西沙群岛造礁石珊瑚主要疾病调查与初步研究

记录了2010年5-10月及2011年4-8月在西沙群岛海域开展珊瑚疾病调查的结果,发现普哥滨珊瑚(Porites pukoensis)、扁枝滨珊瑚(Porites andrewsi)、蔷薇珊瑚(Montipora spp.)、杯形珊瑚(Pocillopora spp.)、鹿角珊瑚(Acropora spp.) 、菊花珊瑚(Goniastrea spp.)、澄黄滨珊瑚(Porites lutea)和滨珊瑚(Porites spp.)等共14种珊瑚主要出现了白化、白斑病、黑化、黄色炎症样病症、粉红颗粒状综合症等9种不同症状的疾病,目前该海域为珊瑚疾病的频发区。其中,普哥滨珊瑚的黄色炎症样病症和扁枝滨珊瑚的白化最为常见。普哥滨珊瑚黄色炎症样病症主要出现在永兴岛附近海区,患病部位存在大量黄色脓样分泌物,患病部位水螅体生长正常、萎缩或缺失,有时骨骼部分缺失,患病部位面积一般为0.02~12.00 cm2;该疾病由机械损伤或其他原因引起,因机械损伤引起的伤口一般在2~3个月可以恢复,其中小面积伤口的黄色物质可在10~20d内消失、伤口基本恢复正常,而其他原因产生的黄色物质需1~3个月才能消失,有的甚至在观察期内无明显变化。扁枝滨珊瑚的白化出现在七连屿一带的扁枝滨珊瑚分布区,该病存在整枝完全白化、局部大面积白化、散布白色斑点3种情况,白化部位水螅体缺失。本文为我国西沙海域珊瑚疾病的首次报道,可为今后开展西沙珊瑚疾病研究提供参考。     

Experimental bleaching of a tropical sea anemone in situ

Bleaching (whitening) of cnidarians such as corals and sea anemones has caused widespread degradation of coral reefs around the world and is therefore an urgent issue for coral reef science and conservation. Although cnidarians often bleach in aquaria, methods for experimental induction of bleaching in wild cnidarians are lacking, which impedes scientists’ ability to understand the ultimate effects of bleaching on the broader ecosystem. In this study, we investigated the utility of an in situ method for experimental induction of bleaching in the tropical sea anemone Heteractis crispa. Healthy, wild anemones were covered with opaque black plastic sheets, mesh cages or left undisturbed (controls) and tentacle colour and body size were monitored with a colour reference card and flexible tape, respectively, every 1–3 days for 15 days. Caged and control anemones remained unchanged for the duration of the experiment, but covered anemones commenced whitening after 4–6 days and were completely white after 7–14 days (mean time to bleaching ± SE = 10.1 ± 0.7 days). Experimental bleaching occurred without reduction in anemone body size and was visibly similar to natural bleaching seen previously in H. crispa. We hypothesize that light‐deprivation, reduced water flow, physical contact or some combination of these factors caused the bleaching. This study provides the basis for a simple and rapid method of inducing bleaching in situ, which releases scientists’ dependence on sporadic natural bleaching events or artificial aquarium experiments, and provides a means to investigate the effects of bleaching on other ecosystem components such as fishes.     

Coral Reef Community Structure at Caño Island, Pacific Costa Rica

Abstract. Around the Biological Reserve of Caño Island, Pacific Costa Rica, there are five large coral reef flats (with size ranges of 0.8–4.2 ha) built mainly of dead Pocillopora spp. At present, they are covered mainly by crustose coralline algae and microatolls of Porites lobata . From the upper reef slope to the reef base several corals grow in small patches (e. g., Pavona clavus, Pavona varians, Pavona gigantea, Gardineroseris planulata, Psammocora superficialis, Pocillopora elegans, Pocillopora damicornis); the massive coral Porites Iobata is predominant. Pocilloporid species are predominant on most other eastern Pacific reefs.
The Caño Island reef is typical of a community whose structure has been controlled by both physical (in shallow water) and biological (in deeper water) factors. Shallow reef areas are influenced by strong wave action and extreme low tides. The distribution, abundance, and feeding preferences of corallivorous organisms (e. g., Acanthaster planci, Arothron meleagris, Pseudobalistes naufragium, Quoyula monodonta) on the deeper reef suggest that most pocilloporids are affected and limited by them. Although there is no evidence of any predator on Porites lobata at Caño Island, the triggerfish Pseudobalistes naufragium breaks off fragments of the coral while searching for food. These fragments often survive to form new colonies. Together, this dispersal mechanism, rapid injury recovery, and high resistance to environmental stress seem to enhance the distribution and dominance of the massive coral Porites lobata at Caño Island.     

