Extent and effect of Black Band Disease on a Caribbean reef

The effect of Black Band Disease (BBD) among colonies ofMontastrea annularis, M. cavernosa, Diploria strigosa, D. labryinthiformis, S. siderea andColpophyllia natans was determined at 7 shallow locations in the Virgin Islands. Between September 1988 and November 1988, 0.2% of 9204 colonies of these species were infected with BBD in 6908 m² of reef at 22 randomly chosen areas. Infected colonies were not clumped suggesting that the disease is not highly infectious between colonies. BBD infection rates in areas surveyed 4 times between August 1988 and September 1989 in Greater Lameshur Bay, St. John, USVI, were significantly lower in winter compared to summer. BBDs were found on 5.5% of the colonies ofD. strigosa in Fall 1988, and 7 out of 12 infected colonies lost >75% of their tissue in 6 months. Low level, chronic BBD infections could convert 3.9% of the living cover ofD.strigosa to free space per year, thereby creating substrata for successional processes.     

Mass Coral Bleaching in 2010 in the Southern Caribbean

Ocean temperatures are increasing globally and the Caribbean is no exception. An extreme ocean warming event in 2010 placed Tobago''s coral reefs under severe stress resulting in widespread coral bleaching and threatening the livelihoods that rely on them. The bleaching response of four reef building taxa was monitored over a six month period across three major reefs systems in Tobago. By identifying taxa resilient to bleaching we propose to assist local coral reef managers in the decision making process to cope with mass bleaching events. The bleaching signal (length of exposure to high ocean temperatures) varied widely between the Atlantic and Caribbean reefs, but regardless of this variation most taxa bleached. Colpophyllia natans, Montastraea faveolata and Siderastrea siderea were considered the most bleaching vulnerable taxa. Interestingly, reefs with the highest coral cover showed the greatest decline reef building taxa, and conversely, reefs with the lowest coral cover showed the most bleaching but lowest change in coral cover with little algal overgrowth post-bleaching.     

Nearshore coral growth declining on the Mesoamerican Barrier Reef System

Anthropogenic global change and local stressors are impacting coral growth and survival worldwide, altering the structure and function of coral reef ecosystems. Here, we show that skeletal extension rates of nearshore colonies of two abundant and widespread Caribbean corals (Siderastrea siderea, Pseudodiploria strigosa) declined across the Belize Mesoamerican Barrier Reef System (MBRS) over the past century, while offshore coral conspecifics exhibited relatively stable extension rates over the same temporal interval. This decline has caused nearshore coral extension rates to converge with those of their historically slower growing offshore coral counterparts. For both species, individual mass coral bleaching events were correlated with low rates of skeletal extension within specific reef environments, but no single bleaching event was correlated with low skeletal extension rates across all reef environments. We postulate that the decline in skeletal extension rates for nearshore corals is driven primarily by the combined effects of long‐term ocean warming and increasing exposure to higher levels of land‐based anthropogenic stressors, with acute thermally induced bleaching events playing a lesser role. If these declining trends in skeletal growth of nearshore S. siderea and P. strigosa continue into the future, the structure and function of these critical nearshore MBRS coral reef systems is likely to be severely impaired.     

Impact of the 2005 coral bleaching event on <Emphasis Type="Italic">Porites porites</Emphasis> and <Emphasis Type="Italic">Colpophyllia natans</Emphasis> at Tektite Reef,US Virgin Islands

A thermal stress anomaly in 2005 caused mass coral bleaching at a number of north-east Caribbean reefs. The impact of the thermal stress event and subsequent White-plague disease type II on Porites porites and Colpophyllia natans was monitored using a time series of photographs from Tektite Reef, Virgin Islands National Park, St. John. Over 92% of the P. porites and 96% of the C. natans experienced extensive bleaching (>30% of colony bleached). During the study, 56% of P. porites and 42% of C. natans experienced whole-colony mortality within the sample plots. While all whole-colony mortality of P. porites was directly attributed to coral bleaching, the majority (82%) of the C. natans colonies that experienced total mortality initially showed signs of recovery from bleaching, before subsequently dying from White-plague disease type II.     

