Survival of hurricane-generated coral fragments and a disturbance model of reef calcification/growth rates

Summary Hurricane Gerta, with winds reaching 150 km/h, crossed the Belize barrier reef on September 18, 1978. Breakage and scouring of corals occurred in all zones of the reef to a depth of approximately 25 m. Survivorship of storm-generated coral fragments and detached colonies is strongly size dependent, conforming to the power function Y=4.44X^0.66 where Y is the percent of fragments and X is the fragment size. Forty-six percent of detached Acropora palmata branches, which are larger ( =37.6 cm long) than fragments of other species ( =16.7 cm long), survived. Overall, 39% of fragments and detached colonies survived. This high survivorship, which probably increased the total number of colonies present, and redistribution of corals may explain the rapid recovery of reefs from all but the severest hurricanes. Storms appear to prevent coral reefs from reaching a mature state characterized by low calcification and growth rates. Therefore, we suggest that long-term reef calcification and growth rates are highest on reefs periodically distrubed by storms of intermediate intensity.Smithsonian Tropical Research Institute, Box 2072, Balboa, Republic of Panama     

Stability of a coral reef fish community following a catastrophic storm

In January 1980, a severe 3 day storm struck the normally protected leeward coral reefs of Kona, Hawaii. Waves generated by the storm, which was estimated to be a once in 20–40 year occurrence, were in excess of 6 m and caused extensive reef destruction and shoreline alteration. Shallow nearshore areas were denuded of most bottom cover and marine life. Damage to corals was extensive with broken colonies of the coral Porites compressa occurring down to depths of 27 m. Pronounced algal blooms occurred in a clearly defined sequence subsequent to the storm. The patterns of both coral destruction and algal succession were similar to those described on other storm damaged reefs. Fish mortality directly attributable to the storm was slight and the few dead fishes noted were either surge zone or tide pool species. After the storm the shallow reef flat was devoid of resident fishes while deeper areas contained many fishes which had moved from shallower water. This habitat shift substantially reduced the immediate impact of the storm on the fish community. Despite considerable habitat destruction that resulted from the storm, there were no decreases in species or population abundances on five 25 m² quadrats monitored for 23 months before and 16 months after the storm. Similarly, the numbers of triggerfish sheltering within an area increased even though the storm reduced the number of available shelter holes. The shelter and space-related carrying capacity of these areas prior to the storm may therefore not have been reached. Recolonization of evacuated areas by fishes began shortly after the storm and within 16 months many areas had regained their prestorm appearances. Large numbers of individuals remained however, in their shifted locations.     

Biodiversity, host specificity, and dominance by eusocial species among sponge-dwelling alpheid shrimp on the Belize Barrier Reef

Alpheid shrimp represent an abundant and diverse, but poorly characterized, component of the cryptic biodiversity of coral reefs worldwide. Sponge‐inhabiting alpheids provide a promising model system for exploring patterns of cryptic reef biodiversity because their habitats (hosts) are discrete and qualitatively distinct units. We tabulated data from 14 years of collections at Carrie Bow Cay, Belize to quantify patterns of diversity, host specificity, and dominance among sponge‐dwelling shrimp (Synalpheus), with special attention to eusocial species. From > 600 sampled sponges of 17 species, we recognized at least 36 Synalpheus shrimp species. Of these, 15 (42%) were new to science. Species accumulation curves suggest that we have sampled most of the Synalpheus diversity at Carrie Bow Cay. Diversity of sponge‐dwelling Synalpheus was slightly higher in shallow water, probably because of greater habitat diversity, than in deep water. Host specificity was surprisingly high, with > 50% of all shrimp species found in only a single sponge species each, although some shrimp species used as many as six hosts. Cohabitation of individual sponges by multiple shrimp species was rarer than expected by chance, supporting previous distributional and behavioural evidence that competition for hosts is strong and moulds patterns of host association. The fauna of most well‐sampled sponge species was dominated, both in numbers of individuals and in frequency of occurrence, by eusocial species. Eusocial shrimp species also inhabited a significantly greater number of sponge species than did non‐social shrimp. Consequently, > 65% of shrimp in our quantitative samples belonged to the four eusocial species, and on a per‐species basis, eusocial species were 17 times as abundant as non‐social species. Our data suggest that the highly diverse sponge‐dwelling shrimp assemblage of the Belize Barrier Reef is structured by competition, and that eusociality has allowed a small number of species to dominate the sponge resource.     

