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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) [...]

Abstract. This study tested the bleaching response of the Pacific coral Seriatopora caliendrum to short-term exposure to high temperature and elevated partial pressure of carbon dioxide (pC[O.sub.2]). Juvenile colonies collected [...]

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 [...]

Early life stages of the coral Seriatopora caliendrum were used to test the hypothesis that the depression of dark respiration in coral recruits by high pC[O.sub.2] is caused by perturbed protein metabolism. First, the contribution of protein anabolism to respiratory costs under high pC[O.sub.2] was evaluated by measuring the aerobic respiration of S. caliendrum recruits with and without the protein synthesis inhibitor emetine following 1 to 4 days at 45 Pa versus 77 Pa pC[O.sub.2]. Second, protein catabolism under high pC[O.sub.2] was evaluated by measuring the flux of ammonium (N[H.sub.4.sup.+]) from juvenile colonies of S. caliendrum incubated in darkness at 47 Pa and 90 Pa pC[O.sub.2]. Two days after settlement, respiration of recruits was affected by an interaction between emetine and pC[O.sub.2], with emetine reducing respiration 63% at 45 Pa pC[O.sub.2] and 27% at 77 Pa pC[O.sub.2]. The interaction disappeared 5 days after settlement, when respiration was reduced 27% by emetine under both pC[O.sub.2] conditions. These findings suggest that protein anabolism accounted for a large proportion of metabolic costs in coral recruits and was affected by high pC[O.sub.2], with consequences detected in aerobic respiration. Juvenile S. caliendrum showed net uptake of N[H.sub.4.sup.+] at 45 Pa pC[O.sub.2] but net release of N[H.sub.4.sup.+] at 90 Pa pC[O.sub.2], indicating that protein catabolism, N[H.sub.4.sup.+] recycling, or both were affected by high pC[O.sub.2]. Together, these results are consistent with the hypothesis that high pC[O.sub.2] affects protein metabolism in corals., Introduction Ocean acidification (OA) caused by the dissolution of atmos[pH.sub.e]ric pC[O.sub.2] in seawater is a serious threat to marine life (Hoegh-Guldberg et al., 2007). Of the many taxa likely to [...]

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 [...]

. Juvenile colonies of massive Porites spp. were exposed to manipulated pH and bicarbonate ([HC[O.sub.3.sup.-]]) in situ to test the hypothesis that ocean acidification (OA) does not affect respiration and calcification. Incubations lasted 28 h and exposed corals to ambient temperature and light with ecologically relevant water motion. Three treatments were applied: (1) ambient conditions of pH 8.04 and 1751 µmol] [HC[O.sub.3.sup.-]] k[g.sup.-1] (Treatment 1), (2) pC[O.sub.2]-induced ocean acidification of pH 7.73 and 2011 µmol [HC[O.sub.3.sup.-]] k[g.sup.-1] (Treatment 2), and (3) pC[O.sub.2] and HC[O.sub.3.sup.-]-enriched seawater of pH 7.69 and 2730 µmol HC[O.sub.3.sup.-] k[g.sup.-1] (Treatment 3). The third treatment providing elevated [HC[O.sub.3.sup.-]] was used to test for stimulatory effects of dissolved inorganic carbon on calcification under low pH and low saturation of aragonite ([Ω.sub.arag]), but it does not reflect conditions expected to occur under C[O.sub.2]-driven OA. Calcification of juvenile massive Porites spp. was affected by treatments, with an 81% elevation in Treatment 3 versus Treatment 1, but no difference between Treatments 1 and 2; respiration and the metabolic expenditure concurrent with calcification remained unaffected. These findings indicate that juvenile massive Porites spp. are resistant to short exposures to OA in situ, and separately, that they can increase calcification at low pH and low [Ω.sub.arag] if [HC[O.sub.3.sup.-]] is elevated. Juvenile Porites spp. may therefore be limited by dissolved inorganic carbon under ambient pC[O.sub.2] conditions., Introduction Coral reefs are threatened by natural and anthropogenic factors, including global climate change and ocean acidification (OA) (Hoegh-Guldberg et al., 2007; Wilkinson, 2008). OA poses a particularly severe threat, [...]

