic disturbances, and issues pertaining to protection and management. The present chapter updates Cortés (2003), and several earlier reviews of eastern Pacific coral reef biology (e.g., Durham and Barnard 1952; Squires 1959; Durham 1966; Glynn and Wellington 1983; Cortés 1986, 1997, 2011; Glynn 2001). An updated biogeographic analysis of zooxanthellate Scleractinia is examined first to review species relationships within the eastern Pacific region, and secondly extra- regional faunal affinities. This analysis will serve as a framework for brief introductions to the main coral reef localities from Mexico to Ecuador, including the Galápagos Islands. An overview of the more distant eastern tropical Pacific coral outposts of Rapa Nui and Salas y Gómez Islands will conclude the chapter. Eastern Pacific Millepora records are also reviewed, and compared to hydrocoral occurrences in the central and southeastern Pacific. Each eastern Pacific coral reef locality is examined in terms of its community structure, species richness, physical environ- mental conditions, and chief ecological interactions. The treatments are admittedly unbalanced, with more informa- tion provided for newly discovered or less well-known areas. It is hoped that this overview will serve to stimulate further research, and provide information for comparisons with other coral reef regions. A comprehensive review of ETP Holocene reef development—including coral frame- work structures, time of reef growth initiation, thicknesses, and accumulation rates—can be found in Toth et al., Chap. 6. 5.2 Eastern Pacific Coral Reef Region The eastern tropical Pacific region consists of a distinct biotic assemblage of marine species isolated from the Car- ibbean Sea by the Central American land bridge. The west American marine biota is also separated from the central/western Pacific region by a wide expanse (5000– 8000 km) of open ocean waters, namely the eastern Pacific Barrier or Ekman’s Barrier (e.g., Darwin 1880; Ekman 1953; Briggs 1974; Grigg and Hey 1992; Veron 1995). Abundant recent evidence indicates that this barrier, which Darwin considered impassable, is best viewed as a filter bridge since numerous shallow-living species from several major taxa— scleractinian corals (Glynn and Ault 2000), bryozoans (Banta 1991), crustaceans (Garth 1991), molluscs (Schel- tema 1988; Emerson 1991), echinoderms (Lessios et al. 1998), and fishes (Robertson and Allen 1996; Robertson et al. 2004; Lessios and Robertson 2006; see Chap. 16, Lessios and Baums)—have crossed this deep water stretch by larval dispersal or rafting. In particular, many marine species shared between the eastern Pacific and central/western Pacific are common members of coral communities and coral reefs. Indeed, the majority of ETP reef-building coral taxa—species in the genera Pocillopora, Porites, Pavona, Gardineroseris—are conspecific with those found west of the ETP filter bridge. Within the eastern Pacific region, four subtropical/tropical biogeographic provinces were early recognized: (1) Cortez Province (middle to upper Gulf of California), (2) Mexican Province (lower Gulf of California to the Gulf of Tehuan- tepec), (3) Panamanian Province (Tangola-Tangola Bay, Gulf of Tehuantepec to the Gulf of Guayaquil), and (4) the Galápagos Islands (Briggs 1974). More recent analyses of coral distributions have recognized an eastern Pacific ocea- nic islands fauna, with coral affinities shared among Clip- perton Atoll, Malpelo Island, Easter Island, and Tabuaeran (=Fanning Atoll) in the Line Islands group (Glynn and Ault 2000; Glynn et al. 2007). Another recent biogeographic analysis, based on the distributions of 1135 resident shore fishes, also recognized the oceanic islands as a distinct faunal subdivision, but concluded that the continental coast is best represented by two provinces, namely (1) the Cortez, comprising the Gulf of California and lower Pacific Baja California areas, and (2) the Panamic, southward to the Gulf of Guayaquil, Ecuador (Robertson and Cramer 2009). With an increasing knowledge of zooxanthellate scler- actinian distributions, particularly during the last two dec- ades, several workers have examined patterns of coral faunal distributions along the eastern tropical Pacific (Glynn 1997; Glynn and Ault 2000; Glynn et al. 2007; Alvarado et al. 2011), and within specific eastern Pacific countries and locations (Reyes-Bonilla 1993a; chapters in Cortés 2003; Reyes-Bonilla and López-Pérez 1998, 2009). The existence of a dispersal barrier within the eastern Pacific, the long-recognized Pacific Central American faunal gap (PCAFG), has been supported mainly by the absence of corals (Glynn and Ault 2000) and reef-associated fishes (Springer 1958; Briggs 1974) between Tangola Tangola (southern Mexico) south to the Gulf of Fonseca (El Salvador/Honduras/Nicaragua). However, the faunal simi- larity of newly discovered coral communities and reef-associated fishes in Nicaragua and El Salvador with central Mexican coastal areas (Michoacán, Colima) is very high, suggesting some degree of genetic connectivity across the PCAFG (Robertson and Cramer 2009; Alvarado et al. 2011). 110 P.W. Glynn et al. http://dx.doi.org/10.1007/978-94-017-7499-4_6 http://dx.doi.org/10.1007/978-94-017-7499-4_16 5.2.1 Zooxanthellate Scleractinian Fauna Here we present an updated biogeographic analysis of zooxanthellate scleractinian coral faunas from 15 ETP localities and four central/south Pacific localities. In the present data-base, the listed ETP fauna consists of 47 species in 11 genera, and the central/south Pacific localities 225 species in 40 genera (Appendix). The central/south Pacific localities include the Hawaiian Islands, Johnston Atoll, Pit- cairn Islands, and Palmyra Atoll, and will be employed for analysis of and comparison with the ETP fauna. The species in this analysis were delineated chiefly from gross mor- phometric characteristics; the sources of this information are listed in the caption to Fig. 5.7. In light of current molecular genetic studies (Flot et al. 2010; Pinzón and LaJeunesse 2011; Pinzón et al. 2013; Boulay et al. 2014; see Chap. 14, Pinzón), and evidence from a combination of genetic and morphological analyses—including both macro- and micromorphometric characteristics (Schmidt-Roach et al. 2014)—it is evident that species delineations across the Indo-Pacific region are still unresolved. On the one hand, genetic studies offer evidence of fewer species of Pocillo- pora in the ETP than recognized morphometrically, three instead of seven species (Pinzón et al. 2013; see Chap. 14, Pinzón). On the other hand, new previously unrecognized cryptic species have come to light in the Pocillopora dam- icornis complex on the Great Barrier Reef (Schmidt-Roach et al. 2014). A major three-way grouping of coral faunas is evident from an agglomerative hierarchical cluster analysis: (a) dominantly equatorial eastern Pacific (EEP) localities (PAN-GLN), (b) ETP oceanic islands (MAL-REV), and (c) central/southern Pacific localities (Fig. 5.2). [Locality acronyms, e.g. PAN = Panama, follow those employed in Fig. 5.2.] A notable east to west increase in species richness is apparent with eastern Pacific localities demonstrating impoverished faunas compared with potential source areas to the west of Ekman’s filter bridge, a long recognized pattern (e.g., Stehli and Wells 1971; Veron 1995). All ETP reef communities consist of fewer than 30 species, whereas central/south Pacific localities exhibit from 44 to 163 species. At Palmyra Atoll, which is in the path of the North Equatorial Counter Current (Maragos et al. 2008a, b), 163 coral species have been recorded. The North Equatorial Counter Current has been considered a likely means of transport across the filter bridge (e.g., Dana 1975; Glynn and Ault 2000), and species-rich Palmyra is a potential source locality. In the EEP cluster, the low species occurrences in the southern Galápa- gos Islands (GLS) and Gulf of California (GOC) are likely due, in large part, to their subtropical locations. Two species-poor mainland sites (NIC, ELS) cluster with the ETP oceanic islands. The recently-discovered coral communities in Nicaragua may reveal additional species upon further study; El Salvador, however, is a marginal coral area with highly turbid waters and is not expected to show a significant increase in species richness. Additional comments on ETP faunal relationships are noted below, in site-specific sections. Eight species in this updated inventory are likely ETP endemics, suggesting a moderate level of speciation in this region (Table 5.1). This number represents 19.5 % of the total ETP fauna reported to date. Latitudinally, all eight coral endemics are concentrated in Mexico, in the northern-most eastern Pacific region. Three Porites endemics, P. arnaudi, P. sverdrupi, and P. baueri, demonstrate restricted distri- butions, known from only one or two localities. All eastern Pacific endemic species are absent from Rapa Nui (Easter Island). Three endemics, Pavona gigantea, Pocillopora effusus, and Porites panamensis, are widely distributed throughout the eastern Pacific, presently reported from eight to 14 localities. 5.2.2 Millepora Zooxanthellate hydrocorals in the genus Millepora can be important contributors to reef frameworks and coral reef growth. Millepora has a very restricted distribution in the ETP. Three species of Millepora were present on reefs in the Gulf of Chiriquí (Panama) before the 1982–83 El Niño event: Millepora intricata Milne-Edwards 1857, Millepora boschmai Weerdt and Glynn 1991, and Millepora platy- phylla Hemprich and Ehrenberg 1834. All three species bleached and experienced high mortality, during and immediately following the period of elevated sea tempera- tures (Glynn and de Weerdt 1991). Living colonies of M. platyphylla could no longer be found in Panama after 1983 (as of 2015), and are now apparently absent from the ETP (Glynn 2011). Millepora boschmai also disappeared from survey sites at Uva Island after 1983, but a small population was found nearby in 1992 (Glynn and Feingold 1992). All colonies from this remnant population disappeared in early 2000, as well as a few known colonies at Coiba Island (Brenes et al. 1993), and none have been observed in the eastern Pacific since that time (Maté 2003). This species was recognized in collections made from two localities in Indonesia by Razak and Hoeksema (2003), including South Sulawesi in 1994 and Sumba in 1984. In Panama, Millepora intricata re-appeared a few years after 1983, ostensibly by sexual recruitment from deep refuge populations (Smith et al. 2014; see Chap. 17, Smith et al.); it is again an important member of coral communities in the Gulf of Chiriquí, Panama (Fig. 5.3). Unlike M. platyphylla and M. boschmai, with populations restricted to shallow habitats (usually � 6–8 m depth), M. intricata occurs in deep 5 Eastern Pacific Coral Reef Provinces, Coral Community Structure … 111 http://dx.doi.org/10.1007/978-94-017-7499-4_14 http://dx.doi.org/10.1007/978-94-017-7499-4_14 http://dx.doi.org/10.1007/978-94-017-7499-4_17 (>11 m depth) as well as shallow reef zones. This allowed M. intricata in deep-water