Coral Madracis Mirabilis Research Articles

Experimental Approaches for the Evaluation of Allelopathic Interactions Between Hermatypic Corals and Marine Benthic Cyanobacteria in the Colombian Caribbean

Blooms of marine benthic cyanobacteria are recurrent in several locations at the Colombian Caribbean. In these events, cyanobacteria grow over the substrate and benthic organisms although their effect has not been fully assessed. This study evaluated interactions between cyanobacteria and hermatypic corals, in order to identify any deleterious effects that could be related to allelopathic mechanisms. Organic extracts from cyanobacteria collected in San Andres, Old Providence and Rosario islands were tested against embryos of the reef-building coral Orbicella annularis. The indirect effect of cyanobacterial extracts was also assessed by resuspending the extracts in seawater and monitoring polyp retraction and recovery of the coral Madracis mirabilis (=auretenra). Additionally, the effect of direct contact between cyanobacterial extracts and the coral Porites porites was assessed by incorporating cyanobacterial extracts into PhytagelTM gels and placed in direct contact with the coral. After 24, 48 and 72 h of exposure, chromatographic profiles of associated zooxanthellae was evaluated by HPLC. A deleterious effect on the zooxanthellae was evidenced by an increase in pheophytin, a degradation product from chlorophyll. The competitive abilities of algae and cyanobacteria should be considered as a constraint to reef restoration initiatives. Cyanobacteria have the ability to compete with corals due to their growth rates, defenses against herbivory and potentially allelopathic mechanisms.

A 3000 year record of Caribbean reef urchin communities reveals causes and consequences of long‐term decline in Diadema antillarum

Urchins are the last abundant grazers of macroalgae on most Caribbean reefs following the historical overexploitation of herbivorous fishes. The long‐spined urchin Diadema antillarum was particularly effective at controlling macroalgae and facilitating coral dominance on Caribbean reefs until its ecological extinction from a catastrophic disease epidemic in the early 1980s. Despite their important role in the structure and functioning of Caribbean reef ecosystems, the natural dynamics of Caribbean reef urchin communities are poorly known due to the paucity of ecological survey data prior to large‐scale human disturbances and the Diadema dieoff. To help resolve the baseline abundances and ecological roles of common urchin taxa, we track changes in urchin abundance and composition over the past 3000 yr from analysis of subfossil urchin spines preserved in reef matrix cores collected in Caribbean Panama. Echinometra consistently dominated the subfossil spine assemblage, while Diadema was consistently rare in the subfossil record in this region. Rather than increasing during a period of heightened human exploitation of their fish competitors and predators, Diadema began declining over a millennium ago. Convergent cross mapping (CCM) causality analyses reveal that Diadema abundance is causally related to coral community composition. Diadema is negatively affected by Acropora cervicornis dominance, likely due to the tight association between this coral and the threespot damselfish, an effective Diadema competitor. Conversely, Diadema positively affects the abundance of the coral Madracis mirabilis, possibly via its control of macroalgae. Causal relationships were not detected among abundances of individual urchin taxa, indicating that inter‐specific echinoid competition is not a factor limiting Diadema recovery. Our detailed record of prehistorical and historical urchin community dynamics suggests that the failure of Diadema to recover over 30 yr after its mass mortality event may be due in part to the prey release of damselfish following the long‐term overfishing of piscivorous fishes.

Nitrogen and phosphorus uptake rates of different species from a coral reef community after a nutrient pulse

Terrestrial runoff after heavy rainfall can increase nutrient concentrations in waters overlying coral reefs that otherwise experience low nutrient levels. Field measurements during a runoff event showed a sharp increase in nitrate (75-fold), phosphate (31-fold) and ammonium concentrations (3-fold) in waters overlying a fringing reef at the island of Curaçao (Southern Caribbean). To understand how benthic reef organisms make use of such nutrient pulses, we determined ammonium, nitrate and phosphate uptake rates for one abundant coral species, turf algae, six macroalgal and two benthic cyanobacterial species in a series of laboratory experiments. Nutrient uptake rates differed among benthic functional groups. The filamentous macroalga Cladophora spp., turf algae and the benthic cyanobacterium Lyngbya majuscula had the highest uptake rates per unit biomass, whereas the coral Madracis mirabilis had the lowest. Combining nutrient uptake rates with the standing biomass of each functional group on the reef, we estimated that the ammonium and phosphate delivered during runoff events is mostly taken up by turf algae and the two macroalgae Lobophora variegata and Dictyota pulchella. Our results support the often proposed, but rarely tested, assumption that turf algae and opportunistic macroalgae primarily benefit from episodic inputs of nutrients to coral reefs.