Elevated temperatures and bleaching on a high latitude coral reef: the 1988 Bermuda event

Sea temperatures were normal in Bermuda during 1987, when Bermuda escaped the episodes of coral bleaching which were prevalent throughout the Caribbean region. Survey transecs in 1988 on 4–6 m reefs located on the rim margin and on a lagoonal patch reef revealed bleaching only of zoanthids between May and July. Transect and tow surveys in August and September revealed bleaching of several coral species;Millepora alcicornis on rim reefs was the most extensively affected. The frequency of bleaching in this species,Montastrea annularis and perhapsDiploria labyrinthiformis was significantly higher on outer reefs than on inshore reefs. This bleaching period coincided with the longest period of elevated sea temperatures in Bermuda in 38 years (28.9–30.9°C inshore, >28° offshore). By December, when temperatures had returned to normal, bleaching of seleractinians continued, but bleaching ofM. alcicornis on the outer reefs was greatly reduced. Our observations suggest that corals which normally experience wide temperature ranges are less sensitive to thermal stress, and that high-latitude reef corals are sensitive to elevated temperatures which are within the normal thermal range of corals at lower latitudes.     

Abundance and distribution of black band disease on coral reefs in the northern Florida keys

The abundance and distribution of black band disease on the reef building coralsMontastraea annularis, M. cavernosa, Colpophyllia natans, Diploria clivosa, D. labyrinthiformis andD. strigosa were determined at Algae Reef, Grecian Rocks and Key Largo Dry Rocks in the Key Largo National Marine Sanctuary, Florida, USA. During July and November of 1992 and July 1993, surveys of permanently marked sites covering 9424m² of reef tract showed that up to 0.72% of 1397 coral colonies of these species were infected with black band disease. The distribution of the disease among the thirty 20-meter diameter sites was clumped, suggesting that the disease is infectious. Year-round monitoring revealed that seasonal disease patterns varied between reefs. Three seasonal patterns were apparent: some coral colonies were infected year round; several colonies exhibited previously unreported reinfection on a seasonal basis; and some exhibited the widely reported pattern of infection limited to the warmer months of the year (sea water temperatures 25 °C or higher).     

Skeletal records of community-level bleaching in Porites corals from Palau

Tropical Pacific sea surface temperature is projected to rise an additional 2–3 °C by the end of this century, driving an increase in the frequency and intensity of coral bleaching. With significant global coral reef cover already lost due to bleaching-induced mortality, efforts are underway to identify thermally tolerant coral communities that might survive projected warming. Massive, long-lived corals accrete skeletal bands of anomalously high density in response to episodes of thermal stress. These “stress bands” are potentially valuable proxies for thermal tolerance, but to date their application to questions of community bleaching history has been limited. Ecological surveys recorded bleaching of coral communities across the Palau archipelago during the 1998 and 2010 warm events. Between 2011 and 2015, we extracted skeletal cores from living Porites colonies at 10 sites spanning barrier reef and lagoon environments and quantified the proportion of stress bands present in each population during bleaching years. Across Palau, the prevalence of stress bands tracked the severity of thermal stress, with more stress bands occurring in 1998 (degree heating weeks = 13.57 °C-week) than during the less severe 2010 event (degree heating weeks = 4.86 °C-week). Stress band prevalence also varied by reef type, as more corals on the exposed barrier reef formed stress bands than did corals from sheltered lagoon environments. Comparison of Porites stress band prevalence with bleaching survey data revealed a strong correlation between percent community bleaching and the proportion of colonies with stress bands in each year. Conversely, annual calcification rates did not decline consistently during bleaching years nor did annually resolved calcification histories always track interannual variability in temperature. Our data suggest that stress bands in massive corals contain valuable information about spatial and temporal trends in coral reef bleaching and can aid in conservation efforts to identify temperature-tolerant coral reef communities.