habitats to survive two of the strongest El Niño events on record (1982–83, 1997–98), and then to re-populate shallow reef sites (Smith et al. 2014). Millepora exaesa is known only from Clipperton Atoll in the eastern Pacific, and colonies are uncommon there (Glynn et al. 1996a, b; Carricart-Ganivet and Reyes-Bonilla 1999; Flot and Adjeroud 2009; Glynn, unpublished observation). The nearest reported central Pacific record of M. exaesa is at Wake Island (167°E), over 5500 km west of Clipperton (Table 5.2). Early surveys showed that Millepora spp. are widespread throughout the Indo-Pacific region, and this has been con- firmed by recent surveys. However, their relatively infrequent reproduction and short-lived dispersive phase (gonochoric medusae) appear inconsistent with their wide- spread global occurrence (Lewis 1989; see also Chap. 15 , Glynn et al.). Veron (2000) shows Millepora present in all parts of the Indian Ocean and the western and southern Pacific (Fig. 5.4). Some early and more recent surveys show that various Millepora species also occur widely across the central Pacific region, e.g. Johnston Atoll (Maragos and Jokiel 1986), the Phoenix Islands (Maragos et al. 2008a, b), Tabuaeran (formerly Fanning, Maragos 1974) and other Line Islands (Maragos et al. 2008a, b); Marquesas (Cheva- lier 1978), Tuamotus (Ricard 1985; Harmelin-Vivien 1985; Montaggioni 1985), Society Islands (Galzin and Pointier 1985), and the Pitcairn Islands (Irving and Dawson 2012; Fig. 5.2 a Relationships of zooxanthellate scleractinian coral faunas at 15 eastern Pacific and four central and south Pacific localities. “Spatial patterns” of an agglomerative, hierarchical cluster analysis were portrayed using a Euclidean distance measure and group-average method for cluster formation. Constructed from presence/absence data in Appendix. b Geographic pattern of coral species richness across EP filter bridge in relation to NECC eastward flow. Circle areas are proportional to species richness. GOC, Gulf of California; TMM, tropical Mexican mainland; REV, Revillagigedo Islands; CLP, Clip- perton Atoll; ELS, El Salvador; NIC, Nicaragua; CRM, Costa Rican mainland; COC, Cocos Island; PAN, Panama; COL, Colombia; MAL, Malpelo Island; ECD, Ecuador; GLS, southern Galápagos Islands; GLN, northern Galápagos Islands; RPN, Rapa Nui (Easter) and Salas y Gómez Islands; HAW, Hawaiian Islands; JOH, Johnston Island; PIT, Pitcairn (Henderson, Oeno, Ducie Islands); PAL Palmyra Atoll 112 P.W. Glynn et al. http://dx.doi.org/10.1007/978-94-017-7499-4_15 USNM collection records) (Fig. 5.4; Table 5.2). Subfossil fragments of Millepora intricata recovered from reef cores revealed radiocarbon dates of *5000 cal year BP, indicat- ing the presence of this hydrocoral species in Panama for much of the Holocene Epoch (Smith et al. 2014). The highly restricted occurrence of Millepora in the ETP is mirrored in the eastern Atlantic where it is known from only two island groups, the Canary and Cape Verde Islands (Clemente et al. 2011). It is hypothesized to be a recent introduction to the eastern Atlantic region (Clemente et al. 2011). 5.3 Intra-regional Précis Coral faunas and coral communities within the eastern tropical Pacific region are reviewed below, from northern Mexico to the southern-most mainland assemblages of Ecuador. The eastern Pacific oceanic islands—Revillagigedo Islands, Clipperton Atoll, Isla del Coco, Galápagos Islands, and Rapa Nui—are also considered along a N–S latitudinal Table 5.1 Regional occurrence of eastern tropical Pacific endemic zooxanthellate Scleractinia at 14 localities Species Localities Present (no. localities) Absent Pavona gigantea MEX EEP (14) RPN Pocillopora effusus MEX EEP (8) RPN Pocillopora inflata MEX EEP (6) RPN, CLP Porites panamensis MEX EEP (9) RPN, CLP Porites arnaudi MEX CLP (2) RPN, EEP Porites sverdrupi MEX (2) EEP, RPN, CLP Porites baueri MEX (1) EEP, RPN, CLP Psammocora brighami MEX (2) EEP (5) RPN MEX (Mexico)—Gulf of California, Revillagigedo Is., tropical Mexican mainland; EEP (equatorial eastern Pacific)—El Salvador, Nicaragua, Costa Rica, Cocos Is, Panama, Colombia, Malpelo, Ecuador, Galápagos Iss; RPN—Easter Is; CLP—Clipperton Atoll Fig. 5.3 Millepora intricata prominence in a coral community at Brincanco Island, Gulf of Chiriquí, Panama (5.4 m depth, 4 April 2012, courtesy Irving Bethencourt). Pocillopora sp. in foreground *30 cm in diameter 5 Eastern Pacific Coral Reef Provinces, Coral Community Structure … 113 gradient. This overview will hopefully provide basic coral community-level information to help evaluate intra-regional similarities and differences. We recognize that these brief intra- and inter-regional treatments would reveal only approximate comparisons at best due to the often great dif- ferences in available habitat area and habitat diversity. Regional Holocene reef development, including the coral taxa that construct frameworks, times of reef initiation, framework thickness, and accumulation rates are reviewed by Toth et al. in Chap. 6. 5.3.1 Gulf of California (Mexico) The northern-most limit of zooxanthellate corals is in the upper reaches of the 1000 km-long Gulf of California (Fig. 5.5). Corals occur commonly over most of the length of the gulf, with increasing species richness in the southerly warmer waters. The higher thermal conditions in the southern gulf are exemplified by satellite imagery of sea surface temperatures (SSTs) in January 2006, with upper gulf SSTs of 14.5–18.3 °C and lower gulf SSTs of 20.1– 22.8 °C (Ledesma-Vázquez et al. 2009). Corals are virtually absent from the western shores of the Baja California peninsula due to the southerly-flowing, cool California Current (see Chap. 3, Fiedler and Lavín). Distributional analyses based on presence/absence data have revealed two coral faunas within the Gulf of California, one in the northern and one in the southern gulf (Reyes-Bonilla and López-Pérez 2009). The northern fauna ranges from Punta Peñasco (31.3°N) to Punta Prieta (27°N), and consists pre- dominantly of encrusting, monospecific Porites panamensis populations. Occasional colonies of Porites sverdrupi are also present on rocky substrates, and Cycloseris curvata, the latter in deeper rhodolith communities. The southern fauna ranges from Loreto to Cabo San Lucas. This fauna is more diverse, consisting of 20 species with a close affinity with tropical mainland Mexico (Fig. 5.2). According to recent assessments, the gulf coral fauna has demonstrated an increase from 16 to 20 species (e.g., Reyes-Bonilla et al. 2005, 2010; Reyes-Bonilla and López-Pérez 2009) (Fig. 5.6). Sixteen of these species belong to the Indo-Pacific fauna, three to the eastern Pacific fauna, and one (P. sver- drupi) is endemic to the gulf and mainland Mexico. The coral assemblages and associated biota in the gulf were classified into four biotopes by Reyes-Bonilla and López-Pérez (2009): (1) isolated colonies or patches, (2) corals in rhodolith communities and other soft bottom habitats, (3) coral communities, and (4) coral reefs. Biotopes 1 and 2 occur in the northern gulf, and coral communities and coral reefs in the southern gulf. Corals, predominantly Porites panamensis, are highly dispersed in type 1 assem- blages, usually amounting to <1 % cover where present. Even at low abundance, however, Halfar et al. (2005) demonstrated a potentially high carbonate sediment pro- duction rate for P. panamensis at Bahía de Los Ángeles (Fig. 5.5). Only a single rhodolith community, with associ- ated fungiid corals, was reported in the northern gulf, while five were reported in the southern gulf. Three of these communities occurred at 25–30 m depth between La Paz and Monserrat Island near Loreto. Diaseris distorta is pre- dominant with the occasional presence of Cycloseris curvata Table 5.2 Documented collection records of Millepora species in the central and south eastern Pacific Ocean Location Longitude Taxa Authority Wake Is. 167°E Millepora 2 spp. Lobel and Lobel (2008) Millepora tuberosa (exaesa)a Maragos, unpublished record, 1979–2005 Phoenix Iss. 172°E Millepora sp. Maragos (1974) Johnson Atoll 169°E Millepora dichotoma Maragos et al. (2008a, b) Millepora tenera Maragos and Jokiel (1986) Cook Iss. 160–162° W Millepora Maragos (1974) Line Iss. 157–169° W Millepora Maragos et al. (2008a, b) Kingman reef 162°W Millepora platyphylla Maragos, personal communication Tabuaeran 159°W Millepora platyphylla Maragos (1973) Moorea Is. 150°W Millepora platyphylla Galzin and Pointier (1985) Tuamotus Iss. 135–150° W Makatea Is. 148°W Millepora sp. Montaggioni (1985) Mataiva Atoll 148°W Millepora platyphylla Delasalle (1985) Tikahau Atoll 148°W Millepora platyphylla Harmelin-Viven (1985) Rangiroa Atoll 147–148° W Millepora platyphylla Riccard (1985) Takapoto Atoll 145°W Millepora platyphylla Salvat and Richard (1985) Marquesas Iss. 138–141° W Millepora platyphylla Chevalier (1978) Pitcairn Iss. 124–131° W Millepora sp. Irving and Dawson (2012) Pitcairn Is. 130°W Millepora platyphylla D. Devaney USNM No. 79568 Henderson Is. 128°W Millepora platyphylla G. Paulay USNM No. 91571, 91572 aMillepora tuberosa is a junior synonym of M. exaesa (see Razak and Hoeksema 2003) 114 P.W. Glynn et al. http://dx.doi.org/10.1007/978-94-017-7499-4_6 http://dx.doi.org/10.1007/978-94-017-7499-4_3 and mobile species of Psammocora, Porites, and rarely Pavona (Table 5.3). Present taxonomic evidence indicates that the coralline flora of rhodolith communities consists of four species in four genera (Steller et al. 2009). This biotope provides shelter and trophic resources for a diverse assem- blage of non-coral invertebrates (bryozoans, molluscs, crustaceans, and echinoderms), fishes, and cryptic biota (Steller et al. 2003, 2009). Coral community biotopes occur commonly at shallow depths (� 10 m) along the southwestern peninsular gulf coast. The predominant coral genera in these communities are Pocillopora and Pavona. While buildups can attain several meters in thickness (height), framework structures per se are not evident. Particularly robust coral communities, e.g. at Cabo Pulmo and La Paz, demonstrated mean coral cover values of 15–20 % with 4–6 species present. Both Pocillopora damicornis and Pocillopora verrucosa con- tribute substantially to these communities. The structural complexity of these coral communities offers numerous shelter sites that greatly increase the diversity of macroin- vertebrates, fishes, and cryptic biota. In addition, metazoan coral symbionts and diverse coral bioeroding organisms inhabit these communities. Gastropod, echinoderm, and fish corallivores are ubiquitous in the gulf and actively prey on all coral species (e.g., Reyes-Bonilla 2003; Hendrickx et al. 2005; Álvarez-Filip et al. 2006; Reyes-Bonilla and López-- Pérez 2009). Acanthaster planci is widespread, especially in the lower half of the gulf where corals are in high abundance (Dana and Wolfson 1970; Barham et al. 1973). Reyes-Bonilla (1993a, b, 2003) reported relatively high population densities of A. planci at Cabo Pulmo, 16 to >40 ind ha−1 over a 13-year period, but with no indica- tion of local coral depletion. True coral reefs, i.e. those with wave-resistant framework