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Most tropical coral reefs are experiencing declining coral cover, yet interpretation of this generality is tempered by spatial variation in coral cover among reefs separated over 20-200 km. This study addresses such landscape scale variation in coral reefs at 12 sites (7-10 m depth) around St. John (18° 18' 37.04 N, 63° 43' 23.17 W) and St. Thomas (18° 20' 43.57 N, 65° 55' 13.88 W), US Virgin Islands. Surveys completed from 2011 to 2021 were used to test for spatial variation in community dynamics among islands, shores, and sites. Community synchrony ([phi]) was used to evaluate portfolio effects in mediating changes in coral communities. From 2011 to 2021, changes in benthic communities differed among sites and times (i.e., there were site x year interactions), and, while coral cover declined at 11 sites, the decline was 2.6-fold faster around St. Thomas than St. John. The loss of coral cover was driven by multiple taxa that differed among sites, thus revealing asynchronous responses to prevailing conditions. Asynchrony suggests that coral communities at some of the sites have the capacity to exploit portfolio effects to modulate stability, yet these effects did not prevent declines in coral cover that reflect island-scale phenomena. In the US Virgin Islands, coral death is overwhelming the capacity for resilience of coral communities that historically may have benefitted from portfolio effects. Until coral assemblages are depleted through taxonomic extirpation, maintenance of the assemblage composition retains the possibility that increased resilience might emerge if environmental challenges can be alleviated., Author(s): Peter J. Edmunds [sup.1] , Tyler B. Smith [sup.2] Author Affiliations: (1) grid.253563.4, 0000 0001 0657 9381, Department of Biology, California State University, , 91330-8303, Northridge, CA, USA (2) [...]

This study tested the hypothesis that sponge assemblages on the reefs of St. John, US Virgin Islands (18.315°N, 64.716°W), changed from 1992 to 2017. Sponges were identified to species or genus in photoquadrats and were quantified at 2-3 y intervals by density, with linear dimensions used to estimate volume as a proxy for biomass. From 1992 to July 2017, overall sponge density (pooled among taxa) increased, although trends varied among the most common species for which density increased (four species), decreased (one species), or showed no linear relationship with time (2 species). Hurricanes Irma and Maria caused a 51% decline in overall sponge density from July to November 2017, with density in November 2017 being 31% lower than in 1992. For the common sponges, densities of 6 declined by 82-100% between July and November 2017, but densities in November 2017 were 13-736% higher than in 1992 for four species, and 47-100% lower than in 1992 for 3 species. Sponge volume did not change linearly between 1992 and November 2017, but it was reduced by 54% following the hurricanes. Multivariate variation over time in benthic community structure was not strongly associated with sponge density alone, although a significant association with rainfall highlighted the potential roles of this environmental factor in directly, or indirectly, mediating changes in community structure. Overall, the mean density of sponges, as well as most of the common sponge species, trended upwards prior to the hurricanes, but these trends reversed following the storms., Author(s): Peter J. Edmunds [sup.1], Matthew Coblentz [sup.1], Janie Wulff [sup.2] Author Affiliations: (1) grid.253563.4, 0000 0001 0657 9381, Department of Biology, California State University, , 18111 Nordhoff Street, 91330-8303, [...]

Coral reefs are threatened by ocean acidification (OA), which depresses net calcification of corals, calcified algae, and coral reef communities. These effects have been quantified for many organisms, but most experiments last weeks-to-months, and do not test for effects on community structure. Here, the effects of OA on back reef communities from Mo'orea, French Polynesia (17.492 S, 149.826 W), were tested from 12 November 2015 to 16 November 2016 in outdoor flumes maintained at mean pCO.sub.2 levels of 364 [micro]atm, 564 [micro]atm, 761 [micro]atm, and 1067 [micro]atm. The communities consisted of four corals and two calcified algae, with change in mass (G.sub.net, a combination of gross accretion and dissolution) and percent cover recorded monthly. For massive Porites and Montipora spp., G.sub.net differed among treatments, and at 1067 [micro]atm (relative to ambient) was reduced and still positive; for Porolithon onkodes, all of which died, G.sub.net was negative at high pCO.sub.2, revealing dissolution (sample sizes were too small for analysis of G.sub.net for other taxa). Growth rates (% cover month.sup.-1) were unaffected by pCO.sub.2 for Montipora spp., P. rus, Pocillopora verrucosa, and Lithophyllum kotschyanum, but were depressed for massive Porites at 564 [micro]atm. Multivariate community structure changed among seasons, and the variation under all elevated pCO.sub.2 treatments differed from that recorded at 364 [micro]atm, and was greatest under 564 [micro]atm and 761 [micro]atm pCO.sub.2. Temporal variation in multivariate community structure could not be attributed solely to the effects of OA on the chemical and physical properties of seawater. Together, these results suggest that coral reef community structure may be more resilient to OA than suggested by the negative effects of high pCO.sub.2 on G.sub.net of their component organisms., Author(s): Peter J. Edmunds [sup.1] , Steve S. Doo [sup.1] , Robert C. Carpenter [sup.1] Author Affiliations: (Aff1) 0000 0001 0657 9381, grid.253563.4, Department of Biology, California State University, , [...]