     

Role of host genetics and heat‐tolerant algal symbionts in sustaining populations of the endangered coral Orbicella faveolata in the Florida Keys with ocean warming

Identifying which factors lead to coral bleaching resistance is a priority given the global decline of coral reefs with ocean warming. During the second year of back‐to‐back bleaching events in the Florida Keys in 2014 and 2015, we characterized key environmental and biological factors associated with bleaching resilience in the threatened reef‐building coral Orbicella faveolata. Ten reefs (five inshore, five offshore, 179 corals total) were sampled during bleaching (September 2015) and recovery (May 2016). Corals were genotyped with 2bRAD and profiled for algal symbiont abundance and type. O. faveolata at the inshore sites, despite higher temperatures, demonstrated significantly higher bleaching resistance and better recovery compared to offshore. The thermotolerant Durusdinium trenchii (formerly Symbiondinium trenchii) was the dominant endosymbiont type region‐wide during initial (78.0% of corals sampled) and final (77.2%) sampling; >90% of the nonbleached corals were dominated by D. trenchii. 2bRAD host genotyping found no genetic structure among reefs, but inshore sites showed a high level of clonality. While none of the measured environmental parameters were correlated with bleaching, 71% of variation in bleaching resistance and 73% of variation in the proportion of D. trenchii was attributable to differences between genets, highlighting the leading role of genetics in shaping natural bleaching patterns. Notably, D. trenchii was rarely dominant in O. faveolata from the Florida Keys in previous studies, even during bleaching. The region‐wide high abundance of D. trenchii was likely driven by repeated bleaching associated with the two warmest years on record for the Florida Keys (2014 and 2015). On inshore reefs in the Upper Florida Keys, O. faveolata was most abundant, had the highest bleaching resistance, and contained the most corals dominated by D. trenchii, illustrating a causal link between heat tolerance and ecosystem resilience with global change.     

Coral assemblages, biofacies, and ecological zones in the mid-Holocene reef deDosits of the Enriquillo Valley, Dominican Republic

Stemann, T. A. & Johnson, K. G. 1992 07 15: Coral assemblages, biofacies. and ecological zones in the mid-Holocene reef deposits of the Enriquillo Valley, Dominican Republic. A large, subaerially exposed mid-Holocene reef in the Enriquillo Valley (southwest Dominican Republic) provides an excellent opportunity to examine the relationship between reefal ecology and reefal deposits. Coral species richness and diversity in the Enriquillo reef are comparable to that found in the recent of the Caribbean, and ecological zonation comprised of a shallow-water branching coral zone and a deeper water mixed-coral zone is apparent. Similar zonation and diversity patterns have been recognized on living Caribbcan reefs with moderate wave exposure. Three statistically discrete biopdcies can be discriminated in the Enriquillo deposits using quadrat point-counting techniques commonly used to census modern reefs. They include a facies dominated by Acropora cervicornis, a low diversity assemblage with abundant, large colonies of Siderastrea siderea and Stephanocoenia intersepta, and a higher diversity assembbdge composed of various taxa including Montastraea spp., Colpophyllia spp., and Agaricia spp. Each facies can be recognized at scales of 1–3 m², though in some cases they extend for more than 20 m². In general, the A. cervicornis facies is spatially segregated from the other two biofacies. although neither the shallow nor the deep-water ecological zone is comprised of a single reef biofacies. Rather, the biofacies described here appear to represent distinct micro-environments resulting from ecological variation at a subzonal scale. Micro-environments of similar scale are most likely preserved in other reef deposits. Recognition of these subzonal biofacies may have important consequences for the stratigraphical and paleoccological interpretation of fossil reefs. Corals, biofacies, reef zonation, coral communities, fossil reefs.     

