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1.
The broadcast spawning elkhorn coral, Acropora palmata, requires outcrossing among different genets for effective fertilization. Hence, a low density of genets in parts of its range emphasizes the need for precise synchrony among neighboring genets as sperm concentration dilutes rapidly in open-ocean conditions. We documented the genet-specific nightly occurrence of spawning of A. palmata over 8 yr in a depauperate population in the Florida Keys to better understand this potential reproductive hurdle. The observed population failed to spawn within the predicted monthly window (nights 2–6 after the full moon in August) in three of the 8 yr of observation; negligible spawning was observed in a fourth year. Moreover, genet-specific patterns are evident in that (1) certain genets have significantly greater odds of spawning overall and (2) certain genets predictably spawn on the earlier and others on the later lunar nights within the predicted window. Given the already low genet density in this population, this pattern implies a substantial degree of wasted reproductive effort and supports the hypothesis that depensatory factors are impairing recovery in this species. 相似文献
2.
The barium contents of Acropora palmata and Montastrea annularis are distinct both in their averages (6 and 9 ppm, respectively) and, more impressively, in their variability (5 to 7 ppm and 6 to 15 ppm). A. palmata contained about 50% more Ba 2+ than M. annularis and exhibited more than three times as much variation, as measured by their respective coefficients of variation. In contrast, the means and coefficients of variation of Sr 2+ in these groups differed by only 6% and 15%. No obvious environmental or post-depositional causes for the inter-and intra-specific variation of Ba 2+ could be found. Previous experiments indicate that the partitioning of Ba 2+ into aragonite depends directly on the rate of precipitation. This suggests that Ba 2+ does not substitute for Ca 2+ but instead is incorporated by occlusion. Since growth rates in A. palmata often exceed those of M. annularis, this appears to be the mechanism which generates higher and more variable concentrations of Ba 2+ in A. palmata. 相似文献
3.
Anthropogenic global change and local stressors are impacting coral growth and survival worldwide, altering the structure and function of coral reef ecosystems. Here, we show that skeletal extension rates of nearshore colonies of two abundant and widespread Caribbean corals ( Siderastrea siderea, Pseudodiploria strigosa) declined across the Belize Mesoamerican Barrier Reef System (MBRS) over the past century, while offshore coral conspecifics exhibited relatively stable extension rates over the same temporal interval. This decline has caused nearshore coral extension rates to converge with those of their historically slower growing offshore coral counterparts. For both species, individual mass coral bleaching events were correlated with low rates of skeletal extension within specific reef environments, but no single bleaching event was correlated with low skeletal extension rates across all reef environments. We postulate that the decline in skeletal extension rates for nearshore corals is driven primarily by the combined effects of long‐term ocean warming and increasing exposure to higher levels of land‐based anthropogenic stressors, with acute thermally induced bleaching events playing a lesser role. If these declining trends in skeletal growth of nearshore S. siderea and P. strigosa continue into the future, the structure and function of these critical nearshore MBRS coral reef systems is likely to be severely impaired. 相似文献
4.
Complex environmental cues dictate the settlement of coral planulae in situ; however, simple artificial cues may be all that
is required to induce settlement of ex situ larval cultures for reef re-seeding and restoration projects. Neuropeptides that
transmit settlement signals and initiate the metamorphic cascade have been isolated from hydrozoan taxa and shown to induce
metamorphosis of reef-building Acropora spp. in the Indo-Pacific, providing a reliable and efficient settlement cue. Here, the metamorphic activity of six GLW-amide
cnidarian neuropeptides was tested on larvae of the Caribbean corals Acropora palmata, Montastraea faveolata and Favia fragum. A. palmata planulae were induced to settle by the exogenous application of the neuropeptide Hym-248 (concentrations ≥1 × 10 −6 M), achieving 40–80% attachment and 100% metamorphosis of competent planulae (≥6 days post-fertilization) during two spawning
seasons; the remaining neuropeptides exhibited no activity. Hym-248 exposure rapidly altered larval swimming behavior (<1 h)
and resulted in >96% metamorphosis after 6 h. In contrast , M. faveolata and F. fragum planulae did not respond to any GLW-amides tested, suggesting a high specificity of neuropeptide activators on lower taxonomic
scales in corals. Subsequent experiments for A. palmata revealed that (1) the presence of a biofilm did not enhance attachment efficiency when coupled with Hym-248 treatment, (2)
neuropeptide-induced settlement had no negative effects on early life-history developmental processes: zooxanthellae acquisition
and skeletal secretion occurred within 12 days, colonial growth occurred within 36 days, and (3) Hym-248 solutions maintained
metamorphic activity following storage at room temperature (10 days), indicating its utility in remote field settings. These
results corroborate previous studies on Indo-Pacific Acropora spp. and extend the known metamorphic activity of Hym-248 to Caribbean acroporids. Hym-248 allows for directed and reliable
settlement of larval cultures and has broad applications to the study and rehabilitation of threatened Acropora populations in the Caribbean. 相似文献
5.