structures, were reported by Reyes-Bonilla and López-Pérez (2009) to be present at five sites in the extreme southern sector of the Baja California peninsula. These reefs are built predominantly by Pocillopora spp., with coral frameworks reaching 2 m in height. The largest and most thoroughly studied reef is located at Cabo Pulmo (Brusca and Thomson 1975; Reyes-Bonilla et al. 1997a, b). It is often cited as the northern-most eastern Pacific coral reef. It covers 150 ha and contributes to its surroundings an estimated 13,500–31,000 tons of CaCO3 annually (Reyes-Bonilla and López-Pérez 2009). This reef has formed on intrusive dikes and rocky hardgrounds. Even though the carbonate production rate of this reef is high, the coarser, reef-derived sediments are transported off-reef, especially during the passage of tropical cyclones, with no appreciable sediment retention. This loss greatly limits vertical reef accretion. Riegl et al. (2007) concluded that the Cabo Pulmo formation, sedimentologi- cally, functions only in a limited way like a coral reef. Compared to natural biotic effects, such as predation and bioerosion, extreme physical conditions have demonstrated the greatest negative influence on coral communities in the Gulf of California. Hurricanes and tropical storms regularly frequent the southern-most sector of the gulf (see Chap. 3, Fiedler and Lavín), and can limit reef development as noted above at Cabo Pulmo. Storm-generated turbulence and sedi- ment transport are responsible for local coral breakage and the burial of fungiid populations (Reyes-Bonilla and López-Pérez 2009). During the past few decades, ENSO-related high and low seawater temperature extremes have caused significant coral bleaching andmortality in the lower gulf (Reyes-Bonilla 2001; Iglesias-Prieto et al. 2004; Paz-García et al. 2012). These thermal-bleaching events can lead to widespread and spatially uniform mortality of Pocillopora spp., approaching 20 %, over 10s–100s of km of coastline. While noteworthy, this level of mortality is significantly lower than that reported in other ETP localities. Reyes-Bonilla (2001) hypothesized Fig. 5.4 Known global distribution of Millepora spp. as of 2014. In the eastern Pacific: Me, M. exaesa; Mp, M. platyphylla; Mb, M. boschmai; Mi, M. intricata. Mp and Mb now regionally extinct. Eastern Atlantic, Canary and Cape Verde Islands, Millepora sp., possibly M. alcicornis. Cross hatching in south-central Pacific denotes records of Millepora occurrences in Line Islands and Pitcairn Islands 5 Eastern Pacific Coral Reef Provinces, Coral Community Structure … 115 http://dx.doi.org/10.1007/978-94-017-7499-4_3 that the relatively low level of thermal bleaching/mortality is possibly a result of local upwelling during the summer season, and proximity of lower gulf waters to the California Current system that contributes to the formation of a cool front at the entrance to the gulf. 5.3.2 Tropical Mainland Mexico Beyond the Gulf of California, the tropical mainland coast of Mexico extends toward the southeast from southern Sinaloa to Chiapas states, a distance of nearly 2000 km (Fig. 5.7). Only two poritid species have been reported from Sinaloa (Porites panamensis, Porites sverdrupi) and, excluding extensive Miocene-Pliocene fossil reefs, no zooxanthellate corals are known from Chiapas. Both of these regions are dominated by coastal lagoons, sandy beaches, estuaries and mangrove ecosystems (Flores-Verdugo et al. 2001). The greatest reef development occurs in Nayarit and Oaxaca, each with 20 and 16 coral species, respectively (Reyes-Bonilla 2003; Reyes-Bonilla et al. 2005). Both of these areas are near upwelling centers; the northern center is located at Banderas Bay, Nayarit (López-Sandoval et al. 2009), and the southern upwelling area occurs along the Huatulco coast, Oaxaca (Steenburgh et al. 1998), which borders the Gulf of Tehuan- tepec (see Chap. 3, Fiedler and Lavín). Pocilloporid fringing Fig. 5.5 Gulf of California (GOC) and Revillagigedo Islands (REV), Mexico. Red diamonds identify surveyed sites 116 P.W. Glynn et al. http://dx.doi.org/10.1007/978-94-017-7499-4_3 reefs occur in both of these areas, usually at sheltered sites; reef frameworks attain vertical heights of up to 6 m, live coral cover commonly ranges between 20 and 50 %, and extends over several ha at several sites (Carriquiry and Reyes-Bonilla 1997; Reyes-Bonilla 2003). Coral communities and small patch reefs are also present in other west Mexican areas, particularly along coastal Guerrero and Michoacan states. Recent exploration has dramatically increased the species richness of zooxanthellate corals over a relatively brief period, from 19 (Reyes-Bonilla 2003) to 26 (Reyes-Bonilla et al. 2005, 2010; Glynn et al. 2007; Boulay et al. 2014), duemainly to continued exploration (Fig. 5.6; Appendix). Table 5.3 Occurrence of zooxanthellate scleractinian corals in three Pacific Mexican regions Species Location Gulf of California Tropical Mainland Mexico Revillagigedo Iss Cycloseris curvata (Hoeksema, 1989) R R R Fungia vaughani Boschma, 1923 R Diaseris distorta (Michelin, 1843) R R R Gardineroseris planulata (Dana, 1846) R Leptoseris papyracea (Dana, 1846) R R Pavona clavus (Dana, 1846) C C C Pavona duerdeni Vaughan, 1907 R R Pavona gigantea Verrill, 1869 A C C Pavona maldivensis (Gardiner, 1905) R Pavona minuta Wells, 1954 R Pavona varians Verrill, 1864 R R R Pocillopora damicornis (Linnaeus, 1758) C A R Pocillopora effusus Veron, 2002 R Pocillopora elegans Dana, 1846 C A C Pocillopora eydouxi Milne Edwards and Haime, 1860 R R C Pocillopora inflata Glynn, 1999 R R Pocillopora meandrina Dana, 1846 A C C Pocillopora capitata Verrill, 1864 A C R Pocillopora verrucosa (Ellis and Solander, 1786) A A A Pocillopora woodjonesi Vaughan, 1918 R Porites arnaudi Reyes-Bonilla and Carricart-Ganivet, 2000 R Porites australiensis Vaughan, 1918 R Porites baueri Squires, 1959 R Porites evermanni Vaughan, 1907 R Porites lichen Dana, 1846 C Porites lobata Dana, 1846 R A Porites lutea Milne Edwards and Haime, 1851 R Porites panamensis Verrill, 1866 A R R Porites sverdrupi Durham, 1947 R Psammocora brighami (Vaughan, 1907) R Psammocora haimeana Milne Edwards and Haime, 1851 R Psammocora profundacella Gardiner, 1898 R R Psammocora stellata Verrill, 1864 C C C Psammocora superficialis Gardiner, 1898 R R Total number species 20 22 24 A abundant (>50 % presence at surveyed sites); C common (20–50 % presence); R rare (<20 % presence). Records are from Reyes-Bonilla et al. (2010). Species names in this and following tables from Wells (1983), Reyes-Bonilla et al. (2005) and Veron (2000) 5 Eastern Pacific Coral Reef Provinces, Coral Community Structure … 117 The coral faunas of tropical mainland Mexico (TMM) and the Gulf of California (GOC) are very similar (Fig. 5.2a), however, mainland Mexico is more speciose (26 vs. 20 species), with several reef-building species (in the genera Pocillopora, Porites, Gardineroseris) that have not been reported from the Gulf. Information on coral community development at the Marías Islands, Nayarit, was lacking until relatively recently, with the delayed publication of field studies conducted in 1997 (Pérez-Vivar et al. 2006). All 10 species of zooxan- thellate corals collected there are known from other Mexican mainland areas. Porites baueri, long considered an endemic species restricted to the Marías Islands and elsewhere on the Nayarit coast (Reyes-Bonilla 1993b), was not found. This species may be synonymous with Porites lobata, which was abundant in the islands in 1997. Including museum collec- tions, the presently known coral fauna of the Marías Islands consists of 16 species. Coral zonation was characterized by Fig. 5.6 Differences in zooxanthellate scleractinian coral species richness at eastern and central Pacific localities before (blue) and after (red) major surveys. Most ‘previous’ records were published in 2003 (Cortés 2003), but some are frommajorworks as early as the latter half of the 1980s.Single bars (ELS, NIC, PAL) denote a lack of data from before the time periods examined. Sources Previous/Current GOC 1/2; TMM 1/2,3; REV 1/2; CLP 4/3,4; ELS -/5; NIC -/6; CRM 7,8,9/3,10; COC 8/3,10; PAN 11, 12/3,12; COL 13/14; MAL 10,13/12,14; ECD 15/16; GLS 15/17; GLN 15/3,4,18; RPN 19/4,20; HAW 21/22,23; JOH 24/25,26; PIT 27/28; PAL -/29. (1) Reyes-Bonilla (2003); (2) Reyes-Bonilla et al. (2010); (3) Boulay et al. (2013); (4)Glynn et al. (2007); (5) Reyes-Bonilla andBarraza (2003); (6) Alvarado et al. (2010), (2011); (7) Cortés and Guzmán (1998); (8) Cortés and Jiménez (2003); (9) Jiménez (2007a, b); (10) Cortés (updated checklist); (11) Holst and Guzmán (1993), Maté (2003); (12) Maté (updated checklist); (13) Zapata and Vargas-Ángel (2003); (14) Zapata (updated checklist); (15) Glynn (2003); (16) Rivera and Martínez (2011); (17) Glynn (updated checklist); (18) Hickman (2008); (19) Glynn et al. (2003); (20) Wieters and Navarrete (updated checklist); (21)Maragos (1995); (22)Maragos (updated checklist); (23)Maragos et al. (2004); (24) Maragos and Jokiel (1986); (25) Lobel and Lobel (2008); (26) Maragos (updated checklist); (27) Paulay (1989); (28) Irving and Dawson (2012); (29) Williams et al. (2008), Maragos (updated checklist) 118 P.W. Glynn et al. shallow populations of Pocillopora, and deeper occurrences, to 10 m depth and deeper, of species of Porites, Pavona, and Psammocora. This is a frequent pattern observed throughout Mexico (Reyes-Bonilla and López Pérez 1998) and else- where in the eastern Pacific (Glynn 1976; Wellington 1982). The community of algal endosymbionts (Symbiodinium) inhabiting particular coral host species was found recently to be a critical factor in defining this depth zonation. From a combination of genetic and photo-physiological analyses of Pocillopora verrucosa and Pavona gigantea, Iglesias-Prieto et al. (2004) demonstrated that the physiological perfor- mance of host-specific zooxanthellae were adapted to dif- ferent depth-related light regimes. Thus, pocilloporid holobionts exhibited optimal growth at shallow depths, whereas the growth rates of massive colonies were highest in deeper waters. It is now recognized that the notable coral development of the Huatulco reef tract is subject to a variety of relatively frequent and severe natural disturbances with high inter-annual variability (Glynn and Leyte-Morales 1997; López-Pérez et al. 2002; López-Pérez and Hernández-Bal- lesteros 2004). These disturbances range from seasonal upwelling events to plankton blooms and high turbidity conditions, hurricanes, ENSO high and low temperature extremes, and sea urchin outbreaks leading to intense graz- ing and bioerosion (e.g., Leyte-Morales 2000; Lirman et al. 2001; Herrera-Escalante et al. 2005; López-Pérez et al. 2007; Benítez-Villalobos et al. 2008). López-Pérez and Hernán- dez-Ballesteros (2004) have proposed that coral mortality caused by such random spatio-temporal disturbances are likely to produce a mosaic of patches at different stages of recovery, thus contributing to dynamic and diverse coral community structures. It would be of interest to study the coral-rich Nayarit area, also subject to upwelling and severe ENSO activity, to determine