Eastern Pacific Coral Reefs Research Articles

Imprint of Regional Oceanography on Foraminifera of Eastern Pacific Coral Reefs

ABSTRACT The marginal marine environments of the eastern tropical Pacific (ETP) serve as an ideal natural laboratory to study how oceanographic and climatic variability influence coral-reef ecosystems. Reefs along the Pacific coast of Panamá span a natural gradient of nutrients, pH, and temperature as a result of stronger seasonal upwelling in the Gulf of Panamá relative to the Gulf of Chiriquí. The ecosystems are not only influenced by spatial and seasonal variations in oceanography but are affected by the climatic variability of the El Niño-Southern Oscillation (ENSO). Foraminifera can be robust indicators of ecosystem condition because the composition of their assemblages and the geochemistry of their tests can change rapidly in response to environmental variability. We studied benthic foraminifera in sediment samples collected from 3 m below mean sea level in the Gulf of Panamá and the Gulf of Chiriquí. Temperature loggers deployed from 2016 to 2019 showed that average temperatures were lower and more variable in the Gulf of Panamá due to seasonal upwelling. All sites in both gulfs were dominated by heterotrophic foraminifera, which was likely the result of nutrient enrichment due to upwelling, combined with ENSO effects. However, the Gulf of Chiriquí was characterized by higher abundances of symbiont-bearing foraminifera than the Gulf of Panamá. The orders Miliolida and Rotaliida dominated the foraminiferal assemblages in both gulfs, with Quinqueloculina and Rosalina being the most abundant genera in the two orders, respectively. Miliolids were less abundant in the Gulf of Panamá than in the Gulf of Chiriquí, whereas rotaliid densities were not significantly different between the two gulfs. Lower pH in the Gulf of Panamá as a result of upwelling may have contributed to the lower abundance of miliolids, which secrete tests of high-magnesium calcite. Geochemical analysis of tests of the symbiont-bearing miliolid Sorites marginalis revealed that foraminiferal Mg/Ca ratios were lower in the Gulf of Panamá than in the Gulf of Chiriquí. The offset in foraminiferal Mg/Ca is consistent with the lower mean annual temperature observed in the Gulf of Panamá due to stronger seasonal upwelling. Because the geochemistry and assemblages of foraminifera reflect differences in environmental conditions, they could potentially be used in tandem with coral proxies to reconstruct past environmental change and project the future of coral-reef systems within the ETP.

Agent-based model of Eastern Pacific damselfish and sea urchin interactions shows increased coral reef erosion under post-ENSO conditions

Significant increases in the population of the echinoid bioeroder Diadema mexicanum that may soon follow severe El Niño events, such as in 1982–1983, can have a significant negative impact on the carbonate budget of coral reefs. We developed a spatially explicit model that uses agent-based modeling techniques to simulate the interactions between damselfish and sea urchins on an eastern Pacific coral reef following an El Niño-Southern Oscillation (ENSO) event where high echinoid abundances and low coral cover were prevalent. Our modeling study suggests that the agonistic behavior of damselfish towards echinoids invading their defended algal lawn territories has a magnifying effect on the degree of bioerosion attributed to echinoids. This is due to the increased likelihood that sea urchins ejected from damselfish territories will form concentrated aggregations and remain grazing and eroding coral for longer periods of time. This is a novel insight that contrasts with the previous understanding of the positive effect that damselfish have on reef carbonate budgets by protecting carbonate substrates that lie within their defended algal lawn territories. The increased degradation of coral stands attributed to the indirect damselfish effect, if it results in sea urchins eroding subsurface coral framework structures, causing instability and collapse (especially during periods of high-water motion), may contribute to the fracturing of large portions of coral framework blocks, affecting the recovery trajectory of reefs following a severe El Niño disturbance event.