Coral mortality and interaction with algae in relation to sedimentation

The impact of sedimentation on coral–algal interactions was studied by monitoring tissue mortality and radial growth in two coral species, Colpophyllia natans and Siderastrea siderea, over a continuum of sediment input intensities. This study sets out to investigate (1) whether sedimentation can facilitate algal overgrowth of corals and (2) whether this was a significant cause of coral mortality. Over a 15-month period, 198 coral colonies were tagged and photographed at six sites along two replicate gradients of sediment input, spanning high inputs near river mouths to low inputs at exposed headlands. Photographs were taken so that they covered the interface between colonies and algae. Radial growth was measured along colony edges in contact with algae and unaffected by tissue loss from causes other than competition with algae. To establish whether algal overgrowth was a significant cause of coral mortality, tissue mortality on the colony surface area visible in the photographs was related to different causes, including sediment smothering, disease, and algal overgrowth. Radial growth became negative with increasing proximity to river mouths in C. natans and remained negative or close to zero throughout the gradients in S. siderea, overall suggesting that sedimentation can facilitate algal overgrowth on corals. However, the analysis of tissue mortality revealed that algal overgrowth was a relatively minor cause of tissue loss. In contrast, the most important cause of coral mortality in relation to sedimentation was from sediment smothering, probably during intense episodes of deposition associated with heavy rainfall. We conclude that sedimentation may lead to reef degradation by causing coral mortality through sediment smothering and burial, and then by suppressing the regrowth of surviving adult colonies through increased competition with algae.     

Short-term ecological consequences of a major oil spill on Panamanian subtidal reef corals

A major oil spill (8,000,000 liters; 50,000 barrels) occurred in Bahía Las Minas on the Caribbean coast of Panama in April 1986, and oil slicks from the refinery landfill and mangroves were still common there after 21/2 years. We studied short-term effects of the spill on common shallow subtidal reef corals, at the individual, population, and community levels. Numbers of corals, total coral cover, and species diversity based on cover decreased significantly with increased amounts of oiling. Cover of the large branching coral Acropora palmata decreased most. Frequency and size of recent injuries on massive corals increased with level of oiling, particularly for Siderastrea siderea. Growth of three massive species (Porites astreoides, Diploria strigosa, and Montastrea annularis, but not S. siderea) was less at oiled reefs in the year of the spill than during the 9 previous years. Subtidal coral reefs, particularly those along protected coasts, may suffer extensive damage from chronic exposure after major oil spills. Mailing Address from the USA: Smithsonian Tropical Research Institute, APO Miami 34002-0011, USA     

Evidence for a host role in thermotolerance divergence between populations of the mustard hill coral (Porites astreoides) from different reef environments

Studying the mechanisms that enable coral populations to inhabit spatially varying thermal environments can help evaluate how they will respond in time to the effects of global climate change and elucidate the evolutionary forces that enable or constrain adaptation. Inshore reefs in the Florida Keys experience higher temperatures than offshore reefs for prolonged periods during the summer. We conducted a common garden experiment with heat stress as our selective agent to test for local thermal adaptation in corals from inshore and offshore reefs. We show that inshore corals are more tolerant of a 6‐week temperature stress than offshore corals. Compared with inshore corals, offshore corals in the 31 °C treatment showed significantly elevated bleaching levels concomitant with a tendency towards reduced growth. In addition, dinoflagellate symbionts (Symbiodinium sp.) of offshore corals exhibited reduced photosynthetic efficiency. We did not detect differences in the frequencies of major (>5%) haplotypes comprising Symbiodinium communities hosted by inshore and offshore corals, nor did we observe frequency shifts (‘shuffling’) in response to thermal stress. Instead, coral host populations showed significant genetic divergence between inshore and offshore reefs, suggesting that in Porites astreoides, the coral host might play a prominent role in holobiont thermotolerance. Our results demonstrate that coral populations inhabiting reefs <10‐km apart can exhibit substantial differences in their physiological response to thermal stress, which could impact their population dynamics under climate change.     