Spatial and temporal variations in sediment accumulation and their impacts on coral communities in the Sanya Coral Reef Reserve,Hainan, China

This study investigated the spatial and temporal variations of sediment accumulation and their impacts on coral communities in four sites at two or three depths (3 m, 6 m and 9 m) at the Sanya Coral Reef Reserve by deploying sediment traps on the sea floor during 2007–2009. Rainfall and typhoon events, which appeared to control sediment accumulation in the sea floor of the coral reef, were positively correlated with total sediment and sand-sized (i.e. 63–2000 µm) sediment accumulation. Sediment accumulation rate significantly decreased with the distance far away from the coast in Sanya. The mean sediment accumulation rates in Ximaozhou, Luhuitou and Xiaodonghai during 2007 to 2009 were close to 20 mg cm⁻² d⁻¹, and they were significantly higher than that in Yalongwan, probably as a result of terrestrial soil erosion caused by strong coast human activities (e.g. coastal construction, dredging and hillside clearing). Correlation analysis revealed that silt-clay-sized sediment accumulation rate was highly negatively correlated with total live coral cover and coral cover in some taxa, such as Montipora and branching Porites. whereas, Diploastrea heliopora was positively correlated with silt-clay-sized sediment accumulation. Correlation analysis also suggested that silt-clay-sized sediment accumulation had a higher efficiency in predicting the spatial variation of total live coral cover in Sanya than did the total sediment accumulation. Based on this investigation, we conclude that high rates of sediment accumulation pose a severe threat to the Sanya Coral Reef Reserve, highlighting the importance of integrated watershed management practices in the Sanya Coral Reef Reserve.     

Gradients in coral reef communities exposed to muddy river discharge in Pohnpei,Micronesia

This study analyzed how coral communities change along a gradient of increasing exposure to a mud-discharging river in the Enipein Catchment, Pohnpei, Micronesia. Using video transects, we quantified benthic communities at five sites along a gradient moving away from the river mouth towards the barrier reef. The most river-impacted site was characterized by a high accumulation of mud, low coral cover and low coral diversity. Although coral cover leveled off at ∼400 m from the river mouth to values found at the outer-most sites, coral diversity continued to increase with increasing distance, suggesting that the most distant site was still impacted by the river discharges. Fungiidae, Pavona, Acropora, Pachyseris and Porites rus all significantly increased in cover with distance from the river, while Turbinaria decreased. The combined presence and abundance of these six species groups, together with coral species richness, may help to indicate the effects of terrestrial runoff in similar runoff-exposed settings around Micronesia, whereas coral cover is not a sensitive indicator for river impact. Coral reefs are important resources for the people of Pohnpei. To prevent further degradation of this important resource, an integrated watershed approach is needed to control terrestrial activities.     

The northernmost coral frontier of the Maldives: The coral reefs of Ihavandippolu Atoll under long-term environmental change

Ihavandippolu, the northernmost atoll of the Maldives, experienced severe coral bleaching and mortality in 1998 followed by several bleaching episodes in the last decade. Coral cover in the 11 study sites surveyed in July–December of 2011 in the 3–5 m depth range varied from 1.7 to 51%. Reefs of the islands located in the center of Ihavandippolu lagoon have exhibited a very low coral recovery since 1998 and remain mostly degraded 12 years after the impact. At the same time, some reefs, especially in the inner part of the eastern ring of the atoll, demonstrate a high coral cover (>40%) with a dominance of branching Acropora that is known to be one of the coral genera that is most susceptible to thermal stress. The last severe bleaching event in 2010 resulted in high coral mortality in some sites of the atoll. Differences in coral mortality rates and proportion between “susceptible” and “resistant” taxa in study sites are apparently related to long-term adaptation and local hydrological features that can mitigate thermal impacts. Abundant herbivorous fish observed in the atoll prevent coral overgrowth by macroalgae even on degraded reefs. Despite the frequent influence of temperature anomalies and having less geomorphologic refuges for coral survivals than other larger Maldivian atolls, a major part of observed coral communities in Ihavandippolu Atoll exhibits high resilience and potential for further acclimatization to a changing environment.     