if disturbance regimes there similarly influence coral community structure and dynamics. Several recent molecular genetic studies have helped to elucidate the connectivity between coral populations and Fig. 5.7 Tropical mainland Mexico (TMM), Sonora to Chiapas. Red diamonds identify surveyed sites 5 Eastern Pacific Coral Reef Provinces, Coral Community Structure … 119 their biogeographic relationships in Mexican waters and beyond. Most of these studies indicate a high degree of genetic structure in local populations and, presumably, limited gene flow. For example, significant geographic dif- ferentiation was reported for Pocillopora damicornis, a broadcast spawning species (Chavez-Romo et al. 2008), and Porites panamensis, a brooder with a brief larval life (Paz-García et al. 2008). Limited gene flow among most sampled localities was also reported for Pavona gigantea, a wide-ranging broadcast spawning species (Saavedra-Sotelo et al. (2011). However, the largest estimated migration rate indicated moderate and unidirectional gene flow from Huatulco to the Marietas Islands in Banderas Bay (Nayarit) and to La Paz. Blancas-López (2009) also observed weak genetic differentiation (i.e. connectivity) among populations of Pocillopora verrucosa, suggesting some level of gene flow among populations of this broadcast spawning species. Among the various physical and biotic factors invoked to explain these patterns, the surface circulation of west Mexico is critical. There is a general northerly set of surface currents, involving the Costa Rica Coastal Current (CRCC) moving along the Huatulco coast and the West Mexican Current that flows from Oaxaca to the entrance of the Gulf of California (see Chap. 3, Fiedler and Lavín). This would potentially allow certain source populations in the south to supply lar- vae that could recruit to downstream Mexican mainland areas and eventually as far north as the Gulf of California. Since the CRCC originates in the equatorial eastern Pacific, it could conceivably serve as a vehicle of transport for coral larvae to reach Mexico from Costa Rica and Panama. 5.3.3 Revillagigedo Islands (Mexico) The volcanic islands making up the Revillagigedo Islands group are dispersed between 19° to 20°N latitude, and range from 750 km (San Benedicto and Socorro Islands) to 1200 km (Clarión Island) to the west of the Mexican mainland coast (Fig. 5.8). Roca Partida, consisting of two small rock peaks with a very limited shallow shelf, is located to the NE of Clarión Island. The number of coral records in the Revillagigedo Islands increased dramatically in the early 1990s, thanks to scuba surveys conducted by Mexican workers. This increase in species richness, from 12 to 21 then to 25, was due mostly to the discovery of Indo-Pacific corals not present on the west Mexican coast or elsewhere in the eastern tropical Pacific (Ketchum and Reyes-Bonilla 1997, 2001). Several of these species are shared with Fig. 5.8 Revillagigedo Islands (REV), Mexico. Red lines skirting the Clarión and Socorro coastlines denote abundant coral growth 120 P.W. Glynn et al. http://dx.doi.org/10.1007/978-94-017-7499-4_3 Clipperton Atoll, located nearly 1000 km to the south (at 10° N), which is occasionally in the path of the North Equatorial Counter Current (Glynn et al. 1996a, b). The current species list for the Revillagigedos totals 25 zooxanthellate sclerac- tinians (Appendix). The strong coral faunal similarities between the Revillagigedos and Clipperton, also involving brachyuran crabs (Garth 1992) and reef fishes (Robertson and Allen 1996), prompted Ketchum and Reyes-Bonilla (1997, 2001) to suggest that this oceanic region should be recognized as a unique biogeographic subregion of the eastern tropical Pacific. The latter workers noted that surface currents would allow dispersal from Clipperton to the Revillagigedos, especially during the summer season, and that both island areas could serve as stepping stones for the migration of inshore marine species from the central to the more northern eastern tropical Pacific region. Traditionally, the W to E biotic migration route was assumed to be closer to the equator, from the Line Islands to Isla del Coco and Central America (Costa Rica, Panama) via the NECC (Dana 1975; Cortés 1997; Glynn and Ault 2000). Based on dis- tributional evidence, it appears that there may be two dis- persal routes, one just north of the equator and one leading to northern Mexican waters via oceanic island stepping stones. The principal fringing reefs of Socorro and Clarión Islands are generally present in bays on western and south- ern shores in the lee of westerly-moving cyclones, which frequent this region (Fig. 5.8; Reyes-Bonilla 2003; see Chap. 3, Fiedler and Lavín). Pocillopora spp. predominate at shallow depths and massive corals (Porites, Pavona) increase in abundance from 5 to 30 m depth; coral rubble also increases with depth. Relatively few coral species were observed at Roca Partida and San Benedicto Island, likely due to the small size of these islands and restricted shelf space. In addition, the Bárcena volcano on San Benedicto Island was active as recently as 1952, and the resulting lava flows, debris, and fine sediments probably devastated near- shore communities and interfered with recovery. The six coral species observed there in 1994 were found principally on large basalt blocks and not on unstable volcanic sedi- ments (Glynn et al. 1996a, b). Moderate numbers of Acanthaster planci were observed at Clarión and San Benedicto Islands in 1994 (Glynn, unpublished observation). On 29 and 30 April, 36 individ- uals were counted on each of two occasions by a single diver between 6 and 17 m near Roco del Cuervo (18° 21′ 13.7″; 114° 41′ 06.2″), off the southeast shore of Clarión Island. The sea stars were feeding mostly on crustose coralline algae, but also on massive Porites lobata colonies, and large and small Pocillopora eydouxi colonies as well as broken branches of Pocillopora spp. Several A. planci also were observed feeding on P. eydouxi in coral communities on the northwestern end of San Benedicto Island on 3 May, 1994. 5.3.4 Clipperton Atoll (France) Clipperton Atoll, the only atoll present in the eastern Pacific region, is located about 1300 km SW of the Mexican main- land and 950 km SSE of the Revillagigedo Islands (Fig. 5.1). Clipperton is volcanic in origin, part of a chain of guyots on the Clipperton fault, bordering the Cocos (south) and Pacific (north) plates. It is an ‘almost atoll’, with a 29 m high tra- chyte rock on the SE shore (Rocher Clipperton, Fig. 5.9), and an enclosed meromictic lagoon (Charpy et al. 2009; Trichet 2009). Present-day shallow, stratified brackish waters and H2S-enriched bottom waters prevent coral growth inside the lagoon. However, before the mid-1800s at least two channels communicated with the open ocean, thus allowing for coral framework construction; fossilized coral deposits are still evident today inside the lagoon (Carricart-Ganivet and Reyes-Bonilla 1999). It is likely that a tectonic uplift event (Trichet 2009) closed off the lagoon between 1839 and 1849 (Charpy et al. 2010). Bottom profiling to 200 m depth around the perimeter of the atoll revealed a prominent 20 m terrace that is generally present at all seaward exposures (Glynn et al. 1996a, b). The 200 m isobath is located relatively close to shore, from 200 to 500 m seaward of the reef flat. With recent coral studies supported by scuba, the known coral fauna has increased from 16 or 17 species (Carricart-Ganivet and Reyes-Bonilla 1999; Flot and Adjer- oud 2009) to 21 species (Fig. 5.7; Appendix). Contributing to this increase is the recognition of additional species of Pocillopora (e.g., P. elegans and P. verrucosa), the naming of a new poritid species (Porites arnaudi), and a molecular genetic study revealing the presence of Porites evermanni (Boulay et al. 2014). These new species’ records are not considered recent introductions, but resident species present for some undetermined time. Pavona gigantea was listed from Clipperton by Durham and Barnard (1952), but has not been observed at the atoll for several decades since. The zooxanthellate sceractinian fauna of Clipperton, consisting of mainly (*90 %) Indo-Pacific species is most closely allied with the Revillagigedo Islands in the EP (Fig. 5.2). In 1994, live coral cover was exceptionally high (10– 100 %) at all insular shelf depths from 8 to 60 m, and crustose coralline algae were abundant (5–40 % cover) between 0.5 and 7 m depth (Glynn et al. 1996a, b). Porites lobata and Pavona varians contributed prominently to live cover, the former up to 50 % of cover between 10 and 30 m, and the latter commonly as high as 100 % between 25 and 60 m and deeper. Monospecific patches of Pavona varians were present at 70 m. Porites arnaudi, noted as Porites sp., was commonly observed, but P. lobata predominated in most areas. Porites arnaudi was often more common on the near-vertical faces of the 20 m terrace (Fig. 5.10). Pocillo- pora sp. patches, 10s to 100s m2 in area, were highly 5 Eastern Pacific Coral Reef Provinces, Coral Community Structure … 121 http://dx.doi.org/10.1007/978-94-017-7499-4_3 dispersed and usually present between 5 and 20 m depth. The corals in most of these patches were dead and encrusted by the coralline alga Porolithon onkodes. The pocilloporid species making up these patches, later identified by Carricart-Ganivet and Reyes-Bonilla (1999), was Pocillo- pora meandrina. More recent workers have not commented on whether the Pocillopora patches were dead or recovering. Pavona minuta, Pavona maldivensis, and Leptoseris scabra were generally minor components of the coral communities. Surveys conducted 10 years later indicated no significant change in the overall robust state of Clipperton’s coral communities (Flot and Adjeroud 2009). Two permanently-marked monitoring sites were established in 2005 at 10–12 m depth on the north and south reef slopes, thus allowing an opportunity to track coral community condition over time (Salvat et al. 2008). Like most ETP localities, the coral reef biota of Clip- perton exhibits a strong affinity with the central/south Pacific region. In addition to the zooxanthellate coral fauna, high proportions of reef algae (Payri et al. 2009), crustaceans (Poupin et al. 2009), molluscs (Kaiser 2009), echinoderms (Solís-Marín and Laguarda-Figueras 2009), and fishes at Clipperton (Robertson and Allen 1996; Robertson et al. 2004; Béarez and Séret 2009) exhibit transpacific distribu- tions. For coral reef fishes, Robertson et al. (2004) noted that pelagic spawners with strong dispersal ability were highly represented among transpacific species. Also, many reef-associated Indo-Pacific invertebrate taxa inhabiting eastern Pacific reefs possess teleplanic larvae (Scheltema 1988; Glynn and Ault 2000). Molecular studies demonstrate gene flow and recent invasions between the Central Pacific and Clipperton Atoll of coral, echinoderm, and fish species Fig. 5.9 Clipperton Atoll (CLP), modified after Glynn et al. 1996a. 50 and 200 m isobaths are based on the 21 bottom-profiling transects shown 122 P.W. Glynn et al. (Lessios et al. 1998; Lessios and Robertson 2006; Baums et al. 2012). Some of these studies have shown east to west gene flow, and connectivity of reef species among eastern Pacific oceanic islands (see Chap. 16, Lessios and Baums). Thus, it is necessary to know the flow regimes and transit times of the North Equatorial Counter Current (NECC), the primary eastward-flowing current in the central and eastern tropical Pacific. Satellite-tracked drifting buoy data analyzed over a 15 year period (1979–1993) revealed a mostly eastward flow of the NECC across the E Pacific ‘barrier’ between 6° and 10°N, occasionally reaching 12–14°N (Glynn et al. 1996a, b). Travel times from the Line Islands in the Central Pacific to Clipperton Atoll were commonly 200 days, although one record during an ENSO event showed the NECC travelling across 46° of lon- gitude in about 60 days. A comparison of west to east distances travelled during non-El Niño and El Niño years indicated a significant increase in NECC velocity during the latter periods. Accordingly, the NECC could offer an effectivemeans of larval transport to Clipperton, which in turn could serve as a stepping stone to other ETP localities, e.g. the Revillagigedo Islands as suggested by Ketchum and Reyes-Bonilla (1997). 