Recurrent storm disturbance and recovery: a long-term study of coral communities in Hawaii

Damage caused by catastrophic storm waves and subsequent recovery was investigated with a series of 15 line transects on a reef off the west coast of Hawaii over a 20-year period (1973–1993). At the initiation of the study, four zones existed across the reef, each defined by a different dominant coral species. An intermediate intensity storm in 1974 caused a decrease in coral cover from 52% to 46% of bottom cover, while breakage and transport of fragments extended the depth of peak coral cover. In 1980, a Kona storm, which generated the largest storm surf on record, destroyed the coral zonation pattern almost entirely. Living coral was reduced from 46% to 10% of bottom cover, with greatest damage in the zones with highest cover. Twelve years later (1992), living coral cover increased to 15% of total bottom cover. Lack of significant correlation between increase of coral cover and initial cover indicated that recovery was from larval settlement, rather than regeneration of viable fragments. Extrapolation of recovery from 1980 to 1992 indicates that the pre-storm (1973) conditions would be reached in 40 years (exponential growth) to 70 years (linear growth). In 1993, following a hurricane and unusually large northwest swell, coral cover was once again reduced to 11%; recovery was set back to a level similar to that in 1980 following the Kona storm. In 1992 and 1993 no evidence of CaCO₃ accretion was observed on the reef bench. Rubble fragments created by storm stress were deposited on the reef slope with little subsequent lithification. While hurricane force waves may occur very infrequently in Hawaii, this source of stress appears to effectively limit Holocene reef growth in all areas except sheltered embayments. The pattern of damage and recovery of this coral ecosystem conforms to the intermediate disturbance hypothesis, in which storms of intermediate intensity produce either an increase or decrease in diversity and cover, depending on the timing of severe storms. On a global scale, timescales of damage and recovery cycles vary substantially depending on the frequency of severe disturbances, and the adaptive capabilities of dominant species.School of Ocean and Earth Science and Technology Contribution No. 3293     

Physical processes in an Indian Ocean atoll

 Detailed measurements of water levels, and tide and wave-induced currents were undertaken to examine physical processes and their relationship with morphology in the Cocos (Keeling) Islands, a medium sized atoll in the Indian Ocean. Results indicate that the atoll structure controls both lagoon circulation and the spatial pattern of energy distribution. Lagoon circulation is tide dominated (currents 16–31 cms^-1) with flushing (2–5 days) of the lagoon occurring through the deep leeward passages. Wave- and tide-driven unidirectional flows through shallow passages (26–65 cms^-1) are important mechanisms of ocean to lagoon water exchange and contribute up to 24% of the lagoon neap tide prism. Reef flats are dominated by wave energy (maximum velocity 140 cms^-1, east) with measurements of the attenuation of wave energy between reef flats and shallow lagoon (80–90%) conforming to measurements from fringing and barrier reefs. Spectral analysis shows that the characteristics of wave energy vary on different sectors of the atoll, with gravity wave energy dominating the east, and infragravity wave energy dominating the southern reef flat and passages. Wave setup at the reef crest is considered to be responsible for an identified 0.1 m higher water level in the southern as opposed to eastern and northern atoll, which promotes higher reef flat growth. Transmission of gravity waves across reef flats requires threshold water depths of 0.65 (east) and 0.70 m (south). The higher southern reef is an effective filter of gravity wave energy for most tidal elevations. Differences in the type and magnitude of physical processes within the atoll are discussed with relation to geomorphic development on Cocos. Accepted: 28 February 1998     

