Spatiotemporal variability of oxygen concentration in coral reefs of Gorgona Island (Eastern Tropical Pacific) and its effect on the coral Pocillopora capitata.

Dissolved oxygen concentration (DO) is one of the main factors limiting benthic species distribution. Due to ocean warming and eutrophication, the ocean is deoxygenating. In the Eastern Tropical Pacific (ETP), deep waters with low DO (<1 mg L-1) may reach coral reefs, because upwelling will likely intensify due to climate change. To understand oxygen variability and its effects on corals, we characterize the Spatio-temporal changes of DO in coral reefs of Gorgona Island and calculate the critical oxygen tension (P crit) to identify the DO concentration that could represent a hypoxic condition for Pocillopora capitata, one of the main reef-building species in the ETP. The mean (±SD) DO concentration in the coral reefs of Gorgona Island was 4.6 ± 0.89 mg L-1. Low DO conditions were due to upwelling, but hypoxia (<3.71 mg L-1, defined as a DO value 1 SD lower than the Mean) down to 3.0 mg O2 L-1 sporadically occurred at 10 m depth. The P crit of P. capitata was 3.7 mg L-1 and lies close to the hypoxic condition recorded on coral reefs during the upwelling season at 10 m depth. At Gorgona Island oxygen conditions lower than 2.3 mg L-1 occur at >20 m depth and coincide with the deepest bathymetric distribution of scattered colonies of Pocillopora. Because DO concentrations in coral reefs of Gorgona Island were comparably low to other coral reefs in the Eastern Tropical Pacific, and the hypoxic threshold of P. capitata was close to the minimum DO record on reefs, hypoxic events could represent a threat if conditions that promote eutrophication (and consequently hypoxia) increase.

Coral reef resilience to thermal stress in the Eastern Tropical Pacific.

Coral reefs worldwide are threatened by thermal stress caused by climate change. Especially devastating periods of coral loss frequently occur during El Niño-Southern Oscillation (ENSO) events originating in the Eastern Tropical Pacific (ETP). El Niño-induced thermal stress is considered the primary threat to ETP coral reefs. An increase in the frequency and intensity of ENSO events predicted in the coming decades threatens a pan-tropical collapse of coral reefs. During the 1982-1983 El Niño, most reefs in the Galapagos Islands collapsed, and many more in the region were decimated by massive coral bleaching and mortality. However, after repeated thermal stress disturbances, such as those caused by the 1997-1998 El Niño, ETP corals reefs have demonstrated regional persistence and resiliency. Using a 44 year dataset (1970-2014) of live coral cover from the ETP, we assess whether ETP reefs exhibit the same decline as seen globally for other reefs. Also, we compare the ETP live coral cover rate of change with data from the maximum Degree Heating Weeks experienced by these reefs to assess the role of thermal stress on coral reef survival. We find that during the period 1970-2014, ETP coral cover exhibited temporary reductions following major ENSO events, but no overall decline. Further, we find that ETP reef recovery patterns allow coral to persist under these El Niño-stressed conditions, often recovering from these events in 10-15 years. Accumulative heat stress explains 31% of the overall annual rate of change of living coral cover in the ETP. This suggests that ETP coral reefs have adapted to thermal extremes to date, and may have the ability to adapt to near-term future climate-change thermal anomalies. These findings for ETP reef resilience may provide general insights for the future of coral reef survival and recovery elsewhere under intensifying El Niño scenarios.

Incomplete datasets obscure associations between traits affecting dispersal ability and geographic range size of reef fishes in the Tropical Eastern Pacific.

Dispersal is thought to be an important process determining range size, especially for species in highly spatially structured habitats, such as tropical reef fishes. Despite intensive research efforts, there is conflicting evidence about the role of dispersal in determining range size. We hypothesize that traits related to dispersal drive range sizes, but that complete and comprehensive datasets are essential for detecting relationships between species' dispersal ability and range size. We investigate the roles of six traits affecting several stages of dispersal (adult mobility, spawning mode, pelagic larval duration (PLD), body size, aggregation behavior, and circadian activity), in explaining range size variation of reef fishes in the Tropical Eastern Pacific (TEP). All traits, except for PLD (148 species), had data for all 497 species in the region. Using a series of statistical models, we investigated which traits were associated with large range sizes, when analyzing all TEP species or only species with PLD data. Furthermore, using null models, we analyzed whether the PLD-subset is representative of the regional species pool. Several traits affecting dispersal ability were strongly associated with range size, although these relationships could not be detected when using the PLD-subset. Pelagic spawners (allowing for passive egg dispersal) had on average 56% larger range sizes than nonpelagic spawners. Species with medium or high adult mobility had on average a 25% or 33% larger range, respectively, than species with low mobility. Null models showed that the PLD-subset was nonrepresentative of the regional species pool, explaining why model outcomes using the PLD-subset differed from the ones based on the complete dataset. Our results show that in the TEP, traits affecting dispersal ability are important in explaining range size variation. Using a regionally complete dataset was crucial for detecting the theoretically expected, but so far empirically unresolved, relationship between dispersal and range size.