Deep‐water Corallium rubrum (L., 1758) from the Mediterranean Sea: preliminary genetic characterisation

The precious red coral Corallium rubrum (L., 1758) lives in the Mediterranean Sea and adjacent Eastern Atlantic Ocean on subtidal hard substrates. Corallium rubrum is a long‐lived gorgonian coral that has been commercially harvested since ancient times for its red axial calcitic skeleton and which, at present, is thought to be in decline because of overexploitation. The depth distribution of C. rubrum is known to range from c. 15 to 300 m. Recently, live red coral colonies have been observed in the Strait of Sicily at depths of c. 600–800 m. This record sheds new light on the ecology, biology, biogeography and dispersal mechanism of this species and calls for an evaluation of the genetic divergence occurring among highly fragmented populations. A genetic characterization of the deep‐sea red coral colonies has been done to investigate biological processes affecting dispersal and population resilience, as well as to define the level of isolation/differentiation between shallow‐ and deep‐water populations of the Mediterranean Sea. Deep‐water C. rubrum colonies were collected at two sites (south of Malta and off Linosa Island) during the cruise MARCOS of the R/V Urania. Collected colonies were genotyped using a set of molecular markers differing in their level of polymorphism. Microsatellites have been confirmed to be useful markers for individual genotyping of C. rubrum colonies. ITS‐1 and mtMSH sequences of deep‐water red coral colonies were found to be different from those found in shallow water colonies, suggesting the possible occurrence of genetic isolation among shallow‐ and deep‐water populations. These findings suggest that genetic diversity of red coral over its actual range of depth distribution is shaped by complex interactions among geological, historical, biological and ecological processes.     

Coral Cover Change Associated to El Niño, Eastern Pacific, Costa Rica, 1992–2001

Abstract. Changes in live and dead coral cover were documented at three localities off the Costa Rican central Pacific coast first in 1992 during the aftermath of the 1991–1992 El Niño; again in the period between 1994 and 1995, and last in January 2001. Recovery of coral communities after the 1991–1992 El Niño was expressed by a significant increase (～40 %) in 1994 of live coral cover at one locality (Manuel Antonio). A subsequent decrease (～50 %) in response to the very strong 1997–1998 episode was recorded at Manuel Antonio and Ballena, mainly due to partial tissue mortality of branching (Pocillopora spp.) and massive (Porites lobata) corals. Mortality of entire colonies associated to that event was scarce and confined to branching and nodular (Psammocora stellata) corals. This species was not found at one locality (Cambutal) in the 2001 survey and it is presumed locally extinct. The recovery of this coral and others will depend on recruits from surviving colonies in deeper waters and other coral communities in the vicinity. Within sites at a given locality, contrasting results in live coral cover variability were found. This is partially due to distinct coral assemblages, coral growth, physical exposure to tidal regime, and, related to the latter, variable duration and intensity of the warming event. In general, predominant meteorological conditions at the studied area are conducive to solar radiation (UV) stress during El Niño years and are related to changes in the atmosphere‐ocean interactions in response to the warming events.     

Long-term impacts of coral bleaching events on the world's warmest reefs

The southern Arabian Gulf houses some of the most thermally tolerant corals on earth, but severe bleaching in the late 1990s caused widespread mortality. More than a decade later, corals still dominated benthos (mean: 40 ± 3% cover on 10 sites spanning > 350 km; range: 11.0-65.6%), but coral communities varied spatially. Sites to the west generally had low species richness and coral cover (mean: 3.2 species per transect, 31% cover), with Porites dominated communities (88% of coral) that are distinct from more diverse and higher cover eastern sites (mean: 10.3 species per transect, 62% cover). These patterns reflect both the more extreme bleaching to the west in the late 1990s as well as the higher faviid dominated recruitment to the east in subsequent years. There has been limited recovery of the formerly dominant Acropora, which now represents <1% of the benthos, likely as a result of recruitment failure. Results indicate that severe bleaching can have substantial long-term impacts on coral communities, even in areas with corals tolerant to environmental extremes.     