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 comparison to some corals, massive Porites spp. is physiologically resilient to environmental assaults and is becoming more abundant on coral reefs. To evaluate the extent to which thick tissues contribute to this physiological resilience, we tested the hypothesis that the Symbio-dinium in Porites lutea are phenotypically and genetically homogeneous with regard to their distribution vertically within the tissue, and in their response to temperature. Symbiodinium density, genetic identity, and photophysiol-ogy were compared between outer and inner tissues defined as adjacent layers--2 mm thick and beneath the skeleton surface. Symbiodinium densities were 5-fold greater and their cells contained less chlorophyll a in outer versus inner tissue, but ITS2 sequence identities were genetically uniform between layers. Maximum photochemical efficiency ([F.sub.v] /[F.sub.m]) in inner and outer tissue from the top and sides of the corals differed 6%-7%, with F rn greater in inner versus outer tissue on the top of colonies. On the tops of colonies, the initial slopes of the rETR versus irradiance relationship were not different between tissue layers, although they tended to be less steep for inner tissue. When exposed for 12 h to 28 °C, 30 °C, or 32 °C at--700 Amol quanta [m.sup.-2] [s.sup.-1], there was a trend for [F.sub.v]/[F.sub.m], of the Sym-biodinium in both tissue layers to be reduced at 32 °C. Our results do not conform well to shade acclimatization in inner versus outer tissue of P. lutea, and they imply within-tissue heterogeneity that may be an important determinant of physiological performance in perforate corals., Introduction Corals vary in biomass and tissue thickness among seasons, depths, and species (Brown et al., 1999; Fitt et al., 2000), but it is unclear how this variation is achieved [...]

To test for threshold effects in the response of coral physiology to increasing seawater flow, field and laboratory experiments were conducted in Moorea. First, the growth of juvenile massive Porites spp. and branching P. irregularis was compared among habitats differing in water motion. Growth of massive Porites spp. responded to flow in a pattern consistent with a threshold effect, whereas growth of P. irregularis increased linearly with flow. Second, a recirculating flume was used to test the effect of flow on photophysiology ([increment of F]/[F.sub.m] effective photochemical efficiency) for massive Porites spp.; [increment of F]/[F.sub.m]' displayed a threshold response at 23 cm [s.sup.-1] and 28 ° C, but not at 31 ° G. Finally, intra-colony variation in the response of AF/Fm' to flow and temperature was explored to evaluate the functional significance of colony shape in small corals. [increment of F]/[F.sub.m]' on the top and upstream surfaces of massive Porites spp. responded with a threshold effect of flow at 28 ° C (but not 31 ° C), but [increment of F]/[F.sub.m]' on downstream surfaces was unresponsive to flow. [increment of F]/[F.sub.m]' for P. irregularis was less responsive to flow than for massive Porites spp., suggesting that the photophysiological response of corals to varying flow speeds may differ between species and morphologies. Together, these results emphasize that flow can have diverse effects on the physiology of corals, with the outcome depending on flow speed, temperature, location on the colony, and perhaps morphology., Introduction Over the last 25 years, large-scale bleaching of scleractinian corals through the loss of Symhiodinium algae, their chlorophyll, or both has become common (Fitt et ai, 2001), and is [...]

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 [...]

To better understand the consequences of climate change for scleractinian corals, Stylophora pistillata was used to test the effects of temperature on the settlement and physiology of coral larvae. Freshly released larvae were exposed to temperatures of 23°C, 25°C (ambient), and 29°C at light intensities of ≅ 150 µmol photons [m.sup.-2] [s.sup.-1]. The effects were assessed after 12 h as settlement to various substrata (including a choice between crustose coralline algae [CCA] and limestone) and as maximum quantum yield of PSII ([F.sub.v]/[F.sub.m]) in the larvae versus in their parents. Regardless of temperature, 50%-73% of the larvae metamorphosed onto the plastic of the incubation trays or in a few cases were drifting in the water, and 14% settled on limestone. However, elevated temperature (29 °C) reduced the percentage of larvae swimming by 81%, and increased the percentage choosing CCA nearly 7-fold, both relative to the outcomes at 23°C. Because temperature did not affect settlement on limestone or plastic, increased settlement on CCA reflected temperature-mediated choices by larvae that otherwise would have remained swimming. Interestingly, [F.sub.v]/[F.sub.m] was unaffected by temperature, but it was 4% lower in the larvae than in the parents. These results are important because they show that temperature can affect the settlement of coral larvae and because they reveal photophysiological differences between life stages that might provide insights into the events associated with larval development., Introduction High diversity and relatively high productivity are classic characteristics of tropical coral reefs (Hatcher, 1997; Paulay, 1997), yet these features are being eroded by declining coral cover and impaired [...]