With the continuing decline of Acropora palmata throughout the Caribbean region, impacts of the gastropod corallivore, Coralliophila abbreviata, are becoming more noticeable. A snail removal experiment was performed in remnant A. palmata populations in the Florida Keys National Marine Sanctuary to quantify the area of coral tissue consumed by ambient snail
aggregations and to assess the possible effectiveness of snail removal in conserving live coral tissue. Corals where ambient
snail aggregations were removed maintained significantly more live tissue area during the 2-month experiment than those where
feeding snail aggregations were left in place. The corals with feeding snails left in place lost more than 3 cm 2 tissue day −1 on average. Thus, removal of C. abbreviata may be an effective measure for conserving depressed A. palmata populations, though secondary effects of such a manipulation remain to be carefully evaluated.
Accepted: 26 May 2000 相似文献
6.
The movements of larvae between marine populations are difficult to follow directly and have been the subject of much controversy, especially in the Caribbean. The debate centres on the degree to which populations are demographically open, such that depleted populations can be replenished by recruitment from distant healthy populations, or demographically closed and thus in need of local management. Given the depressed state of many tropical reef populations, the understanding of these movements now bears critically on the number, placement, and size of marine reserves. Most genetic analyses assume that dispersal patterns have been stable for thousands of generations, thus they commonly reflect past colonization histories more than ongoing dispersal. Recently developed multilocus genotyping approaches, however, have the demonstrated ability to detect both migration and population isolation over far shorter timescales. Previously, we developed five microsatellite markers and demonstrated them to be both Mendelian and coral-specific. Using these markers and Bayesian analyses, we show here that populations of the imperiled reef-building coral, Acropora palmata, have experienced little or no recent genetic exchange between the western and the eastern Caribbean. Puerto Rico is identified as an area of mixing between the two subregions. As a consequence of this regional isolation, populations in the western and eastern Caribbean should have the potential to adapt to local conditions and will require population-specific management strategies. 相似文献
7.
Coral reefs are in severe decline. Infections by the human pathogen Serratia marcescens have contributed to precipitous losses in the common Caribbean elkhorn coral, Acropora palmata, culminating in its listing under the United States Endangered Species Act. During a 2003 outbreak of this coral disease, called acroporid serratiosis (APS), a unique strain of the pathogen, Serratia marcescens strain PDR60, was identified from diseased A. palmata, human wastewater, the non-host coral Siderastrea siderea and the corallivorous snail Coralliophila abbreviata. In order to examine humans as a source and other marine invertebrates as vectors and/or reservoirs of the APS pathogen, challenge experiments were conducted with A. palmata maintained in closed aquaria to determine infectivity of strain PDR60 from reef and wastewater sources. Strain PDR60 from wastewater and diseased A. palmata caused disease signs in elkhorn coral in as little as four and five days, respectively, demonstrating that wastewater is a definitive source of APS and identifying human strain PDR60 as a coral pathogen through fulfillment of Koch's postulates. A. palmata inoculated with strain PDR60 from C. abbreviata showed limited virulence, with one of three inoculated fragments developing APS signs within 13 days. Strain PDR60 from non-host coral S. siderea showed a delayed pathogenic effect, with disease signs developing within an average of 20 days. These results suggest that C. abbreviata and non-host corals may function as reservoirs or vectors of the APS pathogen. Our results provide the first example of a marine "reverse zoonosis" involving the transmission of a human pathogen (S. marcescens) to a marine invertebrate (A. palmata). These findings underscore the interaction between public health practices and environmental health indices such as coral reef survival. 相似文献
8.
