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1.
The relative performance of (i) percent live cover, (ii) colony density, (iii) generic richness, (iv) partial colony mortality, and (v) colony size of hard corals were evaluated to determine which variables best discriminated the coral communities near a small river in Okinawa, Japan. An analysis of their variance was undertaken across a combination of sites at three depths, at increasing distance from a river's influence (Zatsun River). The river provides a periodic and localized input of sediment and fresh water to the adjacent coral reef; the effects of which we assume attenuate at increasing distance from the river mouth. The mean frequency of partially dead coral colonies (i.e., the proportion of live coral colonies that were partially dead) presented the clearest and most reliable response to river affect, and the power to discriminate among sites improved steadily with increasing depth. Spatial examination of the prevalence of partial mortality, regardless of how long ago the infliction occurred, provides a clear window to long-term processes involving population and community change and indeed the reef building capacity of the communities. 相似文献
2.
Partial mortality and fission on colonies of four common massive coral species were examined at sites differing in their exposure to river sediments in St. Lucia, West Indies. Rates of partial mortality were higher close to the river mouths, where more sediments were deposited, than away from the rivers in two coral species. Frequency of fission showed no significant trend. The percent change in coral cover on reefs from 1995 to 1998 was negatively related to the rate of partial mortality estimated in 1998 in all species. This suggests that partial mortality rates could reflect longer-term temporal changes in coral communities. Similar conclusions could also be reached using a less precise measure and simply recording partial mortality on colonies as <50% and >/=50% dead tissue. We conclude that partial mortality in some species of massive reef corals, expressed as the amount of dead tissue per colony, could provide a rapid and effective means of detecting sediment stress on coral reefs. 相似文献
3.
The accelerating deterioration of the coral reefs of Eilat has raised debate over the exact causes and how they affect the reefs. The hypothesis of the present study was that a low recruitment rate of reef-building coral species may play an important role in the decline of the Eilat reefs. Our goal was to assess spatial and temporal recruitment patterns in Eilat, focusing on examining the possible impact of human activities. The results of coral recruitment to 10 series of ceramic tiles on metal racks, revealed very low overall recruitment relative to other geographical regions. In addition, we found that recruitment rates and recruit survival were lowest at sites closest to the major eutrophication sources in Eilat. The low recruitment rates may be chronically too low to compensate for the elevated coral mortality rates of recent years. The significant differences between the present study and a similar study carried out during the same period using a different method, emphasize the crucial need for a standardized method for recruitment assessment in coral reefs worldwide. 相似文献
4.
Six reef sites were chosen along the west coast of the southern islands of Singapore, at an increasing distance from the densely populated metropolitan area, to study the spatial patterns of coral reef communities on the upper reef slope ( approximately 4m) and the associated environmental conditions. Chronic exposure to high sediment load was the most obvious form of anthropogenic stress. Recruitment rates on ceramic tiles were low (1.4+/-1.0-20+/-14.7 recruits m(-2) yr(-1)) but decreased towards the main island of Singapore as did hard coral cover and coral density. Coral fauna consisted of genera generally found in deeper waters (e.g., fungiids, foliose Oxypora, Leptoseris, and Echinopora) or those well-adapted to turbid waters (e.g., Porites, Pectinia, Leptastrea, Montipora). Light extinction coefficient (K) and % live coral cover (%LCC) showed a strong and inverse curvilinear relationship (%LCC=13.60 *K(-3.40)). Similarly, the rate of sediment deposition (DFSPM) (RR=1.51-0.17 *DFSPM) and water clarity (RR=3.56-2.92 *K) exhibited strong and inverse relationships with recruitment rates (RR). Although measured levels of the downward flux of suspended particulate matter and suspended solids were well within "normal" levels recorded in the literature, it was the proportion of benthic space, generic coral composition, and site history that offered compelling evidence of chronic exposure to increased sediment load. Clearly a reduction in both water clarity and live-coral cover has taken place since monitoring efforts began in the early 1970s, in fact coral cover has more than halved at all sites examined since the 1980s and benthic space was predominantly occupied by dead corals covered with sediment and filamentous algae. 相似文献
5.
