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Highly abundant and widespread populations of the introduced eastern Pacific ophiuroid brittle star Ophiothela mirabilis occur in southeast Florida, extending the range of this new non-native species from southern Brazil northward to the Caribbean Sea and Florida, now spanning about 6000 km of latitude along western Atlantic tropical/subtropical shores. This brittle star species, representing two lineages, is an epizoite on shallow-occurring (3–15 m depth) plexaurid octocorals (e.g., Eunicea spp., Muricea elongata, and Plexaurella dichotoma). Overall body color (disk and arms) is commonly beige or orange; a few individuals display combinations of both colors: orange disk/beige arms or beige disk/orange arms. Population densities in situ commonly ranged between 5 and 12 individuals of O. mirabilis per 10-cm-long octocoral branch with up to six arms generally curled around their octocoral host’s branches. In a 33-day experiment, M. elongata colony surface areas with reduced (contracted) polyps and reduced polyp extension lengths were not statistically different between octocorals with brittle stars versus octocorals without brittle stars. At the end of 33 days, brittle star densities demonstrated an overall decline. In a 66-day experiment, increasing brittle star densities resulted in reduced extended polyp areas in M. elongata, but no changes in Eunicea flexuosa. Polyp extension lengths decreased in both octocoral hosts with increasing densities of O. mirabilis. Overall, experimental brittle star densities did not change, with several octocoral hosts revealing increases in O. mirabilis by means of fissiparity. The presence and increasing densities of O. mirabilis causing a reduction in octocoral polyp extension were greatest in M. elongata but did not result in visible adverse effects to host condition. Black spotting on octocoral stems, a sign of tissue deterioration, was not observed during or after the two experiments. Nearly all experimental octocorals demonstrated tissue growth in the 66-day experiment, expanding over relatively large areas of the supporting pedestals.

Widespread and large populations of the exotic eastern Pacific ophiuroid brittle star Opthiothela mirabilis now occur in southeastern Florida, extending the range of this recently introduced species from southern Brazil northward to the eastern Caribbean Sea and Florida. The Florida brittle stars, representing two lineages, are epibionts on shallow (3-18 m depth), tropical/subtropical plexaurid (e.g., Eunicea spp., Muricea elongata) and gorgoniid (Antillogorgia spp.) octocorals. The scope of this study includes recent distributional records of O. mirabilis in south Florida, field abundances in relation to the cohabiting endemic ctenophore Coeloplana waltoni, behavioral observations of the ophiuroid, ctenophore and the predatory amphipod Caprella penantis, as well as a laboratory experiment testing the effects of the alien ophiuroid on the native ctenophore. Individuals of O. mirabilis have been collected near St. Lucie Inlet, extending its northern-most range by about 110 km since 2019. Two years of field sampling have demonstrated significant declines of the native, benthic ctenophore with increasing abundances of the exotic ophiuroid. Evidence suggests that the ophiuroid is negatively affecting the abundances of the ctenophore through interference competition, greatly aided by its abrasive armature of calcareous spines, plates and hooks. Sporadic and intense predation by a caprellid amphipod (Caprella penantis) also probably contributes to the ctenophore’s decline, but to a lesser extent than that caused by the ophiuroid. Adding to the risk of extinction of C. waltoni is its narrow requirement of living octocorals as hosts and restricted distribution in southeast Florida and the Bahamas.

The invasive brittle star Ophiothela mirabilis (family Ophiotrichidae), a tropical Indo-Pacific endemic species, first reported in Atlantic waters off southern Brazil in 2000, has extended its range northward to the Caribbean Sea, to the Lesser Antilles in 2011, and was first reported in south Florida in January 2019. Its occurrence in southeast Florida extends along nearly 70 km of coastline, from near the Port of Miami, Miami-Dade County, northward to Deerfield Beach, Broward County. It occurs abundantly as an epizoite on octocorals, attaining population densities of 25 individuals and more per 10-cm long octocoral stem. The surface texture of octocoral hosts (rough, smooth) did not affect the densities of the ophiuroid epizoites, and there were significantly greater abundances on octocorals during two winter sampling periods than in the summer. Beige and orange-coloured morphs are sometimes present on the same octocoral stem. Gut content analysis supported a suspension feeding mode, revealing essentially identical ingested items in both colour morphs with a preponderance of amorphous detritus and filamentous algae. Molecular genetic evidence (COI & 16s) has established the identity of O. mirabilis and its relationship to invasive Brazilian populations. The orange and beige morphs form two distinct, but closely related lineages that may represent two separate introductions. The orange morph shares haplotypes with Brazilian and Caribbean specimens suggesting a further range expansion of the ‘original’ invasion. The beige morph, however, shares haplotypes with specimens from the Mexican Pacific and Peru and potentially represents a secondary introduction. Traits promoting dispersal and establishment of this species in new habitats are manifold: vagility and ability to cling tightly to diverse host taxa (e.g. sponges, cnidarians, bryozoans, and echinoderms), frequent asexual reproduction (fissiparity), suspension feeding, including a wide range of dietary items, possession of integument-covered ossicles and arm spines offering protection from predators, and an effective competitive edge over associated microbiota for substrate space.

Two benthic ctenophores, Coeloplana waltoni and Vallicula multiformis, are contrasted in terms of their coastal environments, habitats, abundances, seasonal occurrences, and behavior in south Florida. Coeloplana waltoni occurs as an epibiont on octocorals in open water settings, and V. multiformis is present in bio-fouling communities, associated with macroalgae, bryozoans, and inanimate substrates in protected, back-water habitats. In our study, individuals of C. waltoni were found under moderate to strong current flow and relatively constant temperature and salinity (T/S) conditions, whereas individuals of V. multiformis occurred at sites of low current flow and more variable T/S conditions. In C. waltoni, individuals generally adhered tightly to host colony surfaces, whereas in V. multiformis, individuals often disassociated from substrates and floated free. Mean population densities of C. waltoni ranged ~500–850 individuals 100 mL−1 (measured as the displacement volume of the octocoral habitat), and densities of V. multiformis ranged 5–360 individuals 100 mL−1 (measured as the displacement volume of the biofouling habitat). Abundance of C. waltoni was significantly highest in the 2014 warm season (June–October) when numerous minute (≤0.5 mm body length) juveniles were present. Vallicula multiformis was abundant in the 2015 and 2016 warm seasons (July–October), and also relatively abundant in the 2016 cool season (March–April). Ctenophore abundance and surface seawater temperature indicate a significant positive response to warm-season conditions in C. waltoni, whereas numbers of V. multiformis did not show any effect of seawater temperature. Recently settled individuals of V. multiformis (≤1.0 mm) occurred throughout the year. Individuals of V. multiformis recruited to fiber-coated sponges during warm and cool periods, with mean body sizes increasing in one cohort from 1.41 to 6.46 mm over a 39-d period, suggesting a growth rate of ~4% d−1. Feeding in both species involves tentacle capture of water-borne zooplankton and particulate organic matter. Individuals of C. waltoni were also observed inserting tentacles into octocoral polyps, possibly pilfering food. Chlorophyll a was detected in extracts of both ctenophore species. The high abundances and feeding behavior of benthic ctenophores could have a strong influence on octocoral and biofouling communities.