Ocean color images acquired from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) from 1998 to 2006 were used to examine
the patterns of physical connectivity between land and reefs, and among reefs in the Mesoamerican Barrier Reef System (MBRS)
in the northwestern Caribbean Sea. Connectivity was inferred by tracking surface water features in weekly climatologies and
a time series of weekly mean chlorophyll- a concentrations derived from satellite imagery. Frequency of spatial connections between 17 pre-defined, geomorphological
domains that include the major reefs in the MBRS and river deltas in Honduras and Nicaragua were recorded and tabulated as
percentage of connections. The 9-year time series of 466 weekly mean images portrays clearly the seasonal patterns of connectivity,
including river plumes and transitions in the aftermath of perturbations such as hurricanes. River plumes extended offshore
from the Honduras coast to the Bay Islands (Utila, Cayo Cochinos, Guanaja, and Roatán) in 70% of the weekly mean images. Belizean
reefs, especially those in the southern section of the barrier reef and Glovers Atoll, were also affected by riverine discharges
in every one of the 9 years. Glovers Atoll was exposed to river plumes originating in Honduras 104/466 times (22%) during
this period. Plumes from eastern Honduras went as far as Banco Chinchorro and Cozumel in Mexico. Chinchorro appeared to be
more frequently connected to Turneffe Atoll and Honduran rivers than with Glovers and Lighthouse Atolls, despite their geographic
proximity. This new satellite data analysis provides long-term, quantitative assessments of the main pathways of connectivity
in the region. The percentage of connections can be used to validate predictions made using other approaches such as numerical
modeling, and provides valuable information to ecosystem-based management in coral reef provinces.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
10.
Carcharhinid sharks can make up a large fraction of the top predators inhabiting tropical marine ecosystems and have declined in many regions due to intense fishing pressure. There is some support for the hypothesis that carcharhinid species that complete their life-cycle within coral reef ecosystems, hereafter referred to as “reef sharks”, are more abundant inside no-take marine reserves due to a reduction in fishing pressure (i.e., they benefit from marine reserves). Key predictions of this hypothesis are that (a) individual reef sharks exhibit high site-fidelity to these protected areas and (b) their relative abundance will generally be higher in these areas compared to fished reefs. To test this hypothesis for the first time in Caribbean coral reef ecosystems we combined acoustic monitoring and baited remote underwater video (BRUV) surveys to measure reef shark site-fidelity and relative abundance, respectively. We focused on the Caribbean reef shark ( Carcharhinus perezi), the most common reef shark in the Western Atlantic, at Glover''s Reef Marine Reserve (GRMR), Belize. Acoustically tagged sharks (N = 34) were detected throughout the year at this location and exhibited strong site-fidelity. Shark presence or absence on 200 BRUVs deployed at GRMR and three other sites (another reserve site and two fished reefs) showed that the factor “marine reserve” had a significant positive effect on reef shark presence. We rejected environmental factors or site-environment interactions as predominant drivers of this pattern. These results are consistent with the hypothesis that marine reserves can benefit reef shark populations and we suggest new hypotheses to determine the underlying mechanism(s) involved: reduced fishing mortality or enhanced prey availability. 相似文献
11.
The degree of internal bioerosion was examined in the dead basal portions of live branches of the scleractinian coral Acropora formosa collected from six reefs across the continental shelf in the central region of the Great Barrier Reef, Australia. The bioeroders included the sponges Cliona spp. and Cliothosa spp., the boring bivalve Lithophaga sp., and sipunculid and polychaete worms. Total internal bioerosion exhibited higher means and variances inshore and at the mid-shelf than the outer shelf specimens, which were characterized by low means and low variances. Bioerosion by Cliothosa and all sponges combined declined slightly across the shelf. Bivalves accounted for a small proportion of the internal bioerosion in A. formosa. The bioerosion pattern exhibited by worms (polychaetes and sipunculids) was similar in pattern to that of the sponges. All groups exhibited lowest levels of bioerosion at the outer shelf. Highest variance in the data was observed at the intra-branch/intra-colony and the intercolony levels. Inter-site variance was high in worms and vivalves. Boring sponges generally dominated the bioeroder community. The relative abundance of Cliona declined on the outer shelf while the relative abundance of worms increased. Percent bioerosion in Acropora formosa was 2–3 times higher than in Porites lobata in this region. The low level of bioerosion at the outer shelf versus the inner- and mid-shelf areas may be partially due to lower levels of productivity and lower concentrations of terrestrially derived organic matter. Other potential factors may include higher fish grazing/predation activity on the outer shelf. 相似文献
12.