Spatio-temporal variation in rate of carbonate deposition by encrusting organisms in different reef microhabitats from Eastern Pacific coral reefs

AbstractReef encrusting calcifiers (non-scleractinian species) constitute assemblages that participate in the carbon cycle at coral reefs. Despite their apparent secondary role in building the reef framework, they contribute to the reef consolidation binding sediments and inducing larval recruitment from other epilithic invertebrates. The contribution of encrusting calcifiers on reef accretion was examined by the assessment of their rate of carbonate deposition on four different simulated reef microhabitats using calcification accretion units (CAUs) during 12 months at Playa Las Gatas and Islote Zacatoso, two coral communities from the coast of the Mexican Pacific. Encrusting calcifiers from Playa Las Gatas, the most impacted site, showed a rate of carbonate deposition (mean ± SD) four times higher than at Islote Zacatoso (10.02 ± 3.22 g CaCO3m−2d−1vs2.48 ± 1.01 g CaCO3m−2d−1). Overall, the rate of carbonate deposition on surfaces protected from sedimentation and light was up to 1.8 times higher than on exposed ones (11.40 ± 4.35 g CaCO3m−2d−1vs6.18 ± 3.13 g CaCO3m−2d−1). Carbonate deposition by calcareous algae was higher on the well-lit exposed surfaces while filter-feeding invertebrates showed the major contribution on the shaded cryptic surfaces. Although rate of carbonate deposition by encrusting calcifiers seems to be lower than hermatypic corals, it seems to be relevant on coral reefs affected by anthropogenic impacts where coral calcification is low. Under global demise of coral reefs by environmental degradation and climate change, encrusting calcifiers may become relevant for the process of carbonate deposition.

Temporal variation in invertebrate recruitment on an Eastern Pacific coral reef

The recruitment of marine invertebrate larvae to coral reef ecosystems is critical for the continued productivity of these highly biodiverse habitats. Despite such importance, little is known about temporal variation patterns of invertebrate larval recruitment in coral reefs ecosystems, aside from studies focused only on reef corals themselves. Given this knowledge deficiency, recruitment onto dead coral branches was monitored over a one-year period in the Central Mexican Pacific, and recruit assemblage and density both changed over time. In particular, recruitment was higher in the warmer months, possibly due to reproductive processes and/or increases in metabolic rates associated with high temperatures and seasonal/local events such as upwellings that increase the food resources available for the recruits which just before the warm season, when the recruitment is more more prevalent during the warm season. The most common invertebrate recruits were malacostracans, ostracods, gastropods, maxillopods, and polychaetes, and foraminifers were commonly observed, as well. Future works in this region will seek to understand whether recruit density and diversity change in response to elevated temperatures associated with global climate change.

Cleaning interactions by gobies on a tropical eastern Pacific coral reef.

The present study describes the cleaning interactions among species of cleaner gobies Tigrigobius spp. and Elacatinus puncticulatus (family Gobiidae) and the client fish species they clean in a coral reef of Gorgona Island, Colombia. In 419 cleaning events, we observed 27 species acting as clients of Tigrigobius spp., whereas only nine were clients of E. puncticulatus. Paranthias colonus and Cephalopholis panamensis were the species most commonly cleaned by Tigrigobius spp., while Ophioblennius steindachneri and Stegastes acalpulcoensis were the clients most commonly cleaned by E. puncticulatus. The abundance (but not the body size) of clients was an important variable predicting the cleaning frequency observed for clients of Tigrigobius spp., but this was not the case for clients of E. puncticulatus. Additionally, Tigrigobius spp. preferred cleaning planktivores, sessile invertebrate feeders and territorial herbivores (Ivlev's index >0·15), whereas E. puncticulatus did not exhibit any preference. We observed two major peaks of cleaning activity for Tigrigobius spp., one in the early morning and another one in the late afternoon. These results suggest that Tigrigobius spp. is a specialized cleaner goby, whereas E. puncticulatus is a facultative cleaner that cleans sporadically.

Comparison between Caribbean and eastern Pacific coral reefs

The temporal and spatial distance separating the Caribbean and the eastern Pacific is short, as little as 50 km (Leschine 1981) and around 3.5 million years (Coat.es et al. 1992). This se­paration has resulted in very different oceanographic settings and coral reefs on both sides of the Central American isthmus (Glynn 1982). In this paper I extend Glynn's comparisons to include historical development of the reefs and more recent contrasting data from both sides.