Unraveling the structure and composition of Varadero Reef, an improbable and imperiled coral reef in the Colombian Caribbean.

Coral reefs are commonly associated with oligotrophic, well-illuminated waters. In 2013, a healthy coral reef was discovered in one of the least expected places within the Colombian Caribbean: at the entrance of Cartagena Bay, a highly-polluted system that receives industrial and sewage waste, as well as high sediment and freshwater loads from an outlet of the Magdalena River (the longest and most populated river basin in Colombia). Here we provide the first characterization of Varadero Reef's geomorphology and biological diversity. We also compare these characteristics with those of a nearby reference reef, Barú Reef, located in an area much less influenced by the described polluted system. Below the murky waters, we found high coral cover of 45.1% (±3.9; up to 80% in some sectors), high species diversity, including 42 species of scleractinian coral, 38 of sponge, three of lobster, and eight of sea urchin; a fish community composed of 61 species belonging to 24 families, and the typical zonation of a Caribbean fringing reef. All attributes found correspond to a reef that, according to current standards should be considered in "good condition". Current plans to dredge part of Varadero threaten the survival of this reef. There is, therefore, an urgent need to describe the location and characteristics of Varadero as a first step towards gaining acknowledgement of its existence and garnering inherent legal and environmental protections.

Age and growth of the round stingray Urotrygon rogersi, a particularly fast-growing and short-lived elasmobranch.

We examined the age and growth of Urotrygon rogersi on the Colombian coast of the Eastern Tropical Pacific Ocean by directly estimating age using vertebral centra. We verified annual deposition of growth increments with marginal increment analysis. Eight growth curves were fitted to four data sets defined on the basis of the reproductive cycle (unadjusted or adjusted for age at first band) and size variables (disc width or total length). Model performance was evaluated using Akaike's Information Criterion (AIC), AIC weights and multi-model inference criteria. A two-phase growth function with adjusted age provided the best description of growth for females (based on five parameters, DW∞  =  20.1 cm, k  =  0.22 yr⁻¹) and males (based on four and five parameters, DW(∞)  =  15.5 cm, k  =  0.65 yr⁻¹). Median maturity of female and male U. rogersi is reached very fast (mean ± SE  =  1.0 ± 0.1 year). This is the first age and growth study for a species of the genus Urotrygon and results indicate that U. rogersi attains a smaller maximum size and has a shorter lifespan and lower median age at maturity than species of closely related genera. These life history traits are in contrast with those typically reported for other elasmobranchs.

Tidepool fish assemblages of Gorgona Island, Colombian Pacific coast: a local and regional comparison / Ensambles de peces de poza de isla Gorgona, costa pacífica colombiana: una comparación local y regional

The ecology of tidepool fishes has been extensively investigated worldwide over the past 40 years. As in many other ecological fields, studies in temperate zones outnumber studies carried out in tropical areas. Here, we document the short-term spatio-temporal variation of a tidepool fish assemblage from the Tropical Eastern Pacific (Gorgona Island, Colombia), compare our data with previous surveys made in 1993 and provide the first latitudinal comparison of tidepool fish assemblages in the Eastern Pacific coast (43°N to 36°S). During April-July 2006, monthly samplings were carried in 18 tidepools located at three sites this Island. A relatively species-rich tidepool fish assemblage (53 species) was found at Gorgona Island. Labrisomidae, Gobiidae and Gobiesocidae were the dominant resident components of this assemblage, whereas Pomacentridae, Muraenidae and Labridae constituted the transient component. Although the same dominant species were observed in surveys from 1993 and 2006, suggesting a high persistence of this assemblage over time, clear differences in the relative abundance of some species were also detected. These differences were partly the result of using different sampling methodologies (rotenone vs clove oil). Comparisons with other studies performed in tropical and temperate areas of the Eastern Pacific coast indicate a clear latitudinal pattern in the composition of these assemblages that correspond to well-documented biogeographic subdivisions of the marine fauna in this region. Further investigation of the ecological role that tidepool fishes play in rocky intertidal and subtidal areas of Gorgona Island and the whole Tropical Eastern Pacific region will benefit our understanding of the functioning of these important coastal ecosystems. Rev. Biol. Trop. 62 (Suppl. 1): 373-390. Epub 2014 February 01.