Coral-grounds are reef communities that colonize rocky substratum but do not form framework or three-dimensional reef structures. To investigate why, we used video transects and underwater photography to determine the composition, structure and status of a coral-ground community located on the edge of a rocky terrace in front of a tourist park, Xcaret, in the northern Mesoamerican Reef tract, Mexico. The community has a relatively low coral, gorgonian and sponge cover (<10%) and high algal cover (>40%). We recorded 23 species of Scleractinia, 14 species of Gorgonacea and 30 species of Porifera. The coral community is diverse but lacks large coral colonies, being dominated instead by small, sediment-tolerant, and brooding species. In these small colonies, the abundance of potentially lethal interactions and partial mortality is high but decreases when colonies are larger than 40 cm. Such characteristics are consistent with an environment control whereby storm waves periodically remove larger colonies and elevate sediment flux. The community only survives these storm conditions due to its slope-break location, which ensures lack of burial and continued local recruitment. A comparison with similar coral-ground communities in adjacent areas suggests that the narrow width of the rock terrace hinders sediment stabilization, thereby ensuring that communities cannot escape bottom effects and develop into three-dimensional reef structures on geological time scales. 相似文献
13.
Juvenile coral abundance and community composition depend on the spatial scale studied. To investigate this, an evaluation was made of juvenile coral density with hierarchical spatial analysis in the northern Mesoamerican Barrier Reef System (MBRS) at ~10 m depth. Study scope included semi-protected and unprotected areas located in this region. A total of 19 juvenile coral taxa were found, including 10 scleractinian species, 8 scleractinian coral genera not identified to species, and 1 Millepora species (Hydrozoa-Milleporidae). In terms of relative abundance, Agaricia spp., Siderastrea spp., and Porites spp. were the main juvenile taxa in the coral community at the surveyed sites, reefs, and regions levels. Greater variance was seen at smaller scales, at site level for taxa richness, and at the transect level for juvenile density, and lower variance was seen at larger scales (reefs and regions). The variance component contribution from each scale likely differed from other studies because of the different factors affecting the community and the different extensions of each scale used in each study. Densities (1–6.4 juvenile corals/m 2) and dominant taxa found in this study agree with other studies from the Western Atlantic. Detected variability was explained by different causal agents, such as low grazing rates by herbivorous organisms, turbidity, and/or sediment suffocation and some nearby or distant localized disturbance (human settlement and a hurricane). 相似文献
15.
An outbreak of necrotic patches was observed affecting Acropora palmata in the Mexican Caribbean in the summer of 1999. This study documents the tissue loss produced by these patches. Following a marked initial increase in the number of patches, there was a decrease in the appearance of new patches but the size of the patches increased throughout the study. In some cases patches expanded but in most cases they enlarged due to fusion of 2 or more patches. Patches recovered but not sufficiently to overcome damage in most colonies surveyed. Percentage tissue loss does not appear to be directly related to temperature but may be related to a combination of factors associated with prolonged summer doldrum-like conditions. The necrotic patch syndrome can have a substantial impact in tissue loss in affected A. palmata colonies. 相似文献
16.
High concentrations of acrylate, 542–683 μmol g −1 of the non-skeletal dry mass (DM), were measured in the Great Barrier Reef coral, Acropora millepora, using quantitative nuclear magnetic resonance spectroscopy (qNMR). As the amount of NaCl salt in the samples was substantial
but variable, the total carbon (TC) in the coral extracts was determined, and the carbon due to acrylate found to represent
13–15% of the TC present in the total organic extracts (TOE). Acrylate, a C 3 compound, is thus a substantial carbon source in the coral holobiont and is known to be derived from dimethylsulfoniopropionate
(DMSP), which has previously been found in corals and other organisms that harbor Symbiodinium spp. The reason for such high levels of acrylate in the corals is unknown; possible functions include antimicrobial and/or
antioxidant roles, as well as playing a role in the structuring of the healthy resident coral bacteria. 相似文献
17.