5.3.5 El Salvador The recently described coral assemblages of El Salvador and Nicaragua are populated by a combined total of 14 Fig. 5.10 Porites arnaudi, cas- cading skirt-like growth form, 18 m, NE exposure, Clipperton Atoll, 23 April 1994 (photo credit M. Kazmers, Shark Song) 5 Eastern Pacific Coral Reef Provinces, Coral Community Structure … 123 http://dx.doi.org/10.1007/978-94-017-7499-4_16 zooxanthellate species. Notable differences, however, are the occurrences of Porites lobata at El Salvador only (Reyes-Bonilla and Barraza 2003), and Pavona clavus, Pavona varians, and Gardineroseris planulata in Nicaragua but not at El Salvador (Alvarado et al. 2011). No structural coral reef development has been reported from these areas (see Chap. 6, Toth et al.), although coral community patches are present. The coastal stretch between Guatemala and northwestern Nicaragua (Gulf of Fonseca) is known as the “Pacific Central American Faunal Gap (PCAFG)”, originally named due to the absence of rocky shore fishes (Springer 1958). The Guatemalan coast and the northern sector of El Salvador consist of sandy beaches and mangrove forests. Until recently the PCAFG was also understood to separate the coral faunas of southern Mexico and Costa Rica (Glynn and Ault 2000). At Los Cóbanos (El Salvador), there is an abrupt change in the orientation of the coastline with the appearance of low rocky outcrops and platforms (Fig. 5.11a). The remainder of the Salvadoran coast consists of high energy sandy beaches or muddy estuaries. The littoral fringe of the Gulf of Fonseca consists of rocky outcrops and one of the most extensive mangrove ecosystems of Central America. The southern Nicaraguan coast consists of a combination of rocky headlands and sandy beaches (Cortés 2007). The occurrence of coral populations within the PCAFG could serve as a dispersal corridor, and explain the close associa- tion of southern and northern ETP coral faunas (Fig. 5.2). The rocky outcrops of Los Cóbanos support the best developed and most diverse coral communities in El Sal- vador (Reyes-Bonilla and Barraza 2003). Small pocilloporid coral communities occur on basalt outcrops, most no larger Fig. 5.11 a Northwestern El Salvador (ELS); b southern Nicaragua (NIC), Central America. Coral development on Nicaraguan coast is within the Department of Rivas. Ten meter isobaths from US Navy Hydrographic chart no. 21026 124 P.W. Glynn et al. http://dx.doi.org/10.1007/978-94-017-7499-4_6 than 30 m2, that occupy a total of 159 km2 of a large terrace (8000 ha) that borders the coast. Thirteen coral species (eight zooxanthellate and five azooxanthellate) were reported at this site. Lemus et al. (1994) performed the first quanti- tative coral surveys at Los Cóbanos in 1993 and 1994; these workers sampled Porites lobata and reported highly diver- gent live cover values between 0.41 and 62 % for this spe- cies. The mean diameter of the sampled Porites colonies was *50 cm. At Punta Remedios (Fig. 5.11a), they repor- ted 0.42 % live coral cover, 34.6 % algae, and 44.8 % sand and rock. Only dead Pocillopora fragments were noted at this site. New sites at Los Cóbanos (Playa El Faro, Playa Salinitas or Decameron Beach) were sampled in 2006 by Segovia-Prado and Navarrete-Calero (2007). They reported high live cover of large Porites colonies: El Faro—33.7 % cover, 161 colonies, mean diameter = 121 cm; Salinitas— 65.4 % cover, 75 colonies, mean diameter = 146 cm. Algal cover also was high: El Faro—41.7 %; Salinitas—29.5 %. These mixed coral/algal communities were classified into five distinct assemblages, based on generic prevalence: (1) Padina-Halimeda-Codium, (2) Porites-Padina-Hal- imeda, (3) Porites-Acanthophora-Padina, (4) Porites-Pad- ina-Hypnea, and (5) Porites-Dictyota-Galaxaura. Concerns were raised over possible threats to corals by the invasive alga Acanthophora spicifera, and a high incidence of bio- eroders (Lithophaga, Cliona) and potential space competi- tors (vermetid gastropods). Reyes-Bonilla and Barraza (2003) noted other macroalgae, invertebrates (e.g., octoco- rals, molluscs) and reef-associated fishes observed at Los Cóbanos. A potentially significant physical threat noted by Reyes-Bonilla and Barraza (2003) is the seasonally high rainfall period from May to October with associated severe coastal erosion and transport of suspended sediments. At Playa el Zope (Los Cóbanos), López and Jiménez (2008) found healthy colonies of Psammocora obtusangula and Psammocora stellata interspersed with Porites lobata. They reported 81 colonies of P. obtusangula (mean length � width = 10.8 � 7.2 cm) and two small colonies of P. stellata (<6 cm2). Several P. obtusangula colonies bore small wounds resembling fish bite marks. The most recent near-shore surveys at Los Cóbanos, in 2009 and at the same sites sampled by Lemus et al. (1994), and Segovia-Prado and Navarrete-Calero (2007), failed to reveal living or dead Pocillopora and reported only low Porites lobata cover of 0.1 and 5.5 % (Alvarado, unpub- lished data). A live Pocillopora community was reported in the early literature at Los Cóbanos, the Punta Remedios site (Orellana-Amador 1985; Gotuzzo 1996), but has not been re-located in recent surveys (Reyes-Bonilla and Barraza 2003). All Pocillopora spp. collected in this study were identified from dead beach fragments (Appendix). At rela- tively deep (10–15 m) offshore sites, only azooxanthellate corals were observed, with Tubastraea coccinea predomi- nant. Considering the high variability of live coral cover reported over the years by different workers, and the uncertain location of sampling sites, this coastal sector is in need of a systematic and technologically advanced survey protocol. 5.3.6 Nicaragua Before 2010, coral surveys along the Pacific coast of Nicaragua indicated the possibility of isolated colonies of Pocillopora close to the Costa Rican border in the area of San Juan del Sur (Durham and Barnard 1952; Glynn and Ault 2000; Spalding et al. 2001; Ryan and Zapata 2003; Cortés 2007). The presumed meagre occurrence of corals in this area may be related to severe and prolonged upwelling (Glynn et al. 1983). In July 2009, Alvarado et al. (2010, 2011) quantitatively assessed the composition of ten coral communities along the southern coast of Nicaragua, including sites in the Department of Rivas,Municipalities of San Juan del Sur, and Tola (11° 23′ N; 86° 02′W and 11° 07′N; 85° 47′W; Fig. 5.11b). They reported the presence of 39 species of macroalgae, 13 scler- actinian corals (nine zooxanthellate and four azooxanthellate species), two crustaceans, five molluscs, 11 echinoderms, and 52 reeffishes. Mean coral cover across all sites was 9.0 ± 1.9 (SD)%, with the highest cover at Guacalito-La Anciana (18.5 ± 8.8%) and Punta Pie deGigante (16.7 ± 5.3%). The most common species were Gardineroseris planulata and Pavonagiganteawith notably high cover at PuntaGigante and La Anciana (Fig. 5.11b). A relatively large and vibrant Pocillopora incipient reef was present in the Punta El Toro embayment with mean live cover of 14.5 ± 7.9 %. The Rivas coral biotopes, such as those present at Punta Gigante, La Anciana, and Punta El Toro, were small, patchy, and confined to a series of small coves and islets protected from wave assault. These communities were dominated by Pavona gigantea. The coral reef fish assemblages were less diverse than those reported for more developed eastern Pacific reef areas elsewhere, but were similar to those in marginal environments, such as upwelling centers (Alvarado et al. 2011). The coral-rich area between Punta Gigante and La Anciana, a 13-km coastal stretch, was touted by Alvarado and co-workers as a hotspot—despite the lack of reef develop- ment—and in urgent need of protection and management. 5.3.7 Mainland Costa Rica A dramatic increase in coral species richness, from 10 to 26 species, is evident in faunal inventories when passing from Nicaragua to Costa Rica (Table 5.4; Appendix). This 5 Eastern Pacific Coral Reef Provinces, Coral Community Structure … 125 disparity is likely due to a combination of factors: (a) the recent discovery of coral communities in Nicaragua, (b) a concentrated research effort on coral reefs in Costa Rica since the 1980s, (c) the relatively large area of varied coastal habitats along Costa Rica’s coast, and (d) the stressful conditions associated with upwelling along the southeastern Nicaraguan coast. The mainland coastline of Costa Rica consists of diverse marine ecosystems as well as islets and islands of various sizes, and differences in proximity to the coast (Denyer and Cárdenas 2000; Cortés and Wehrtmann 2009). The presently recognized tally of 26 zooxanthellate coral species from mainland Costa Rica has been relatively stable during the past decade, thanks to the sustained studies of local workers (e.g., Guzmán and Cortés 1989a; Cortés 1990; Jiménez 1997, 2001a, b; Cortés and Guzmán 1998). This inventory takes into account a single new record for Costa Rica, Porites evermanni, revealed in a molecular genetic study (Boulay et al. 2014), and Porites rus, not Table 5.4 Reef building corals from Pacific Costa Rica Location 1 2 3 4 5 6 7 8 9 10 11 Suborder ASTROCOENIINA, Family Pocilloporidae 1. Pocillopora capitata Verrill, 1864 CA CA CA CA CA 2. Pocillopora damicornis (Linnaeus, 1758) RB RB CA RB RB RB RB RB RB RB 3. Pocillopora elegans Dana, 1846 RB RB RB RB RB RB RB RB RB RB 4. Pocillopora eydouxi Milne Edwards and Haime, 1860 RB CA CA CA CA CA RB 5. Pocillopora inflata Glynn, 1999 RB RB CA CA CA CA 6. Pocillopora meandrina Dana, 1846 CA CA CA CA CA 7. Pocillopora verrucosa (Ellis and Solander, 1786)a RB CA RB Suborder Fungiina, Family Poritidae 8. Porites evermanni Vaughan, 1907 RB RB RB RB CA 9. Porites lobata Dana, 1846 CA CA CA RB RB RB RB RB RB RB 10. Porites panamensis Verrill, 1866 CA CA CA CA CA CA CA CA CA 11. Porites rus (Forskål, 1775) CA Family SIDERASTREIDAE 12. Psammocora obtusangula (Lamarck, 