A computational method for quantifying morphological variation in scleractinian corals

Morphological variation in marine sessile organisms is frequently related to environmental factors. Quantifying such variation is relevant in a range of ecological studies. For example, analyzing the growth form of fossil organisms may indicate the state of the physical environment in which the organism lived. A quantitative morphological comparison is important in studies where marine sessile organisms are transplanted from one environment to another. This study presents a method for the quantitative analysis of three-dimensional (3D) images of scleractinian corals obtained with X-ray Computed Tomography scanning techniques. The advantage of Computed Tomography scanning is that a full 3D image of a complex branching object, including internal structures, can be obtained with a very high precision. There are several complications in the analysis of this data set. In the analysis of a complex branching object, landmark-based methods usually do not work and different approaches are required where various artifacts (for example cavities, holes in the skeleton, scanning artifacts, etc.) in the data set have to be removed before the analysis. A method is presented, which is based on the construction of a medial axis and a combination of image-processing techniques for the analysis of a 3D image of a complex branching object where the complications mentioned above can be overcome. The method is tested on a range of 3D images of samples of the branching scleractinian coral Madracis mirabilis collected at different depths. It is demonstrated that the morphological variation of these samples can be quantified, and that biologically relevant morphological characteristics, like branch-spacing and surface/volume ratios, can be computed.

Tissue Age Affects Calcification in the Scleractinian CoralMadracis mirabilis

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.

Negligible risks to corals from antifouling booster biocides and triazine herbicides in coastal waters of the Chagos Archipelago

The Chagos Archipelago is the most isolated and biologically diverse group of atolls in the central Indian Ocean. It contains 5 islanded atolls, including the world’s largest atoll, the Great Chagos Bank. Following the abandonment of the copra plantations, in 1973, most islands are uninhabited and have rarely been visited. The only exception is Diego Garcia, part of which is a strategic military base with appropriate infrastructure to support long range aircraft and ships which visit and reside for extended periods in the lagoon which provides anchorage. In 1996, a research programme was undertaken in Chagos (Sheppard and Seaward, 1999) to assess the atolls biodiversity, biogeographic role with respect to fisheries, and the degree of their pristine condition. Analyses of sediment samples from throughout the Archipelago revealed that hydrocarbons present were predominantly of biogenic origin (Readman et al., 1999). However, these studies also revealed some petrogenic and pyrogenic polycyclic aromatic hydrocarbons (PAHs) at sub to low ng g 1 dry sediment. Organochlorine analyses revealed that only some polychlorinated biphenyl (PCB) congeners and the pesticide lindane were above limits of detection. It was concluded that atmospheric transport (from industrial parts of the world) was the major route for the introduction of organochlorines to the region. A parallel study (Everaarts et al., 1999), based upon analysis of anthropogenic organic contaminants and toxic metals in sediments and biota, confirmed that, at least in 1996, Chagos belonged to the category of least impacted coastal areas. During recent years, antifouling products used in boat paints have tended to incorporate organic ‘‘booster’’ biocides to enhance performance and to move away from tributyltin compounds (which were restricted in most countries due to their demonstrated toxicity to non-target organisms at very low concentrations). The booster biocide products are primarily herbicidal and contain active ingredients including: Irgarol 1051 (2-methylthio-4-tert-butylamino-6-cyclopropylamino-s-triazine), Sea-Nine 211 /kathon 5287 (4,5-dichloro-2-n-octyl-4-isothiazolin-3-one), chlorothalonil (2,4,5,6-tetrachloroisophthalonitrile), dichlofluanid (1,1-dichloro-N-[(dimethylamino)sulfonyl]-1-fluoro-Nphenylmethanesulfenamide), diuron (DCMU, [3-(3,4-dichlorophenyl)-1,1-dimethylurea]), TCMS pyridine, TCMTB, zinc pyrithione and zineb. Irgarol 1051 has recently been shown to be a potent inhibitor of coral photosynthesis in both isolated endosymbiotic coral zooxanthellae (i.e. isolated algal symbionts in vitro) and in the intact coral symbionts (i.e. in vivo) for a number of Atlantic and Pacific coral species (Owen et al., 2002, 2003; Jones and Kerswell, 2003; reviewed by Jones (2005)). In in vitro experiments, Owen et al. (2002) report no CðHCO 3 Þ incorporation in zooxanthellae isolated from the common branching coral Madracis mirabilis after a 6 h exposure to 63 ng l 1 Irgarol 1051 . In vivo, the The objective of BASELINE is to publish short communications on different aspects of pollution of the marine environment. Only those papers which clearly identify the quality of the data will be considered for publication. Contributors to Baseline should refer to ‘Baseline—The New Format and Content’ (Mar. Pollut. Bull. 42, 703–704).