Effects of Seasonal Upwelling on Inorganic and Organic Matter Dynamics in the Water Column of Eastern Pacific Coral Reefs.

The Gulf of Papagayo at the northern Pacific coast of Costa Rica experiences pronounced seasonal changes in water parameters caused by wind-driven coastal upwelling. While remote sensing and open water sampling already described the physical nature of this upwelling, the spatial and temporal effects on key parameters and processes in the water column have not been investigated yet, although being highly relevant for coral reef functioning. The present study investigated a range of water parameters on two coral reefs with different exposure to upwelling (Matapalo and Bajo Rojo) in a weekly to monthly resolution over one year (May 2013 to April 2014). Based on air temperature, wind speed and water temperature, three time clusters were defined: a) May to November 2013 without upwelling, b) December 2013 to April 2014 with moderate upwelling, punctuated by c) extreme upwelling events in February, March and April 2014. During upwelling peaks, water temperatures decreased by 7°C (Matapalo) and 9°C (Bajo Rojo) to minima of 20.1 and 15.3°C respectively, while phosphate, ammonia and nitrate concentrations increased 3 to 15-fold to maxima of 1.3 μmol PO4 3- L-1, 3.0 μmol NH4 + L-1 and 9.7 μmol NO3 - L-1. This increased availability of nutrients triggered several successive phytoplankton blooms as indicated by 3- (Matapalo) and 6-fold (Bajo Rojo) increases in chlorophyll a concentrations. Particulate organic carbon and nitrogen (POC and PON) increased by 40 and 70% respectively from February to April 2014. Dissolved organic carbon (DOC) increased by 70% in December and stayed elevated for at least 4 months, indicating high organic matter release by primary producers. Such strong cascading effects of upwelling on organic matter dynamics on coral reefs have not been reported previously, although likely impacting many reefs in comparable upwelling systems.

Drift logs are effective agents of physical coral fragmentation in a tropical eastern Pacific coral reef

Drift logs are effective agents of physical coral fragmentation in a tropical eastern Pacific coral reef

Short-term assessment of the sediment deposition rate and water conditions during a rainy season on La Azufrada coral reef, Gorgona Island, Colombia

One of the major stresses on corals is the settlement of suspended sediment on their surfaces. This leads to the blocking of light, the covering of the coral mucus surface and an increased risk of disease. For this reason sediment deposition on a reef is considered a highly important variable in coral reef studies. With the use of sediment traps and oceanographic sensors, the sediment deposition rate and water conditions during a rainy season (April-May 2009) on a Tropical Eastern Pacific coral reef (La Azufrada) at Gorgona Island in Colombia were investigated. To quantify sediment deposition, sediment traps were established in nine stations along the coral reef (three stations per reef zone: backreef, flat and slope). To minimize disturbance by aquatic organisms in the sediment traps these were filled with hypersaline borax-buffered 10% formaline solution before their deployment; animals found in the filter contents were fixed and stored in a 4% formalin solution, frozen and identified in the laboratory. To determine the water conditions, discrete samples of water from 1 m and 10 m depths were collected using a Niskin bottle. Oceanographic variables (temperature, salinity and dissolved oxygen) as well as turbidity, chlorophyll and nutrient concentration (nitrite, nitrate and phosphorus) were measured in the samples from both depths. Vertical records of temperature and salinity were carried out with a Seabird-19 CTD nearest to La Azufrada and water transparency was measured using a Secchi disk. We found a mean trap collection rate of 23.30±4.34gm-2d-1 and did not detect a significant difference in the trap collection rate among reef zones. The mean temperature and salinity in the coral reef depth zone (0-10m layer) were 26.98±0.19°C and 32.60±0.52, respectively. Fourteen taxonomic groups of invertebrates were detected inside the sediment traps with bivalves and copepods being the most abundant and frequen. The findings presented here constitute the first report of both the potential sediment deposition rates and the water conditions of La Azufrada coral reef. Rev. Biol. Trop. 62 (Suppl. 1): 107-116. Epub 2014 February 01.