Settlement specificity can regulate recruitment but remains poorly understood for coral larvae. We studied larvae of the corals, Acropora palmata and Montastraea faveolata, to determine their rates of settlement and metamorphosis in the presence of ten species of red algae, including eight species of crustose coralline algae, one geniculated coralline and one encrusting peyssonnelid. Twenty to forty percent of larvae of A. palmata settled on coralline surfaces of Hydrolithon boergesenii, Lithoporella atlantica, Neogoniolithon affine, and Titanoderma prototypum, whereas none settled and metamorphosed on Neogoniolithon mamillare. Larvae of M. faveolata had 13–25 % settlement onto the surface of Amphiroa tribulus, H. boergesenii, N. affine, N. munitum, and T. prototypum, but had no settlement on the surface of N. mamillare, Porolithon pachydermum, and a noncoralline crust Peyssonnelia sp. Some of these algal species were common on Belizean reefs, but the species that induced the highest rates of larval settlement and metamorphosis tended to be rare and primarily found in low-light environments. The shallow coral, A. palmata, and the deeper coral, M. faveolata, both had increased larval settlement rates in the presence of only a few species of red algae found at deeper depths suggesting that patterns of coral distribution can only sometimes be related to the distribution of red algae species. 相似文献
18.
The branching coral Acropora palmata is a foundation species of Caribbean reefs that has been decimated in recent decades by anthropogenic and natural stressors. Declines in population density and genotypic diversity likely reduce successful sexual reproduction in this self-incompatible hermaphrodite and might impede recovery. We investigated variation among genotypes in larval development under thermally stressful conditions. Six two-parent crosses and three four-parent batches were reared under three temperatures and sampled over time. Fertilization rates differed widely with two-parent crosses having lower fertilization rates (5–56 %, mean 22 % ± 22 SD) than batches (from 31 to 87 %, mean 59 % ± 28 SD). Parentage analysis of larvae in batch cultures showed differences in gamete compatibility among parents, coinciding with significant variation in both sperm morphology and egg size. While all larval batches developed more rapidly at increased water temperatures, rate of progression through developmental stages varied among batches, as did swimming speed. Together, these results indicate that loss of genotypic diversity exacerbates already severe limitations in sexual reproductive success of A. palmata. Nevertheless, surviving parental genotypes produce larvae that do vary in their phenotypic response to thermal stress, with implications for adaptation, larval dispersal and population connectivity in the face of warming sea surface temperatures. 相似文献
20.
White pox disease (WPD) affects the threatened elkhorn coral, Acropora palmata. Owing in part to the lack of a rapid and simple diagnostic test, there have been few systematic assessments of the prevalence of acroporid serratiosis (caused specifically by Serratia marcescens) versus general WPD signs. Six reefs in the Florida Keys were surveyed between 2011 and 2013 to determine the disease status of A. palmata and the prevalence of S. marcescens. WPD was noted at four of the six reefs, with WPD lesions found on 8 to 40% of the colonies surveyed. S. marcescens was detected in 26.9% (7/26) of the WPD lesions and in mucus from apparently healthy colonies both during and outside of disease events (9%; 18/201). S. marcescens was detected with greater frequency in A. palmata than in the overlying water column, regardless of disease status ( P = 0.0177). S. marcescens could not be cultured from A. palmata but was isolated from healthy colonies of other coral species and was identified as pathogenic pulsed-field gel electrophoresis type PDR60. WPD lesions were frequently observed on the reef, but unlike in prior outbreaks, no whole-colony death was observed. Pathogenic S. marcescens was circulating on the reef but did not appear to be the primary pathogen in these recent WPD episodes, suggesting that other pathogens or stressors may contribute to signs of WPD. Results highlight the critical importance of diagnostics in coral disease investigations, especially given that field manifestation of disease may be similar, regardless of the etiological agent. 相似文献
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