Preliminary Examination of Short-Term Cellular Toxicological Responses of the Coral Madracis mirabilis to Acute Irgarol 1051 Exposure

Irgarol 1051 is an s-triazine herbicide formulated with Cu2O in antifouling paints. Recent studies have shown that Irgarol 1051 inhibits coral photosynthesis at environmentally relevant concentrations, consistent with its mode of action as a photosystem II inhibitor. Related toxicologic effects of this herbicide on coral cellular physiology have not yet been investigated. We used cellular diagnostics to measure changes in 18 toxicologic cellular parameters in endosymbiotic algal (dinoflagellate) and cnidarian (host) fractions of the common branching coral Madracis mirabilis associated with in vivo 8- and 24-hour exposures to a nominal initial Irgarol 1051 concentration of 10 microg L(-1). Responses measured were (1) xenobiotic response, which includes total and dinoflagellate multixenobiotic resistance (MXR), cnidarian cytochrome (CYP) P450-3 and P450-6 classes, cnidarian, and dinoflagellate glutathione-s-transferase (GST); (2) oxidative damage and response, which includes cnidarian and dinoflagellate Cu/Zn and Mn superoxide dismutase (SOD), cnidarian and dinoflagellate glutathione peroxidase (GPx), cnidarian catalase, and total protein carbonyl); (3) metabolic homeostasis, which includes chloroplast and invertebrate small heat-shock proteins (sHsp), cnidarian protoporphyrinogen oxidase IX (PPO), cnidarian ferrochelatase, and cnidarian heme oxygenase; and (4) protein metabolic condition, which includes cnidarian and dinoflagellate heat shock proteins (hsp70 and hsp60), total ubiquitin, and cnidarian ubiquitin ligase. Acute responses to Irgarol 1051 exposure included significant increases in total and dinoflagellate MXR, dinoflagellate Cu/Zn SOD, dinoflagellate chloroplast sHsp, and cnidarian PPO. Irgarol 1051 exposure resulted in decreases in cnidarian GPx, cnidarian ferrochelatase, cnidarian catalase, and cnidarian CYP 450-3 and -6 classes. Related implications of Irgarol 1051 exposure to coral cellular condition are discussed.

Intermittent upwelling and subsidized growth of the scleractinian coral Madracis mirabilis on the deep fore-reef slope of Discovery Bay, Jamaica

A 1 yr study was conducted across a 45 m depth gradient on the north shore of Jamaica to explore the hypothesis that depth-specific variability associated with thermocline oscillations effects growth rates of the scleractinian coral Madracis mirabilis. Multiple periods of high-frequency temperature variability were detected at 30 to 55 m depth, indicative of vertical transport of subther- mocline water onto the reef slope at semidiurnal and shorter intervals. Cooling, expressed as cumu- lative degree-days below the depth-averaged daily temperature increased from 1.6°C d at 10 m to 50°C d at 45 and 55 m depth. The sum of the daily temperature variance increased almost 3-fold from 3.7 to 9.9°C 2 from 10 to 55 m. Coral growth rates showed a bimodal distribution as a function of depth, with fastest growth (3.86 to 4.12 g yr -1 ) at 10 and 30 m, reduced growth (2.46 to 3.21 g yr -1 ) at 20 and 45 m, and slowest growth (0.97 g yr -1 ) at 55 m. To assess possible differences among sites differing with respect to the intensity of internal-wave forcing, growth rates of M. mirabilis were compared at 20 and 30 m depth in Jamaica with previous results from the Florida Keys. Overall growth rates were greater in Florida than in Jamaica, corresponding to greater internal-wave activity in Florida, and a similar effect of enhanced growth at 30 m was observed at both sites. Vertical oscillations of the thermocline are a widespread phenomenon, and may contribute to patterns of coral growth in a variety of deep reef environments.

