Soundscapes from a Tropical Eastern Pacific reef and a Caribbean Sea reef

Underwater soundscapes vary due to the abiotic and biological components of the habitat. We quantitatively characterized the acoustic environments of two coral reef habitats, one in the Tropical Eastern Pacific (Panama) and one in the Caribbean (Florida Keys), over 2-day recording durations in July 2011. We examined the frequency distribution, temporal variability, and biological patterns of sound production and found clear differences. The Pacific reef exhibited clear biological patterns and high temporal variability, such as the onset of snapping shrimp noise at night, as well as a 400-Hz daytime band likely produced by damselfish. In contrast, the Caribbean reef had high sound levels in the lowest frequencies, but lacked clear temporal patterns. We suggest that acoustic measures are an important element to include in reef monitoring programs, as the acoustic environment plays an important role in the ecology of reef organisms at multiple life-history stages.     

Spatial and temporal patterns in the coral assemblage at Clipperton Atoll: a sentinel reef in the Eastern Tropical Pacific

Coral Reefs - Isolated coral reef habitats are unique systems to study the natural dynamics of coral traits and their natural acclimatization, adaptation, and recovery from global-scale stressors...     

Population genetics of an ecosystem-defining reef coral Pocillopora damicornis in the Tropical Eastern Pacific

Background

Coral reefs in the Tropical Eastern Pacific (TEP) are amongst the most peripheral and geographically isolated in the world. This isolation has shaped the biology of TEP organisms and lead to the formation of numerous endemic species. For example, the coral Pocillopora damicornis is a minor reef-builder elsewhere in the Indo-West Pacific, but is the dominant reef-building coral in the TEP, where it forms large, mono-specific stands, covering many hectares of reef. Moreover, TEP P. damicornis reproduces by broadcast spawning, while it broods mostly parthenogenetic larvae throughout the rest of the Indo-West Pacific. Population genetic surveys for P. damicornis from across its Indo-Pacific range indicate that gene flow (i.e. larval dispersal) is generally limited over hundreds of kilometers or less. Little is known about the population genetic structure and the dispersal potential of P. damicornis in the TEP.

Methodology

Using multilocus microsatellite data, we analyzed the population structure of TEP P. damicornis among and within nine reefs and test for significant genetic structure across three geographically and ecologically distinct regions in Panama.

Principal Findings/Conclusions

We detected significant levels of population genetic structure (global R_ST = 0.162), indicating restricted gene flow (i.e. larvae dispersal), both among the three regions (R_RT = 0.081) as well as within regions (R_SR = 0.089). Limited gene flow across a distinct environmental cline, like the regional upwelling gradient in Panama, indicates a significant potential for differential adaptation and population differentiation. Individual reefs were characterized by unexpectedly high genet diversity (avg. 94%), relatively high inbreeding coefficients (global F_IS = 0.183), and localized spatial genetic structure among individuals (i.e. unique genets) over 10 m intervals. These findings suggest that gene flow is limited in TEP P. damicornis populations, particularly among regions, but even over meter scales within populations.     

Bacterioplankton nutrient metabolism in the Eastern Tropical North Pacific

Bacterioplankton nutrient metabolism in the Eastern Tropical North Pacific (ETNP) was assessed using specific activities of intracellular nitrogen (N) assimilation enzymes and hydrolytic ectoenzymes during amendment experiments, mesocosms, and diel studies of in situ rates. Glutamine synthetase (GS) and assimilatory nitrate reductase (ANR) were used to investigate N bioavailability, alkaline phosphatase (AP) to assess phosphorous (P) bioavailability and β-glucosidase (β-Glu) to detect shifts in the use of labile dissolved organic carbon (DOC). Conditions regulating activity of each enzyme were tested using incubations of < 0.6 mm size-fractionated seawater amended with different combinations of N, P, and DOC as glucose. Overall, N-deficiency was indicated by pronounced growth stimulation and repression of GS and ANR activity in incubations amended with dissolved free amino acid and ammonium. Phosphate and glucose amendments produced little or no growth stimulation, but did influence activity of all enzymes measured. Enzyme activities of bacterioplankton in mesocosms of whole plankton indicated enhanced N-deficiency and glucoside hydrolysis when the plankton community was released from any P-deficiency. Spatially, enzyme activity of bacterioplankton during two diel studies (at one slope and one open-ocean station) suggested greater N-deficiency at surface depths than within the chlorophyll maximum where activity of AP and b-Glu was often greatest. There was also greater GS and ANR activity at the open-ocean station, which had lower concentrations of dissolved inorganic N (DIN) relative to soluble reactive P (SRP), than along the continental slope of Mexico. These data suggest that bacterioplankton in surface waters of the ETNP require a large flux of DOC to drive N-deficiency; whereas, bacterioplankton deeper in the chlorophyll maximum depend on hydrolysis of complex DOC and DOP to meet their carbon demand in the presence of elevated nutrients with a low DIN:SRP ratio.     