Scleractinian coral population size structures and growth rates indicate coral resilience on the fringing reefs of North Jamaica

Coral reefs throughout the world are under severe challenges from many environmental factors. This paper quantifies the size structure of populations and the growth rates of corals from 2000 to 2008 to test whether the Discovery Bay coral colonies showed resilience in the face of multiple acute stressors of hurricanes and bleaching. There was a reduction in numbers of colonies in the smallest size class for all the species at all the sites in 2006, after the mass bleaching of 2005, with subsequent increases for all species at all sites in 2007 and 2008. Radial growth rates (mm yr⁻¹) of non-branching corals and linear extension rates (mm yr⁻¹) of branching corals calculated on an annual basis from 2000–2008 showed few significant differences either spatially or temporally. At Dairy Bull reef, live coral cover increased from 13 ± 5% in 2006 to 20 ± 9% in 2007 and 31 ± 7% in 2008, while live Acropora species increased from 2 ± 2% in 2006 to 10 ± 4% in 2007 and 22 ± 7% in 2008. These studies indicate good levels of coral resilience on the fringing reefs around Discovery Bay in Jamaica.     

A potential new threat on the coral reefs of Puerto Rico: The recent emergence of Ramicrusta spp.

The rapid appearance of Ramicrusta spp. is described and analyzed from 40 permanent monitoring coral reef stations in Puerto Rico. Before 2016, Ramicrusta had not been observed from any of the reef monitoring stations. By 2018, it was present at 76% of all the monitoring stations. Ramicrusta was the dominant substrata type at all of the shallow reef sites sampled on the east coast (e.g., Fajardo, Culebra, and Vieques), reaching a cover (±SE) as high as 63.0 ± 5.8%. The spread of Ramicrusta occurred at the expense of historically resilient living benthic elements, such as turf algae. Since its detection in 2016, colonization of hard substrata by Ramicrusta remained constant, with the exception of two shallow reefs in Fajardo and Culebra, where the cover was significantly reduced by the scouring and or abrasive effects of two major hurricanes. The ecological implications of Ramicrusta prevalence on Puerto Rican reefs remain unclear; however, increasing herbivory might be a useful mitigation tool in the reduction of Ramicrusta abundance on coral reefs.     

Climate change and coral reef bleaching: An ecological assessment of long-term impacts,recovery trends and future outlook

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

Benthic organic carbon flux and oxygen penetration reflect different plankton provinces in the Southern Ocean

For the investigation of organic carbon fluxes reaching the seafloor, oxygen microprofiles were measured at 145 sites in different sub-regions of the Southern Ocean. At 11 sites, an in situ oxygen microprofiler was deployed for the measurement of oxygen profiles and the calculation of organic carbon fluxes. At four sites, both in situ and ex situ data were determined for high latitudes. Based on this data set as well as on previous published data, a relationship was established for the estimation of fluxes derived by ex situ measured O₂ profiles. The fluxes of labile organic matter range from 0.5 to 37.1 mg C m^?2 d^?1. The high values determined by in situ measurements were observed in the Polar Front region (water depth of more than 4290 m) and are comparable to organic matter fluxes observed for high-productivity, upwelling areas like off West Africa. The oxygen penetration depth, which reflects the long-term organic matter flux to the sediment, was correlated with assemblages of key diatom species. In the Scotia Sea (～3000 m water depth), oxygen penetration depths of less than 15 cm were observed, indicating high benthic organic carbon fluxes. In contrast, the oxic zone extends down to several decimeters in abyssal sediments of the Weddell Sea and the southeastern South Atlantic. The regional pattern of organic carbon fluxes derived from microsensor data suggests that episodic and seasonal sedimentation pulses are important for the carbon supply to the seafloor of the deep Southern Ocean.     

Hurricanes and coral bleaching linked to changes in coral recruitment in Tobago

Knowledge of coral recruitment patterns helps us understand how reefs react following major disturbances and provides us with an early warning system for predicting future reef health problems. We have reconstructed and interpreted historical and modern-day recruitment patterns, using a combination of growth modelling and in situ recruitment experiments, in order to understand how hurricanes, storms and bleaching events have influenced coral recruitment on the Caribbean coastline of Tobago. Whilst Tobago does not lie within the main hurricane belt results indicate that regional hurricane events negatively impact coral recruitment patterns in the Southern Caribbean. In years following hurricanes, tropical storms and bleaching events, coral recruitment was reduced when compared to normal years (p = 0.016). Following Hurricane Ivan in 2004 and the 2005–2006 bleaching event, coral recruitment was markedly limited with only 2% (n = 6) of colonies estimated to have recruited during 2006 and 2007. Our experimental results indicate that despite multiple large-scale disturbances corals are still recruiting on Tobago’s marginal reef systems, albeit in low numbers.     