Localization and ecological significance of oroidin and sceptrin in the Caribbean sponge Agelas conifera

The Caribbean sponge Agelas conifera was found to produce a mixture of previously described bromopyrrole alkaloids of which oroidin ( 1) and sceptrin ( 2) were predominant. This sponge harboured large populations of heterotrophic bacteria but no photosynthetic symbionts (cyanobacteria). However, 1 and 2 were not associated with the bacteria but with the sponge cells as shown by their distribution in enriched cell fractions obtained by differential centrifugation and Ficoll density gradients. Spherulous cells, found in great abundance in the sponge ectosome, were assumed to be involved in the production of 1 and 2. The target compounds were detected, although in small amounts, in short-term cultures of sponge cells, validating the possibility of a continuous cell culture source. Laboratory assays showed that organic sponge extracts affected the behaviour of the coral Madracis mirabilis in causing closure and retraction of the polyps at concentrations of the combined compounds 1 and 2 (1:3.3) as low as 0.7 mg/l (0.0125% of the concentration in whole sponges). At higher concentrations (1.4 mg/l) no recovery of the polyps occurred. The extracts, at almost natural concentrations of 1 and 2, deterred feeding by the predatory reef fish Stegastis partitus, supporting other reported research. In field experiments, wounding induced a sharp increase of 1 and 2 in the sponge tissues but prolonged predator exclusion by caging and forced confrontation with coral neighbours did not yield measurable changes in 1 and 2 concentrations. All sponges were found to release measurable amounts of bromopyrrole alkaloids in seawater conditioned for 30 min. Crude and fractionated sponge extracts and pure sceptrin ( 2) were active against bacteria, yeast and filamentous fungi. Taken together, these results support a role of oroidin ( 1) and sceptrin ( 2) in defence mechanisms against predators and possibly against space competitors and invading and fouling organisms.

New nitrogenous eudesmane-type compounds isolated from the Caribbean sponge Axinyssa ambrosia.

Fractionation of an acetone-methanol (1:1) extract of the Caribbean marine sponge Axinyssa ambrosia yielded three new sesquiterpenes whose structures were established by spectroscopic methods as (4R*,5R*,7S*,10R*)-eudesm-11-en-4-ylamine hydrochloride (1), axinyssamine hydrochloride, (4R*,5R*,7S*,10R*)-4-isocyanatoeudesm-11-ene (3), and (4R*,5R*,7S*,10R*)-formamidoeudesm-11-ene (4). Compound 1 exhibited significant cytotoxic activity against cancer cells and was also active in a lethality test using polyps of the scleractinian coral Madracis mirabilis.

Inhibition of coral photosynthesis by the antifouling herbicide Irgarol 1051

International regulation of organotin compounds for use in antifouling paints has led to the development and increased use of replacement compounds, notably the s-triazine herbicide Irgarol 1051. Little is known about the distribution of Irgarol 1051 in tropical waters. Nor has the potential impact of this triazine upon photosynthesis of endosymbiotic microalgae (zooxanthellae) in corals been assessed. In this study Irgarol 1051 was detected in marinas, harbours and coastal waters of the Florida Keys, Bermuda and St. Croix, with concentrations ranging between 3 and 294 ng l −1 . 14C incubation experiments with isolated zooxanthellae from the common inshore coral Madracis mirabilis showed no incorporation of H 14CO 3 − from the sea water medium after 4–8 h exposure to Irgarol 1051 concentrations as low as 63 ng l −1 . Reduction in net photosynthesis of intact corals was found at concentrations of 100 ng l −1 with little or no photosynthesis at concentrations exceeding 1000 ng l −1 after 2–8 h exposure at all irradiances. The data suggest Irgarol 1051 to be both prevalent in tropical marine ecosystems and a potent inhibitor of coral photosynthesis at environmentally relevant concentrations.

Identification of a small heat shock/α-crystallin protein in the scleractinian coralMadracis mirabilis(Duch. and Mitch.)