Environmental determinants of motile cryptofauna on an eastern Pacific coral reef

Coral reef cryptofauna, which live hidden within reef framework structures, are con- sidered to be the most diverse group of coral reef metazoans. They likely comprise more biomass than all surface fauna, providing food sources for fishes and playing important roles as predators, herbivores, detritivores, filter feeders, and scavengers. In an era of global change, it is necessary to determine how these communities are structured across reef habitats as well as to understand how reef framework degradation will impact the cryptofauna and, by extension, ecosystem func- tion. Artificial reef framework units were constructed from coral rubble to approxi mate framework substrates. Forty replicates were subjected to treatments of differing porosity, flow, and coral cover in a fully crossed ANOVA design. After 2 mo in situ, all motile cryptofauna (>2 mm) were counted, weighed, and identified to the lowest possible level. A total of 11 309 specimens were col- lected, comprising >121 species from 6 separate phyla. Cryptofaunal abundances and biomass were higher in low-porosity crypts and biomass was greater in slow-flow environments, highlight- ing the importance of sheltered low-porosity habitats, such as back-reef rubble plains. The pres- ence of live coral was not found to have a significant effect on the motile cryptofauna occupying the dead coral framework below it, suggesting a high degree of resilience in how framework- dwelling fauna respond to coral mortality. These data support the assertion that artificial reefs are capable of facilitating the accumulation of a diverse cryptic community, independent of live coral, provided they contain suitably porous crypts.

Coral growth with thermal stress and ocean acidification: lessons from the eastern tropical Pacific

The rapid growth of scleractinian corals is responsible for the persistence of coral reefs through time. Coral growth rates have declined over the past 30 years in the western Pacific, Indian, and North Atlantic Oceans. The spatial scale of this decline has led researchers to suggest that a global phenomenon like ocean acidification may be responsible. A multi-species inventory of coral growth from Pacific Panama confirms that declines have occurred in some, but not all species. Linear extension declined significantly in the most important reef builder of the eastern tropical Pacific, Pocillopora damicornis, by nearly one-third from 1974 to 2006. The rate of decline in skeletal extension for P. damicornis from Pacific Panama (0.9% year−1) was nearly identical to massive Porites in the Indo-Pacific over the past 20–30 years (0.89–1.23% year−1). The branching pocilloporid corals have shown an increased tolerance to recurrent thermal stress events in Panama, but appear to be susceptible to acidification. In contrast, the massive pavonid corals have shown less tolerance to thermal stress, but may be less sensitive to acidification. These differing sensitivities will be a fundamental determinant of eastern tropical Pacific coral reef community structure with accelerating climate change that has implications for the future of reef communities worldwide.

Coral (Anthozoa: Scleractinia) Recruitment at Bahías de Huatulco, Western México: Implications for Coral Community Structure and Dynamics1

Over the past decades there has been an increasing awareness of community structure and dynamics in eastern Pacific coral reef systems, yet the processes producing these patterns are poorly known. We conducted a quantitative analysis of patterns of sexual and asexual recruitment through fragmentation at six localities in Huatulco, Mexico. Between January 2001 and January 2002, sexual recruitment was evaluated by using terracotta tiles. Fragmentation was addressed twice using quadrats. Two hundred ninety-two corals (291 Porites panamensis Verrill, 1 Pocillopora sp.) were recruited to the settlement tiles. Changes in abundance of recruits among sites were determined by coral cover of P. panamensis at each area. Fragmentation was restricted to Pocillopora spp., and processes producing fragments had no connection with those promoting their reattachment and survival. Sexual and asexual recruitment patterns and potential survival asymmetries displayed by P. panamensis and Pocillopora spp. in the area are of capital importance in the occurrence of local communities and potentially of those of the entire eastern Pacific region. Sexual and asexual recruitment patterns suggest that recovery of frame-building corals following disturbance is highly species-specific. Recovery of P. panamensis following coral removal can be relatively fast, but greatly prolonged for Pocillopora; however, in communities with low to moderate disturbance where patches of Pocillopora were preserved reef recovery can proceed at a moderate to relatively fast pace following disturbance. Coordinated multidisciplinary and interinstitutional efforts, including genetic, histological, and ecological approaches, are necessary to determine unequivocally the processes controlling community structure and dynamics in the area.