Remote monitoring of chlorophyll fluorescence in two reef corals during the 2005 bleaching event at Lee Stocking Island, Bahamas

Zooxanthellae fluorescence was measured in situ, remotely, and in near real-time with a pulse amplitude modulated (PAM) fluorometer for a colony of Siderastrea siderea and Agaricia tenuifolia at Lee Stocking Island, Bahamas during the Caribbean-wide 2005 bleaching event. These colonies displayed evidence of photosystem II (PS II) inactivation coincident with thermal stress and seasonally high doses of solar radiation. Hurricane-associated declines in temperature and light appear to have facilitated the recovery of maximum quantum yield of PS II within these two colonies, although both corals responded differently to individual storms. PAM fluorometry, coupled with long-term measurement of in situ light and temperature, provides much more detail of coral photobiology on a seasonal time scale and during possible bleaching conditions than sporadic, subjective, and qualitative observations. S. siderea displayed evidence of PS II inactivation over a month prior to the issuing of a satellite-based, sea surface temperature (SST) bleaching alert by the National Oceanic and Atmospheric Administration (NOAA). In fact, recovery had already begun in S. siderea when the bleaching alert was issued. Fluorescence data for A. tenuifolia were difficult to interpret because the shaded parts of a colony were monitored and thus did not perfectly coincide with thermal stress and seasonally high doses of solar radiation as in S. siderea. These results further emphasize the limitations of solely monitoring SST (satellite or in situ) as a bleaching indicator without considering the physiological status of coral-zooxanthellae symbioses. Communicated by Environment Editor Prof. Rob van Woesik     

Caribbean massive corals not recovering from repeated thermal stress events during 2005–2013

Massive coral bleaching events associated with high sea surface temperatures are forecast to become more frequent and severe in the future due to climate change. Monitoring colony recovery from bleaching disturbances over multiyear time frames is important for improving predictions of future coral community changes. However, there are currently few multiyear studies describing long‐term outcomes for coral colonies following acute bleaching events. We recorded colony pigmentation and size for bleached and unbleached groups of co‐located conspecifics of three major reef‐building scleractinian corals (Orbicella franksi, Siderastrea siderea, and Stephanocoenia michelini; n = 198 total) in Bocas del Toro, Panama, during the major 2005 bleaching event and then monitored pigmentation status and changes live tissue colony size for 8 years (2005–2013). Corals that were bleached in 2005 demonstrated markedly different response trajectories compared to unbleached colony groups, with extensive live tissue loss for bleached corals of all species following bleaching, with mean live tissue losses per colony 9 months postbleaching of 26.2% (±5.4 SE) for O. franksi, 35.7% (±4.7 SE) for S. michelini, and 11.2% (±3.9 SE) for S. siderea. Two species, O. franksi and S. michelini, later recovered to net positive growth, which continued until a second thermal stress event in 2010. Following this event, all species again lost tissue, with previously unbleached colony species groups experiencing greater declines than conspecific sample groups, which were previously bleached, indicating a possible positive acclimative response. However, despite this beneficial effect for previously bleached corals, all groups experienced substantial net tissue loss between 2005 and 2013, indicating that many important Caribbean reef‐building corals will likely suffer continued tissue loss and may be unable to maintain current benthic coverage when faced with future thermal stress forecast for the region, even with potential benefits from bleaching‐related acclimation.     

Catastrophic mortality on inshore coral reefs of the Florida Keys due to severe low‐temperature stress

Coral reefs of the Florida Keys typically experience seasonal temperatures of 20–31 °C. Deviation outside this range causes physiological impairment of reef‐building corals, potentially leading to coral colony death. In January and February 2010, two closely spaced cold fronts, possibly driven by an unusually extreme Arctic Oscillation, caused sudden and severe seawater temperature declines in the Florida Keys. Inshore coral reefs [e.g., Admiral Reef (ADM)] experienced lower sustained temperatures (i.e., < 12 °C) than those further offshore [e.g., Little Grecian Reef (LG), minimum temperature = 17.2 °C]. During February and March 2010, we surveyed ADM and observed a mass die‐off of reef‐building corals, whereas 12 km away LG did not exhibit coral mortality. We subsequently measured the physiological effects of low‐temperature stress on three common reef‐building corals (i.e., Montastraea faveolata, Porites astreoides, and Siderastrea siderea) over a range of temperatures that replicated the inshore cold‐water anomaly (i.e., from 20 to 16 to 12 °C and back to 20 °C). Throughout the temperature modulations, coral respiration as well as endosymbiont gross photosynthesis and maximum quantum efficiency of photosystem II were measured. In addition, Symbiodinium genotypic identity, cell densities, and chlorophyll a content were determined at the beginning and conclusion of the experiment. All corals were significantly affected at 12 °C, but species‐specific physiological responses were found indicating different coral and/or Symbiodinium cold tolerances. Montastraea faveolata and P. astreoides appeared to be most negatively impacted because, upon return to 20 °C, significant reductions in gross photosynthesis and dark respiration persisted. Siderastrea siderea, however, readily recovered to pre‐treatment rates of dark respiration and gross photosynthesis. Visual surveys of inshore reefs corroborated these results, with S. siderea being minimally affected by the cold‐water anomaly, whereas M. faveolata and P. astreoides exhibited nearly 100% mortality. This study highlights the importance of understanding the physiological attributes of genotypically distinct coral‐Symbiodinium symbioses that contribute to tolerance, recovery, and consequences to an environmental perturbation. These data also document effects of a rarely studied environmental stressor, possibly initiated by remote global climate events, on coral‐Symbiodinium symbioses and coral reef communities.     