Diet of the coral hawkfish Cirrhitichthys oxycephalus (Family: Cirrhitidae) in a fringing coral reef of the Eastern Tropical Pacific

Coral Reefs - Hawkfishes are small demersal reef predators. Although their association with the coral substrate has been widely documented for some species, information regarding their feeding...     

Seasonal variations in the diversity,abundance, and composition of species in an estuarine fish community in the Tropical Eastern Pacific,Mexico

The ichthyofauna of the Chacahua Lagoon in the western Oaxaca State of Mexico was sampled every 2 months, using a trawl net over seven sampling cycles. The estuary mouth closed in late January, generating hypersaline conditions in the system. A total of 33 species belonging to 20 families were recorded; most of them marine species, showing tropical and subtropical affinities. The most abundant species were Diapterus peruvianus, Centropomus robalito, Anchovia macrolepidota, Lile stolifera, and Lutjanus novemfasciatus. Total fish abundance and species richness were not significantly affected by the mouth closing, and this was related to the presence of a permanently open entrance channel with an adjacent lagoon, which allowed easy exchange of fish between these two systems. Canonical correspondence analysis (CCA) revealed that salinity and dissolved oxygen were the most important environmental variables in determining the observed variability in fish community composition. Two fish groups were evident: the fish assemblage of the low-salinity period (open-mouth phase), in which Eucinostomus currani, Sciades guatemalensis, Centropomus armatus, Citharichthys stigmaeus, and Caranx caninus constituted the majority of the catch; and the fish assemblage of the high-salinity period (closed-mouth phase), with A. macrolepidota, L. stolifera, and Harengula thrissina as the most abundant species. Multivariate analyses showed differences in the composition of the fish community between both periods. Other species, such as the permanent residents D. peruvianus and C. robalito, which showed the widest range in tolerance of ambient salinity, were caught during both periods. Seasonal succession of fish populations may be related to differences in life cycle and tolerance of the environment among those species adapting to ecological conditions.     

Different speciation processes in a cryptobenthic reef fish from the Western Tropical Atlantic

Hydrobiologia - Cladocerans feed on a variety of phytoplankton food sources, which are variable across space and time. Different phytoplankton groups represent different nutritional quality to...     

Spatial predictability of juvenile fish species richness and abundance in a coral reef environment

Juvenile reef fish communities represent an essential component of coral reef ecosystems in the current focus of fish population dynamics and coral reef resilience. Juvenile fish survival depends on habitat characteristics and is, following settlement, the first determinant of the number of individuals within adult populations. The goal of this study was to provide methods for mapping juvenile fish species richness and abundance into spatial domains suitable for micro and meso-scale analysis and management decisions. Generalized Linear Models predicting juvenile fish species richness and abundance were developed according to spatial and temporal environmental variables measured from 10 m up to 10 km in the southwest lagoon of New Caledonia. The statistical model was further spatially generalized using a 1.5-m resolution, independently created, remotely sensed, habitat map. This procedure revealed that : (1) spatial factors at 10 to 100-m scale explained up to 71% of variability in juvenile species richness, (2) a small improvement (75%) was gained when a combination of environmental variables at different spatial and temporal scales was used and (3) the coupling of remotely sensed data, geographical information system tools and point-based ecological data showed that the highest species richness and abundance were predicted along a narrow margin overlapping the coral reef flat and adjacent seagrass beds. Spatially explicit models of species distribution may be relevant for the management of reef communities when strong relationships exist between faunistic and environmental variables and when models are built at appropriate scales.     