High Complexity Food Webs in Low-diversity Eastern Pacific Reef?Coral Communities

Community-wide feeding interrelationships in a low-diversity coral reef off the Pacific coast of Panama (Uva Island reef) demonstrate complex pathways involving herbivore, strong corallivore, and carnivore interactions. Four trophic levels with 31 interguild links are identified in a generalized food web, and documented feeding interrelationships with 287+ species links are portrayed in a coral–corallivore subweb. The importance of trophic groups changes greatly with time, from unknown causes over annual to decadal-scale periods, and during very strong El Nino–Southern Oscillation events such that intermittent intense herbivory by echinoids (Diadema) and corallivory by gastropod mollusks, the crown-of-thorns sea star Acanthaster, hermit crabs, and fishes result in high levels of coral mortality and bioerosion of reef substratum. Intraregional differences in species composition and abundances affecting food-web interactions are briefly described for nonupwelling (Uva Island) and upwelling areas (Pearl Islands) in Panama. Seasonal upwelling in the Pearl Islands results in high plankton productivity, which likely augments production in invertebrates, fishes, marine mammals, and seabirds, but these pathways still remain largely unquantified. The corallivore Acanthaster is absent from upwelling centers in Panama and from upwelling and nonupwelling areas in the southern and central Galapagos Islands, and the highly destructive, facultative corallivore Eucidaris galapagensis occurs only in the latter offshore islands and at Cocos Island. Relatively recent declines in the abundances of manta rays, sharks, and spiny lobsters are correlated with, but not necessarily causally linked to, increasing fishing activities in the late 1970s to early 1980s. The extent to which the complex yet highly unstable Uva Island food web is representative of other eastern Pacific coral reef ecosystems remains to be investigated.

A biogeographic analysis and review of the far eastern Pacific coral reef region

New information on the presence and relative abundances of 41 reef-building (zooxanthellate) coral species at 11 eastern Pacific and 3 central Pacific localities is examined in a biogeographic analysis and review of the eastern Pacific coral reef region. The composition and origin of the coral fauna and other reef-associated taxa are assessed in the context of dispersal and vicariance hypotheses. A minimum variance cluster analysis using coral species presence–absence classification data at the 14 localities revealed three eastern Pacific reef-coral provinces: (1) equatorial– mainland Ecuador to Costa Rica, including the Galapagos and Cocos Islands; (2) northern– mainland Mexico and the Revillagigedo Islands; (3) island group– eastern Pacific Malpelo Island and Clipperton Atoll, and central Pacific Hawaiian, Johnston and Fanning Islands. Coral species richness is relatively high in the equatorial (17–26 species per locality) and northern (18–24 species) provinces, and low at two small offshore island localities (7–10 species). A high proportion (36.6%, 15 species) of eastern Pacific coral species occurs at only one or two localities; of these, three disappeared following the 1982–83 ENSO event, three occur as death assemblages at several localities, and five are endangered with known populations of ten or fewer colonies. Principal component analysis using ordinal relative density data for the 41 species at the 14 localities indicated three main species groupings, i.e., those with high, mid, and narrow spatial distributions. These groupings correlated with species population-dynamic characteristics. These results were compared with data for riverine discharges, ocean circulation patterns, shoreline habitat characteristics, and regional sea surface temperature data to help clarify the analyses as these measures of environmental variability affect coral community composition. Local richness was highest at localities with the highest environmental variability. Recent information regarding the strong affinity between eastern and central Pacific coral faunas, abundance of teleplanic larvae in oceanic currents, high genetic similarity of numerous reef-associated species, and appearances of numerous Indo-west Pacific species in the east Pacific following ENSO activity, suggest the bridging of the east Pacific filter bridge (formerly east Pacific barrier).