Some of the best-known disturbances affecting coral reefs are storms, yet their impacts on light are poorly known. Here, we describe the underwater light on a reef off St. John, US Virgin Islands (18°18'37.04N, 63°43'23.17W), during two hurricanes and multiple tropical waves that occurred between 17 August 2017 and 30 November 2017. Photosynthetically active radiation (PAR) was recorded at 19-m depth and at the surface, and rainfall was measured as a cause of turbidity affecting underwater light. Hurricanes Irma and Maria reduced maximum daily underwater photosynthetic photon flux density (PPFD) to < 14 [micro]mol photons m.sup.-2 s.sup.-1 (< 0.001% of surface PPFD) and, from 1 September to 30 November, were associated with rainfall that was higher (107 cm) than has been recorded over this period since 1972. These reductions in underwater PPFD are unprecedented since at least 2014, and the corresponding values of the diffuse attenuation coefficients (K.sub.d-PAR 0.268-0.426) are among the lowest recorded on a coral reef. Our study reveals the capacity for hurricanes to render a photic habitat temporarily aphotic, and over 69 days (and relative to 2016), to contribute to a 20% reduction in summed, daily integrated underwater PPFD. Large reductions in underwater PPFD have negative implications for photosynthetic taxa, but through the turbidity that reduces underwater light, they create opportunities for population growth by suspension feeding invertebrates., Author(s): Peter J. Edmunds [sup.1] , Georgios Tsounis [sup.1] , Ralf Boulon [sup.2] , Lorenzo Bramanti [sup.3] Author Affiliations: (Aff1) 0000 0001 0657 9381, grid.253563.4, Department of Biology, California State [...]

Many tropical corals have declined in abundance in the last few decades, and evaluating the causal basis of these losses is critical to understanding how coral reefs will change in response to ongoing environmental challenges. Motivated by the likelihood that marine environments will become increasingly unfavorable for coral growth as they warm and become more acidic (i.e., ocean acidification), it is reasonable to evaluate whether specific phenotypic traits of the coral holobiont are associated with ecological success (or failure) under varying environmental conditions including those that are adverse to survival. Initially, we asked whether it was possible to identify corals that are resistant or sensitive to such conditions by compiling quantitative measures of their phenotypic traits determined through empirical studies, but we found only weak phenotypic discrimination between ecological winners and losers, or among taxa. To reconcile this outcome with ecological evidence demonstrating that coral taxa are functionally unequal, we looked beyond the notion that phenotypic homogeneity arose through limitations of empirical data. Instead, we examined the validity of contemporary means of categorizing corals based on ecological success. As an alternative means to distinguish among functional groups of corals, we present a demographic approach using integral projection models (IPMs) that link organismal performance to demographic outcomes, such as the rates of population growth and responses to environmental stress. We describe how IPMs can be applied to corals so that future research can evaluate within a quantitative framework the extent to which changes in physiological performance influence the demographic underpinnings of ecological performance., Introduction Rising concentrations of atmospheric carbon dioxide (C[O.sub.2]) from the burning of fossil fuels have resulted in global climate change (GCC) that has increased global sea surface temperatures (SST) and [...]