Coral disease outbreak at Navassa,a remote Caribbean island

In November 2004, a high prevalence of coral disease was observed at several sites around Navassa, an uninhabited Caribbean island between Haiti and Jamaica. At least fifteen mounding and foliaceous scleractinian species were affected with ‘white disease’ signs. Coral disease incidence was observed to be absent in quantitative surveys in 2002, but in 2004 average prevalence (i.e., % of colonies) of active disease ranged up to 15% and an additional 19% prevalence of colonies with patterns of recent mortality consistent with disease. Large and/or Montastraea spp. colonies were disproportionately affected and the anticipated loss of these large, reef-building colonies will impact coral community structure. One or more potential factors may influence the initiation and persistence of disease outbreak conditions at Navassa including recent hurricane disturbance, regional patterns of increasing disease impact in deep or remote Caribbean reefs, or vectoring of disease by the corallivorous worm, Hermodice carunculata.     

Extraordinary aggressive behavior from the giant coral reef fish, Bolbometopon muricatum, in a remote marine reserve

Human impacts to terrestrial and marine communities are widespread and typically begin with the local extirpation of large-bodied animals. In the marine environment, few pristine areas relatively free of human impact remain to provide baselines of ecosystem function and goals for restoration efforts. Recent comparisons of remote and/or protected coral reefs versus impacted sites suggest remote systems are dominated by apex predators, yet in these systems the ecological role of non-predatory, large-bodied, highly vulnerable species such as the giant bumphead parrotfish (Bolbometopon muricatum) has received less attention. Overfishing of Bolbometopon has lead to precipitous declines in population density and avoidance of humans throughout its range, contributing to its status as a candidate species under the U. S. Endangered Species Act and limiting opportunities to study unexploited populations. Here we show that extraordinary ecological processes, such as violent headbutting contests by the world's largest parrotfish, can be revealed by studying unexploited ecosystems, such as the coral reefs of Wake Atoll where we studied an abundant population of Bolbometopon. Bolbometopon is among the largest of coral reef fishes and is a well known, charismatic species, yet to our knowledge, no scientific documentation of ritualized headbutting exists for marine fishes. Our observations of aggressive headbutting by Bolbometopon underscore that remote locations and marine reserves, by inhibiting negative responses to human observers and by allowing the persistence of historical conditions, can provide valuable opportunities to study ecosystems in their natural state, thereby facilitating the discovery, conservation, and interpretation of a range of sometimes remarkable behavioral and ecological processes.     

Taking a detour: invasion of an octocoral into the Tropical Eastern Pacific

The tropical snowflake octocoral Carijoa riisei, which is thought to be native to the Indo-Pacific biogeographical region, has been increasingly reported from the Colombian Tropical Eastern Pacific (TEP) over the past two decades. Massive mortalities of native octocorals, particularly in Pacifigorgia spp. and Muricea spp., were observed due to C. riisei overgrowth. However, the area of origin of TEP C. riisei remains unknown and its potential invasive status has not been addressed yet. We evaluated geographical scenarios for the colonization of the Colombian TEP by conducting phylogeographical analyses based on nuclear and mitochondrial sequences of 306 individual specimens from across the species’ (native/non-native) range and applying hypothesis-specific operational criteria. Additionally, we assessed whether C. riisei has to be considered an invasive species based on the previously proposed ‘unified framework for biological invasions’. Our results showed relatively high genetic differentiation between Colombian TEP populations, on the one side, and Indo-Pacific and Hawaiian populations, on the other side. In contrast, we could not identify genetic differentiation and significant isolation by distance (IBD) between Colombian TEP and Tropical Atlantic populations. C. riisei might have been introduced from the Atlantic into the Colombian TEP, possibly via the Panama Canal. Based on the criteria of the ‘unified framework for biological invasions’, we also conclude that this octocoral constitutes an invasive species. Our study may serve as a basis for establishing strategies to protect native species from one of the very few invasive coral species worldwide.     