Wave-energy distribution and hurricane effects on Margarita Reef,southwestern Puerto Rico

Wave measurements at Margarita Reef in southwestern Puerto Rico show that wave height decreases as waves travel across the forereef and into the backreef. Wave spectra reveal the presence of two wave trains impinging on the reef during the study: trade-wind waves and locally generated seas. Significant wave height calculated from the spectra show an average reduction of 19.5% from 20- to 10-m isobaths and 26% from 20- to 5-m isobaths. The significant wave height decreases an average of 82% for waves traveling across the reef crest and into the backreef. Wave-energy reduction is 35% from 20- to 10-m isobaths and 45% from 20- to 5-m isobaths. Energy loss across the reef crest is 97% which translates into the formation of strong across-the-reef currents capable of moving coarse sediment. Refraction diagrams of waves impinging on the reef from the SE provide a display of wave energy distribution around the reef. The transmission coefficients calculated for trade-wind waves and locally generated seas have means of 18% and 39%, respectively. A wave height model with negligible energy dissipation, produces wave height estimates that are, in general, within the ±15% error bands. Results of wave-energy changes from this study were applied to waves representative of hurricane conditions at the reef. Aerial photographs of the reef before and after the passage of hurricanes were compared to assess the reef changes. Changes observed in the photographs are interpreted as products of sediment transport by hurricane-generated waves. The patterns of change agree with the refraction diagrams suggesting that waves were the main agents of change at margarita Reef during severe storms. Correspondence to: A. Lugo-Fernández}     

Wave-current interactions on a shallow reef (Nicaragua,Central America)

Measurements of wave height and currents associated with normal trade-wind conditions have been made on a linear reef that parallels the northern and northeastern coast of Great Corn Island, eastern shelf of Nicaragua, Central America. Analyses indicate that waves breaking over the reef crest generate lagoonward flow normal to the reef. Average reef-normal flow was in the range of 10 to 20 cm/s; however, individual wave surges reached values of up to 180 cm/s. The strength of the over-the-reef flow is modulated by the tide. Lagoon currents are weak (2–5 cm/s) and change direction with the tide as the lagoon fills and drains. Long-period oscillations in water level (30 s to 20 min) and in the current were observed, and may be important in transporting fine-grained sediments out of the reef-lagoon system. Strong, short-duration surge currents ( <5 s) transport coarse sediment from the breaker zone to the seaward margin of the backreef lagoon.     

The impacts of tourism on coral reef conservation awareness and support in coastal communities in Belize

Marine recreational tourism is one of a number of threats to the Belize Barrier Reef but, conversely, represents both a motivation and source of resources for its conservation. The growth of tourism in Belize has resulted in the fact that many coastal communities are in varying stages of a socio-economic shift from dependence on fishing to dependence on tourism. In a nation becoming increasingly dependent on the health of its coral reef ecosystems for economic prosperity, a shift from extractive uses to their preservation is both necessary and logical. Through examining local perception data in five coastal communities in Belize, each attracting different levels of coral reef related tourism, this analysis is intended to explore the relationship between tourism development and local coral reef conservation awareness and support. The results of the analysis show a positive correlation between tourism development and coral reef conservation awareness and support in the study communities. The results also show a positive correlation between tourism development and local perceptions of quality of life, a trend that is most likely the source of the observed relationship between tourism and conservation. The study concludes that, because the observed relationship may be dependent on continued benefits from tourism as opposed to a perceived crisis in coral reef health, Belize must pay close attention to tourism impacts in the future. Failure to do this could result in a destructive feedback loop that would contribute to the degradation of the reef and, ultimately, Belize’s diminished competitiveness in the ecotourism market.