A nivel mundial, la ecología de peces de charcos intermareales ha sido ampliamente investigada durante los últimos 40 años, especialmente en zonas templadas. En este trabajo, se documenta la variación espacio-temporal en corta escala de un ensamblaje de peces de charcos intermareales en el Pacífico Oriental Tropical (Isla Gorgona, Colombia), y se comparan nuestros resultados, con los resultados obtenidos durante muestreos realizados en la misma localidad en 1993. Además se realiza la primera comparación latitudinal de estos ensamblajes para la costa oriental del Océano Pacífico (43°N a 36°S). Durante abril a junio de 2006, se realizaron muestreos mensuales en 18 charcos intermareales distribuidos en tres localidades de Isla Gorgona, estableciendo un ensamblaje de peces de charcos intermareales con una alta riqueza de especies (53 especies). Labrisomidae, Gobiidae and Gobiesocidae fueron los componentes residentes dominantes en el ensamblaje, mientras que Pomacentridae, Muraenidae and Labridae fueron los componentes transitorios. Aunque el registro de las mismas especies dominantes en 1993 y 2006 sustenta la idea de una alta persistencia temporal de este ensamblaje, se detectaron diferencias significativas en la abundancia relativa de las especies. Estas diferencias podrían ser el resultado de las diferentes técnicas de captura utilizadas durante 1993 y 2006 (rotenona vs aceite de clavo). Al comparar los estudios sobre peces intermareales realizados en la zona tropical y zona templada de la costa oriental del Océano Pacífico, se identificó un claro patrón latitudinal en la composición de los ensamblajes, que es consecuente con la ampliamente documentada subdivisión biogeográfica de la fauna marina de esta región. Para comprender el funcionamiento de los ecosistemas costeros del Pacífico Oriental tropical, es necesario que futuros esfuerzos de investigación se encaminen a conocer el papel ecológico de los peces intermareales en esta región.

A comparison of visual and collection-based methods for assessing community structure of coral reef fishes in the Tropical Eastern Pacific / Una comparación de métodos visuales y basados ​​en colecciones para evaluar la estructura de la comunidad de peces de arrecifes de coral en el Pacífico Oriental Tropical

Gorgona Island, the major insular area in the Colombian Pacific Ocean, is characterized by a remarkably high biological and ecosystem diversity for this area of the world. Coral reefs are well developed and their fish communities have been described using conventional visual surveys. These methods, however, are known to be biased towards detecting larger and more mobile species, tending to ignore small and cryptobenthic species. The two main objectives of this study were to describe the assemblage structure of the cryptobenthic fish fauna and estimate the extent to which this fauna is underestimated by visual surveys.At the beginning and the end of the warm season, we compared the cryptobenthic fish assemblage recorded using visual surveys against the one recorded using “enclosed anesthetic/rotenone samples” on isolated coral colonies (N=54 beginning of warm season; N=17 end of warm season). The crypthobenthic fish fauna associated to coral colonies was characterized by small body sizes and was composed mainly by species of the families Antennaridae, Blennidae, Gobiidae, Labrisomidae, Muraenidae, Serranidae, Scorpaenidae and Syngnathidae. Conventional visual surveys underestimated overall species richness by 28-36% and number of individuals by 16-35%. Noteworthy, four species recorded during this study using “enclosed anesthetic/rotenone samples” were new records for Gorgona Island. Although both sampling methods can detect a largely overlapping group of species, the “enclosed anesthetic/rotenone samples” method was able to detect more individuals and species, including several species that visual surveys fail to detect. Although this study is the first effort to describe the cryptobenthic fish assemblage associated to coral reefs in the Tropical Eastern Pacific, our results suggest that these assemblages are an important component of the reef fish community in the region in terms of biodiversity and functional roles. Rev. Biol. Trop. 62 (Suppl. 1): 359-371. Epub 2014 February 01.

Métodos de muestreo convencionales (censos visuales) usados en el estudio de peces arrecifales han llevado a una constante subestimación de la riqueza de especies, ya que estos tienden a ignorar especies pequeñas y crípticas. En este estudio describimos la estructura del ensamblaje de peces criptobentónicos en Isla Gorgona, Colombia y estimamos el grado en que este ensamblaje es subestimado al usar censos visuales. Al comienzo y al final de la estación cálida comparamos la capacidad de detección de censos visuales vs “muestreos cerrados con anestésico/rotenona” (N=54 comienzo; N=17 final). La fauna criptobentónica se caracterizó por mantener individuos de tamaños corporales pequeños, pertenecientes principalmente a las familias Antennaridae, Blennidae, Gobiidae, Labrisomidae, Muraenidae, Serranidae, Scorpaenidae and Syngnathidae. Los censos visuales subestimaron la riqueza de especies en un 28-36% y el número de individuos en un 16-35%. Aunque un gran número de especies son detectadas usando ambos métodos, los “muestreos cerrados con anestésico/rotenona” detectan un mayor rango de especies. Este estudio, el primer esfuerzo para describir el ensamblaje de peces criptobentónicos asociados a arrecifes coralinos en Colombia, sugiere que la fauna criptobentónica puede ser un componente importante de la comunidad arrecifal en términos de biodiversidad y papel funcional.