The influence of multiple factors upon reef fish abundance and species richness in a tropical coral complex

The present study was conducted on Tamandaré reefs, northeast Brazil and aimed to analyse the importance of different factors (e.g. tourism activity, fishing activity, coral abundance and algal abundance) on reef fish abundance and species richness. Two distinct reef areas (A ver o mar and Caieiras) with different levels of influence were studied. A total of 8239 reef fish individuals were registered, including 59 species. Site 1 (A ver o mar) presented higher reef fish abundance and richness, with dominance of roving herbivores (29.9 %) and mobile invertebrate feeders (28.7 %). In contrast, at Site 2 (Caieiras) territorial herbivores (40.9 %) predominated, followed by mobile invertebrate feeders (24.6 %). Concerning the benthic community, at Site 1 macroalgae were recorded as the main category (49.3 %); however, Site 2 was dominated by calcareous algae (36.0 %). The most important variable explaining more than 90 % of variance on reef fish abundance and species richness was macroalgae abundance, followed by fishing activity. Phase shifts on coral reefs are evident, resulting in the replacement of coral by macroalgae and greatly influencing reef fish communities. In this context, it is important to understand the burden of the factors that affect reef fish communities and, therefore, influence the extinction vulnerability of coral reef fishes.     

Marine reserves and reproductive biomass: a case study of a heavily targeted reef fish

Recruitment overfishing (the reduction of a spawning stock past a point at which the stock can no longer replenish itself) is a common problem which can lead to a rapid and irreversible fishery collapse. Averting this disaster requires maintaining a sufficient spawning population to buffer stochastic fluctuations in recruitment of heavily harvested stocks. Optimal strategies for managing spawner biomass are well developed for temperate systems, yet remain uncertain for tropical fisheries, where the danger of collapse from recruitment overfishing looms largest. In this study, we explored empirically and through modeling, the role of marine reserves in maximizing spawner biomass of a heavily exploited reef fish, Lethrinus harak around Guam, Micronesia. On average, spawner biomass was 16 times higher inside the reserves compared with adjacent fished sites. Adult density and habitat-specific mean fish size were also significantly greater. We used these data in an age-structured population model to explore the effect of several management scenarios on L. harak demography. Under minimum-size limits, unlimited extraction and all rotational-closure scenarios, the model predicts that preferential mortality of larger and older fish prompt dramatic declines in spawner biomass and the proportion of male fish, as well as considerable declines in total abundance. For rotational closures this occurred because of the mismatch between the scales of recovery and extraction. Our results highlight how alternative management scenarios fall short in comparison to marine reserves in preserving reproductively viable fish populations on coral reefs.     

Low functional richness and redundancy of a predator assemblage in native forest fragments of Chiloe island, Chile

1. Changes in land use and habitat fragmentation are major drivers of global change, and studying their effects on biodiversity constitutes a major research programme. However, biodiversity is a multifaceted concept, with a functional component linking species richness to ecosystem function. Currently, the interaction between functional and taxonomic components of biodiversity under realistic scenarios of habitat degradation is poorly understood. 2. The expected functional richness (FR)-species richness relationship (FRSR) is positive, and attenuated for functional redundancy in species-rich assemblages. Further, environmental filters are expected to flatten that association by sorting species with similar traits. Thus, analysing FRSR can inform about the response of biodiversity to environmental gradients and habitat fragmentation, and its expected functional consequences. 3. Top predators affect ecosystem functioning through prey consumption and are particularly vulnerable to changes in land use and habitat fragmentation, being good indicators of ecosystem health and suitable models for assessing the effects of habitat fragmentation on their FR. 4. Thus, this study analyses the functional redundancy of a vertebrate predator assemblage at temperate forest fragments in a rural landscape of Chiloe island (Chile), testing the existence of environmental filters by contrasting an empirically derived FRSR against those predicted from null models, and testing the association between biodiversity components and the structure of forest fragments. 5. Overall, contrasts against null models indicate that regional factors determine low levels of FR and redundancy for the vertebrate predator assemblage studied, while recorded linear FRSR indicates proportional responses of the two biodiversity components to the structure of forest fragments. Further, most species were positively associated with either fragment size or shape complexity, which are highly correlated. This, and the absence of ecological filters at the single-fragment scale, rendered taxonomically and functionally richer predator assemblages at large complex-shaped fragments. 6. These results predict strong effects of deforestation on both components of biodiversity, potentially affecting the functioning of remnants of native temperate forest ecosystems. Thus, the present study assesses general responses of functional and taxonomic components of biodiversity to a specific human-driven process.     