A quick and cost-effective method for modelling water renewal in shallow coral reef lagoons

Water renewal exerts a preponderant role in eutrophication, yet few hydrodynamic indicators exist for performing quick and cost-effective assessments of ecosystem vulnerability. Using field data, we closed the water budget of a shallow coral reef lagoon recently exposed to high levels of nutrient loading that triggered green tides. Then, we tested the relevance of modelling flushing-time, a proxy of water renewal, from oceanic and atmospheric open access data. Water inflows in the lagoon were mainly driven by waves breaking on exposed reefs, but tide and wind also influenced water renewal during low-wave periods. Modelling flushing-time as a function of the wave features (significant wave height, direction, and period), tide, and wind direction provided the most convincing model, with greater contribution of wave height, and adequately reproduced observations for an independent dataset. Using this model to hindcast flushing-time over the period 2000–2019 highlighted that green tides that recently struck the area in January 2018 and June 2019 followed periods of slow water renewal, which therefore contributed to amplify the blooms. The analysis also demonstrated that renewal events even slower than those recorded in 2018–2019 are frequent in this lagoon, which highlights the high vulnerability of this UNESCO World Heritage Site to other pulses of nutrient loading. Since the methodology developed in this study can be easily applied to many other coastal barrier and fringing reefs, it offers a promising perspective for quick and cost-effective assessments of coral reef vulnerability to eutrophication and other ecosystem crises magnified by slow water renewal.

     

Biodiversity and Association of Dinoflagellates in Coral Reef Rubble,Carrie Bow Cay,Belize

The species diversity and distribution of benthic dinoflagellates are illustrated from the back reef sand habitats at Carrie Bow Cay. Sand appears an ideal environment for nurturing a variety of species. Sand supported blooms of toxic, nontoxic, and parasitic assemblages of dinoflagellates. Morphology of dinoflagellates is illustrated in SEM and LM pictures; including the life cycle of a parasitic dinoflagellate's vegetative stage, sporogenetic stages, and the morphology of the feeding organelle. The feeding organelle of the primary dinoflagellate cysts is a hold fast and a peduncle‐like infestation tube, a ‘sucker organelle’, that inserts itself into copepod eggs. The parasitic dinoflagellate continues feeding on crustacean eggs since it is the only food source during vegetative cell division within the cyst. This is the first observation of the presence of parasitic dinoflagellates in shallow coral reef water. The study attempts to provide new knowledge on dinoflagellate associations and morphology of sand‐welling species in the microscopic food web of shallow warm tropical waters. Even, sand‐inhabiting invertebrates are not exempt from parasitic dinoflagellates.     

Wave and tidal flushing in a near-equatorial mesotidal atoll

Most of the atolls found worldwide are under microtidal regimes, and their circulation mechanisms are widely documented and well known. Here, we describe the flushing mechanisms of a small-sized mesotidal atoll, based on water-level, wave and current data obtained during two different periods (total of 60 d). Rocas is the only atoll in the South Atlantic Ocean and is built primarily of coralline algae. Two reef passages connect the atoll lagoon to the ocean. Synchronous current profilers were deployed at the two reef passages, one inside and one outside the atoll, to characterize the influence of tides and waves on the circulation. Results showed that wind waves drove a setup on the exposed side of the atoll and that currents were predominately downwind, causing outflow at both reef passages. Waves breaking on the windward side supplied water to the atoll causing the lagoon water level to rise above ocean water level, driving the outflow. However, unlike microtidal atolls, at Rocas Atoll the water level drops significantly below the reef rim during low tides. This causes the reef rim to act as a barrier to water pumping into the lagoon by waves, resulting in periodic activation of the wave pumping mechanism throughout a tidal cycle. As result, inflow occurs in the wider passage during 27% of each tidal cycle, starting at low tides and reversing direction during mid-flood tide when the water level exceeded approximately 1.6 m (while overtopping the atoll’s rim). Our findings show that tides play a direct role in driving circulation on a mesotidal atoll, not only by modulating wave setup but also by determining the duration of wave pumping into the lagoon.