With coral reefs impacted by climate change, attention is turning to the extent to which scleractinian corals can acclimatize to new physical conditions. The implicit assumption that acclimatization is beneficial has not been tested for scleractinians, although it has been investigated in other systems and has been referred to as the beneficial acclimation hypothesis (Bah). This study tests this hypothesis for scleractinians in experiments on massive Porites spp. from Moorea, French Polynesia (17° 28.564S, 149° 49.018 W). Corals were acclimated for 15-21 days to three temperatures within the range experienced in the collection habitat and then transferred to each of the same temperatures for a treatment period of 14-15 days. The response of the holobiont was measured as growth, the response of the Symbiodinium populations as maximum photochemical efficiency of open reaction centers II ([F.sub.v]/[F.sub.m]). An ANOVA with polynomial contrasts was used to distinguish among the BAH, three alternative hypotheses and a null hypothesis describing the consequences of acclimation. In the first experiment (2009), massive Porites spp. were unresponsive to temperature. In the second experiment (2013), the BAH was not supported, but growth of the holobiont conformed to the 'hotter is better' (HIB) hypothesis; the response of Symbiodinium populations conformed to developmental buffering. These results suggest that acclimation by massive Porites spp. to temperatures experienced routinely in the natural environment does not have clear beneficial value for growth or photochemical efficiency (i.e., BAH was not supported), but they reveal that acclimation to increased temperature can have value in responding to a variety of subsequent temperatures (i.e., support for HIB)., Introduction The extent to which communities are biologically accommodated or physically controlled has long interested ecologists (Sanders 1968), but now the roles of physical processes in shaping ecosystem structure are [...]

To evaluate the effects of temperature and pC[O.sub.2] on coral larvae, brooded larvae of Pocillopora damicornis from Nanwan Bay, Taiwan (21[degrees]56.179'N, 120[degrees]44.85'E), were exposed to ambient (419-470 [micro]atm) and high (604-742 [micro]atm) pC[O.sub.2] at ~25 and ~29[degrees]C in two experiments conducted in March 2010 and March 2012. Larvae were sampled from four consecutive lunar days (LD) synchronized with spawning following the new moon, incubated in treatments for 24 h, and measured for respiration, maximum photochemical efficiency of PSII ([F.sub.v]/[F.sub.m]), and mortality. The most striking outcome was a strong effect of time (i.e., LD) on larvae performance: respiration was affected by an LD x temperature interaction in 2010 and 2012, as well as an LD x pC[O.sub.2] x temperature interaction in 2012; [F.sub.v]/[F.sub.m] was affected by LD in 2010 (but not 2012); and mortality was affected by an LD x pC[O.sub.2] interaction in 2010, and an LD x temperature interaction in 2012. There were no main effects of pC[O.sub.2] in 2010, but in 2012, high pC[O.sub.2] depressed metabolic rate and reduced mortality. Therefore, differences in larval performance depended on day of release and resulted in varying susceptibility to future predicted environmental conditions. These results underscore the importance of considering larval brood variation across days when designing experiments. Subtle differences in experimental outcomes between years suggest that transgenerational plasticity in combination with unique histories of exposure to physical conditions can modulate the response of brooded coral larvae to climate change and ocean acidification., Introduction Tropical coral reefs are threatened by global climate change (GCC) and ocean acidification (OA), with large numbers of corals killed by bleaching since the 1980s (Hoegh-Guldberg 1999), and the [...]

Octocorals have increased in abundance on a number of Caribbean reefs, but this trend has largely been reported with functional group or genus resolution. A species-level analysis of octocoral communities in St. John, US Virgin Islands was conducted to better understand how this taxon will respond to changing conditions based on their synecology at two sites that are 1.5 km apart and differ in physical conditions. East Cabritte is characterized by moderate wave energy, low sedimentation, and clear water, while contrasting conditions characterize Europa Bay. Surveys conducted in 2014 and 2015 showed that the abundance and size of adult octocorals differed between sites, with taller and denser communities at East Cabritte than Europa Bay (mean height of 32 versus 20 cm; 18 versus 8 colonies m.sup.-2). Octocoral diversity and evenness were similar between sites, although multivariate octocoral community structure differed between sites regardless of whether octocorals were resolved to genera or species. Genus-resolution masked differences between sites for speciose genera like Eunicea. The broad overlap in species representation at both sites suggests that diversity is less responsive than community structure to differing environmental conditions, perhaps because the ecological niches of these species are broad. With 35 octocoral species, and diversity and abundances comparable to those studied > 40 years ago on shallow Caribbean reefs, the dense octocoral communities appearing on some present-day reefs reflect expanded benthic occupancy by a well-known (rather than a novel) community type., Author(s): Georgios Tsounis [sup.1] , Peter J. Edmunds [sup.1] , Lorenzo Bramanti [sup.2] , Bonnie Gambrel [sup.3] , Howard R. Lasker [sup.3] Author Affiliations: (1) California State University Northridge, 0000 [...]