Throughout the Galápagos, differences in coral reef development and coral population dynamics were evaluated by monitoring populations from 2000–2019, and environmental parameters (sea temperatures, pH, NO3−, PO43−) from 2015–19. The chief goal was to explain apparent coral community differences between the northern (Darwin and Wolf) and southern (Sta. Cruz, Fernandina, San Cristóbal, Española, Isabela) islands. Site coral species richness was highest at Darwin and Wolf. In the three most common coral taxa, a declining North (N)-South (S) trend in colony sizes existed for Porites lobata and Pocillopora spp., but not for Pavona spp. Frequent coral recruitment was observed in all areas. Algal competition was highest at Darwin, but competition by bioeroding sea urchins and burrowing fauna (polychaete worms, bivalve mollusks) increased from N to S with declining coral skeletal density. A biophysical model suggested strong connectivity among southern islands with weaker connectivity to Wolf and even less to Darwin. Also, strong connectivity was observed between Darwin and Wolf, but from there only intermittently to the south. From prevailing ocean current trajectories, coral larvae from Darwin and Wolf drift primarily towards Malpelo and Cocos Islands, some reaching Costa Rica and Colombia. Mean temperature, pH, and PO43− declined from N to S. Strong thermocline shoaling, especially in the warm season, was observed at most sites. A single environmental factor could not explain the variability in observed coral community characteristics, with minimum temperature, pH and nutrient levels the strongest determinants. Thus, complex environmental determinants combined with larval connectivity patterns may explain why the northern Galápagos Islands (Darwin, Wolf) have higher coral richness and cover and also recover more rapidly than central/southern islands after region-wide disturbances. These northern islands are therefore potentially of critical conservation importance as important reservoirs of regional coral biodiversity and source of larvae.

Siderastrea glynni Budd & Guzman, 1994 was erroneously erected from live colonies of S. siderea (Ellis & Solander, 1768) unintentionally transferred from the Caribbean to the Pacific side of the Isthmus of Panama. These corals had been used in experiments conducted in the early 1980s by KH Kleemann at Uraba Island, Taboga Islands, Gulf of Panama, at the same site of the subsequent S. glynni discovery. Here, we offer evidence that live fragments deposited at Uraba Island in 1982 are the same found by Guzman in 1992, and were inadvertently introduced from colonies of Caribbean S. siderea that were presumed to be dead. This morphological study builds on and supports recent genetic analyses of the S. glynni holobiont. In light of these findings, S. glynni should be regarded as a subjective junior synonym of S. siderea.

A new species of Echiura, Anelassorhynchus panamensis (Family: Echiuridae), is described from the eastern tropical Pacific Ocean. The specimens examined are from collections in the invertebrate museum, Rosenstiel School of Marine and Atmospheric Science, University of Miami, and were collected from a coral reef in Panama. This species is distinguished in possessing a proboscis that is divided distally into numerous lobes of different shapes and sizes, an opaque integument with closely aligned transverse wrinkles, a pair of microscopic ventral setae, two pairs of tubular, postsetal gonoducts with elongated coiled gonostomes and tubular anal vesicles. Peculiar coelomic organs were found in the holotype and in one paratype. This new reef-associated echiuran demonstrated consistently high spatial and temporal abundances. Quantitative sampling of A. panamensis along the Uva Island fore-reef coral rubble/sand microhabitat revealed median population densities between 2–8 individuals per 20 liters of sed...

Significant increases in the population of the echinoid bioeroder Diadema mexicanum that may soon follow severe El Nino 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 Nino-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 Nino disturbance event.

The remote northernmost Galapagos Islands, Darwin and Wenman, exhibited well-developed coral communities in 1975, which were severely degraded during the 1982–1983 El Nino warming event. Mapping of the coral reef at Darwin, herein Wellington Reef, shows it presently to be the largest known structural reef in the Galapagos. It consists of numerous 1- to 3-m-high Porites framework towers or stacks and overlies a carbonate (coral/calcareous sediments) basement. Pre-disturbance Wellington Reef was constructed chiefly by Porites lobata and Pocillopora elegans, and Wenman coral cover was dominated by Pavona clavus and Porites lobata. Subsequent surveys in 2012 have demonstrated robust recovery in spite of ENSO thermal shock events, involving both high and low stressful temperatures that have caused tissue bleaching and mortality. No losses of coral species have been observed. Radiocarbon dating of 1- to 3-m-high poritid framework stacks, from their peaks to bases, revealed modern ages of up to 690 yr. Incremental stack growth rates ranged from 0.15–0.39 to 1.04–2.40 cm yr−1. The former are equivalent to framework accretion rates of 1.5–3.9 m Kyr−1, the latter to coral skeletal growth rates of 1.0–2.4 cm yr−1. Coral recovery in the central and southern Galapagos has been nonexistent to low compared with the northern islands, due chiefly to much higher population densities and destructive grazing pressure of the echinoid Eucidaris galapagensis. Thus, coral reef resistance to ENSO perturbations and recovery potential in the Galapagos are influenced by echinoid bioerosion that varies significantly among islands.

Wellington Reef is the northern-most and largest known coral reef in the Galapagos Islands. This study explores the recovery potential of the Wellington Reef when subjected to predicted future El Nino Southern Oscillation warming events that may cause varying degrees of coral mortality followed by sea urchin bioerosion. We developed a stochastic model that employs empirical data from the Wellington Reef and nearby sites. The model estimates CaCO3 bioerosion of individual coral colonies by the sea urchin Eucidaris galapagensis, which recently caused coral reef collapse in the central and southern Galapagos Islands. Numerous projections of the CaCO3 production potential of Wellington Reef 50 years into the future were generated using a simulation model by subjecting the Wellington Reef to El Nino Southern Oscillation warming events and a range of urchin density levels, resulting in varying degrees of coral mortality and subsequent bioerosion by E. galapagensis. Moderate increases in sea urchin abundance above current low levels were found to significantly increase the likelihood of Wellington Reef collapse. The large differences in the recovery of the Galapagos coral reefs across a small latitudinal scale where differences in local echinoid abundances exist make this study of the recovery potential of the Wellington Reef important in understanding the contrast between a resilient reef and ones that are susceptible to collapse. This study suggests a delicate tipping point for triggering an echinoderm-elevated bioerosive phase that results in the degradation of a healthy reef ecosystem.

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. Consejo Nacional de Ciencia y Tecnología/[108302]/CONACYT/Costa Rica Consejo Nacional de Ciencia y Tecnología/[183534]/CONACYT/Costa Rica UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Ciencias del Mar y Limnología (CIMAR)

Species intolerant of changing climate might avoid extinction within refugia buffered from extreme conditions. Refugia have been observed in the fossil record but are not well documented or understood on ecological time scales. Using a 37-year record from the eastern Pacific across the two most severe El Nino events on record (1982-1983 and 1997 1998) we show how an exceptionally thermally sensitive reef-building hydrocoral, Millepora intricata, twice survived catastrophic bleaching in a deeper-water refuge (> 11 m depth). During both events, M. intricata was extirpated across its range in shallow water, but showed recovery within several years, while two other hydrocorals without deep-water populations were driven to regional extinction. Evidence from the subfossil record in the same area showed shallow-water persistence of abundant M. intricata populations from 5000 years ago, through severe El Nino-Southern Oscillation cycles, suggesting a potential depth refugium on a millennial timescale. Our data confirm the deep refuge hypothesis for corals under thermal stress.