Isolation by distance and vicariance drive genetic structure of a coral reef fish in the Pacific Ocean

We studied the genetic diversity of a coral reef fish species to investigate the origin of the differentiation. A total of 727 Acanthurus triostegus collected from 15 locations throughout the Pacific were analyzed for 20 polymorphic loci. The genetic structure showed limited internal disequilibrium within each population; 3.7% of the loci showed significant Hardy-Weinberg disequilibrium, mostly associated with Adh*, and we subsequently removed this locus from further analysis of geographic pattern. The genetic structure of A. triostegus throughout the tropical Pacific Ocean revealed a strong geographic pattern. Overall, there was significant population differentiation (multilocus F(ST) = 0.199), which was geographically structured according to bootstraps of neighbor-joining analysis on Nei's unbiased genetic distances and AMOVA analysis. The genetic structure revealed five geographic groups in the Pacific Ocean: western Pacific (Guam, Philippines, Palau, and Great Barrier Reef); central Pacific (Solomons, New Caledonia, and Fiji); and three groups made up of the eastern populations, namely Hawaiian Archipelago (north), Marquesas (equatorial), and southern French Polynesia (south) that incorporates Clipperton Island located in the northeastern Pacific. In addition, heterozygosity values were found to be geographically structured with higher values grouped within Polynesian and Clipperton populations, which exhibited lower population size. Finally, the genetic differentiation (F(ST)) was significantly correlated with geographic distance when populations from the Hawaiian and Marquesas archipelagos were separated from all the other locations. These results show that patterns of differentiation vary within the same species according to the spatial scale, with one group probably issued from vicariance, whereas the other followed a pattern of isolation by distance. The geographic pattern for A. triostegus emphasizes the diversity of the evolutionary processes that lead to the present genetic structure with some being more influential in certain areas or according to a particular spatial scale.     

Vertical distribution and phylogenetic composition of bacteria in the Eastern Tropical North Pacific Ocean

The vertical community structure of bacteria along a depth profile in the Eastern Tropical North Pacific Ocean (13 degrees N, 104 degrees W) was studied by flow cytometry measurement and 16S rRNA gene clone libraries analysis. Picoeukaryotes and Synechococcus peaked at 30 m and decreased sharply below 50 m, while Prochlorococcus peaked at both 30 and 100 m layers and disappeared below 200 m. Heterotrophic bacteria peaked above shallow thermocline and decreased along the depth profile. Sequences of total 322 clones from four clone libraries (10, 100, 1000, and 3000 m) clustered into nine major lineages. gamma-Proteobacteria dominated all the depths and occupied almost the whole bacterial community at the 3000 m. alpha-Proteobacteria was abundant throughout the water column except near the sea bottom, and delta-Proteobacteria peaked at the 1000 m depth. Cyanobacteria were primarily limited to the photic zone, and the genetic diversity of Prochlorococcus showed a good correlation with niche adaptation. The appearance of the Cytophaga-Flexibacter-Bacteroides (CFB) group did not show a clear relationship with depth. Actinobacteria were found both in the photic zone and in deep water. Planctomyetes, Acidobacteria, and Verrucomicrobia were present as minor groups and more dominant in the deeper layers of water.     

The effect of patch reef size on fish species richness in a shallow coral reef shore zone where territorial herbivores are abundant

Small patch reefs can harbor many reef fishes because most fishes have a drifting larval phase to randomly disperse over patchy habitats. We examined the species–area relationship (SAR) of damselfish (Pomacentridae) assemblages over 84 small patch reefs (0.05–45.4 m²) using an enlarged section of a high-resolution color aerial photograph as a field map (1/2500) in a shallow coral reef shore zone (<2 m deep, 3.6 ha, Shiraho Reef, Ishigaki Island, Japan). This study confirmed that the logarithmic function is better than other functions (including the power function) to explain the SAR in this scale. Actual species richness (24) over the entire study site was much higher than the species richness (15.4) extrapolated from the regression line in semi-log space. Better estimates were obtained using random placement models and computer simulations. These results suggest that several small patch reefs are likely to have higher species richness than a single large reef of equivalent area at the study site. The total number of individuals of the four most abundant territorial herbivores increased almost linearly with patch reef area, but that of other species roughly increased with the square root of the area. While no territorial species were found in the smallest reefs, the large territorial herbivore, Hemiglyphidodon plagiometopon, was abundant and had negative effects on species richness in large reefs. Although the well-known single-large-or-several-small (SLOSS) debate has largely been settled, this dichotomy can be important in places where territorial herbivores do not occupy the smallest reefs.     