Fish community structure on coral habitats with contrasting architecture in the Tropical Eastern Pacific / Estructura de la comunidad de peces en hábitats de coral con arquitectura contrastante en el Pacífico Oriental Tropical

Reefscape architecture, shaped by dominant coral morphologies, can play a major role in determining the structure and composition of fish assemblages by affecting niche and resource availability and mediating interspecific interactions. To explore the role of dominant coral morphologies on reef fish communities, we carried out a comparative study of the fish community associated with a Massive Coral Community (MCC) and a Branching Coral Community (BCC) at Gorgona Island, Tropical Eastern Pacific (TEP). On each community, the benthic substrate was assessed through the “chain transect method” while the fish assemblage was evaluated through visual surveys on belt transects. We found differences between both fish assemblages in terms of the abundance, diversity (H’), and evenness (J’). The BCC, despite being formed by morphologically complex pocilloporid colonies, had a simple and relatively flat architecture that attracted principally small and territorial fishes. Significant higher abundances of Chromis atrilobata and Thalassoma lucasanum at the BCC boosted the total fish abundance but caused low fish evenness and diversity. Conversely the MCC, composed of massive coral species with considerable sizes and diversity of shapes, held a complex and high-relief reefscape capable of sustaining a more diverse and even fish community, although with the same species richness as the BCC. Fishes with large sizes, roving behavior and piscivore-feeding preferences were especially attracted to the MCC. Although, massive coral species are important in determining a diverse and complex reefscape architecture, both dominant coral morphologies (massive and branching) attract and provide resources to different types of fish according to their size, mobility and trophic group. Our results suggest that a loss of massive coral species and a community shift towards stress-resistant taxa (such as Pocillopora spp.), could alter the structure and function of fish assemblages in the TEP due to the habitat loss for large, mobile and piscivore species. Rev. Biol. Trop. 62 (Suppl. 1): 343-357. Epub 2014 February 01.

La arquitectura del paisaje arrecifal, definida por la morfología de los corales dominantes, puede desempeñar un papel importante en la estructura y composición de las comunidades de peces al afectar la disponibilidad de nichos y recursos y modificar las interacciones interespecíficas. Hicimos un estudio comparativo entre la comunidad de peces asociada a una comunidad de corales masivos (CCM) y a una de corales ramificados (CCR) en la isla Gorgona, Pacífico Oriental Tropical. En cada formación coralina, el sustrato bentónico se evaluó a través de “transectos de cadena”, mientras que la comunidad de peces se valoró con el uso censos visuales en transectos de banda. Hubo diferencias en la abundancia, diversidad (H’) y equitatividad (J’) de las dos comunidades de peces. La CCR, a pesar de estar formada por colonias morfológicamente complejas de corales pocillóporidos, presentó una arquitectura simple y relativamente plana que atrajo principalmente peces territoriales y de talla pequeña. Abundancias significativamente altas de Chromis atrilobata y Thalassoma lucasanum en la CCR, aumentaron la abundancia total de peces, pero ocasionaron una baja diversidad y equitatividad de la comunidad. Por el contrario, la CCM constituida principalmente por especies de corales masivos con diversos tamaños y formas, presentó una arquitectura compleja y de alto relieve capaz de mantener una comunidad de peces mucho más diversa y equitativa, aunque con la misma riqueza de especies de peces que la CCR. Los peces de gran talla, con comportamiento errante y hábitos carnívoros fueron atraídos a la MCC. En general, nuestro estudio evidenció que aunque las especies de coral con crecimiento masivo son importantes en la formación de una arquitectura compleja, cada una de las morfologías de coral dominante (masivo y ramificado) atrae y brinda recursos a distintos grupos de peces según su tamaño y grupo trófico. La pérdida de corales masivos o un cambio en la comunidad hacia corales pocilóporidos (resistentes al estrés) podrían alterar la diversidad y función comunitaria de peces en el Pacífico Oriental Tropical (POT) debido a la pérdida de hábitat para las especies grandes, móviles y carnívoras.