Immunological evidence is provided for the first time of a small heat shock/α-crystallin protein in the scleractinian coral Madracis mirabilis. The protein, termed cp26, had a molecular weight of 26 000; it reacted with an antibody raised to a small heat shock/α-crystallin protein fromArtemia franciscana and its production in corals was temperature sensitive. Corals collected from seawater at 25.5oC or lower lacked cp26, but the protein was produced in some of these animals when they were heat shocked experimentally. When exposed naturally to high environmental temperatures for relatively short times, corals contained cp26 and responded to heat shock in the laboratory. Corals growing at elevated temperatures tended to die when subjected to additional heat stress. Specifically, M. mirabilis died at about 31-33oC, as indicated by visual inspection of the animals, low recovery of protein in cell-free extracts, and loss of protein bands in SDS-polyacrylamide gels. Death was accompanied by the appearance of a diffuse, unidentified protein band on western blots that reacted with an antibody to cp26. Madracis mirabilis clearly reacts to heat shock by production of cp26; further study is required to determine if this small heat shock/α-crystallin protein will be a useful biomarker of stress in corals.

Identification of a small heat shock/α-crystallin protein in the scleractinian coral <i>Madracis mirabilis</i> (Duch. and Mitch.)

Immunological evidence is provided for the first time of a small heat shock/α-crystallin protein in the scleractinian coral Madracis mirabilis. The protein, termed cp26, had a molecular weight of 2...

Fragmentation in Madracis mirabilis (Duchassaing and Michelotti): how common is size-specific fragment survivorship in corals?

Fragmentation is an important asexual mode of reproduction for many coral species and other marine invertebrates. General life history theory and models of coral fragmentation predict that intra- and inter-specific variation in fragment size should be positively related to survival and inversely related to dispersal distance. To test these predictions I examined fragmentation in the Caribbean branching coral Madracis mirabilis, which produces relatively small fragments. The effects of intra-specific variation in fragment size on fragment survival and dispersal in M. mirabilis were examined by following the fate of 60 labeled fragments for 11 months at three sites. Fragment dispersal distance was limited (generally <20 cm), was not significantly related to fragment size, and varied among sites, being greatest at a shallow forereef site. Although the smallest fragments displayed the lowest survivorship (≈50%), there was no apparent increase in survivorship with size among larger fragments (i.e., those 5–15 cm in length), and there was no overall significant relationship between fragment size and survivorship. In contrast, fragment survivorship varied greatly among sites (29–81%), being the highest at two forereef sites (10 and 20 m depth) and lowest at a lagoon site with high sedimentation (10 m depth). Although natural fragments of M. mirabilis are smaller than almost any other known fragmenting coral species, they can have a high rate of survivorship in forereef environments. The results of this and other studies do not support the predicted general inter- and intra-specific relationships between fragment size and survivorship and suggest that fragment survivorship is highly context and species specific, and is also greatly influenced by factors other than fragment size.

Metabolic consequences of phenotypic plasticity in the coral Madracis mirabilis (Duchassaing and Michelotti): the effect of morphology and water flow on aggregate respiration

Phenotypic plasticity has been documented in a number of reef coral species for a variety of morphological traits, but its ecological importance is not well understood. In the branching coral Madracis mirabilis (Duchassaing and Michelotti) spacing among branches varies across environmental gradients and in general is inversely related to the rate of water movement. This polymorphism is due in part to variation in branch diameter which is phenotypically plastic in this species. Branch spacing can affect biomechanical processes such as the surface roughness of aggregated branches and flow dynamics within an aggregate, both of which could affect colony metabolism. We examined the metabolic consequences of variation in branch spacing and flow speed on small M . mirabilis aggregates to determine if plasticity for this trait could be beneficial. The dark respiration of aggregates with different amounts of branch spacing was measured under three flow speeds (3.1, 4.7 and 8.4 cm s −1) in respiration chambers. Aggregates with the greatest branch spacing had the highest respiration rates in all three flow conditions and the respiration of each morphology increased with flow speed. Increased branch spacing may decrease the thickness of the diffusive boundary layer, thereby maintaining mass transport and hence high respiration rates in low flow. This and previous studies suggest that phenotypically plastic branch spacing may represent an important adaptation in M . mirabilis, enabling aggregates to tolerate a variety of flow conditions.

Breaking internal waves on a Florida (USA) coral reef:a plankton pump at work?