On Caribbean reefs, a striking trend of the last 25 years has been the decline in cover of the framework-building coral Montastraea annularis, a species that has dominated reefs throughout the region for millennia. Clearly, such losses are important ecologically, but to evaluate their significance fully, they need to be placed in the context of the proximal causes and balanced against the potential for gains in cover through growth and recruitment. In this study, a population of M. annularis in St. John, U.S. Virgin Islands, was censused annually from 1988 to 2003 to quantify coral cover and construct a size-based demographic model. The model was developed to explore the mechanisms of change in coral cover and to ascertain likely trajectories for future population growth. Over the study period, the cover of M. annularis declined from 41% in 1988, to ~12% by 1999 (a 72% decline) but remained unchanged statistically for the last five years of the study. Between 1988 and 2003, colony abundances declined by 57% (from 47 colonies/[m.sup.2] to 20 colonies/[m.sup.2]), and the losses were driven mostly by the death and fission of medium to large colonies (i.e., [greater than or equal to] 151 [cm.sup.2]). By 2003, the population had proportionally more small colonies (70% were [less than or equal to] 50 [cm.sup.2]) and fewer large colonies (3% were >250 [cm.sup.2]) than in 1988 (60% and 6%, respectively), and the changes in population structure had accelerated [greater than or equal to] 14% in terms of the rate of change in population size and the time necessary to attain equilibrium of colony size structure. Importantly, this analysis revealed an ongoing and imminent population decline coincident with the recent period of apparently stable coral cover. Fifty-year projections indicate the strong likelihood of extirpation of M. annularis at this particular site in St. John (in contrast to a continuation of constant low cover) and suggest that the 1988 population structure cannot be restored by recruitment. It is unlikely that the population decline will reverse until there is an amelioration of the conditions that kill individual colonies. Key words: Caribbean; coral; demographics; marine protected area; Montastraea annularis; St. John; Seleractinia; U.S. Virgin Islands; Yawzi Point.

In this study, two factorial experiments were used to investigate the role of tissue age in affecting the phenotypic expression of calcification in scleractinian corals. Both experiments tested whether calcification was altered by tissue age and whether corals of different ages exploit plasticity to differing degrees by altering calcification rates under new environmental conditions. To isolate age and size effects, branches of the Caribbean coral Madracis mirabilis were broken into a distal portion that was functionally young and a proximal portion that was functionally old. Fragments were transplanted from a deep (17 m) to a shallow (9 m) site in a Jamaican lagoon to test whether age affected the plasticity of calcification. Both experiments demonstrated that calcification scaled isometrically in the two age groups, and although scaling exponents were indistinguishable statistically among ages, young fragments calcified faster than old fragments. Thus, the effect of age on calcification rate was absolute and independent of size. However, the interactive effect of age and depth was not significant, demonstrating that ability to alter calcification rate (i.e., the extent of phenotypic plasticity for this trait) was unaffected by age. Together, these patterns are consistent with the hypothesis that the proximal modules (i.e., polyps) of M. mirabilis are subject to physiological senescence, as has been reported for other clonal organisms, including algae, fungi, plants, bryozoans, ascidians, and other cnidarians., Introduction The modular design of many benthic marine invertebrates, including cnidarians, bryozoans, and ascidians, has profound implications for their biology (Jackson et al., 1985). In particular, the ecological success of [...]

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 [...]

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 [micro]m 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.

The recruitment and survival of juvenile corals is central to the maintenance of coral reef communities and the repopulation of denuded reef substrata. Although it is widely accepted that the mortality of scleractinians is inversely proportional to size, the biotic and abiotic factors that drive this trend remain unclear. Here we measure the mortality of corals on the reefs of St. John (U.S. Virgin Islands) to demonstrate that small corals are more likely to die than their larger counterparts, and we explore whether the photophysiological performance of juveniles in two size classes can provide some insight into why smaller corals are so vulnerable. To evaluate photophysiological performance, we examined chlorophyll fluorescence in two size classes (mean diameters 15 mm and 45 mm) of juvenile colonies of Porites astreoides exposed for short periods to ambient and elevated temperatures. Our results show that the photophysiology of these size classes differs under ambient conditions, with dark-adapted quantum yield ([F.sub.v]/[F.sub.m]) being significantly higher in smaller compared to bigger juveniles. As expected, the photophysiology of both size classes is negatively impacted by thermal stress, and although size-related trends are evident in our data, the interaction between size and temperature is not statistically significant. Thus, while there is size dependency in the photophysiological performance of juvenile colonies of P. astreoides, the link between this aspect of scleractinian biology and the higher mortality of small juvenile corals in the face of high thermal stress remains unclear., As a context for this study, we draw on mortality data for different size classes of corals at five sites on the shallow reefs of St. John. Between 1996 and [...]