Corals in the genus Pocillopora are the primary framework builders of eastern tropical Pacific (ETP) reefs. These corals typically associate with algal symbionts (genus Symbiodinium) in clade C and/or D, with clade D associations having greater thermal tolerance and resistance to bleaching. Recently, cryptic "species" delineations within both Pocillopora and Symbiodinium have been suggested, with host–symbiont specificity used as a supporting taxonomic character in both genera. In particular, it has been suggested that three lineages of Pocillopora (types 1–3) exist in the ETP, of which type 1 is the exclusive host of heat-tolerant Symbiodinium D1. This host specificity has been used to support the species name "Symbiodinium glynni" for this symbiont. To validate these host–symbiont relationships and their taxonomic utility, we identified Pocillopora types and their associated Symbiodinium at three sites in the ETP. We found greater flexibility in host–symbiont combinations than previously reported, with both Pocillopora types 1 and 3 able to host and be dominated by Symbiodinium in clade C or D. The prevalence of certain combinations did vary among sites, showing that a gradient of specificity exists which may be mediated by evolutionary relationships and environmental disturbance history. However, these results limit the utility of apparent host–symbiont specificity (which may have been a result of undersampling) in defining species boundaries in either corals or Symbiodinium. They also suggest that a greater diversity of corals may benefit from the thermal tolerance of clade D symbionts, affirming the need to conserve Pocillopora across its entire geographic and environmental range.

Eastern Pacific reef ecosystems are home to a diverse assemblage of corallivorous fishes and invertebrates. It is therefore not surprising that there is a rich history of research on corallivores in the eastern Pacific. In fact, much of what is known today on the topic of corallivory has built upon studies from the eastern Pacific region. Here we review the progression of our understanding of eastern Pacific corallivory and corallivores. We discuss the behavior and ecology of these specialized consumers, dividing our analysis into the larger conspicuous taxa such as the crown-of-thorns sea star (Acanthaster planci) and the guineafowl puffer (Arothron meleagris), as well as into the smaller cryptic species such as the pustulate egg shell (Jenneria pustulata) and coral crustacean guards (Trapezia spp., Alpheus lottini). The majority of species that consume coral tissues are facultative corallivores, feeding on corals only incidentally. Both the negative and positive interactions of corallivores to their prey/hosts are reviewed. We address detrimental direct consumption of coral and how it can ultimately influence growth form, species distributions, population structure, and the asexual reproduction of corals. We examine the cleaning behavior of some corallivorous species as well as their territorial tendencies, which may potentially lead to the exclusion of more lethal coral predators. Despite the high diversity of corallivore taxa, no population outbreaks have been observed in the eastern Pacific; coral colony growth rates and reef accretion proceed apace. Finally, we explore the far-reaching implications of the corallivore feeding strategy, touching on the connections that ultimately link coral biomass with higher trophic levels and the rest of the reef ecosystem.

During the Nineteenth and early Twentieth Centuries several renowned researchers—e.g., C. Darwin, J. Dana, A. Agassiz, A.E. Verrill, and T.W. Vaughan—remarked on the absence of coral reefs in the eastern tropical Pacific (ETP), concluding this was due mainly to the influence of cool currents and upwelling centers. From later surveys in southern Mexico in the 1920s (R.H. Palmer), and the Allan Hancock Expeditions across the eastern tropical Pacific in the 1930s (C. Wyatt Durham), workers began to recognize the presence of modest structural coral reef development at several sites in the ETP. A new era of coral reef studies began in the 1970s, and has increased in pace and intellectual depth to the present. This latest surge in coral science was a result of locally active researchers, especially in Mexico, Costa Rica, Panama, and Colombia, and more recently in Ecuador and Chile. Progress in coral research in El Salvador and Nicaragua was thwarted from the 1970s to the early 1990s because of political turmoil and violence in this sector of the eastern Pacific. The establishment of national research funding agencies in Latin American countries, such as CONACYT (Mexico), CONICIT (Costa Rica), COLCIENCIAS (Colombia), and FONDECYT (Chile), has greatly benefitted coral reef research as well as scholarship opportunities for resident students to pursue advanced studies in marine science. The availability of vessels to support research in remote areas and at offshore sites has also facilitated ETP coral studies. Contrary to early views, structural coral reefs were discovered in major upwelling centers—southern Mexico (Huatulco), Costa Rica (Guanacaste), and Panama (Gulf of Panama). The number of known coral species approximately doubled from the late 1940s to 2000, from 60 (total scleractinians) and 120 and >40 species, respectively. Additionally, reports of the appearance or disappearance of extralimital coral species (e.g., in the genera Montipora, Siderastrea, Acropora, and Millepora) have added to the excitement and adventure of eastern Pacific studies. On site observations during two very strong El Nino-Southern Oscillation (ENSO) disturbances, 1982–83 and 1997–98, demonstrated that acute temperature stress can cause widespread coral bleaching and mortality and interference with reef growth. More recently, ETP waters have been found to have low pH and aragonite saturation state, which can also weaken carbonate structures and interfere with reef development. Recognizing the economic, scientific, and esthetic value of ETP coral reefs, several national and international agencies are now supporting coral research, which will have a salutary effect in increasing our knowledge and understanding of these long-neglected ecosystems.

Sexual reproductive activity has been demonstrated in all reef-building (zooxanthellate) scleractinian corals examined from Mexico to the equatorial eastern Pacific (Galapagos Islands). Eleven of 13 species spawn gametes, six are gonochoric, three hermaphroditic, and four exhibit significant mixed sexuality (both gonochoric and hermaphroditic). Four or 30.1 %, two species each of Pocillopora and Porites, produce autotrophic ova. Porites panamensis is the only known zooxanthellate brooder. Also sexually active are the azooxanthellate scleractinian Tubastraea coccinea and the zooxanthellate hydrocoral Millepora intricata. Reproductive structures, sex ratios, age at sexual maturity, sexuality, and developmental mode have been determined from largely histological evidence. Agariciid corals, comprising more than one-third of investigated species, exhibit predominantly mixed sexual systems with sequential cosexual hermaphroditic cycles in four species. Mixed sexuality is also minimally exhibited in populations of two dominantly gonochoric species. Several eastern Pacific corals spawn mostly on lunar day 17 and 1–2 days following; however, multispecific spawning has not been observed probably because of seasonal, diel, and variable timing in spawning behavior. Factors contributing to the high fecundity of eastern Pacific corals include (1) seasonally prolonged reproductive activity, (2) small size of mature gametes allowing for production of high numbers, (3) split spawning with bimonthly gamete production in some species, (4) alternation of sex maturation in gamete development, and possibly (5) their low latitudinal location under relatively constant and high thermal conditions. Coral community persistence, reef growth and recovery are highly dependent on both sexual and asexual reproductive processes. Asexual fragmentation by physical and biotic causes is particularly important, especially for branching pocilloporid species and the fungiid coral Diaseris distorta. Asexual propagation in massive and encrusting poritid and agariciid species is also common-place, often the result of bioerosion and colony breakage by foraging reef fishes. Some research areas in need of attention are noted, for example (a) timing of spawning and the behavior of gamete release of several species, (b) life cycles of Pocillopora spp. and Millepora intricata, and (c) effects of anthropogenic stressors on eastern Pacific coral reproduction and recruitment.