     

Pleistocene facies of Belize barrier and atoll reefs

The knowledge of Pleistocene reef facies of Belize, Central America, is largely limited to outcrops in the northernmost part of the country. Otherwise, Pleistocene limestone, which forms the basement of the modern barrier and atoll reefs, occurs in the subsurface and is to a major extent unstudied. Based on the study of 40 m of core from 25 rotary core holes collected on central and southern Belize barrier and on atoll reefs, five Pleistocene reef facies are distinguished in the present study. They include (1) Acropora palmata grainstone, (2) Acropora cervicornis grainstone, (3) biogenic grainstone, (4) mollusk packstone, and (5) mollusk-foram wackestone. Facies 1 and 3 occur on marginal reefs, facies 2 is found on marginal and lagoonal reefs, and facies 4 and 5 mark lagoon shoals and lagoons, respectively. Most of the facies have equivalents in the Pleistocene of the wider Caribbean and also in the modern of the study area. Diagenetic features include dissolution, caliche formation, laminated blocky low-magnesium-calcite and dogtooth spars. Age data from Pleistocene corals obtained during earlier studies are discussed, and indicate deposition during marine isotope stage 5, between 140–80 ka bp.     

Pleistocene paleogeography and sea levels on the Cayman Islands,British West Indies

The sea level high, 120 000 to 130 000 years ago, did not lead to the complete inundation of Grand Cayman. Deposition associated with that highstand, which produced the limestones of the Ironshore Formation, occurred in small embayments on the south, east, and north coasts and in a large lagoon that covered the central and western parts of Grand Cayman. Limestones in the western part of that lagoon contain tidal (?) channels and large scour surfaces which resulted from storm activity. Overlying the lagoonal deposits are limestones that were deposited on a high-energy, prograding beach. These successions occur 2 to 7 m above present day sea level. Evidence obtained from wave-cut notches and the sedimentology of the Ironshore Formation on each of the Cayman Islands indicates that the late Pleistocene highstand was about 6 m above present day sea level. By comparing the present day elevations of the features used to determine this position, it is evident that Grand Cayman, Cayman Brac, and Little Cayman have not undergone independent vertical movement over the last 125 000 years.     

The dynamics of benthic microbial communities at Davies Reef,central Great Barrier Reef

The dynamics of benthic microbial communities were examined within different functional zones (reef crest, reef flat, lagoon) of Davies Reef, central Great Barrier Reef, in winter. Bacterial numbers did not change significantly across the reef with a mean abundance of 1.3 (±0.6) x 10⁹ cells g^-1 DW of sediment. Bacterial production, measured as thymidine incorporation into DNA, ranged from 1.2 (±0.2) to 11.6 (±1.5) mg C m^-2h^-1 across the reef and was significantly lower in a reef crest basin than in the other zones. Bacterial growth rates () across the reef (0.05 to 0.33 g^-1) correlated only with sediment organic carbon and nitrogen. Protozoan and meiofaunal densities varied by an order of magnitude across the reef and correlated with one or more sediment variables but not with bacterial numbers or growth rates. Nutrient flux rates were similar to those found at other reefs in the central and southern Great Barrier Reef and are significantly lower than rates measured in temperate sand communities. In the front lagoon, bioturbation and feeding acitivity by thalassinid shrimps (Callianassa spp.) negatively influenced microbial and meiofaunal communities with a net import of organic matter necessary to support the estimated rates of bacterial productivity. In lagoonal areas not colonized by shrimps, primary productivity (400–1100 mg C m^-2d^-1) from algal mats was sufficient to support bacterial growth. It is suggested that deposit-feeding macrobenthos such as thalassinid crustaceans play a major role in the tructuring and functioning of lower trophic groups (bacteria, microalgae, protozoa, meiofauna) in coral reef sedments, particularly in laggons.     