For poikilothermic organisms in aquatic environment, temperature strongly affects metabolism and modulates the extent to which it is mass transfer limited. The effects of temperature on metabolism are translated into organism performance depending on the organism size, morphology, and the flow regime to which they are exposed. Environmental forcing of metabolism is particularly germane to tropical reef corals, because they increasingly are exposed to upward temperature perturbations to which they display variable responses that remain incompletely understood. In this study, we tested the effects of colony size and seawater turbulence on the response of the common Indo-Pacific branching coral, Pocillopora verrucosa, to different seawater temperatures. Using whole-colony calcification as a response variable, 12 tanks (each 150 l) were used in two trials lasting 14 days to contrast the effects of seawater turbulence (two levels) and temperature (25.5 vs 29.5 °C) on colonies varying in size from ~ 4 to 13-cm diameter. Turbulence in the tanks was measured as the root mean square (rms) turbulent flow speed (q.sub.rms), which quantified the variation in speed of complex and non-linear flow, regardless of direction. Treatments contrasted low (q.sub.rms = 0.63 cm s.sup.-1) and high (q.sub.rms = 2.07 cm s.sup.-1) turbulence that were ecologically relevant for shallow coral reefs. The effects of turbulent flow speed and temperature on calcification (mg day.sup.-1) differed among colony sizes: at 25.5 °C, calcification increased with tissue surface area at a slower rate under high, compared to low turbulent flow speeds; at low turbulent flow speeds, calcification increased with tissue surface area more slowly at 29.5 versus 25.5 °C. These results show that the response of branching corals to temperatures depends on colony size and turbulent flow speed. This outcome suggests that spatial heterogeneity in turbulent flow regimes across a coral reef may provide opportunities for branching corals to exploit colony size to modulate susceptibility to rising temperature., Author(s): Peter J. Edmunds [sup.1] , Scott C. Burgess [sup.2] Author Affiliations: (1) Department of Biology, California State University, 0000 0001 0657 9381, grid.253563.4, , 18111 Nordhoff Street, 91330-8303, Northridge, [...]

Recently, it has been suggested that there are conditions under which some coral species appear to be resistant to the effects of ocean acidification. To test if such resistance can be explained by environmental factors such as light and food availability, the present study investigated the effect of 3 feeding regimes crossed with 2 light levels on the response of the coral Porites rus to 2 levels of [pCO.sub.2] at 28[degrees]C. After 1, 2, and 3 weeks of incubation under experimental conditions, none of the factors-including [pCO.sub.2]-significantly affected area-normalized calcification and biomass-normalized calcification. Biomass also was unaffected during the first 2 weeks, but after 3 weeks, corals that were fed had more biomass per unit area than starved corals. These results suggest that P. rus is resistant to short-term exposure to high [pCO.sub.2], regardless of food availability and light intensity. P. rus might therefore represent a model system for exploring the genetic basis of tolerance to OA., Introduction A wide range of local and global disturbances threaten tropical coral reefs (Hughes et al. 2003), but of these, ocean acidification (OA) and rising seawater temperature pose the greatest [...]