Bleaching of corals on the Great Barrier Reef: differential susceptibilities among taxa

Large-scale coral bleaching episodes are potentially major disturbances to coral reef systems, yet a definitive picture of variation in assemblage response and species susceptibilities is still being compiled. Here, we provide a detailed analysis of the bleaching response of 4160 coral colonies, representing 45 genera and 15 families, from two depths at four sites on reefs fringing inshore islands on the Great Barrier Reef. Six weeks after the onset of large-scale bleaching in 1998, between 11 and 83% of colonies along replicate transects were affected by bleaching, and mortality was 1 to 16%. There were significant differences in bleaching response between sites, depths and taxa. Cyphastrea, Turbinaria and Galaxea were relatively unaffected by bleaching, while most acroporids and pocilloporids were highly susceptible. The hydrocorals (Millepora spp.) were the most susceptible taxa, with 85% mortality. Spatial variation in assemblage response was linked to the taxonomic composition of reef sites and their bleaching history. We suggest, therefore, that much of the spatial variation in bleaching response was due to assemblage composition and thermal acclimation. Accepted: 14 January 2000     

Susceptibility of central Red Sea corals during a major bleaching event

A major coral bleaching event occurred in the central Red Sea near Thuwal, Saudi Arabia, in the summer of 2010, when the region experienced up to 10–11 degree heating weeks. We documented the susceptibility of various coral taxa to bleaching at eight reefs during the peak of this thermal stress. Oculinids and agaricids were most susceptible to bleaching, with up to 100 and 80 % of colonies of these families, respectively, bleaching at some reefs. In contrast, some families, such as mussids, pocilloporids, and pectinids showed low levels of bleaching (<20 % on average). We resurveyed the reefs 7 months later to estimate subsequent mortality. Mortality was highly variable among taxa, with some taxa showing evidence of full recovery and some (e.g., acroporids) apparently suffering nearly complete mortality. The unequal mortality among families resulted in significant change in community composition following the bleaching. Significant factors in the likelihood of coral bleaching during this event were depth of the reef and distance of the reef from shore. Shallow reefs and inshore reefs had a higher prevalence of bleaching. This bleaching event shows that Red Sea reefs are subject to the same increasing pressures that reefs face worldwide. This study provides a quantitative, genus-level assessment of the vulnerability of various coral groups from within the Red Sea to bleaching and estimates subsequent mortality. As such, it can provide valuable insights into the future for reef communities in the Red Sea.     