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 166:83-97 (1998) - doi:10.3354/meps166083 Breaking internal waves on a Florida (USA) coral reef: a plankton pump at work? James J. Leichter1,*, Gregory Shellenbarger2, Salvatore J. Genovese3, Stephen R. Wing4 1Woods Hole Oceanographic Institution, Department of Biology, MS #34, Woods Hole, Massachusetts 02543, USA 21 Lincoln Street, Marblehead, Massachusetts 01945, USA 3Northeastern University, Marine Science Center, Nahant, Massachusetts 01908, USA 4Department of Marine Science, University of Otago, 304 Castle Street, Dunedin, New Zealand *E-mail: jleichter@whoi.edu Temperature, salinity, flow speeds, and plankton concentrations can be highly variable on the slope of Conch Reef, Florida Keys (USA), as warm surface water is mixed with cool, subsurface water forced onshore by broken internal waves. In August 1995 the water column seaward of the reef exhibited strong temperature and density stratification with a sharp pycnocline and associated subsurface chlorophyll a maximum layer at 45 to 60 m depth. On the reef slope, near-bottom zooplankton sampling at 22 to 28 m showed high concentrations of calanoid copepods, crab zoea, and fish larvae associated with upslope flow of cool, chlorophyll-rich water. In contrast to these periods of high concentrations, zooplankton concentrations were low during periods of long-shore and offshore flow of warm surface waters. Both the frequency of internal bore arrival and the mean duration of cool water events increase with increasing depth on the reef slope. Delivery of zooplankton to the reef is, therefore, also expected to increase with depth. A short-term settlement experiment showed increased settlement of serpulid worms at 20 and 30 m depth compared with 15 m, and a 15.5 mo transplant experiment showed significantly enhanced growth rates of the suspension-feeding coral Madracis mirabilis (Scleractinia: Pocilloporidae) at 30 m depth relative to growth at 15 or 20 m. Internal tidal bores appear to be a predictable, periodic source of cross-shelf transport to Florida coral reefs and an important influence on the spatial and temporal heterogeneity of suspended food particles and larval delivery to the benthos. Internal waves · Internal bores · Zooplankton · Transport Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 166. Publication date: May 28, 1998 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1998 Inter-Research.

Clonal Variation for Phenotypic Plasticity in the Coral Madracis Mirabilis

Clonal Variation for Phenotypic Plasticity in the Coral Madracis Mirabilis

Effects of water flow and branch spacing on particle capture by the reef coral Madracis mirabilis (Duchassaing and Michelotti)

The scleractinian coral Madracis mirabilis forms colonies composed of many narrow branches whose spacing varies across habitats; this is especially evident along a depth gradient. Environmental factors such as irradiance and water movement co-vary along this gradient and both factors could have effects on branch spacing. We examined the effects of water flow on particle capture by Madracis mirabilis in a laboratory flume at Discovery Bay, Jamaica, using hydrated Artemia cysts as experimental particles. Isolated branches of Madracis showed highest particle capture rates in the 10–15 cm s −1 range of flow speeds, although capture was still occurring at about one fourth the maximum rate even at 40–50 cm s −1. The ability to capture particles at these higher flow speeds results from polyps on downstream sides of branches capturing particles from turbulent eddies in the wake of the branch. At high flows, these polyps are not deformed (flattened) as are the upstream polyps. Two aggregation densities were tested at three flow speeds and both flow and particle capture were measured at each branch. Low density aggregations, comparable to those in low flow and deep reef habitats, captured particles best at the lowest flow speeds tested and capture was relatively uniform through the aggregation. High density aggregations captured particles best at high flow speeds, especially near the downstream end of the aggregation. At low flow speeds, the highest capture rates occurred at the upstream end of the aggregation. Flow speed decreased downstream within aggregations at both low and high densities, especially at higher flow speeds. Turbulence intensity also changed within aggregations, increasing behind the first row of branches at all flow speeds and in both aggregation densities. Total capture rate per polyp was highest at intermediate flow speeds (10–15 cm s −1) for single branches and for aggregations due to high encounter rates, while capture efficiency (flux adjusted capture rate) was greatest at low flow speeds. Patterns of flow and particle capture within aggregations suggest that high density aggregations function better in high flow environments. Low density aggregations were able to capture only one fourth as many particles as high density aggregations at the higher speeds used in these experiments. Conversely, high density aggregations captured only about half as many particles at the low flow speed, compared to low density aggregations. Factors other than flow, especially light interception, are likely to affect branch spacing as well. Shallow reef habitats, with high irradiance and high flow conditions, may thus favor tight branch spacing as a response to both environmental variables.

Clonal variation for phenotypic plasticity in the coral Madracis mirabilis

Clonal variation for phenotypic plasticity in the coral Madracis mirabilis

Fish predation on the scleractinian coral Madracis mirabilis controls its depth distribution in the Florida Keys, USA

Fish predation on the scleractinian coral Madracis mirabilis controls its depth distribution in the Florida Keys, USA