The Skeleton Eroding Band Disease on Coral Reefs of Aqaba, Red Sea

Abstract.  The occurrence and distribution of the coral disease Skeleton Eroding Band (SEB) has been studied at the Jordanian coast in the Gulf of Aqaba, the northernmost extension of the Red Sea. The SEB syndrome is caused by the colonial, heterotrich ciliate Halofolliculina corallasia : an advancing front of these protists destroys polyps, coenosarc, and surface of the coenosteum. In recent years SEB was registered in reefs of Australia, Mauritius, and the Red Sea. Along the Jordanian coast, disease frequency at four study sites was investigated and afflicted coral genera and species were documented. The study sites were MSS (Marine Science Station)-north, MSS-south, the tourist area near the middle of the coast, and the industrial area adjacent to the Saudi Arabian border. Corals and infections were counted inside randomly placed 1 m² frames in reef flats and in 5, 10, and 15 m depths. In order of increasing affectedness of sample sites, MSS-south was the healthiest (12%, 4%, 4%, 16% of infected corals from shallow to deep), followed by MSS-north (19%, 28%, 24%, 24%), the tourist area (51%, 23%, 16%, 41%), and the industrial area (14%, 30%, 39%, 31%). By far the most frequently encountered coral species were Acropora spp. and Stylophora sp., while relative infection-rates were highest among Seriatopora sp. (75%), as well as Stylophora sp., Hydnophora sp., and Galaxea sp. (50% each). This was followed in steadily decreasing order from 44% to 5% by Pocillopora , Mycedium , Montipora , Echinopora , Acropora , Lobophyllia , Goniastrea , Millepora , Platygyra , Fungia , Favia , Porites , Goniopora , Favites , and Pavona . SEB was found to a depth of 30 m, but may occur even deeper.     

珊瑚脂质是其共生虫黄藻密度降低时的重要能量来源

近年来珊瑚白化现象日益严峻。白化意味着珊瑚共生虫黄藻密度的降低,然而目前关于珊瑚体内的脂质在虫黄藻密度降低时对维持能量供给稳定的意义尚不清楚。本研究以2020年3月和6月在西沙群岛采集的帛琉蜂巢珊瑚(Favia palauensis)和澄黄滨珊瑚(Porites lutea)样品为材料,通过生理参数(虫黄藻密度、脂质含量)与地球化学指标(虫黄藻的稳定氮同位素δ¹⁵N_z值)相结合的方法,探讨了珊瑚脂质对虫黄藻密度及其光合作用强度变化的响应。结果显示,夏季两种珊瑚的虫黄藻密度和δ¹⁵N_z值均显著下降,意味着夏季虫黄藻密度降低导致了其光合作用强度的降低。与此同时,两种珊瑚的脂质含量也显著下降,并且脂质含量与虫黄藻密度、δ¹⁵N_z值之间均呈正相关关系,这说明珊瑚脂质含量与虫黄藻光合作用强度的变化之间存在耦合关系。当光合作用强度降低时,珊瑚可以通过消耗其自身储存的脂质更好地维持能量供给的稳定,这对提高环境胁迫的适应能力以及抗白化能力具有重要意义。     

Population structure and connectivity in the Atlantic scleractinian coral Montastraea cavernosa (Linnaeus, 1767)

Coral reefs are increasingly threatened worldwide by a variety of biological and physical factors, including disease, bleaching and ocean acidification. Understanding levels of connectivity among widespread populations can assist in conservation efforts and the design of marine protected areas, as larval dispersal scales affect population demography. This study examined genetic connectivity and morphological variation of the broadcast spawning coral Montastraea cavernosa (L., 1767) among five locations in the Caribbean and Western Atlantic. Analysis of mtDNA and nuclear rRNA internal transcribed spacers, at both the local and regional scale, revealed that the majority of variation existed within locations rather than among them. Likewise, the majority of pairwise comparisons were non‐significant between sites and locations. These results suggest that moderate to high gene flow occurs within and among populations of M. cavernosa in the Western Atlantic. The phylogeographic signature and significant pairwise comparisons among several locations, however, indicate that populations are also partially maintained through self‐seeding and that gene flow may be restricted over large geographic distances. Additionally, while some anatomical variation is likely attributable to phenotypic plasticity, variations in skeletal morphology between Jamaica and other locations correspond with significant pairwise genetic distances and the presence of private sequence types (limited to a single location), suggesting selection to local environmental conditions.     