Energetic responses of zooxanthellate reef corals along depth gradients have relevance to the refugia potential of mesophotic coral ecosystems (MCEs). Previous observations suggested that MCEs in the Caribbean are thermally buffered during the warmest parts of the year and occur within or just below the chlorophyll maximum, suggesting abundant trophic resources. However, it is not known if mesophotic corals can maintain constant energy needs throughout the year with changing environmental and biological conditions. The energetic content of tissues from the stony coral species Orbicella faveolata and Agaricia lamarcki was measured on the southern insular shelf of St. Thomas, US Virgin Islands (USVI), using micro-bomb calorimetry. Three sites for each species, at depths of 6m, 25m, 38m and 63m, were selected to capture energetic differences across the major vertical range extent of both species in the USVI—and sampled over five periods from April 2013 to April 2014. Mesophotic colonies of O. faveolata exhibited a significant reduction in energetic content during the month of September 2013 compared to mid-depth and shallow colonies (p = 0.032), whereas A. lamarcki experienced similar energetic variability, but with a significant reduction in energy content that occurred in July 2013 for colonies at sites deeper than 25m (p = 0.014). The results of calorimetric analyses indicate that O. faveolata may be at risk during late summer stress events, possibly due to the timing of reproductive activities. The low-point of A. lamarcki energy content, which may also coincide with reproduction, occurs prior to seasonal stress events, indicating contrasting, species-specific responses to environmental variability on MCEs.

Two zooxanthellate, scleractinian species present in the equatorial eastern Pacific, Psammocora stellata and Psammocora profundacella, were examined in terms of their reproductive biology and ecology at four study sites, non-upwelling (Cano Island, Costa Rica, and Uva Island, Panama), upwelling (Gulf of Panama, Panama), and seasonally varying thermal environments (Galapagos Islands). Both species were gonochoric broadcast spawners lacking zooxanthellae in mature ova. Mature gametes and spawned gonads are present around full moon; however, no spawning was observed naturally or in outdoor aquaria. Mature gametes occurred in P. stellata at Cano Island for nearly 6 months, and year round at Uva Island, both non-upwelling sites. Reproductively active colonies occurred mostly in the warmer months in the Gulf of Panama and Galapagos Islands. In the Galapagos Islands, where collecting effort was greatest for P. profundacella, mature gametes were also most prevalent during the warm season. Annual fecundity was high in both species, 1.3–1.8 × 104 ova cm−2 year−1 in P. stellata and 1.2–2.0 × 104 ova cm−2 year−1 in P. profundacella. Compared to other eastern Pacific corals, P. stellata was relatively resistant to ENSO-related bleaching and mortality, especially populations inhabiting deep (12–20 m) coral communities. Rapid recovery and persistence of Psammocora spp. can be attributed to several factors: (a) relative resistance to bleaching, (b) deep refuge populations, (c) broadcast spawning, (d) protracted seasonal reproduction, (e) high fecundity, and (f) asexual propagation.

Coral reef degradation and loss have been extensively documented worldwide during the last few decades. While much attention has been directed toward the mortality of reef-building corals vis-a-vis various observed disturbances (e.g., bleaching, diseases, overfishing, nutrification), the fate of other reef-associated metazoans, especially invertebrates, has not received sufficient attention. living and dead corals, reef frameworks, and carbonate sediments provide essential habitat niches for a multitude of symbiotic and cryptic species. Thirty-one animal phyla contain species that inhabit coral reefs with known global species richness estimated at 93,000. possibly as many as 1,000,000 reef-associated metazoans occur globally. many of these species are undiscovered because of their cryptic or sibling nature. metazoan reef associates have important functional roles on reefs, e.g., increasing survivorship of coral hosts, aiding in reef framework construction (calcification, consolidation), providing trophic resources, affecting coral mortality (corallivores) and erosion (bioerosion). despite widespread bleaching and mortality, no reef-building corals (scleractinia) have yet to become globally extinct. Three populations of Millepora spp. (Hydroida) were severely impacted in pacific panama during the 1982-83 el nino-southern oscillation event. present status indicates recovery of Millepora intricata milne-edwards and Haime, 1860 to shallow reef zones from relatively deep (10-15 m) refugia. furthermore, two hydrocoral species have suffered regional extinctions in the eastern pacific with populations still present in the Indo-pacific (Millepora platyphylla Hemprich and ehrenberg, 1834) and eastern Indian ocean (Millepora boschmai de Weerdt and Glynn, 1991). Considering the large numbers of obligate symbionts and other coral reef metazoan associates, there is a strong likelihood of large-scale extinctions following the loss of reef-building corals.

The reproductive ecology of the zooxanthellate reef coral Pavona clavus was investigated at several sites in Costa Rica, Panama, and the Galapagos Islands (Ecuador) over the period 1985–2009. Pavona clavus displayed stable gonochorism as only five hermaphrodites were found in 590 samples. At four of five locations, sex ratios were skewed toward female dominance; however, at Saboga Island (Panama) male colonies predominated. In Panama, sexual maturity was observed in an estimated eight-year-old female colony, and several colonies of 10–20 years of age demonstrated gametogenesis. Sexual activity was observed at all study sites, but gamete development occurred in only 14–31% of colonies sampled sporadically. Seasonality of gametogenic activity occurred predominantly during the warm/wet season, June to August, at mainland sites (Cano Island, Costa Rica, and Gulfs of Chiriqui and Panama, Panama). This pattern was repeated in the Galapagos Islands, but mainly from March to May when seasonally high sea temperatures and rainfall prevailed there. Histological sampling and field observations indicated that spawning was centered around the full moon, most frequently on lunar day 17, and near sunset (1,800 h). Mean fecundity (mature ova cm−2 live tissue) estimates were significantly different for two sites and ranged from ~1,780 (Saboga Island, Gulf of Panama, seasonally upwelling) to ~4,280 (Uva Is, Gulf of Chiriqui, non-upwelling). Assuming three annual spawning events colony−1 (August, September, October), extrapolation of minimum and maximum fecundities yield 5,340 and 12,840 ova cm−2 year−1. Seasonal, lunar, and diel spawning patterns in nine zooxanthellate species at Uva Island indicate asynchronous coral community spawning.