1816) CA CA CA CA RB CA 13. Psammocora stellata Verrill, 1864 CA RB RB CA CA CA CA CA RB CA 14. Psammocora superficialis Gardiner, 1898 CA CA CA CA CA CA CA CA CA CA Family Agariciidae 15. Gardineroseris planulata (Dana, 1846) RB RB CA CA CA RB RB 16. Leptoseris papyracea (Dana, 1846) CA RB CA CA 17. Leptoseris scabra (Vaughan, 1907) CA CA 18. Pavona chiriquiensis Glynn et al. 2001 CA CA CA CA CA 19. Pavona clavus (Dana, 1846) CA RB RB CA CA CA CA RB RB 20. Pavona frondifera (Lamarck, 1816) CA CA RB CA CA 21. Pavona gigantea Verrill, 1869 RB RB CA RB CA CA CA CA CA CA 22. Pavona maldivensis (Gardiner, 1905) CA CA CA CA CA CA CA 23. Pavona varians Verrill, 1864 CA CA CA CA CA CA CA CA CA 24. Pavona minuta Wells, 1954 CA Family Fungiidae 25. Cycloseris curvata (Hoeksema, 1989) CA CA CA 26. Diaseris distorta (Michelin, 1843) CA CA Total number species 3 14 17 21 17 13 11 13 11 19 22 RB = Main reef builder, CA = coral community associate. Areas 1 = Bahía Salinas, 2 = Península de Santa Elena, 3 = Islas Murciélago, 4 = Bahía Culebra, 5 = Península de Nicoya, 6 = Pacífico Central, 7 = Parque Nacional Marino Ballena, 8 = Península de Osa, 9 = Golfo Dulce, 10 = Reserva Biológica Isla del Caño and 11 = Parque Nacional Isla del Coco. RB reef building reported; CA coral community associate aThis species was not recognized in the field until recently; it is probably more widespread than indicated 126 P.W. Glynn et al. observed again since its discovery at Bahía Sámara (sector 5, Fig. 5.12) in the early 1980s (Cortés and Murillo 1985). Pavona chiriquiensis, initially described from populations in Panama, is now known to occur at several sites along the Costa Rican coast. New distributional records for P. chiriquiensis in the central and south Pacific include the Tokelau Islands (*172°W), American Samoa (*170°W), the northern and southern Phoenix Islands (*170°W), and the Line Islands (155°–160°W) (Maragos, unpublished records). A cluster analysis of presence/absence data demonstrates a close affinity with the coral faunas of Panama and Colombia (Fig. 5.2). The northwestern Pacific sector of Costa Rica is charac- terized by a marked dry season (January–April), with strong easterly trade winds that promote seasonal upwelling (Cortés 1996/1997; Jiménez 2001b; Alfaro et al. 2012). Upwelling is most pronounced further north, toward the Nicaraguan border. The dry climate extends south to Golfo de Nicoya, Fig. 5.12 Costa Rica mainland (CRM) partitioned into 10 coastal and one offshore (Isla del Coco) coral-bearing sectors. Red diamonds identify sites with abundant corals 5 Eastern Pacific Coral Reef Provinces, Coral Community Structure … 127 the largest estuarine environment in Costa Rica. The central coastal section is a transitional zone with an increasing humid climate to the south. The southeastern coast is subject to year-round high rainfall, which supports a tropical rain forest ecosystem (Jiménez and Soto 1985; Herrera 1986; Kappelle et al. 2002). For ease of discussion, mainland Costa Rica is divided into 10 sectors where coral communities and reefs occur, from the Nicaraguan border to Golfo Dulce near Panama (Fig. 5.12). Oceanic Isla del Coco (Cocos Island) is assigned to sector 11, and is considered below in Sect. 5.3.8. The northern-most area, Bahía Salinas (sector 1), is heavily influenced by seasonal upwelling in the Gulf of Papagayo (Alfaro et al. 2012). Water temperature in this area can be as low as 12 oC with low oxygen levels and low pH (recorded by Rixen et al. 2012 in Bahía Culebra; see also Jiménez 2001a; Alfaro and Cortés 2012; Alfaro et al. 2012). Because of these extreme conditions, reef and coral com- munity development are limited; Pavona gigantea is pre- dominant with isolated colonies of Porites panamensis. Upwelling effects generally decrease to the south and southeast towards the Nicoya Peninsula. At Península de Santa Elena (sector 2), relatively large pocilloporid reefs are present; one of these structural reefs is built mainly by Pocillopora eydouxi (Cortés 1996/1997; Bassey-Fallas 2010). Immediately south of Santa Elena, lie the Islas Murciélago (sector 3). Several coral reefs occur in this area; one is constructed of massive Gardineroseris planulata colonies. An extensive pocilloporid reef, consisting of large areas of Pocillopora inflata, was killed during a phyto- plankton bloom in 2007 (Jiménez et al., in preparation). Coral recovery, including sexual and asexual recruitment, is very slow in this cool upwelling zone (Cortés, unpublished data). Bahía Culebra (sector 4) is one of the most intensely studied areas in Pacific Costa Rica (Cortés 2012a). Coral reefs and coral communities have been surveyed and mon- itored in this large bay and surrounding areas since the early to mid-1980s (Cortés and Murillo 1985; Jiménez 1997, 2001b; Jiménez et al. 2001, 2010; Bezy et al. 2006; Cortés et al. 2010; Cortés 2012a). The Matapalo fringing reef in the southern part of sector 4, 1.4 km in length, is possibly the largest coral reef bor- dering mainland Costa Rica (Jiménez 2007a; Fig. 5.13). This reef, first surveyed quantitatively in 1978, was largely Fig. 5.13 Matapalo fringing reef, Punta Gorda, Costa Rica (10 February 2007, *1000 m elevation, courtesy María M. Chavarría). Patches of an invasive green alga, Caulerpa sertularioides, seaward of live coral cover, *10 m depth 128 P.W. Glynn et al. degraded at that time; it consisted of large tracts of dead pocilloporid corals, and at most 0.1 % live cover of Psam- mocora stellata (Glynn et al. 1983). [An aerial view of this reef in 1973, with the name Punta Gorda, is shown in Fig. 5.4a in Glynn et al. 1983.] The death of the reef at that time was attributed to cold-water stress due to intense upwelling near the end of the Little Ice Age (150–300 years BP). The overall live cover of pocilloporid corals on this reef amounted to >40 % when surveyed in 2007. Species rich- ness was high, consisting of 16 living species, and 19 spe- cies total, including freshly dead coralla of three species (Cycloseris curvata, Diaseris distorta, and Leptoseris papyracea). Carbonate buildups or bioherms of Leptoseris papyracea are unique to this area. The Matapalo reef has again experienced recent high coral mortality first observed in 2007, and coincidental with extensive and prolonged harmful algal blooms (Jiménez 2007b). It is likely that recent declines in coral cover are due, at least in part, to coastal development activities and poor waste management pro- moting algal blooms, which are now nearly monthly occurrences. Overall, much of the reef building in the extreme north- western area of Costa Rica (sectors 1–4) has been achieved by massive instead of branching pocilloporid species. For example, the major reef builders north of Islas Murciélago are Pavona gigantea and Gardineroseris planulata. At Bahía Culebra, Pavona clavus is one of the major reef builders (Cortés and Jiménez 2003). Extensive growths of the invasive green alga Caulerpa sertularioides have been reported in northwestern Costa Rica at Bahía Culebra (Fernández and Cortés 2005; Fer- nández-García 2007; Fernández-García et al. 2012), and at the Matapalo reef (Jiménez 2007a). Since 2001, C. sertu- larioides cover has been expanding with negative impacts on coral reefs and communities. At La Penca, Bahía Culebra, a Psammocora reef lost 95 % live cover at the expense of this alga during a 6 year period (Bezy et al. 2006). It is a strong competitor for space, overgrowing and smothering low-profile coral colonies. Caulerpa racemosa blooms are also known to cause coral mortality in Panama (see Fig. 8.31 in Chap. 8, and Fong et al., Chap. 11). Little studied and isolated reefs occur in sector 5 along the outer coastline of Península de Nicoya (Cortés and Jiménez 2003; Bezy et al. 2006; Jiménez et al. 2010). A few small colonies of Porites rus, first observed in the eastern Pacific at Bahía Sámara, about 10 km SE of Punta Guiones, disappeared a few years after their discovery (after 1983) and have not been observed anywhere in the EP since. Porites evermanni was recently reported in coral commu- nities on the Península de Nicoya, in other areas of Costa Rica, and elsewhere in the equatorial eastern Pacific (Boulay et al. 2014). The identity of this species was determined from a molecular genetic study; judging from its widespread occurrence and large population sizes it is probably a long-term resident of the equatorial eastern Pacific. Reef-building no longer occurs in the Gulf of Nicoya due to high suspended sediment loading and freshwater dilution. Currently only dead pocilloporid frameworks are present in the gulf, usually in sheltered environments. The central Pacific coastline (sector 6) extends from the east margin of the outer Gulf of Nicoya to Punta Dominical. Isolated reefs and coral communities also have been reported in this area (Cortés and Jiménez 2003). Parque Nacional Marino Ballena (sector 7) is exceptional in the central Pacific coastal area because of its well-developed reefs (Alvarado et al. 2005). These reefs have been impacted by El Niño warming events (Jiménez and Cortés 2001) and excessive terrigenous sedimentation resulting from coastal develop- ment (Alvarado et al. 2005, 2009). The Reserva Biológica Isla del Caño (Caño Island Bio- logical Reserve, sector 8) is located about 15 km west of Península de Osa. Well-developed coral reefs are present at Isla del Caño, from drying reef flats (unusual in the ETP) with abundant Pocillopora spp., crustose coralline algae and Porites microatolls to deep patch reefs constructed of Porites lobata and Pavona clavus (Guzmán and Cortés 1989a; Macintyre et al. 1993; Cortés and Jiménez 2003). These coral communities have been intensely studied, including corallivore activity (Guzmán 1988a, b), coral growth rates (Guzmán and Cortés 1989b), zooplankton ecology (Guzmán and Obando 1988), and meiofaunal populations of reef sediments (Guzmán et al. 1987a). Also, coral mortality associated with algal blooms (“red tides”) was documented at Isla del Caño following the 1982–83 El Niño warming event (Guzmán et al. 1987b, 1990). Finally, Glynn et al. (1991, 1994, 1996a, b, 2000, 2008, 2011, 2012; see Chap. 15, Glynn et al.) have completed long-term studies on the reproductive activities of eleven reef-building coral species and one abundant azooxanthellate coral at Isla del Caño. This work has demonstrated a potentially important role of sexual reproduction in recovery processes in Costa Rica (Guzmán and Cortés 2001), and at several other areas in the equatorial ETP (Glynn and Colley 2008; Glynn et al. 2012). Coral communities and reefs occur on the seaward side of the Península de Osa (sector 9), but are generally only pre- sent in sheltered locations due to high wave assault (Cortés and Jiménez 1996, 2003). Golfo Dulce (sector 10), a fjord-like embayment (Hebbeln and Cortés 2001), is pro- tected from high seas; numerous coral communities and a large fringing reef are present in this gulf (Cortés 1990; Macintyre et al. 1993; Cortés and Jiménez 2003). One of the upper gulf reefs (Punta Islotes), constructed primarily of Porites lobata, initiated growth over 5000 years ago (Cortés et al. 1994). Highest accretion occurred between 2500 and 500 years BP, and then slowed due to changes in the local 5 Eastern Pacific Coral Reef Provinces, Coral Community Structure … 129 http://dx.doi.org/10.1007/978-94-017-7499-4_8 http://dx.doi.org/10.1007/978-94-017-7499-4_8 http://dx.doi.org/10.1007/978-94-017-7499-4_11 http://dx.doi.org/10.1007/978-94-017-7499-4_15 geological setting that increased freshwater input. Reef growth ceased during the last 60 years due to high terrige- nous sediment loads. 