Invertebrate colonization on artificial substrates in a coral reef at Gorgona Island, Colombian Pacific Ocean / Colonización de invertebrados sobre sustratos artificiales en un arrecife de coral en la Isla Gorgona, Océano Pacífico colombiano

Habitat colonization is a fundamental process in marine population dinamics and community ecology. Marine invertebrate colonization of artificial hard substrates and its spatial variation was studied over the course of one year at La Azufrada coral reef, Gorgona Island, Colombia. Five sets of artificial plates (terracotta and ceramic) were deployed parallel to the bottom in each of three reef zones (backreef, flat and slope). Plates were recovered after 12 months of their installation. The community that developed on the artificial substrate plates was composed of 24 taxa, among which corals were remarkably absent. Species richness on plates did not differ between reef zones, type of plate material or plate surfaces. The resulting community was dominated by barnacles (Balanus trigonus) with a mean density of 26 787.8 (±47 301.0) individuals/m² (mean±1S.D.). The density of this species was significantly higher on plates deployed on the reef slope than on the reef flat or back reef, and was lower on the upper than on the lower or lateral surfaces of plates. The dominance of B. trigonus on artificial plates during this experiment suggests a possible synergistic effect between its reproductive traits and competitive ability for space, which prevents the successful recruitment of other reef organisms such as corals. Rev. Biol. Trop. 62 (Suppl. 1): 161-168. Epub 2014 February 01.

La colonización de hábitat disponible es un proceso fundamental de la ecología de poblaciones y comunidades de organismos marinos. La colonización sobre sustratos artificiales por invertebrados y su variación espacial fue estudiada por un año en el arrecife coralino de La Azufrada, Isla Gorgona (Colombia). Cinco juegos de baldosas (terracota y grés) fueron dispuestos en tres zonas arrecifales (trasarrecife, planicie y talud). Las baldosas fueron recuperadas y examinadas después de 12 meses posteriores a su instalación. La comunidad desarrollada estuvo compuesta por 24 taxa siendo notable la ausencia de corales. No se encontraron diferencias en la riqueza de especies entre las zonas arrecifales, los materiales utilizados y las superficies de las baldosas. Las baldosas fueron dominadas por cirripedios (Balanus trigonus) con una densidad de 26 787.8 (±47 301.0) ind/m² (media±1D.E). La densidad de esta especie fue significativamente más alta en el talud y menor en las superficies superiores. La dominancia de B. trigonus durante el experimento sugiere un posible efecto sinérgico entre sus características reproductivas y su habilidad competitiva por el espacio evitando que otros organismos, como los corales, recluten exitosamente.

Mid-term coral-algal dynamics and conservation status of a Gorgona Island (Tropical Eastern Pacific) coral reef.

Colombian coral reefs, as other reefs worldwide, have deteriorated significantly during the last few decades due to both natural and anthropogenic disturbances. The National Monitoring System for Coral Reefs in Colombia (SIMAC) was established in 1998 to provide long-term data bases to assess the changes of Colombian coral reefs against perturbations and to identify the factors responsible for their decline or recovery. On the Pacific coast, data on coral and algal cover have been collected yearly during seven consecutive years (1998-2004) from 20 permanent transects in two sites at La Azufrada reef, Gorgona Island. Overall, coral cover was high (55.1%-65.7%) and algal cover low (28.8%-37.5%) and both exhibited significant changes among years, most notably on shallow areas. Differences between sites in both coral and algal cover were present since the study began and may be explained by differences in sedimentation stress derived from soil runoff. Differences between depths most likely stem from the effects of low tidal sub-aerial exposures. Particularly intense sub-aerial exposures occurred repeatedly during January-March, 2001 and accounted for a decrease in coral and an increase in algal cover on shallow depths observed later that year. Additionally, the shallow area on the Northern site seems to be negatively affected by the combined effect of sedimentation and low tidal exposure. However, a decrease in coral cover and an increase of algal cover since 2001 on deep areas at both sites remain unexplained. Comparisons with previous studies suggest that the reef at La Azufrada has been more resilient than other reefs in the Tropical Eastern Pacific (TEP), recovering pre-disturbance (1979) levels of coral cover within a 10 year period after the 1982-83 El Niño, which caused 85% mortality. Furthermore, the effects of the 1997-98 El Niño, indicated by the difference in overall live coral cover between 1998 and 1999, were minor (< 6% reduction). Despite recurrent natural disturbances, live coral cover in 2004 was as high as that existing before 1982 at La Azufrada, and one of the highest observed on healthy coral reefs in the TEP region.

First record and impact of the crown-of-thorns starfish, Acanthaster planci (Spinulosida: Acanthasteridae) on corals of Malpelo Island, Colombian Pacific.