Comparisons between historical and recent ecological datasets indicate that shallow reef habitats across the central Galapagos Archipelago underwent major transformation at the time of the severe 1982/1983 El Nino warming event. Heavily grazed reefs with crustose coralline algae ('urchin barrens') replaced former macroalgal and coral habitats, resulting in large local and regional declines in biodiversity. Following recent threat assessment work- shops, a total of five mammals, six birds, five reptiles, six fishes, one echinoderm, seven corals, six brown algae and nine red algae reported from coastal environments in Galapagos are now recognized as globally threatened. The 2008 International Union for the Conservation of Nature (IUCN) Red List includes 43 of these species, while two additional species (Galapagos damsel Azurina eupalama and 24-rayed sunstar Heliaster solaris) not seen for 425 years also fulfil IUCN threatened species criteria. Two endemic species (Galapagos stringweed Bifurcar- ia galapagensis and the damselfish A. eupalama) are now regarded as probably extinct, while an additional six macroalgal species (Dictyota galapagensis, Spatoglossum schmittii, Desmar- estia tropica, Phycodrina elegans, Gracilaria skottsbergii and Galaxaura barbata) and the seastar H. solaris are possibly extinct. The removal of large lobster and fish predators by artisanal fishing probably magnified impacts of the 1982/1983 El Nino through a cascade of indirect effects involving population expansion of grazing sea urchins. Marine protected areas with adequate enforcement are predicted to ameliorate but not eliminate ecosystem impacts caused by increasing thermal anomalies associated with El Nino and global climate change.

Since the early 1980s, episodes of coral reef bleaching and mortality, due primarily to climate-induced ocean warming, have occurred almost annually in one or more of the world's tropical or subtropical seas. Bleaching is episodic, with the most severe events typically accompanying coupled ocean–atmosphere phenomena, such as the El Nino-Southern Oscillation (ENSO), which result in sustained regional elevations of ocean temperature. Using this extended dataset (25+ years), we review the short- and long-term ecological impacts of coral bleaching on reef ecosystems, and quantitatively synthesize recovery data worldwide. Bleaching episodes have resulted in catastrophic loss of coral cover in some locations, and have changed coral community structure in many others, with a potentially critical influence on the maintenance of biodiversity in the marine tropics. Bleaching has also set the stage for other declines in reef health, such as increases in coral diseases, the breakdown of reef framework by bioeroders, and the loss of critical habitat for associated reef fishes and other biota. Secondary ecological effects, such as the concentration of predators on remnant surviving coral populations, have also accelerated the pace of decline in some areas. Although bleaching severity and recovery have been variable across all spatial scales, some reefs have experienced relatively rapid recovery from severe bleaching impacts. There has been a significant overall recovery of coral cover in the Indian Ocean, where many reefs were devastated by a single large bleaching event in 1998. In contrast, coral cover on western Atlantic reefs has generally continued to decline in response to multiple smaller bleaching events and a diverse set of chronic secondary stressors. No clear trends are apparent in the eastern Pacific, the central-southern-western Pacific or the Arabian Gulf, where some reefs are recovering and others are not. The majority of survivors and new recruits on regenerating and recovering coral reefs have originated from broadcast spawning taxa with a potential for asexual growth, relatively long distance dispersal, successful settlement, rapid growth and a capacity for framework construction. Whether or not affected reefs can continue to function as before will depend on: (1) how much coral cover is lost, and which species are locally extirpated; (2) the ability of remnant and recovering coral communities to adapt or acclimatize to higher temperatures and other climatic factors such as reductions in aragonite saturation state; (3) the changing balance between reef accumulation and bioerosion; and (4) our ability to maintain ecosystem resilience by restoring healthy levels of herbivory, macroalgal cover, and coral recruitment. Bleaching disturbances are likely to become a chronic stress in many reef areas in the coming decades, and coral communities, if they cannot recover quickly enough, are likely to be reduced to their most hardy or adaptable constituents. Some degraded reefs may already be approaching this ecological asymptote, although to date there have not been any global extinctions of individual coral species as a result of bleaching events. Since human populations inhabiting tropical coastal areas derive great value from coral reefs, the degradation of these ecosystems as a result of coral bleaching and its associated impacts is of considerable societal, as well as biological concern. Coral reef conservation strategies now recognize climate change as a principal threat, and are engaged in efforts to allocate conservation activity according to geographic-, taxonomic-, and habitat-specific priorities to maximize coral reef survival. Efforts to forecast and monitor bleaching, involving both remote sensed observations and coupled ocean–atmosphere climate models, are also underway. In addition to these efforts, attempts to minimize and mitigate bleaching impacts on reefs are immediately required. If significant reductions in greenhouse gas emissions can be achieved within the next two to three decades, maximizing coral survivorship during this time may be critical to ensuring healthy reefs can recover in the long term.

Adult individuals of the pearlfish Carapus mourlani (Petit, 1934) occur commonly in the mantle cavity of the opisthobranch mollusc Dolabella auricularia (Lightfoot, 1786) in shallow marine waters of the Gulf of Chiriqui, Pacific Panama. Nearly 30% of the molluscan hosts collected during the day on a coral reef contained one or two fish. Feeding observations of a captive fish as well as the intact condition of the host's ctenidium and other internal organs suggest that C. mourlani is an inquiline commensal and not parasitic. Fish curl around the ctenidium during the day and capture microcrustaceans when the fish emerge from their host at night to feed. From low-light infrared video recordings, Carapus was observed to accurately grasp rapidly swimming amphipods in nearly total darkness and ingest them. This symbiotic relationship appears to benefit Carapus by allowing the fish to avoid predators during the day and to forage at night.

Ocean acidification describes the progressive, global reduction in seawater pH that is currently underway because of the accelerating oceanic uptake of atmospheric CO 2 . Acidification is expected to reduce coral reef calcification and increase reef dissolution. Inorganic cementation in reefs describes the precipitation of CaCO 3 that acts to bind framework components and occlude porosity. Little is known about the effects of ocean acidification on reef cementation and whether changes in cementation rates will affect reef resistance to erosion. Coral reefs of the eastern tropical Pacific (ETP) are poorly developed and subject to rapid bioerosion. Upwelling processes mix cool, subthermocline waters with elevated pCO 2 (the partial pressure of CO 2 ) and nutrients into the surface layers throughout the ETP. Concerns about ocean acidification have led to the suggestion that this region of naturally low pH waters may serve as a model of coral reef development in a high-CO 2 world. We analyzed seawater chemistry and reef framework samples from multiple reef sites in the ETP and found that a low carbonate saturation state (Ω) and trace abundances of cement are characteristic of these reefs. These low cement abundances may be a factor in the high bioerosion rates previously reported for ETP reefs, although elevated nutrients in upwelled waters may also be limiting cementation and/or stimulating bioerosion. ETP reefs represent a real-world example of coral reef growth in low-Ω waters that provide insights into how the biological–geological interface of coral reef ecosystems will change in a high-CO 2 world.

Formerly attributed to human activity, the demise of a bank–barrier reef off southeastern Barbados known as Cobbler’s Reef is now thought to be largely the result of late Holocene, millennial-scale storm damage. Eleven surface samples of the reef crest coral Acropora palmata from nine sites along its 15-km length plot above the western Atlantic sea-level curve from 3,000 to 4,500 cal years ago (calibrated, calendar 14C years). These elevated clusters suggest that the reef complex suffered extensive storm damage during this period. The constant heavy wave action typical of this area and consequent low herbivory maintain conditions favoring algal growth, thereby limiting the reestablishment of post-storm reef framework. Site descriptions and detailed line surveys show a surface now composed mainly of reworked fragments of A. palmata covered with algal turf, macroalgae and crustose coralline algae. The reef contains no live A. palmata and only a few scattered coral colonies consisting primarily of Diploria spp. and Porites astreoides, along with the hydrocoral Millepora complanata. A few in situ framework dates plot at expected depths for normal coral growth below the sea-level curve during and after the period of intense storm activity. The most recent of these in situ samples are 320 and 400 cal years old. Corals of this late period likely succumbed to high turbidity associated with land clearance for sugarcane agriculture in the mid-1600s.