5.3.8 Isla del Coco (Costa Rica) Isla del Coco (sector 11), is located over 500 km offshore of Costa Rica, about half way between the Pacific coast of Central America and the Galápagos Islands (Cortés 2008). It is a volcanic island situated on the northeastern-trending Coco Volcanic Cordillera (Rojas and Alvarado 2012). The island and surrounding waters are a marine protected area— Parque Nacional Isla del Coco—the largest MPA in Costa Rica, and is now imbedded in the Área Marina de Manejo de Montes Submarinos (Sea Mounts Marine Management Area). Twenty-two zooxanthellate scleractinians make up the Isla del Coco coral fauna, compared to 25 species total for all 10 Costa Rican mainland sectors (Table 5.4; Appendix). Of all eastern tropical Pacific coral localities, the Isla del Coco coral fauna demonstrates its closest affinity with the Costa Rican mainland (Fig. 5.2; Cortés 2012b). Pavona xarifae, once considered a unique Isla del Coco record in the eastern tropical Pacific, has been synonymized with Pavona minuta by Veron (2000). Veron’s synonymy is recognized here; therefore P. minuta is now more broadly distributed, considered present at Clipperton Atoll, in the Revillagigedo Islands, and at Palmyra Atoll (Appendix). Verification is necessary, however, ideally from specimens collected at their type localities and subjected to the same genomic and morphological analyses. Coral reefs are best developed on the northern island shelf (from Punta María to Wafer Bay, and at Weston and Cha- tham bays), which is protected from southern swells (Guz- mán and Cortés 1992; Cortés 2014). The largest Costa Rican coral reefs occur at Isla del Coco, with one reef exceeding 2 km in length (Fig. 5.14). Porites lobata is the chief framework species, with colonies of Pavona clavus, Pavona gigantea, and Gardineroseris planulata also contributing to reef building; some reef areas have extensive cover of Pocillopora spp. as well (i.e., P. elegans, P. damicornis, and P. eydouxi). Severe coral bleaching and high levels of coral mortality occurred at Isla del Coco during the 1982–83 El Niño warming event (Guzmán and Cortés 1992; Macintyre et al. 1993). Pre-El Niño coral cover of 80-90 % on some reefs declined to 3-26 % after the event. However, by 2002 recovery had been impressive and continues to the present (as of 2015). Since the mid- to late-1990s, Leptoseris scabra, a wide-ranging Indo-Pacific species, appeared for the first time on Isla del Coco reefs and now plays a role there in reef consolidation. The appearance of other species not reported from Isla del Coco before the mid-1990s include Pavona maldivensis, Pavona frondifera, Pavona chiriquiensis, and Fig. 5.14 Isla del Coco (COC), Costa Rica. Red patches denote location of coral reefs (modified after Cortés and Jiménez 2003) 130 P.W. Glynn et al. Pocillopora inflata. All three Pavona species are known to occur at Palmyra Atoll, Line Islands (Appendix), and Pocillopora inflata may be present in the Phoenix Islands (Obura 2002). The sudden appearance of these species at Isla del Coco, in the downstream path of the North Equatorial Counter Current (NECC), prompted Guzmán and Cortés (1992, 2007) to suggest that long-distance dispersal may be an important factor in the recovery of these eastern Pacific reefs following ENSO disturbances. Summarizing for all Costa Rican reef sites subject to disturbance and long-term monitoring, a gradient of coral recovery is apparent that is related to increasing anthro- pogenic impacts and levels of protection (Cortés et al. 2010). The emerging pattern, from coral reefs exhibiting rapid to slow recovery, is as follows: Isla del Coco, Isla del Caño, Parque Nacional Marino Ballena, and Bahía Culebra. Coral cover at oceanic Isla del Coco, the most remote of the monitored sites, exhibited higher levels of recovery than the reefs at Isla del Caño, a moderate distance off-shore and relatively un-disturbed by humans. The lowest levels of coral recovery occurred at Parque Nacional (PN) Marino Ballena and Bahía Culebra, both on-shore areas subject to diverse coastal stresses. The PN Marino Ballena is protected whereas the coral reefs at Bahía Culebra are not. The degree of protection of these four areas is greatest at Isla del Coco and least at Bahía Culebra. A similar pattern was reported by Edgar et al. (2010) who found that eastern Pacific MPAs with higher controls and regulation had greater fish biomass and more coral cover than areas with limited or no protection. 5.3.9 Panama Panama has been the focus of coral reef ecological studies since the early 1970s. The initial research in Panama during the 1970s was directed toward documenting the presence of structural coral reefs in the eastern Pacific region (see Chap. 1 for a historical perspective). With the discovery of numerous reefs, interests then turned to investigation of the physical and biotic controls of their distributions, particu- larly in relation to the different oceanographic conditions in the Gulfs of Panama and Chiriquí (Fig. 5.15). As in southern Mexico (Gulf of Tehuantepec), and the border region between Nicaragua and Costa Rica (Gulf of Papagayo), the low elevation of the Central American Cordillera in Panama, Fig. 5.15 Isthmus of Panama (PAN), framed are Las Perlas MPA, Gulf of Panama, and the Coiba National Park, Gulf of Chiriquí. Red diamonds identify sites with high coral cover. See Figs. 5.16 and 5.17 for actual MPA boundaries 5 Eastern Pacific Coral Reef Provinces, Coral Community Structure … 131 http://dx.doi.org/10.1007/978-94-017-7499-4_1 at 80°W, allows seasonal (January–April) NE Trade Wind flow across the isthmus, thus causing upwelling in the Gulf of Panama and further south across the Panama Bight and along coastal Colombia. Upwelling, with accompanying low water temperatures and high nutrient conditions, promotes phytoplankton blooms that can interfere with coral growth. The high Tabasará mountain range in western Panama, reaching 3000 m elevation and more in some areas, reduces by more than two-thirds the Trade wind flow, thus pre- venting upwelling in the Gulf of Chiriquí, but allowing brief SST shoaling and cooling of the upper surface layer more commonly than previously suspected (D’Croz and O’Dea 2007). The extent of reef building is notable in this warm and more thermally stable enclave. Structural coral reefs are also present in the seasonally variable Gulf of Panama, but are not so well developed as in the Gulf of Chiriquí (see Chap. 6, Toth et al.). Coral community development, and the presence of coral reefs, is greatest on the numerous islands present on the isthmian shelf. With the exception of the hydrocoral Millepora intricata, which often contributes importantly to coral communities and reef frameworks in the Gulf of Chiriquí (Fig. 5.3), the chief frame-building scleractinian species in both gulfs are Pocillopora damicornis, Pocillopora elegans, Porites lobata, Pavona clavus, Pavona gigantea, and Gar- dineroseris planulata. Zooxanthellate scleractinian species richness is virtually the same in both gulfs (Maté 2003). Three uncommon transitory species, Leptoseris papyracea, Diaseris distorta and Cycloseris curvata, are sometimes found in deeper (12–25 m), offreef, sedimentary habitats. A single, small, living population of C. curvata is presently known in the Gulf of Chiriquí; only dead skeletons of the other two species have been reported from Panama. Like Costa Rica, the Panamanian coral fauna has remained relatively stable during the past decade, with 25 presently recognized zooxanthellate scleractinian species. Recent additions are Porites evermanni, Pavona minuta, Pavona duerdeni, and Siderastrea glynni (Fig. 5.7; Appen- dix). The validity of S. glynni is in question; possibly it is not a resident endemic, but a human-introduced Caribbean species (Forsman et al. 2005). Panama’s coral species rich- ness is equal to that of Costa Rica, with both faunas demonstrating a strong affinity (Fig. 5.2). It is not incon- ceivable that the high species richness of Indo-Pacific corals in Panama, Costa Rica, and Colombia is at least in part associated with the inflow of the NECC into this equatorial region (see Chap. 3, Fiedler and Lavín). The NECC may also be responsible for the sporadic occurrence of Indo-Pacific cnidarian vagrants in equatorial eastern Pacific waters, e.g., Porites rus (Costa Rica), Millepora platyphylla (Panama), and Acropora valida (Colombia) as well as ephemeral occurrences of non-cnidarian invertebrate and fish species (Glynn and Ault 2000; see Chap. 16, Lessios and Baums). Perhaps the most influential environmental driver affect- ing Panama’s coral populations is ENSO. The ENSO warm phase (El Niño) in particular, but also the cool phase (La Niña) can cause coral bleaching and mortality. Mean overall coral mortality in Panama following the 1982–83 El Niño disturbance ranged from 76 to 90 % (Wellington and Glynn 2007). Coral mortality during the 1997–98 El Niño was much lower, amounting to only � 13 % in the Gulf of Chiriquí, and no detectable mortality in the Gulf of Panama. The low coral mortality in the Gulf of Chiriquí was attrib- uted to endosymbiont resistance (see Chap. 13, Baker et al.), and the absence of coral mortality in the Gulf of Panama to upwelling, which prevented high stressful temperatures (Glynn et al. 2001). Biotic disturbances may follow thermally-induced coral mortality. For example, bioerosion of dead corals can accelerate with increasing sea urchin population densities, which could lead to coral framework loss and the cessation of reef growth (Glynn 1988; Eakin 1992, 1996, 2001). Acanthaster planci, where abundant in the Gulf of Chiriquí in the 1970s and early 1980s, posed a threat to some uncommon corals that survived El Niño bleaching. How- ever, this corallivore’s numbers decreased dramatically on reefs after the mid-1990s and is now mostly present in coral communities where it is no longer a threat (see Chap. 10, Enochs and Glynn). Past ENSO impacts can be detected from changes in coral colony morphology, increases in non-coral benthic cover, eroded reef structures, and increa- ses in coral rubble accumulations. ENSO-related coral mortality has not been observed in Panama during the last 18 years, and significant recovery of live coral cover has occurred on reefs in the Gulfs of Panama and Chiriquí (Baker et al. 2008). The demonstrated capacity for sustained high levels of sexual reproduction as well as asexual regeneration (Glynn and Fong 2006) has likely figured importantly in the recovery of coral communities. Continued study of coral sexual reproduction has demonstrated that the reproductive modes and spawning patterns of Pavona