The Lagoon at Caroline/Millennium Atoll,Republic of Kiribati: Natural History of a Nearly Pristine Ecosystem

A series of surveys were carried out to characterize the physical and biological parameters of the Millennium Atoll lagoon during a research expedition in April of 2009. Millennium is a remote coral atoll in the Central Pacific belonging to the Republic of Kiribati, and a member of the Southern Line Islands chain. The atoll is among the few remaining coral reef ecosystems that are relatively pristine. The lagoon is highly enclosed, and was characterized by reticulate patch and line reefs throughout the center of the lagoon as well as perimeter reefs around the rim of the atoll. The depth reached a maximum of 33.3 m in the central region of the lagoon, and averaged between 8.8 and 13.7 m in most of the pools. The deepest areas were found to harbor large platforms of Favia matthaii, which presumably provided a base upon which the dominant corals (Acropora spp.) grew to form the reticulate reef structure. The benthic algal communities consisted mainly of crustose coralline algae (CCA), microfilamentous turf algae and isolated patches of Halimeda spp. and Caulerpa spp. Fish species richness in the lagoon was half of that observed on the adjacent fore reef. The lagoon is likely an important nursery habitat for a number of important fisheries species including the blacktip reef shark and Napoleon wrasse, which are heavily exploited elsewhere around the world but were common in the lagoon at Millennium. The lagoon also supports an abundance of giant clams (Tridacna maxima). Millennium lagoon provides an excellent reference of a relatively undisturbed coral atoll. As with most coral reefs around the world, the lagoon communities of Millennium may be threatened by climate change and associated warming, acidification and sea level rise, as well as sporadic local resource exploitation which is difficult to monitor and enforce because of the atoll''s remote location. While the remote nature of Millennium has allowed it to remain one of the few nearly pristine coral reef ecosystems in the world, it is imperative that this ecosystem receives protection so that it may survive for future generations.     

The geological effects of hurricanes on coral reefs and the interpretation of storm deposits

Hurricanes occur in belts 7° to 25° north and south of the equator. Reefs growing in these belts suffer periodic damage from hurricane-generated waves and storm surge. Corals down to 20m depth may be broken and removed, branching colonies being much more susceptible to breakage than upright massive forms. Sand cays may be washed away and former storm ridges may migrate to leeward across reef flats to link with islands. Reef crest and reef front coral debris accumulate as talus at the foot of the fore-reef slope, on submarine terraces and grooves, on the intertidal reef flat as storm ridges of shingle or boulders and isolated blocks of reef framework, as accreting beach ridges of leeward migrating shingle, as lobes and wedges of debris in back-reef lagoons, as drapes of carbonate sand and mud in deep off-reef locations in the fore-reef and lagoonal areas. In addition to the coarse debris deposited, other features may aid the recognition of former hurricane events, including the assemblage of reef biota, its species composition and the structure of the skeletons; graded internal sediments in framework cavities; characteristic sequences of encrusting organisms; characteristic shapes of reef flat microatoll corals; and submarine cement crusts over truncated reef surfaces. The abundance of reef flat storm deposits whose ages cluster around 3000–4000 y BP in certain parts of the world most likely relate to a slight fall in relative sea level rather than an increase in storminess during that period. A higher frequency of storms need not result in more reef flat storm deposits. The violence of the storm relative to normal fair-weather conditions influences the extent of damage; the length of time since the previous major storm influences the amount of coral debris created; the length of time after the hurricane, and before a subsequent storm influences the degree of stabilization of reef-top storm deposits and hence their chances of preservation.     