Composition,abundance, distribution and seasonality of larval fishes in the shallow nearshore of the proposed Greater Addo Marine Reserve,Algoa Bay,South Africa

The larval fish assemblage was investigated in the shallow, nearshore region of a proposed marine protected area in eastern Algoa Bay, temperate South Africa, prior to proclamation. Sampling was conducted at six sites along two different depth contours at ∼5 m and ∼15 m to assess shore association. Larvae were collected by means of stepped oblique bongo net tows deployed off a ski-boat, twice per season for 2 years between 2005 and 2007. In total, 6045 larval fishes were collected representing 32 families and 78 species. The Gobiidae, Cynoglossidae, Clupeidae, Engraulidae and Sparidae were the dominant fish families. Catches varied significantly among seasons peaking in spring with a mean of ∼200 larvae/100 m³. Mean overall larval density was higher along the deeper contour, at ∼15 m (40 larvae/100 m³). The preflexion stage of development dominated catches at the ∼5 m (80%) and ∼15 m (73%) depth contours. Body lengths of Argyrosomus thorpei, Caffrogobius gilchristi, Diplodus capensis, Heteromycteris capensis and Solea turbynei, all estuary associated species, were larger at the shallow sites nearer to shore. Larvae of coastal species that produce benthic eggs dominated catches (75%) in the shallow sites (∼5 m) but were less abundant (32%) farther from shore at the deeper (∼15 m) sites. All developmental stages of D. capensis, Engraulis capensis, H. capensis, Sardinops sagax and two Pomadasys species were found in the study area. It appears that some species use the shallow nearshore as a nursery area.     

Parrotfish mediation in coral mortality and bioerosion by the encrusting,excavating sponge Cliona tenuis

The parrotfish Sparisoma viride often grazes live coral from edges undermined by the Caribbean encrusting and excavating sponge Cliona tenuis. To test whether parrotfish biting action has an effect on the dynamics of the sponge–coral interaction, we manipulated access of parrotfishes to the sponge–coral border in two species of massive corals. When parrotfish had access to the border, C. tenuis advanced significantly more slowly into the coral Siderastrea siderea than into the coral Diploria strigosa. When fish bites were prevented, sponge spread into S. siderea was further slowed down but remained the same for D. strigosa. Additionally, a thinner layer of the outer coral skeleton was removed by bioerosion when fish were excluded, a condition more pronounced in D. strigosa than in S. siderea. Thus, the speed of sponge‐spread and the extent of bioerosion by parrotfish was coral species‐dependent. It is hypothesized that coral skeleton architecture is the main variable associated with such dependency. Cliona tenuis spread is slow when undermining live S. siderea owing to the coral’s compact skeleton. The coral’s smooth and hard surface promotes a wide and shallow parrotfish bite morphology, which allows the sponge to overgrow the denuded area and thus advance slightly faster. On the less compact skeleton of the brain coral, D. strigosa, sponge spread is more rapid. This coral’s rather uneven surface sustains narrower and deeper parrotfish bites which do not facilitate the already fast sponge progress. Parrotfish corallivory thus acts synergistically with C. tenuis to further harm corals whose skeletal architecture slows sponge lateral spread. In addition, C. tenuis also appears to mediate the predator–prey fish–coral interaction by attracting parrotfish biting.     

Symbiodinium (internal transcribed spacer 2) diversity in the coral host Agaricia lamarcki (Cnidaria: Scleractinia) between shallow and mesophotic reefs in the Northern Caribbean (20–70 m)

This study investigated differences in Symbiodinium diversity in the scleractinian coral species Agaricia lamarcki between shallow (20–25 m) and mesophotic (50–70 m) depths in the Northern Caribbean. Corals were sampled in each of four shallow sites (20–25 m; n = 18) and three mesophotic sites (50–70 m; n = 18) from Mona Island (Puerto Rico) and the US Virgin Islands during a mesophotic exploratory cruise and from the La Parguera shelf edge, off Southwestern Puerto Rico. Symbiodinium diversity was assessed using internal transcribed spacer 2 sequences clustered into operational taxonomic units (OTUs). Clustering resulted in eight clade C OTUs and one clade D OTU. Of these, there were three common Symbiodinium OTUs consisting of C3 and D1a.N14 in shallow reefs and C11.N4 in mesophotic reefs. Statistical tests (permutational multivariate analysis of variance and analysis of similarity) showed significant differences between clade C Symbiodinium OTUs in A. lamarcki colonies located at shallow and mesophotic depths, indicating symbiont zonation. Symbiodinium diversity in A. lamarcki from the Northern Caribbean is comparable to previous reports in the Southern Caribbean for this species. This is the first report of the thermal tolerant species Symbiodinium trenchii (D1a) in A. lamarcki.