clavus, Psammo- cora stellata and Psammocora profundacella (Glynn et al. 2011, 2012) are similar to those of seven previously inves- tigated species (Pocillopora, two spp; Porites lobata; agariciids, 4 spp), namely (a) broadcast spawning of minute ova at or a few days following full moon, (b) high annual fecundity due to frequent and prolonged spawning, and (c) reproduction most active during periods of high but not stressful sea water temperature (see Chap. 15, Glynn et al.). Year-round gametogenesis occurred in non-upwelling Gulf of Chiriquí, but ceased during the 3-month upwelling season in the Gulf of Panama. Gametogenesis continued during 132 P.W. Glynn et al. http://dx.doi.org/10.1007/978-94-017-7499-4_6 http://dx.doi.org/10.1007/978-94-017-7499-4_3 http://dx.doi.org/10.1007/978-94-017-7499-4_16 http://dx.doi.org/10.1007/978-94-017-7499-4_13 http://dx.doi.org/10.1007/978-94-017-7499-4_10 http://dx.doi.org/10.1007/978-94-017-7499-4_15 mild El Niño warming events (Colley et al. 2006). Glynn and Colley (2008) hypothesized that broadcast spawning coral species can better tolerate and survive unstable envi- ronmental conditions in the eastern Pacific than brooding species. Tubastraea coccinea, a ubiquitous azooxanthellate brooder in Panama (and elsewhere in the eastern Pacific), releases planulae during new and full lunar phases, mostly during high thermal periods (Glynn et al. 2008). This species also is highly fecund, and is reproductively mature when colonies possess as few as 2 to <10 polyps. During the past decade (early to mid 2000s) detailed mapping of the presence and abundances of coral and octocoral communities has been undertaken in two of Panama’s largest MPAs, the Pearl Islands (Gulf of Panama), and Coiba Island (Gulf of Chiriquí) and surroundings (Guzmán et al. 2004, 2008). [As a cautionary note, the live coral cover on these maps (1) includes corals and octocorals, (2) none of the islands supports a continuous fringing reef, and (3) coral cover on the relatively small structural reefs (not shown) often exceeds 40 %. The reader is referred to Guzmán et al. (2004, 2008) for details on the sampling methodology.] Moderate to high coral cover, 20 to >40 %, was reported in both of these archipelagos (Figs. 5.16 and 5.17) with the highest coral cover recorded on the smaller islands (Table 5.5). The high coral cover category in the Coiba Islands (18.4 %) was slightly over twice as high as Fig. 5.16 Live coral cover in Pearl Islands MPA (168,800 ha), Gulf of Panama, Panama. The *7 km wide Trollope Bank is shown to the SE of El Rey Island. MPA boundaries in blue. Modified after Guzmán et al. (2008) 5 Eastern Pacific Coral Reef Provinces, Coral Community Structure … 133 that recorded in the Pearl Islands (8.1 %). Nearly 80% of the surveyed areas in the Pearl Islands supported low coral cover (<20 %) compared with � 35 % in the Coiba Islands. It is necessary to consider at least three factors contributing to this difference: (a) deforestation, land use and sedimentation, all of which have been greatest in the Pearl Islands, (b) up- welling versus non-upwelling environments, the latter gen- erally promoting more robust coral growth, and (c) phytoplankton blooms causing copious mucus produc- tion that can smother corals (Guzmán et al. 1990). In these island-wide surveys a distinction was made between coral communities (CC) and coral reefs (CR), which revealed some intriguing differences: (a) scleractinian corals and octocorals demonstrated higher species richness in CC compared to CR, (b) coral cover was higher in CC than CR in the Coiba Islands preserve, but higher in CR than CC in the Pearl Islands, (c) uncommon, rare or endangered cnidarians were encountered more frequently in CC than CR, and (d) a negative relationship between live coral cover and species richness emerged in the Coiba Islands, with CC consisting of a greater variety of cnidarian species than CR. A similar trend to that in ‘a’ above was reported by Benfield et al. (2008) for reef fish assemblages in the Pearl Islands, which were significantly more diverse and species rich in CC than CR. These results prompted Guzmán et al. (2004, 2008) to hypothesize that CC may serve as refugia and Fig. 5.17 Live coral cover in Coiba MPA (270,125 ha), Gulf of Chiriquí, Panama. MPA bound- ary in blue. Modified after Guz- mán et al. (2004) 134 P.W. Glynn et al. source areas for larvae that could repopulate CR that become degraded during large-scale disturbances such as El Niño bleaching/mortality events. Building on Abele’s (1976) demonstration of a species-rich community of decapod crustaceans associated with living pocilloporid corals (55 species), several recent studies have revealed an impressive number of motile, cryptic invertebrates and fishes that seek refuge in living and dead coral frameworks and rubble. For example, the biomass and abundances of various invertebrate taxa (Polychaeta, Gastropoda, Crustacea, Holothuroidea, Ophiuroidea) asso- ciated with live corals are generally higher than those shel- tering among dead corals and coral rubble (Enochs and Hockensmith 2009; Enochs 2012). Species richness, how- ever, is significantly higher in dead and degraded coral rubble (261–370 species) compared with live coral habitats (112–219). Among some of the several key reasons for this are (a) the inimical defenses of live corals (nematocysts, mucus secretions), (b) the agonistic and competitive nature of obligate coral metazoan symbionts, and (c) the greater habitat heterogeneity and niche diversity of rubble sub- strates. These results show that an abundant and speciose cryptic fauna is still present on highly degraded reefs that can continue to function in various reef processes, e.g. providing prey for reef fishes, scavenging, biodegradation, remineralization, bioerosion, interalia (Enochs et al. 2011; Enochs 2012; Enochs and Manzello 2012a, b). Recent studies of the diversity, community structure and trophic relationships of coral-associated fishes have increased our understanding of their diverse and pivotal ecological roles in the ETP (Dominici-Arosemena and Wolff 2006; Benfield et al. 2008; Glynn 2008; Robertson and Allen 2008; Glynn et al. 2014). A large number of faculta- tive corallivores, and cryptic fishes residing in coral rubble, many of the latter invertivore and piscivore predators, have been identified (Glynn 2006, 2008). Some of these taxa may play critical roles in limiting the settlement and survival of recruiting species. 5.3.10 Mainland Colombia In spite of the adverse climatic and oceanographic conditions (Glynn and Ault 2000; Zapata and Vargas-Ángel 2003), isolated colonies of scleractinian corals occur along most of the 1450 km of the Colombian Pacific coast. Corals are most common in the northern half of the coast from the Panama-Colombia border south to Cabo Corrientes, a stretch dominated by igneous rocky shores. South of Cabo Corri- entes to the Ecuador-Colombia border the coast is composed of alluvial sediments and dominated by soft bottoms and mangroves intermixed with some stretches of soft sedi- mentary rock from the Tertiary. The Colombian Pacific coastal region is one of the rainiest regions of the world, with annual precipitation exceeding 10,000 mm at some locali- ties. High freshwater discharge from the western slopes of the Andes and the adjacent lowlands into the Pacific Ocean significantly reduces salinity and increases turbidity and sedimentation, particularly in the southern half of the region (Restrepo and Kjerfve 2000; Alory et al. 2012). Yet, the best developed coral reefs and coral communities of the Colombian Pacific are located in this southern portion at Gorgona Island, which is adjacent to this stretch of coastline, Table 5.5 Live coral cover at various islands surveyed at Coiba and Pearl Islands MPAs Location Area of live coral cover (km2) High (>40 %) Moderate (20-40 %) Low (<20 %) Coiba Islands Brincanco 12.237 – – Uva 14.587 – 4.747 Canal de Afuera 6.377 7.822 4.951 Coibita 2.384 7.829 – Coiba 9.531 135.693 93.053 Jicarón 13.532 7.156 13.707 Jicarita 3.227 – – Total = 336.84 61.88 (18.4 %) 158.50 (47.1 %) 116.46 (34.6 %) Pearl Islands Pacheca – 3.261 1.260 Saboga – 5.037 1.359 Contadora 1.387 2.133 – Chapera 2.418 1.432 – Mogo Mogo 4.500 – – Gibraleon – – 5.898 Bayoneta – – 6.947 Casaya – – 12.248 La Mina – – 7.120 Viveros – – 37.279 Señorita – 2.168 – Pedro González 3.477 – 9.725 San José 2.920 5.110 13.100 San Telmo – – 3.131 Puerco – – 3.336 Cane – 1.560 3.600 El Rey – 1.800 38.320 Total = 180.52 14.70 (8.1 %) 22.50 (12.5 %) 143.32 (79.4 %) Estimated areas digitized using Arc Map 10.1 software from Guzmán et al. (2004, 2008) 5 Eastern Pacific Coral Reef Provinces, Coral Community Structure … 135 but located sufficiently far offshore to reduce the limiting influence of the coastal environment. Accordingly, Kleypas et al. (1999) listed Gorgona Island and Ensenada de Utría, also in Colombia (see below), as the two lowest salinity localities with coral reefs in the eastern Pacific. Therefore, coral communities and true reefs (carbonate frameworks) are few, small, patchily distributed and poorly developed. Consequently, coral communities and reefs in this area of the eastern Pacific are species-poor (� 12 scleractinian coral species per site) and the entire coral fauna is composed of about 28 species, although taxonomic difficulties, particu- larly within the genus Pocillopora, make this number somewhat uncertain (Table 5.6). Four localities along Colombian Pacific shores have been reported to have significant coral communities or coral reefs: Cabo Marzo and Punta Cruces, Punta Tebada, Ensenada de Utría, and Gorgona Island (Fig. 5.18). The northernmost area is a prominent rocky point located at Cabo Marzo (Fig. 5.19) where a significant coral formation occurs. Known locally as El Acuario, the shallow (� 3 m) substrate here is composed of a solid rock bed with boulders dominated by filamentous algae (47 % mean cover), scleractinian corals (33 % mean cover) and octocorals. Branching corals of the genus Pocil- lopora are the most common (27 % mean cover) followed by massive colonies of Pavona gigantea. There is, however, little indication of significant reef framework development at this site. Six species of zooxanthellate scleractinian corals occur at El Acuario (Zapata et al. 2008; Table 5.6). A small coral patch consisting of sparse Pocillopora damicornis colonies and associated rubble is also located in neighboring Bahía Aguacate. Further south at Punta Cruces, in a cove in front of the hamlet known as Piñas (Fig. 5.19), there also is a coral community dominated by massive and encrusting cor- als covering nearly 38 % of the rocky substrate. Coral assemblages characterized by high colony densi- ties, but lacking a framework buildup are common in the Utría and Tebada region. Largely, these communities develop on rocky banks, shoals, and vertical walls, partic- ularly in small embayments and coves, ranging in depth from about 1 to 10 m; moderately strong swells and vigor- ous water circulation are prevalent in these habitats, how- ever. Despite the high energy of the environment, the dominant taxa are branching Pocillopora specie