I tested the hypothesis that high pC[O.sub.2] (76.6 Pa and 87.2 Pa vs. 42.9 Pa) has no effect on the metabolism of juvenile massive Porites spp. after 11 days at 28 °C and 545 µmol quanta [m.sup.-2] [s.sup.-1]. The response was assessed as aerobic dark respiration, skeletal weight (i.e., calcification), biomass, and chlorophyll fluorescence. Corals were collected from the shallow (3-4 m) back reef of Moorea, French Polynesia (17°28.614'S, 149°48.917'W), and experiments conducted during April and May 2011. An increase in pC[O.sub.2] to 76.6 Pa had no effect on any dependent variable, but 87.2 Pa pC[O.sub.2] reduced area-normalized (but not biomass-normalized) respiration 36 %, as well as maximum photochemical efficiency ([F.sub.v]/[F.sub.m]) of open RCIIs and effective photochemical efficiency of RCIIs in actinic light (ΔF/[F'.sub.m]); neither biomass, calcification, nor the energy expenditure coincident with calcification (J [g.sup.-1]) was effected. These results do not support the hypothesis that high pC[O.sub.2] reduces coral calcification through increased metabolic costs and, instead, suggest that high pC[O.sub.2] causes metabolic depression and photochemical impairment similar to that associated with bleaching. Evidence of a pC[O.sub.2] threshold between 76.6 and 87.2 Pa for inhibitory effects on respiration and photochemistry deserves further attention as it might signal the presence of unpredictable effects of rising pC[O.sub.2]., Introduction Amidst efforts to evaluate the effects of ocean acidification (OA) on the calcification of scleractinian corals (Erez et al. 2011), much of which has revealed negative implications (Doney et [...]

In this study, juvenile colonies of massive Porites spp. (a combination of P. lutea and P. lobata) from the lagoon of Moorea (W 149°50', S 17°30') were damaged and exposed to contrasting conditions of temperature and flow to evaluate how damage and abiotic conditions interact to affect growth, physiological performance, and recovery. The experiment was conducted in April and May 2008 and consisted of two treatments in which corals were either undamaged (controls) or damaged through gouging of tissue and skeleton in a discrete spot mimicking the effects of corallivorous fishes that utilize an excavating feeding mode. The two groups of corals were incubated for 10 days in microcosms that crossed levels of temperature (26.7 and 29.6°C) and flow (6 and 21 cm s.sup.-1), and the response assessed as overall colony growth (change in weight), dark-adapted quantum yield of PSII (F.sub.v/F.sub.m), and healing of the gouged areas. The influence of damage on growth was affected by temperature, but not by flow. When averaged across flow treatments, damage promoted growth by 25% at 26.7°C, but caused a 25% inhibition at 29.6°C. The damage also affected F.sub.v/F.sub.m in a pattern that differed between flow speeds, with a 10% reduction at 6 cm s.sup.-1, but a 4% increase at 21 cm s.sup.-1. Regardless of damage, F.sub.v/F.sub.m at 21 cm s.sup.-1 was 11% lower at 26.7°C than at 29.6°C, but was unaffected by temperature at 6 cm s.sup.-1. The lesions declined in area at similar rates (4-5% day.sup.-1) under all conditions, although the tissue within them regained a normal appearance most rapidly at 26.7°C and 6 cm s.sup.-1. These findings show that the response of poritid corals to sub-lethal damage is dependent partly on abiotic conditions, and they are consistent with the hypothesis that following damage, calcification and photosynthesis can compete for metabolites necessary for repair, with the outcome affected by flow-mediated mass transfer. These results may shed light upon the ways in which poritid corals respond to biting by certain corallivorous fishes., Author(s): Peter J. Edmunds [sup.1] , Hunter S. Lenihan [sup.2] Author Affiliations: (1) grid.253563.4, 0000000106579381, Department of Biology, California State University, , 91330-8303, Northridge, CA, USA (2) grid.133342.4, 0000000419369676, Bren [...]

We tested the rarely considered hypothesis that the ultraviolet portion (UVR, 280-400 nm) of the light spectrum affects patterns of recruitment in reef-building corals. The premise for this hypothesis rests in the fact that biologically relevant intensities of UVR penetrate to considerable depths (> 24 m) in the clear waters surrounding many coral reefs, and that reef organisms allocate substantial resources to prevent and repair UVR damage. The ability of larvae spawned by the brown morph of the Caribbean coral, Porites astreoides, to detect and avoid UVR was assessed in petri dishes where one-half of the dish was shielded from UVR and the other exposed. Observations made every 30 min between 10:30 and 13:30 h showed significantly higher densities of larvae swimming in regions shielded from UVR. To determine how this behavior affects settlement patterns, larvae collected from P. astreoides adults at 18 m depth were released into chambers deployed at 17 m depth where they were given a choice of three different light regions in which to settle: PAR (PAR = 400-700 nm), PAR + UVAR (UVAR = 320-400 nm), and PAR + UVAR + UVBR (UVBR = 280-320 nm). At the end of the experiment, greater numbers of P. astreoides larvae had settled in the region of the tube where UVR was reduced than would be expected if dispersion were random. To our knowledge, this is the first demonstration in any reef-building coral species that planula larvae can detect UVR and that it affects their choice of a settlement site. These results indicate that the capacity to detect and avoid habitats with biologically damaging levels of UVR may be one factor contributing to the successful recruitment of coral larvae., Introduction Most sessile marine invertebrates have a pelagic larval stage that results from spawned gametes and external fertilization, or internal fertilization followed by brooding and release of fully developed larvae [...]