Three surveys at Easter Island (Rapa Nui) spanning the period 1999–2005, and examination of private and museum collections, have revealed a depauperate zooxanthellate scleractinian fauna. Collections were all made off island shelf exposures, from tide pools to 70 m with scuba, and by dredging to 100 m. With synonymies, reassignments, and two new records in the families Pocilloporidae and Faviidae, the Easter Island coral fauna now comprises 13 species. Pocilloporid and poritid coral abundances were generally high on all island shelves protected from southern swells. A cluster analysis of the coral fauna relationships of 19 south, central, and far-eastern Pacific sites indicates a strong affinity between those of Easter Island and the far-eastern Pacific equatorial region (e.g., Colombia, Ecuador, Panama, and the Galapagos Islands). The precipitous drop in coral species richness from the Pitcairn Island group (61 species) to Easter Island suggests the presence of a dispersal barrier between these ...

Bioerosion, involving the weakening and breakdown of calcareous coral reef structures, is due to the chemical and mechanical activities of numerous and diverse biotic agents. These range in size from minute, primarily intra-skeletal organisms, the microborers (e.g., algae, fungi, bacteria) to larger and often externally-visible macroboring invertebrate (e.g., sponges, polychaete worms, sipunculans, molluscs, crustaceans, echinoids) and fish (e.g., parrotfishes, acanthurids, pufferfishes) species. Constructive coral reef growth and destructive bioerosive processes are often in close balance. Dead corals are generally subject to higher rates of bioerosion than living corals, therefore, bioerosion and reef degradation can result from disturbances that cause coral mortality, such as sedimentation, eutrophication, pollution, temperature extremes, predation, and coral diseases. The effects of intensive coral reef bioerosion, involving El Nino-Southern Oscillation, Acanthaster predation, watershed alterations, and over-fishing, are re-examined after ~20 years (early 1990s–2010). We review the evidence showing that the biologically-mediated dissolution of calcium carbonate structures by endolithic algae and clionaid sponges will be accelerated with ocean acidification. The CaCO3 budget dynamics of Caribbean and eastern tropical Pacific reefs is reviewed and provides sobering case studies on the current state of coral reefs and their future in a high-CO2 world.

Twenty-seven radiocarbon dates of cores recovered from six drill holes indicate that the relief of the ridge on the seaward edge of the Holandes Cays, San Blas, off the Caribbean coast of Panama, was formed by storm deposits about 2,000 to 2,800 years ago. Although crustose coralline algae are a dominant component of the surface cover on this outer ridge, they played a minor role in the construction of the framework of this bioherm, which therefore cannot be classified as an algal ridge. The framework of the ridge consists dominantly of Agaricia/Millepora rubble that is extensively lithified by micritic submarine Mg-calcite cement. The present-day surface of this area in the Holandes Cays is primarily one of widespread bioerosion with very little indication of substrate accumulation over the past 2,000 years.

Since 1982, coral reefs worldwide have been subjected to an increased frequency of the phenomenon known as coral bleaching. Bleaching involves the dramatic loss of pigmented, single-celled endosymbiotic algae that live within the gastrodermal cells of a coral host that depends on this relationship for survival. Prior to the 1980s, and as early as the 1920s when coral reef research intensified, localized bleaching events were reported and attributed to factors such as extremely low tides, hurricane damage, torrential rainstorms, freshwater runoff near reefs, or toxic algal blooms [Glynn, 1993]. However, these early occurrences have recently been overshadowed by geographically larger and more frequent bleaching events whose impact has expanded to regional and global proportions.

The reproductive ecology of two eastern Pacific zooxanthellate coral species was examined as part of a continuing series of studies relating bleaching/mortality events caused by the El Nino–Southern Oscillation disturbance, and is described for study sites in Costa Rica, Panama, and the Galapagos Islands (Ecuador). This study deals with the sibling agariciid species Pavona varians and Pavona sp.a over a 13 yr period (1985 to 1997). Both Pavona species are broadcast-spawners with some gonochoric, but mostly sequential hermaphroditic colonies. Minimum colony sizes (and ages) at first reproduction were 5 cm (5 yr) and 3 cm (2 to 3 yr), respectively, in P. varians and Pavona sp.a. In the Panama and Galapagos populations, gonochoric colonies spawn eggs or sperm at least monthly. Six fecundity attributes were not significantly different in the two species, but the eggs of P. varians are white to beige and positively buoyant, and those of Pavona sp.a are dark green and neutrally to negatively buoyant. Eggs of both species lack zooxanthellae. Both species are reproductively active year-round, with maximum activity in the dry season in the nonupwelling Gulf of Chiriqui, and in the wet season in the upwelling Gulf of Panama. Spawning is predominantly during full moon, and possibly also at new moon at most study sites. Spawning in P. varians and Pavona sp.a is 12 h out of phase, with the former species spawning ∼1 h before sunrise and the latter about 1 h after sunset. The fecundity of Pavona spp. at Cano and the Galapagos Islands was much greater (19 900 to 27 900 eggs cm−2 yr−1) than at all Panama sites (14 800 to 19 800 eggs cm−2 yr−1). Intraspecific crosses in both species resulted in swimming planula larvae after 25 to 36 h. Recruitment of P. varians was highest in Panama, moderate in Costa Rica, and nil in the Galapagos Islands, matching, respectively, the contributions of P. varians to the pre-1982/1983 El Nino coral-population abundances in these areas. Recruitment success of P. varians at Uva Island was significantly related to maximum monthly positive sea surface-temperature (SST) anomalies that occurred in the year preceding recruitment over the period 1982 to 1996; recruitment failed when SST anomalies exceeded 1.6 to 1.9 C° during the severe ENSO events of 1982/1983 and 1997/1998.

The objective of this paper was to modify an existing size-structured pop- ulation model for the coral Gardineroseris planulata developed from field measurements at the Uva Island reef, Panama, for use at the regional scale (Tropical Eastern Pacific). The modified model can be used to aid in prediction of changes in coral population dynamics in response to ENSO events of different frequency and magnitude. The earlier model incorporates coral growth, predation by the sea star Acanthaster planci, and mortality associated with El Ninio-Southern Oscillation (ENSO) events. The regional model was modified from the earlier local version by extending the coral growth-temperature rela- tionship to include the lower temperatures observed in areas of strong seasonal upwelling. In addition, ENSO-associated mortality was modified by incorporating a dynamic function that relates partial mortality of corals in different size classes to the rate of temperature change during an ENSO event. This function is based on data from three reef areas (Uva Island and the Pearl Islands, Panama, and the Galapagos Islands, Ecuador), which represent a regional gradient from an area characterized by relatively high annual temperature with low variability to areas with lower annual temperature subject to seasonal upwelling. Model predictions of coral population size structure in different areas agreed with field obser- vations. Predictions for coral recovery after an ENSO event were most accurate for the Uva Island population and least accurate for the Galapaigos Islands population. We also tested the effect of various ENSO frequencies on the size structure of the coral population. Increasing ENSO frequency in the upwelling area resulted in an increase in the proportion of small colonies, while the same increase in ENSO frequency in the thermally stable reef area had little effect on the population. Sensitivity analysis suggested that more accurate estimates of growth of the smallest and largest colonies in upwelling areas as well as predation on intermediate-size colonies are important to improve predictive capability.