Cryptic genetic diversity and spatial patterns of admixture within Belizean marine reserves

Despite the potential for long-distance gene flow in the sea, there is growing evidence of cryptic genetic diversity in many marine taxa. Understanding the geographic distribution of cryptic lineages, as well as the spatial patterns of admixture among them, can have important implications for conservation planning. Here, we explore patterns of divergence in a coral reef fish, the neon goby Elacatinus lori, across the species’ range. First, we use targeted amplicon sequencing to describe the spatial pattern of genetic divergence using two marker types (57 anonymous ddRAD-derived loci and mtDNA cytb). Second, we quantify the degree of admixture and hybridization between two previously-unidentified divergent lineages within Belize. Third, we assess whether the existing group of marine protected areas (MPAs) in Belize protects this cryptic genetic diversity. The results provide strong evidence for two divergent genetic lineages of E. lori within Belize, separated geographically by only 30 km of low-suitability habitat. There is a sharp genetic cline across these 30 km, and evidence of admixture and introgression at the boundary regions of the habitat break. We also show that the broadly-distributed arrangement of MPAs within Belize protects both major lineages as well as subtle structure within-lineages, and therefore may confer protection to co-distributed species that exhibit similar spatial patterns of divergence.     

The influence of sea level and cyclones on Holocene reef flat development: Middle Island,central Great Barrier Reef

The geomorphology and chronostratigraphy of the reef flat (including microatoll ages and elevations) were investigated to better understand the long-term development of the reef at Middle Island, inshore central Great Barrier Reef. Eleven cores across the fringing reef captured reef initiation, framework accretion and matrix sediments, allowing a comprehensive appreciation of reef development. Precise uranium–thorium ages obtained from coral skeletons revealed that the reef initiated ~7873 ± 17 years before present (yBP), and most of the reef was emplaced in the following 1000 yr. Average rates of vertical reef accretion ranged between 3.5 and 7.6 mm yr^?1. Reef framework was dominated by branching corals (Acropora and Montipora). An age hiatus of ~5000 yr between 6439 ± 19 and 1617 ± 10 yBP was observed in the core data and attributed to stripping of the reef structure by intense cyclones during the mid- to late-Holocene. Large shingle ridges deposited onshore and basset edges preserved on the reef flat document the influence of cyclones at Middle Island and represent potential sinks for much of the stripped material. Stripping of the upper reef structure around the outer margin of the reef flat by cyclones created accommodation space for a thin (<1.2 m) veneer of reef growth after 1617 ± 10 yBP that grew over the eroded mid-Holocene reef structure. Although limited fetch and open-water exposure might suggest the reef flat at Middle Island is quite protected, our results show that high-energy waves presumably generated by cyclones have significantly influenced both Holocene reef growth and contemporary reef flat geomorphology.     

Spatial and temporal variation in predation on reef fishes by coral trout (Plectropomus leopardus,Serranidae)

The diet of coral trout Plectropomus leopardus (Serranidae) was studied over a two year period at One Tree Island, Great Barrier Reef, Australia. Rapid visual counts demonstrated that P. leopardus were most abundant on the reef slope habitat and inner edge of the enclosed lagoon. Few P. leopardus were found at sites from inner lagoon. It was hypothesized that diet would vary among habitats, times and size classes of coral trout. Ninety-two percent of P. leopardus that contained prey had consumed fish and 87% had only eaten fish. Many types of reef fish were taken by P. leopardus (e.g. Pomacentridae, Scaridae, Blenniidae and Labridae). Most pelagic prey (Clupeidae and Engraulididae) were taken on the reef slope, while some prey were solely or pimarily taken in the lagoon (e.g. Blenniidae and crustaceans). Most pelagic prey were taken on the reef slope in summer by P. leopardus>250 mm (SL). Plectropomus leopardus (<200 mm) from the lagoon had a higher proportion of invertebrates in the diet than fish from the reef slope. Plectropomus leopardus of all sizes ate small fish, while largest fish generally consumed largest prey (especially adult scarids and labrids). I argue that interactions among multiple species of prey and predators need more attention, because piscivores may respond to prey in different ways according to habitat type as well as the number and type of other prey types present. Furthermore, different sizes of fish (e.g. coral trout) may impact assemblages of prey in different ways.