The crown-of-thorns starfish, Acanthaster planci, is a major coral predator widely distributed in the Indo-Pacific region, where population outbreaks have caused dramatic impacts on coral reefs. In the Tropical Eastern Pacific (TEP) A. planci occurs at low population densities; it has been significantly abundant only in Panama and Cocos Island. We have recently found two individuals of A. planci at Malpelo Island, a small oceanic island with significant coral communities located off the Colombian Pacific coast. The recent discovery of A. planci at Malpelo is significant in light of recent reports of its increased frequency of observation at Cocos Island and occurrence at the Galapagos Islands. The individuals found at Malpelo have been repeatedly sighted since 2004, actively feeding on nine species of coral. Although densities of A. planci are low at Malpelo and other oceanic islands of the TEP, these islands may act as stepping stones for the colonization of other coral reef areas in the region. However, the low densities of A. planci suggest that it currently poses no threat to coral reefs in the TEP.

Mid-term coral-algal dynamics and conservation status of a Gorgona Island (Tropical Eastern Pacific) coral reef

Colombian coral reefs, as other reefs worldwide, have deteriorated significantly during the last few decades due to both natural and anthropogenic disturbances. The National Monitoring System for Coral Reefs in Colombia (SIMAC) was established in 1998 to provide long-term data bases to assess the changes of Colombian coral reefs against perturbations and to identify the factors responsible for their decline or recovery. On the Pacific coast, data on coral and algal cover have been collected yearly during seven consecutive years (1998-2004) from 20 permanent transects in two sites at La Azufrada reef, Gorgona Island. Overall, coral cover was high (55.1%-65.7%) and algal cover low (28.8%-37.5%) and both exhibited significant changes among years, most notably on shallow areas. Differences between sites in both coral and algal cover were present since the study began and may be explained by differences in sedimentation stress derived from soil runoff. Differences between depths most likely stem from the effects of low tidal sub-aerial exposures. Particularly intense sub-aerial exposures occurred repeatedly during January-March, 2001 and accounted for a decrease in coral and an increase in algal cover on shallow depths observed later that year. Additionally, the shallow area on the Northern site seems to be negatively affected by the combined effect of sedimentation and low tidal exposure. However, a decrease in coral cover and an increase of algal cover since 2001 on deep areas at both sites remain unexplained. Comparisons with previous studies suggest that the reef at La Azufrada has been more resilient than other reefs in the Tropical Eastern Pacific (TEP), recovering pre-disturbance (1979) levels of coral cover within a 10 year period after the 1982-83 El Niño, which caused 85% mortality. Furthermore, the effects of the 1997-98 El Niño, indicated by the difference in overall live coral cover between 1998 and 1999, were minor (<6% reduction). Despite recurrent natural disturbances, live coral cover in 2004 was as high as that existing before 1982 at La Azufrada, and one of the highest observed on healthy coral reefs in the TEP region. Rev. Biol. Trop. 58 (Suppl. 1): 81-94. Epub 2010 May 01.

A través del Sistema Nacional de Monitoreo de Arrecifes Coralinos en Colombia (SIMAC) se han colectado anualmente (1998-2004) datos de cobertura de corales y algas en 20 transectos de 10m localizados en dos profundidades de dos sitios del arrecife de La Azufrada, Isla Gorgona (costa Pacífica). En general, la cobertura coralina fue alta (55.1% - 65.7%) y la de algas baja (28.8% - 37.5%), con una significativa variación entre años, más notablemente en áreas someras. Las diferencias entre sitios tanto en cobertura de coral como de algas estuvieron presentes desde que comenzó el estudio y pueden ser explicadas por diferencias en estrés por sedimentación (escorrentía terrestre). Las diferencias entre las profundidades muy probablemente se deben a los efectos de exposiciones aéreas durante mareas bajas. Las exposiciones aéreas particularmente intensas y repetidas entre enero-marzo de 2001 explican la disminución de la cobertura de coral, y aumento de la de algas en áreas someras observadas más tarde ese año. Adicionalmente, el área somera del sitio norte parece ser negativamente afectada por el efecto combinado de la sedimentación y la exposición mareal. Sin embargo, una tendencia a la disminución de la cobertura coralina y aumento de la de algas desde 2001 en las áreas profundas de ambos sitios permanece sin explicación. Comparaciones con estudios previos indican que el arrecife de La Azufrada ha sido más elástico que otros arrecifes del Pacífico Oriental Tropical (POT). A pesar de las perturbaciones naturales recurrentes, la cobertura coralina en 2004 fue tan alta como la existente antes de 1982 en La Azufrada, y una de las más altas observadas en arrecifes coralinos saludables de la región del POT.