Using a long-term data set of Gardineroseris planulata (Dana) on Uva Island reef, Panama, we developed a simulation model that relates size-specific schedules of growth and partial mortality to predation by Acanthaster planci (Linnaeus) and El Nino–Southern Oscillation (ENSO)-related elevation of water temperature. We compared the model predictions to field observations for both the subpopulation of colonies that was used for model development and for the entire population. No statistically significant differences in the size-frequency distributions of the real and modeled coral populations were found for the subpopulation during any of 9 yr or for the entire population during 4 yr. These results suggested that the model relationships were reflecting field conditions. Longer-term (100 yr) simulations were conducted to assess the relative importance of predation and ENSO-related colony losses in determining the size structure of the coral population. Predation by A. planci was of overwhelming importance due to both stronger effects of predation (larger transitions) and the frequency of predation (yearly) compared to ENSO (episodically). Even the least-frequent predation scenario skewed the distribution toward smaller colonies, while simulations where populations were subjected to frequent ENSO events (≥3 yr) still maintained colonies in the largest size class. The model results suggested that sea star predators may not have been in the present abundance on this reef prior to the last 30 yr; with predators present, the model predicts that the distribution would be skewed toward smaller colonies.

Coral reef bleaching, the temporary or permanent loss of photosynthetic microalgae (zooxanthellae) and/or their pigments by a variety of reef taxa, is a stress response usually associated with anthropogenic and natural disturbances. Degrees of bleaching, within and among coral colonies and across reef communities, are highly variable and difficult to quantify, thus complicating comparisons of different bleaching events. Small-scale bleaching events can often be correlated with specific disturbances (e.g. extreme low/high temperatures, low/high solar irradiance, subaerial exposure, sedimentation, freshwater dilution, contaminants, and diseases), whereas large scale (mass) bleaching occurs over 100s to 1000s of km2, which is more difficult to explain. Debilitating effects of bleaching include reduced/no skeletal growth and reproductive activity, and a lowered capacity to shed sediments, resist invasion of competing species and diseases. Severe and prolonged bleaching can cause partial to total colony death, resulting in diminished reef growth, the transformation of reef-building communities to alternate, non-reef building community types, bioerosion and ultimately the disappearance of reef structures. Present evidence suggests that the leading factors responsible for large-scale coral reef bleaching are elevated sea temperatures and high solar irradiance (especially ultraviolet wavelengths), which may frequently act jointly.

Coral reef geomorphology and community composition were investigated in the tropical northeastern Pacific during April 1994. Three areas were surveyed in the Revillagigedo Islands (Mexico), and an intensive study was conducted on Clipperton Atoll (1,300 km SW of Acapulco), including macro-scale surface circulation, sea surface temperature (SST) climatology, geomorphology, coral community structure, zonation, and biogeography. Satellite-tracked drifter buoys from 1979–1993 demonstrated complex patterns of surface circulation with dominantly easterly flow (North Equatorial Counter Current, NECC), but also westerly currents (South Equatorial Current, SEC) that could transport propagules to Clipperton from both central and eastern Pacific regions. The northernmost latitude reached by the NECC is not influenced by El Nino-Southern Oscillation (ENSO) events, but easterly flow velocity evidently is accelerated at such times. Maximum NECC flow rates indicate that the eastern Pacific barrier can be bridged in 60 to 120 days. SST anomalies at Clipperton occur during ENSO events and were greater at Clipperton in 1987 than during 1982–1983. Shallow (15–18 m)and deep (50–58 m) terraces are present around most of Clipperton, probably representing Modern and late Pleistocene sea level stands. Although Clipperton is a well developed atoll with high coral cover, the reef-building fauna is depauperate, consisting of only 7 species of scleractinian corals belonging to the generaPocillopora, Porites, Pavona andLeptoseris, and 1 species of hydrocoral in the genusMillepora. The identities of the one Pocilpopora species and one of the twoPorites species are still unknown. Two of the remaining scleractinians (Pavona minuta, Leptoseris scabra) and the hydrocoral (Millepora exaesa), all formerly known from central and western Pacific localities, represent new eastern Pacific records. Scleractinian corals predominate (10–100% cover) over insular shelf depths of 8 to 60m, and crustose coralline algae are dominant (5–40% cover) from 0.5 to 7m. Spur and groove features, constructed of alternating frameworks ofPocillopora andPorites, and veneered with crustose coralline algae, are generally well developed around most atoll exposures. Although crustose coralline algae predominate in the breaker zone (with up to 100% cover), a prominent algal ridge is absent with only a slight buildup (ca. 10 cm) to seaward. Frequent grazing by the pufferfishArothron meleagris results in the removal of large amounts of live tissue and skeleton fromPorites lobata. Acanthaster planci is present, but rare. The grazing of large diadematid sea urchins, (2 species each ofDiadema andEchinothrix) on dead corals cause extensive erosion in some areas. Large numbers of corals on the 15–18 m terrace had recently suffered partial (P. lobata, 60–70% maximum of all colonies sampled) or total (Pocillopora sp., 80% maximum) mortality. The lengths of regenerating knobs and the rates of linear skeletal growth inP. lobata, determined by sclerochronologic analysis, indicated a period of stress during 1987. Massive skeletal growth is significantly higher at intermediate (16–17 m) than shallow (6–8 m) depths with mean extension rates of 1.5 mm yr−1 inP. lobata and 1.4 mm yr−1 inP. minuta at intermediate depths. Skeletal growth inP. lobata was depressed during the 1987 El Nifio event at Clipperton. The branching coralPocillopora sp. demonstrated high and similar skeletal growth rates at both shallow (25.4 mm yr−1) and intermediate (26.5 mm yr−1) depths. The presence of widely distributed Indo-Pacific zooxanthellate corals at Clipperton and the Revillagigedo Islands indicates that these NE Pacific Islands probably serve as a stepping stone for dispersal into the far eastern Pacific region.