First documented hurricane strikes on eastern Pacific coral reefs reveal only slight damage

First documented hurricane strikes on eastern Pacific coral reefs reveal only slight damage

Biology and geology of eastern Pacific coral reefs

The tropical eastern Pacific region has historically been characterized as devoid of coral reefs. The physical conditions of the region are apparently not conducive to reef growth: low temperatures, low salinity, and high nutrient loads. But recent work has demonstrated persistent coral growth in some locations at relatively high accretion rates, dating at least 5600 y before present. Coral reefs of the eastern Pacific are typically small (a few hectares), with discontinuous distribution and low species diversity. On a global scale, the eastern Pacific reefs may be considered minimum examples of coral reefs, as they have developed in possibly one of the most restrictive environments in the history of coral reefs. Disturbances are frequent, bioerosion intense, and recovery seems to be extremely slow. There is a general paucity of fossil corals and reefs on the American Pacific coast, probably due to the low preservation potential. In this review, distinct characteristics of the eastern Pacific and its coral reefs are highlighted. These factors make the region one of the smallest natural marine laboratories to study coral community structure and function on a regional level. The eastern Pacific is not only a testing ground for biological theory, but it is also a laboratory for paleoclimatic and oceanographic reconstruction.

Reef coral reproduction in the eastern Pacific: Costa Rica, Panamá, and Galápagos Islands (Ecuador). II. Poritidae

A comparative study of the reproductive ecology of the zooxanthellate, scleractinian corals Porites lobata Dana and P. panamensis Verrill was conducted from 1985 to 1991 in eastern Pacific reef environments that were severly impacted by the 1982–1983 El Nino warming events. P. lobata, a presumed broadcast spawner of large colony size, is widely distributed in the equatorial eastern Pacific, whereas P. panamensis, a brooder of small colony size, is abundant only on some reefs in Panama. Both species were gonochoric with nearly 1:1 sex ratios in large study populations except for P. lobata at Cano Island that had 14% hermaphroditic colonies. Mature, unfertilized oocytes contained numerous zooxanthellae in both Porites species, and all planula developmental stages contained zooxanthellae in P. panamensis. Year-round sampling revealed high proportions of colonies with gonads, ranging from 30 to 68% in P. lobata and from 60 to 68% in P. panamensis. No clear relationship between numbers of reproductive colonies and the thermal stability of the habitat was evident in P. lobata: percent colonies with gonads at non-upwelling sites was 48 to 68% at Cano Island (Costa Rica) and Uva Island (Panama), and at upwelling sites 30 to 50% at Saboga Island and Taboga Island (Panama), and the Galapagos Islands (Ecuador). Similarly, 90% of all P. panamensis colonies were reproductive at Uva Island (a non-upwelling site), and 86% were reproductive at Taboga Island (an upwelling site). Upwelling at Taboga Island is seasonal, nevertheless P. panamensis produced mature gonads or planulae over most of the year (11 mo), whereas P. lobata exhibited reproductive activity during only 2 mo (May and June). No clear lunar periodicity was observed in P. panamensis (Taboga Island), but a high proportion of P. lobata showed increased gonadal development around full and new moon, especially at Cano and Uva Islands. Estimated fecundities were relatively high for P. lobata at Cano (4000 eggs cm-2 yr-1) and Uva (5200 eggs cm-2 yr-1) Islands, and notably low (70 to 110 eggs cm-2 yr-1) in the Galapagos Islands. P. panamensis mean fecundity at Taboga Island was 720 planulae cm-2 yr-1 or 4.0 mm3 cm-2 yr-1, which was lower than the egg volume production of P. lobata at Cano and Uva Islands (7.0 to 10.0 mm3 cm-2 yr-1). The capacity of P. lobata and P. panamensis to reproduce sexually supports the notion that eastern Pacific coral reef recovery may not be dependent on long-distance dispersal from central Pacific areas. However, sexual recruits of P. lobata are absent or uncommon at all eastern Pacific study sites while recruits of P. panamensis were common to abundant only at the Uva Island study site. Asexual fragmentation in P. lobata augments recruitment locally, but plays no role in P. panamensis recruitment.