Bacterial communities inhabiting the healthy tissues of two Caribbean reef corals: interspecific and spatial variation

Bacterial communities inhabiting healthy tissues of the reef-building corals Diploria strigosa and Montastraea annularis were evaluated across a human-induced environmental gradient along the southern coast of Curaçao, Netherlands Antilles. Variations in bacterial communities inhabiting coral tissues were determined using terminal restriction fragment length polymorphisms (T-RFLP) of 16S rRNA genes, and the ¹⁵N value of coral tissue was used to assess the relative amount of human contaminants at each reef locality. Bacterial communities of D. strigosa were more variable than M. annularis, but there were no systematic differences in the populations of healthy M. annularis and D. strigosa. The ¹⁵N value of coral tissues showed as much as a 1.5 increase in the impacted versus the non-impacted localities. While M. annularis showed no significant variation in bacterial community structure due to local reef conditions, the bacterial communities of D. strigosa showed dramatic shifts in community structure. The most abundant bacterial taxa inhabiting D. strigosa display increased dominance at impacted localities. By linking variations in microbial communities with an understanding of variations in local environmental conditions, this study provides a means of assessing potential factors that may impact the microbial habitat of coral tissues as well as overall reef health.     

Parrotfish abundance and selective corallivory on a Belizean coral reef

Parrotfish are important members of coral reef communities because they consume macroalgae that would otherwise outcompete reef-building corals for space. However, some Caribbean parrotfish species also feed directly on live corals, and thus have the potential to negatively impact coral fitness and survival. This study investigates selective grazing by parrotfish on particular coral species, differences in grazing incidence among reef habitats and intraspecific discrimination among colonies of several coral species. We also investigate spatial and temporal patterns of parrotfish species abundance across habitats on the Belize barrier reef, and examine correlations between parrotfish abundance and grazing intensity across reef habitats. We found that members of the Montastraea annularis species complex, major builders of Caribbean reefs, were preferred targets of parrotfish grazing across all reef habitats, while M. cavernosa, Agaricia agaricites, Diploria strigosa, Porites astreoides and Porites porites were not preferred; Siderastrea siderea was preferentially grazed only in the spur and groove habitats. Parrotfish grazing preferences varied across habitats; M. annularis was grazed most often in shallow habitats, whereas M. franksi was consumed more at depth. Although it was not possible to directly observe parrotfish grazing on corals, we did find a positive correlation between Sparisoma aurofrenatum abundance and M. franksi grazing incidence across habitats. Finally, when we compared our results to parrotfish abundances measured by a previous study, we found that Sparisoma viride and Sp. aurofrenatum, two species known to be corallivorous, had increased abundances between 1982 and 2004. In light of escalating threats on Caribbean reef corals, it would be important for future studies to evaluate the impact of parrotfish corallivory on coral survival.     

Species‐specific responses to climate change and community composition determine future calcification rates of Florida Keys reefs

Anthropogenic climate change compromises reef growth as a result of increasing temperatures and ocean acidification. Scleractinian corals vary in their sensitivity to these variables, suggesting species composition will influence how reef communities respond to future climate change. Because data are lacking for many species, most studies that model future reef growth rely on uniform scleractinian calcification sensitivities to temperature and ocean acidification. To address this knowledge gap, calcification of twelve common and understudied Caribbean coral species was measured for two months under crossed temperatures (27, 30.3 °C) and CO₂ partial pressures (pCO₂) (400, 900, 1300 μatm). Mixed‐effects models of calcification for each species were then used to project community‐level scleractinian calcification using Florida Keys reef composition data and IPCC AR5 ensemble climate model data. Three of the four most abundant species, Orbicella faveolata, Montastraea cavernosa, and Porites astreoides, had negative calcification responses to both elevated temperature and pCO₂. In the business‐as‐usual CO₂ emissions scenario, reefs with high abundances of these species had projected end‐of‐century declines in scleractinian calcification of >50% relative to present‐day rates. Siderastrea siderea, the other most common species, was insensitive to both temperature and pCO₂ within the levels tested here. Reefs dominated by this species had the most stable end‐of‐century growth. Under more optimistic scenarios of reduced CO₂ emissions, calcification rates throughout the Florida Keys declined <20% by 2100. Under the most extreme emissions scenario, projected declines were highly variable among reefs, ranging 10–100%. Without considering bleaching, reef growth will likely decline on most reefs, especially where resistant species like S. siderea are not already dominant. This study demonstrates how species composition influences reef community responses to climate change and how reduced CO₂ emissions can limit future declines in reef calcification.