First record and impact of the crown-of-thorns starfish, Acanthaster planci (Spinulosida: Acanthasteridae) on corals of Malpelo Island, Colombian Pacific

The crown-of-thorns starfish, Acanthaster planci, is a major coral predator widely distributed in the Indo-Pacific region, where population outbreaks have caused dramatic impacts on coral reefs. In the Tropical Eastern Pacific (TEP) A. planci occurs at low population densities; it has been significantly abundant only in Panama and Cocos Island. We have recently found two individuals of A. planci at Malpelo Island, a small oceanic island with significant coral communities located off the Colombian Pacific coast. The recent discovery of A. planci at Malpelo is significant in light of recent reports of its increased frequency of observation at Cocos Island and occurrence at the Galapagos Islands. The individuals found at Malpelo have been repeatedly sighted since 2004, actively feeding on nine species of coral. Although densities of A. planci are low at Malpelo and other oceanic islands of the TEP, these islands may act as stepping stones for the colonization of other coral reef areas in the region. However, the low densities of A. planci suggest that it currently poses no threat to coral reefs in the TEP. Rev. Biol. Trop. 58 (Suppl. 1): 139-143. Epub 2010 May 01.

La estrella de mar corona de espinas Acanthaster planci, es un importante depredador de coral ampliamente distribuido en la región del Indo-Pacifico, donde explosiones poblacionales han causado dramáticos impactos sobre los arrecifes coralinos. En el Pacifico Oriental Tropical (POT) A. planci ocurre con densidades poblacionales bajas; solamente en Panamá e Isla de Cocos su abundancia ha sido significativa. Nosotros encontramos recientemente al menos dos individuos de A. planci en la Isla de Malpelo, una pequeña isla oceánica con comunidades coralinas importantes localizada en el Pacífico Colombiano. El hallazgo de A. planci en Malpelo es significativo a la luz de reportes recientes de un incremento en su frecuencia de observación en Isla de Cocos y su registro en Galápagos. Los individuos encontrados en Malpelo han sido repetidamente observados alimentándose activamente de nueve especies de coral desde 2004. Aunque las densidades de A. planci son bajas en Malpelo y otras islas oceánicas del POT, éstas pueden actuar como trampolín de dispersión para la colonización de otras áreas arrecifales en la región. Sin embargo, las bajas densidades de A. planci sugieren que actualmente ella no representa amenaza alguna para los arrecifes del POT.

Efecto de la herbivoría y coralivoría por peces en la supervivencia de corales trasplantados en el Caribe colombiano

Effect of herbivorous and corallivorous fishes on the survival of transplanted corals in the Colombian Caribbean. To examine the effects of herbivorous and corallivorous fishes on the survival of transplanted colonies of Montastraea annularis, Diploria labyrinthiformis and Porites astreoides, both transplanted and native colonies were full-cage enclosed and compared to open (uncaged) colonies, while caging effects were assessed with a partial-cage (roof treatment). To evaluate if transplant stress increased the corals availability to fish predation, comparisons of fish foraging intensity among transplanted versus native colonies were made. To determine the density of herbivorous and corallivorous fishes on the transplants area visual censuses were made. The transient herbivorous fishes (Scaridae and Acanthuridae) were the most abundant fishes, and the corallivorous fishes (mainly Chaetodontidae) were the scarcest. A negative effect of territorial herbivorous fishes on M. annularis transplants survival was observed, mainly early on the study. Fish foraging intensity was similar on transplanted and native colonies, but differed among coral species, being lowest on D. labyrinthiformis. Fast macroalgal growth inside full-cages due to reduced fish grazing was observed. This caused partial bleaching and partial mortality in some colonies, mainly of P. astreoides. No significant difference in healthy tissue percentages among full-cage and uncaged colonies on M. annularis and D. labyrinthiformis was found, while in P. astreoides there were evident differences. The results indicate a damselfish negative effect on transplants survival early on the study, which can change depending on the fish and coral species involved. Results also indicate a fish grazing positive effect, caused by the reduction of coral-algae competition pressure, mainly on P. astreoides. Parrotfishes seem to affect corals survival both negatively through direct biting, and positively by controlling algal growth. Overall, coral transplant success was almost unaffected by fish foraging activity although several differences among coral species were obvious in relation to colony shape. Additionally, the interaction among herbivorous fish grazing and coral-algae competition balance appear important in determining transplant survival. Rev. Biol. Trop. 55 (3-4): 825-837. Epub 2007 December, 28.