Sporadic Disturbances in Fluctuating Coral Reef Environments: El Niño and Coral Reef Development in the Eastern Pacific

The disastrous effects of the intense 1982-83 El Nino-Southern Oscillation (ENSO) bring new insight into the long-term development of eastern Pacific coral reefs. The 1982-83 ENSO sea surface warming event caused extensive reef coral bleaching (loss of symbiotic zooxanthellae), resulting in up to 70-95% coral mortality on reefs in Costa Rica, Panama, Colombia and Ecuador. In the Galapagos Islands (Ecuador), most coral reefs experienced >95% coral mortality. Also, several coral species experienced extreme reductions in population size, and local and regional extinctions. The El Nino event spawned secondary disturbances, such as increased predation and bioerosion, that continue to impact reef-building corals. The death of Pocillopora colonies with their crustacean guards eliminated coral barriers now allowing the corallivore Acanthaster planci access to formerly protected coral prey

Reef coral reproduction in the eastern Pacific: Costa Rica, Panama, and Galapagos Islands (Ecuador)

Reproductive ecology of two major reef-building corals in the eastern Pacific [Pocillopora damicornis (Linnaeus) andPocillopora elegans Dana] was investigated between 1984 and 1990 in Costa Rica, Panama (Gulf of Chiriqui and Gulf of Panama), and the Galapagos Islands (Ecuador) following the 1982–83 El Nino disturbance. Mature spermatocytes and oocytes were found in both species and were usually present in the same polyp in nearly equal ratios. Numerous zooxanthellae were observed in mature, unfertilized oocytes. Although spawning in field populations was not observed, it is likely that both pocilloporids are simultaneous hermaphroditic spawners, as evidenced by the disappearance of mature gametes after full moon. This is in contrast with most known pocilloporid corals that brood and release planula larvae. Corals were reproductively most active in the thermally stable environments of Costa Rica and the Gulf of Chiriqui (Panama) where 32 to 90% of all colonies contained gametes. In the moderately varying thermal conditions in the Galapagos Islands, 16 to 40% of colonies contained gametes, and in the pronounced seasonal upwelling environment of the Pearl Islands (Panama) only 6 to 18% of colonies contained gametes. Year-round reproduction occurred in Costa Rica and the Gulf of Chiriqui, whereas reproduction was confined to warm periods in the seasonally varying environments of the Galapagos Islands and the Gulf of Panama. Pocilloporid corals in Costa Rica and the Gulf of Chiriqui demonstrated lunar spawning activity, with mature gametes present a few days before and after full moon. Some limited spawning may have occurred also at new moon. While frequent gamete maturation has been demonstrated in this study, the relatively low rates of larval recruitment occurring on eastern Pacific coral reefs disturbed by the 1982–83 El Nino suggest that the recovery of important frame-building corals could be greatly prolonged.

Population and feeding responses of the corallivorous pufferfish Arothron meleagris to coral mortality in the eastern Pacific

Arothron meleagris occurs at densities r a n g n g from 0 to 320 fish ha-' of live coral on eastern Pacific coral reefs of Costa h c a , Panama, Colombia and the Galapagos Islands. On reefs in Panama and Costa h c a , over 50n& of corals died during the 1982-83 El Nino event and 4 0 % of remaining corals at Cano Island, Costa Rica, died during red tides in 1985. The population density of A. meleagns is not related to coral density on different reefs and fish densities did not change in a consistent manner follow~ng the coral mortalities. Diets and feeding preferences of A. meleagris at different sites are not related in a consistent way to the abundance of various corals or to changes in coral abundances following coral mortalities. At Cafio Island A. meleagn's prefers Pontes lobata over the less abundant Pocillopora damicornis. At Uva Island, Panama, where P. damlcornis is the more abundant species, A. rneleagns does not prefer either coral. The relationship between the availability and consumption of the uncommon coral Psamrnocora stellata also differs among localities. Changes in this fish's diet following the mass coral mortalities varied among sites. At Cano Island fish switched first to coralline algae and then to corals. Fish do grow when expenmentally fed only coralline algae, but grow better when fed corals. The ability of the puffer to switch diets and maintain its populations following coral mortality may affect the recovery of coral populations. Even when uncommon, the puffer may have an impact on rare corals.