Tropical reef corals are ecologically important examples of mutualistic symbioses whose success is defined by the interwoven biologies of their symbiotic partners. These associations are exquisitely regulated, yet the equilibrium [...]

Morphological plasticity is common among clonal organisms, including scleractinian corals, yet the role of phenotypic plasticity in coral ecology and evolution is largely unexplored. Additionally, it is unclear how much variation in plastic responses exists among individuals, populations, and species, and thus how much potential there is for natural selection to act on coral reaction norms. In the branching coral Madracis mirabilis, corallite architecture and density, branch diameter and spacing, and overall aggregate morphology all vary among environments. To examine the role of phenotypic plasticity in generating these patterns, clonal replicates of five genotypes of M. mirabilis were transplanted from each of two source populations into four treatment environments on the north coast of Jamaica. Flow rate, sedimentation, irradiance, water temperature, and salinity all varied among these environments. DNA fingerprinting was used to ensure that the 10 transplanted genotypes were genetically distinct. Six morphological traits (intersepta area, septa length, columella area, corallite area, corallite spacing, and branch tip diameter) were measured after transplantation to determine whether they were altered in response to environmental conditions. Because these traits were correlated, principal components analysis was used to define new, uncorrelated traits for analysis. Four of the five corallite traits and branch diameter were significantly affected by the environment, demonstrating that morphological variation among environments in M. mirabilis is due in large part to phenotypic plasticity. No difference was detected between the two source populations in the magnitude or direction of their plastic responses, but there was substantial variation among genotypes (genotype x environment interaction). Many of the phenotypic changes of both populations resulted in the transplants becoming morphologically similar to resident conspecifics in each treatment environment. Genotypes from both populations were able to maintain similar growth rates under diverse environmental conditions. Such morphological convergence by phenotypic plasticity may expand the ecological range of this species by enabling genotypes to tolerate spatially and temporally variable environments. Key words: genotype x environment interaction; Madracis mirabilis; phenotypic plasticity; reaction norm; Scleractinia; skeletal structure., INTRODUCTION Scleractinian corals typically display a striking degree of morphological variation in colony shape and corallite structure along environmental gradients (Foster 1980, Brown et al. 1985), and among geographic regions [...]

The transition of many Caribbean reefs from coral to macroalgal dominance has been a prominent issue in coral reef ecology for more than 20 years. Alternative stable state theory predicts that these changes are reversible but, to date, there is little indication of this having occurred. Here we present evidence of the initiation of such a reversal in Jamaica, where shallow reefs at five sites along 8 km of coastline now are characterized by a sea urchin-grazed zone with a mean width of 60 m. In comparison to the seaward algal zone, macroalgae are rare in the urchin zone, where the density of Diadema antillarum is 10 times higher and the density of juvenile corals is up to 11 times higher. These densities are close to those recorded in the late 1970s and early 1980s and are in striking contrast to the decade-long recruitment failure for both Diadema and scleractinians. If these trends continue and expand spatially, reefs throughout the Caribbean may again become dominated by corals and algal turf.

STEVEN V. VOLLMER [*] Abstract. Although most physiological traits scale allometrically in unitary organisms, it has been hypothesized that modularity allows for isometric scaling in colonial modular taxa. Isometry would [...]

SYNOPSIS. The ability of scleractinian corals to survive changes that are predicted in the global environment over the next century will lie in their physiological mechanisms of acclimatization. Corals display rapid modifications in behavior, morphology and physiology enabling them to photoacclimate to changing light conditions, a scenario that demonstrates considerable biological flexibility. Here we argue that the acclimatization mechanisms in corals are fundamentally similar to those exhibited by other invertebrate taxa. We discuss protein metabolism as a mechanism underlying acclimatization responses in reef corals, and explore the relationship between protein turnover, metabolic rate, growth rate, and acclimatization capacity. Our preliminary analyses suggest that corals with low growth rates (µCa/mgN/h) and high metabolic rates (µ[O.sub.2]/cm2/hr), such as the massive species, acclimatize more effectively than those with high growth rates and low metabolic rates, a feature that is characteristic of branching species. We conclude that studies of protein turnover, combined with temporally relevant investigations into the dynamic aspects of coral dinoflagellate symbioses will provide considerable insight into why corals exhibit such a high level of variation in response to the same environmental challenge. Furthermore, a more detailed understanding of acclimatization mechanisms is essential if we are to predict how a coral assemblage will respond to present and future environmental challenges., INTRODUCTION There is concern regarding the ability of scleractinian corals and reef communities to tolerate changes in the global environment predicted to result from [CO.sub.2] emissions and global warming. In [...]