Metabolic rates provide a valuable means to assess the condition of early life stages of scleractinians, but their small biomass creates a signal-to-noise problem in a confined respirometer. To avoid this problem, measurements of the oxygen diffusion boundary layer (DBL) and Fick's first law were used to calculate the respiration rate of coenosarc tissue on recruits (i.e., colonies 5-14 mm diameter) of Porites lutea (Edwards and Haime, 1860) exposed to two temperatures at a flow speed of 0.6 cm [s.sup.-1]. All experiments were completed in Moorea, French Polynesia, between November and December 2003. At 26.8[degrees]C, the DBL was 565 [+ or -] 55 lm thick, the oxygen saturation adjacent to the tissue was 80 [+ or -] 3%, and the mean respiration of the coenosarc was 1.2 [+ or -] 0.1 [micro]l [O.sub.2] [cm.sup.-2] [h.sup.-1] (all values mean [+ or -] SE, n = 10). Exposure to 29.7[degrees]C for 24-48 h did not affect the DBL thickness but significantly reduced the oxygen saturation adjacent to the tissue (to 74%) and increased the mean respiration rate by 35%. As the small corals differed slightly in size, in a uniform flow speed they experienced dissimilar flow environments as characterized by the Reynolds number (Re), thereby creating the opportunity to test the flow dependency of respiration. At 26.8[degrees]C, respiration and Re were unrelated, but at 29.7[degrees]C, the relationship was positive and statistically significant. Thus, respiration of small corals may not be mass transfer limited at low temperature, but relatively small increases in temperature may result in an increased metabolic rate leading to mass transfer limitation and flow-dependent rates of respiration., Introduction The demographics of individual species drive changes in community structure, yet few studies at the community level include the explicit analyses of birth, death, and growth rates necessary to [...]

Understanding population dynamics is a long-standing objective of ecology, but the need for progress in this area has become urgent. For coral reefs, achieving this objective is impeded by a lack of information on settlement versus post-settlement events in determining recruitment and population size. Declines in coral abundance are often inferred to be associated with reduced densities of recruits, which could arise from mechanisms occurring at larval settlement, or throughout post-settlement stages. This study uses annual measurements from 2008 to 2021 of coral cover, the density of coral settlers (S), the density of small corals (SC), and environmental conditions, to evaluate the roles of settlement versus post-settlement events in determining rates of coral recruitment and changes in coral cover at Moorea, French Polynesia. Coral cover, S, SC, and the SC:S ratio (a proxy for post-settlement success), and environmental conditions, were used in generalized additive models (GAMs) to show that: (a) coral cover was more strongly related to SC and SC:S than S, and (b) SC:S was highest when preceded by cool seawater, low concentrations of Chlorophyll a, and low flow speeds, and S showed evidence of declining with elevated temperature. Together, these results suggest that changes in coral cover in Moorea are more strongly influenced by post-settlement events than settlement. The key to understanding coral community resilience may lie in elucidating the factors attenuating the bottleneck between settlers and small corals., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