The reproductive ecology of Pavona gigantea Verrill and Gardineroseris planulata (Dana) was investigated in the equatorial eastern Pacific region from 1985 to 1994. These zooxanthellate scleractinian corals were adversely affected in this region during the 1982–1983 El Nino warming event. Both species were hermaphroditic, with individual colonies showing sequential cosexual development, thus resulting in dominantly outbreeding reproduction. Sexuality was mixed, with high percentages of gonochoric and hermaphroditic colonies in both species. Approximately 1:1 male-to-female gonad ratios were found in gonochoric and hermaphroditic colonies combined. Broadcast spawning was observed in P. gigantea in the Galapagos Islands, and the sudden disappearance of mature gametes and the presence of spent gonads suggest that G. planulata is also a broadcast spawner. Colonies of both species with ≲200 cm2 (10 cm diam) live tissue were nonreproductive. Estimated ages of the youngest reproductive colonies were 11 yr for P. gigantea and 20 yr for G. planulata. The percentage of all colonies of P. gigantea with gonads at nonupwelling sites (Cano Istand, Costa Rica and Uva Island, Panama) ranged from 37 to 47%, respectively; colonies with gonads from upwelling environments (Saboga and Taboga Islands, Panama) ranged from 31 to 39%, respectively, and reproductively active colonies from the thermally variable Galapagos islands comprised 40% of the collections. Compared with P. gigantea, the numbers of sexually active G. planulata colonies were roughly onehalf at nonupwelling Cano Island (20%) and Uva Island (25%) sites, or less (10%) at the upwelling Saboga Island site. Peak reproductive activity in P. gigantea occurred during the rainy season at all study sites. In the nonupwelling Costa Rican (Cano Island) and Panamainan (Uva Island) sites, mean monthly sea-surface temperatures (SSTs) were high (28 to 29°C), but slightly lower than in the dry season (29°C). In the upwelling Gulf of Panama (Saboga and Taboga Islands), reproduction occurred after mean monthly SSTs increased from 24 to 28–29°C. In the Galapagos Islands, reproductive activity peaked during sea warming, when mean monthly SSTs reached 25°C. Sexually active colonies of G. planulata, present only at the main collection sites of Cano and Uva Islands, were also observed during the wet season. The presence of mature or spawned gonalds in both species mostly around new and full lunar phases suggests that spawning is at least weakly synchronized with moon phase. Fecundity estimates disclosed the following nonsignificant differences between sites for P. gigantea, expressed as egg production cm-2 colony surface surface yr-1: Galapagos (10 300 to 30 800), Uva Island (4900 to 9800), Cano Island (1800 to 7400), Saboga Island (600 to 1300) Taboga Island (1200 to 2400). Fecundity estimates for G. planulata were considerably lower: Uva Island (700 to 1400), Cano Island (500 to 1000). The sexual recruitment of P. gigantea into El Nino-Southern Oscillation (ENSO) 1982–1983-disturbed, equatorial eastern Pacific coral communities has been low, with only moderate recovery evident since 1983. G. planulata has revealed no sexual recruitment where seed populations are absent or rare (Cano Island, Galapagos Islands), and only low recruitment (Panama) in areas with colonies that survived the ENSO disturbance.

As part of a two-phased study, sediment and biota were collected from Pennekamp Coral Reef State Park and Key Largo National Marine Sanctuary and analysed for organochlorine pesticide residues. Phase 1 consisted of an inter-laboratory comparison using replicates of unspiked field samples. The five participating contract-laboratories differed in methodology, detection limits and their ability to detect pesticides. The highest concentration of pesticide reported in Phase 1 samples was 4.4 ng g−1 wet wt aldrin, found in a fillet of Haemulon plumieri. Based on the inter-laboratory comparison, one laboratory was selected to analyse additional samples collected in Phase 2. Pesticides were detected in 43 of the 52 Phase 2 samples. The highest concentration reported in Phase 2 samples was 2.3 ng g−1 α-BHC in Panulirus argus tail muscle. These results suggest that while most samples contained one or more residues, pesticide concentrations were low and trends in residue profiles were minor.

In their Report “Global trajectories of the long-term decline of coral reef ecosystems” (15 Aug., p. [955][1]), J. M. Pandolfi et al. advocate a novel interpretation of the timing and causes of the worldwide decline of reef-building corals. Expanding on an earlier paper ([1][2]), they conclude

Rock and sediment cores reveal that a well-developed fringing reef in Golfo Dulce, Pacific Costa Rica, up to 9 m thick was established on Cretaceous basalt about 5500 y BP. It is presently being smothered with fine sediments and is almost completely dead. This reef is made up of three main facies that are represented by comparable extant reef zones: reef-flat branching coral, fore-reef slope massive coral, and fore-reef talus sediment facies. Reef growth began with the establishment of small patch reefs dominantly formed by the branching coral Pocillopora damicornis. P. damicornis spread across the basalt bench and massive colonies of Porites lobata grew on the outer slopes, eventually blocking the seaward transport of Pocillopora fragments to the fore-reef talus sediments. The reef flourished until 500 years ago. Lower accumulation rates during the past 500 years may be due to deteriorating environmental conditions rather than slower growth after the reef reached sea level. Present-day reef communities are severely degraded with less than 2% living coral cover. The increased turbidity associated with the final stage of degradation of this reef is probably related to human activity on the adjacent shores, including deforestation, mining, and road construction.

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.

Scleractinian corals and their symbiotic dinoflagellate algae build massive, wave-resistant coral reefs that are pre-eminent in shallow tropical seas. This mutualism is especially sensitive to numerous environmental stresses, and has been disrupted frequently during the past decade. Increased seawater temperatures have been proposed as the most likely cause of coral reef bleaching, and it has been suggested that the recent large-scale disturbances are the first biological indication of global warming. This article describes recent bleaching events and their possible link with sea warming and other environmental stresses, and offers some speculation on the fate of coral reefs if the Earth enters a sustained period of warming.

Coral reef bleaching, the whitening of diverse invertebrate taxa, results from the loss of symbiotic zooxanthellae and/or a reduction in photosynthetic pigment concentrations in zooxanthellae residing within the gastrodermal tissues of host animals. Of particular concern are the consequences of bleaching of large numbers of reef-building scleractinian corals and hydrocorals. Published records of coral reef bleaching events from 1870 to the present suggest that the frequency (60 major events from 1979 to 1990), scale (co-occurrence in many coral reef regions and often over the bathymetric depth range of corals) and severity (>95% mortality in some areas) of recent bleaching disturbances are unprecedented in the scientific literature. The causes of small scale, isolated bleaching events can often be explained by particular stressors (e.g., temperature, salinity, light, sedimentation, aerial exposure and pollutants), but attempts to explain large scale bleaching events in terms of possible global change (e.g., greenhouse warming, increased UV radiation flux, deteriorating ecosystem health, or some combination of the above) have not been convincing. Attempts to relate the severity and extent of large scale coral reef bleaching events to particular causes have been hampered by a lack of (a) standardized methods to assess bleaching and (b) continuous, long-term data bases of environmental conditions over the periods of interest. An effort must be made to understand the impact of bleaching on the remainder of the reef community and the long-term effects on competition, predation, symbioses, bioerosion and substrate condition, all factors that can influence coral recruitment and reef recovery. If projected rates of sea warming are realized by mid to late AD 2000, i.e. a 2°C increase in high latitude coral seas, the upper thermal tolerance limits of many reef-building corals could be exceeded. Present evidence suggests that many corals would be unable to adapt physiologically or genetically to such marked and rapid temperature increases.

There are some fundamental generalizations that can be made about the biology and ecology of invertebrates associated with coral reefs. For example, it is widely accepted that coral reefs support the highest biodiversity of all marine ecosystems, and that invertebrates contribute dominantly to this condition. It is also acknowledged that numerous invertebrate taxa are involved in highly complex and coevolved relationships with metazoans, unicellular protists, and multicellular algae. Further, during the past few decades it has been demonstrated that certain invertebrate consumers can have strong and widespread effects on coral abundances, community structure, and the integrity of reef formations.

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