Biogeography of the Tropical Eastern Pacific: distribution and phylogeny of chaenopsid fishes

The Tropical Eastern Pacific Biogeographic Region (TEP) is delimited by steep thermal gradients to the north and south, by a wide expanse of open ocean (the East Pacific Barrier) to the west, and by the Central American land mass to the east. Four provinces within the TEP have been recognized based on the distribution of rocky shore fishes and marine invertebrates: the Cortez, Mexican, Panamic, and Galápagos Provinces. For rocky shore fishes, hypothesized barriers between these provinces are areas lacking rocky outcroppings, specifically the Central American Gap between the Panamic and Mexican Provinces, the Sinaloan Gap between the Mexican and Cortez Provinces, and the Pelagic Gap between the mainland and the Islas Galápagos. The occurrence of 33 chaenopsid fish species within these provinces, as well as other oceanic islands or archipelagos in the TEP (Isla de Malpelo, Isla del Coco, and Islas Revillagigedo) were tallied based on literature records and observations of museum specimens. Chaenopsid distributions within the TEP support these hypothesized provinces and their intervening gaps. Twenty‐one species (64% of the TEP chaenopsid fauna) are restricted to a single mainland province or one of the oceanic islands or archipelagos. Of the mainland provinces, the Cortez and Panamic exhibit similar levels of endemism (50%), but the Mexican Province has only one endemic (10%). Of the remaining chaenopsids in the Mexican Province, three are widespread, occurring in all three mainland provinces, four are shared only with the Cortez Province, and two are shared only with the Panamic Province. Within the TEP, the Pelagic Gap is the most effective (crossed by only 3 of 33 species adjacent to it), followed by the Central American Gap (crossed by 5 of 21 species), and the Sinaloan Gap (crossed by 7 of 17 species). Only one species, Chaenopsis alepidota, which is found off southern California and in the Cortez Province, crosses a barrier delimiting the TEP. Species‐level phylogenetic hypotheses for the Chaenopsidae imply exclusively allopatric speciation for these fishes in the TEP. Of the barriers delimiting the TEP, the most important in the recent evolution of chaenopsids is the Isthmian Barrier which is implicated in six speciation events. Within the TEP, the Central American Gap and Sinaloan Gap are each implicated in three speciation events, while the Pelagic Gap is implicated in three speciation events of island endemics from mainland populations and one inter‐island speciation event.     

Structure of reef fish communities in Catalinas Islands and Ocotal beach, North Pacific of Costa Rica

The reefs are heterogeneous systems that maintain a high diversity of organisms. Fish community structure varies within and among reefs, so it would be expected that reef structure and heterogeneity should affect fish communities inhabiting reefs. Four reef patches at Catalinas Islands (Sur, La Pared, Roca Sucia and Sombrero) and one in Ocotal beach (10 degrees 28'45" N; 85 degrees 52'35" W) were studied with visual censuses (July-December 2003). The structure and composition of fishes between Catalinas islands and Ocotal beach were different, and habitat structure and composition explain most of the variance founded. The presence of the fleshy algae Caulerpa sertularioides in Ocotal, and the corals Tubastrea coccinea and Pocillopora spp. at Catalinas Island explained the variability among sites and how it affected fish community structure and composition. The butterfly fish Johnrandallia nigrirostris, damselfish Microspathodon dorsalis, and surgeon fish Prionurus punctatus were directly correlated with the ahermatipic coral Tubastrea coccinea in Roca Sucia reef, while the angel fish Holacanthus passer was associated to reefs with a major percentage of rocky substrate. Other species such as the damselfish Abudefduf troschelli and Halichoeres dispilus were more abundant at Ocotal, where the algae C sertularioides dominated. The number and abundance of reef fishes was directly correlated with the rugosity index at the reefs of Roca Sucia and Ocotal, but not at reefs of La Pared and Sombrero.