A potential consequence of individuals compensating for density-dependent processes is that rare or infrequent events can produce profound and long-term shifts in species abundance. In 1983-1984 a mass mortality event reduced the numbers of the abundant sea urchin Diadema antillarum by 95-99% throughout the Caribbean and western Atlantic. Following this event, the abundance of macroalgae increased and the few surviving D. antillarum responded by increasing in body size and fecundity. These initial observations suggested that populations of D. antillarum could recover rapidly following release from food limitation. In contrast, published studies of field manipulations indicate that this species had traits making it resistant to density-dependent effects on offspring production and adult mortality; this evidence raises the possibility that density-independent processes might keep populations at a diminished level. Decadal-scale (1983-2011) monitoring of recruitment, mortality, population density and size structure of D. antillarum from St John, US Virgin Islands, indicates that population density has remained relatively stable and more than an order of magnitude lower than that before the mortality event of 1983-1984. We detected no evidence of density-dependent mortality or recruitment since this mortality event. In this location, model estimates of equilibrium population density, assuming density-independent processes and based on parameters generated over the first decade following the mortality event, accurately predict the low population density 20 years later (2011). We find no evidence to support the notion that this historically dominant species will rebound from this temporally brief, but spatially widespread, perturbation.

Evaluating the response of organisms to stress assumes that functional benchmarks are available against which the response can be gauged, but this expectation remains unfulfilled for many taxa. As a result, attempts to describe the organismic effects of environmental degradation and physiological stress can prove misleading. Functional benchmarks and the effects of stress are particularly germane to coral reefs that globally are exposed to significant environmental challenges, and in this study, we compiled data on scleractinian corals to describe a reference against which stress responses can be gauged. Based on this construct, we tested the veracity of well-established contrasts--involving differences in physiological function among depths and families--to evaluate the capacity of available data to support synthetic analyses. Our analysis used 126 papers describing 37 genera, and at least 73 species, and described 13 traits, first independent of depth, and second, by depth. Data appropriate for these analyses were so sparse that depth- and family-level effects were inconspicuous, although the depth contrast revealed a decline in dark respiration and an increase in calcification (both normalized to area) in deeper water. Our analyses of scleractinian literature revealed limitations of the data available for synthetic analyses, as well for describing functional benchmarks within this taxon. We attribute some of these effects to differences in the physical environment under which measurements were made, and suspect that such problems are commonplace for other taxa. Dynamic Energy Budget (DEB) models provide one means to overcome some of these problems, and they can be used for any taxon to quantitatively summarize data for comparative analyses of stressor responses. The suitability of these models is illustrated for scleractinian corals by predicting from first principles the ratio of Symbiodinium to holobiont carbon and the respiration.

To date, coral death has been the most conspicuous outcome of warming tropical seas, but as temperatures stabilize at higher values, the consequences for the corals remaining will be mediated by their demographic responses to the sub-lethal effects of temperature. To gain insight into the nature of these responses, here I develop a model to test the effect of increased temperature on populations of three pocilloporid corals at One Tree Island, near the southern extreme of the Great Barrier Reef (GBR). Using Seriatopora hystrix, S. caliendrum and Pocillopora damicornis as study species, the effects of temperature on growth were determined empirically, and the dynamics of their populations determined under natural temperatures over a 6-month period between 1999 and 2000 [defined as the study year (SY)]. The two data sets were combined in a demographic test of the possibility that the thermal regime projected for the southern GBR in the next 55-83 years--warmer by 3 degrees C than the study year (the SY+3 regime), which is equivalent to 1.4 degrees C warmer than the recent warm year of 1998--would alter coral population trajectories through the effects on coral growth alone; the analyses first were completed by species, then by family after pooling among species. Laboratory experiments showed that growth rates (i.e., calcification) varied significantly among species and temperatures, and displayed curvilinear thermal responses with growth maxima at approximately 27.1 degrees C. Based on these temperature-growth responses, the SY+3 regime is projected to: (1) increase annualized growth rates of all taxa by 24-39%, and defer the timing of peak growth from the summer to the autumn and spring, (2) alter the intrinsic rate of population growth (lambda) for S. hystrix (lambda decreases 26%) and S. caliendrum (lambda increases 5%), but not for P. damicornis, and (3) have a minor effect on lambda (a 0.3% increase) for the Pocilloporidae, largely because lambda varies more among species than it does between temperatures. Ten-year population projections suggest that the effects of a sub-lethal increase in temperature (i.e., the SY+3 regime) are relatively small compared to the interspecific differences in population dynamics, but nevertheless will alter the population size and increase the relative abundance of large colonies at the expense of smaller colonies for all three species, as well as the Pocilloporidae. These effects may play an important role in determining the nuances of coral population structure as seawater warms, and their significance may intensity if the coral species pool is depleted of thermally sensitive species by bleaching.