Para investigar el efecto de los peces herbívoros y coralívoros en la supervivencia de colonias trasplantadas de Montastraea annularis, Diploria labyrinthiformis y Porites astreoides se encerraron colonias trasplantadas y nativas en jaulas y se compararon con colonias libres (control), mientras los efectos del encierro fueron evaluados con un tratamiento de techos. Para saber si el estrés debido al trasplante aumentó la vulnerabilidad de los corales a la depredación por peces, se comparó la intensidad de forrajeo por peces entre colonias trasplantadas y nativas. Se realizaron censos visuales para determinar las densidades de las poblaciones de peces herbívoros y coralívoros en la zona de trasplante. Los peces herbívoros móviles (Scaridae y Acanthuridae) fueron los más abundantes, los peces coralívoros (principalmente Chaetodontidae) fueron los más escasos. Se observó un efecto negativo de los peces herbívoros territoriales en la supervivencia de los trasplantes de M. annularis, principalmente al inicio del estudio. La presión de forrajeo fue similar en colonias trasplantadas y nativas, pero fue diferente entre especies, siendo D. labyrinthiformis la menos depredada. En los tratamientos de colonias protegidas en jaulas se observó un crecimiento acelerado de macroalgas debido a la reducción del forrajeo por peces herbívoros. Esto causó blanqueamiento parcial y mortalidad parcial en algunas colonias, principalmente de P. astreoides. En M. annularis y D. labyrinthiformis no se observaron diferencias significativas en los porcentajes de tejido sano de las colonias entre los tratamientos de jaulas y de control, pero sí en P. astreoides. Los resultados sugieren un efecto negativo de los peces herbívoros territoriales en la supervivencia de las colonias durante los primeros días del trasplante; este efecto puede variar dependiendo de las especies de peces y corales involucradas. Los resultados también indican un efecto positivo del forrajeo por peces, debido a la reducción de la presión competitiva alga-coral, sobretodo en P. astreoides. Los scáridos parecen afectar la supervivencia de los corales tanto de manera negativa, al morder en el tejido vivo, como de manera positiva al controlar el crecimiento de las macroalgas. En general, el éxito del transplante de coral fue poco afectado por la actividad de forrajeo de los peces, aunque algunas diferencias entre las especies de coral parecen estar relacionadas con la forma de las colonias. La interacción entre el forrajeo de peces hervíboros y el balance competitivo alga-coral puede ser importante en determinar la supervivencia al transplante.

[Effect of herbivorous and corallivorous fishes on the survival of transplanted corals in the Colombian Caribbean]. / Efecto de la herbivoría y coralivoría por peces en la supervivencia de corales trasplantados en el Caribe colombiano.

To examine the effects of herbivorous and corallivorous fishes on the survival of transplanted colonies of Montastraea annularis, Diploria labyrinthiformis and Porites astreoides, both transplanted and native colonies were full-cage enclosed and compared to open (uncaged) colonies, while caging effects were assessed with a partial-cage (roof treatment). To evaluate if transplant stress increased the corals availability to fish predation, comparisons of fish foraging intensity among transplanted versus native colonies were made. To determine the density of herbivorous and corallivorous fishes on the transplants area visual censuses were made. The transient herbivorous fishes (Scaridae and Acanthuridae) were the most abundant fishes, and the corallivorous fishes (mainly Chaetodontidae) were the scarcest. A negative effect of territorial herbivorous fishes on M annularis transplants survival was observed, mainly early on the study. Fish foraging intensity was similar on transplanted and native colonies, but differed among coral species, being lowest on D. labyrinthiformis. Fast macroalgal growth inside full-cages due to reduced fish grazing was observed. This caused partial bleaching and partial mortality in some colonies, mainly of P. astreoides. No significant difference in healthy tissue percentages among full-cage and uncaged colonies on M. annularis and D. labyrinthiformis was found, while in P. astreoides there were evilent differences. The results indicate a damselfish negative effect on transplants survival early on the study, which can change depending on the fish and coral species involved. Results also indicate a fish grazing positive effect, caused by the reduction of coral-algae competition pressure, mainly on P. astreoides. Parrotfishes seem to affect corals survival both negatively through direct biting, and positively by controlling algal growth. Overall, coral transplant success was almost unaffected by fish foraging activity although several differences among coral species were obvious in relation to colony shape. Additionally, the interaction among herbivorous fish grazing and coral-algae competition balance appear important in determining transplant survival.

The mid-domain effect revisited.

We revisit the proposition that boundary constraints on species' ranges cause species richness gradients (the mid-domain effect [MDE] hypothesis). In the absence of environmental gradients, species should not retain their observed range sizes as assumed by MDE models. Debate remains regarding the definition of domain limits, valid predictions for testing the models, and their statistical assessment. Empirical support for the MDE is varied but often weak, suggesting that geometric constraints on species' ranges do not provide a general explanation for richness gradients. Criticism of MDE model assumptions does not, however, imply opposition to the use of null models in ecology.