Six reef sites were chosen along the west coasts of Singapore's southern islands, to: (1) quantitatively assess and compare coral community composition and structure, and recruitment rates, (2) assess the relationship between the aforementioned patterns and the environmental conditions, and (3) provide insights on potential processes that incorporate history at these study sites. Chronic exposure to high sediment load was the most obvious form of anthropogenic stress. Recruitment rates on ceramic tiles were low (1.4+/-1.0-20+/-14.7 recruits m(-2)year(-1)) but decreased towards the main island of Singapore as did hard coral cover and coral density. Coral fauna consisted of genera generally found in deeper waters (e.g., fungiids, foliose Oxypora, Leptoseris, and Echinopora) or those well adapted to turbid waters (e.g., Porites, Pectinia, Leptastrea, Montipora). Light extinction coefficient (K) and % live coral cover (%LCC) showed a strong and inverse curvilinear relationship (%LCC=13.60 *K(-3.40)). Similarly, the rate of sediment deposition (DFSPM) (Recruitment rate, RR=1.51-0.17 *DFSPM) and water clarity (RR=3.56-2.92 *K) exhibited strong and inverse relationships with recruitment rates. Although measured levels of the down-ward flux of suspended particulate matter and suspended solids were well within "normal" levels recorded in the literature, it was the proportion of benthic space, generic coral composition, and site history that offered compelling evidence of chronic exposure to increased sediment load. Clearly a reduction in both water clarity and live-coral cover has taken place since monitoring efforts began in the early 1970s, in fact coral cover has more than halved at all sites examined since the 1980s and benthic space was predominantly occupied by dead corals covered with sediment and filamentous algae. 相似文献
6.
Localized declines in coral condition are commonly linked to land-based sources of stressors that influence gradients of water quality, and the distance to sources of stressors is commonly used as a proxy for predicting the vulnerability and future status of reef resources. In this study, we evaluated explicitly whether proximity to shore and connections to coastal bays, two measures of potential land-based sources of disturbance, influence coral community and population structure, and the abundance, distribution, and condition of corals within patch reefs of the Florida Reef Tract. In the Florida Keys, long-term monitoring has documented significant differences in water quality along a cross-shelf gradient. Inshore habitats exhibit higher levels of nutrients (DIN and TP), TOC, turbidity, and light attenuation, and these levels decrease with increasing distance from shore and connections to tidal bays. In clear contrast to these patterns of water quality, corals on inshore patch reefs exhibited significantly higher coral cover, higher growth rates, and lower partial mortality rates than those documented in similar offshore habitats. Coral recruitment rates did not differ between inshore and offshore habitats. Corals on patch reefs closest to shore had well-spread population structures numerically dominated by intermediate to large colonies, while offshore populations showed narrower size-distributions that become increasingly positively skewed. Differences in size-structure of coral populations were attributed to faster growth and lower rates of partial mortality at inshore habitats. While the underlying causes for the favorable condition of inshore coral communities are not yet known, we hypothesize that the ability of corals to shift their trophic mode under adverse environmental conditions may be partly responsible for the observed patterns, as shown in other reef systems. This study, based on data collected from a uniform reef habitat type and coral species with diverse life-history and stress-response patterns from a heavily exploited reef system, showed that proximity to potential sources of stressors may not always prove an adequate proxy for assigning potential risks to reef health, and that hypothesized patterns of coral cover, population size-structure, growth, and mortality are not always directly related to water quality gradients. 相似文献
7.
Coral reef fish communities in the Seychelles are highly diverse and remain less affected by the direct impacts of human activities than those on many other coral reefs in the Indian Ocean. These factors make them highly suitable for a detailed survey of the impacts of the 1998 mass coral mortality, which devastated the coral faunas of the region. Using underwater visual census (UVC) techniques. fish communities were sampled in three localities in the southern Seychelles and one locality in the northern (granitic) Seychelles. Initial surveys were undertaken from the latter site in 1997. Surveys were undertaken at all sites during the coral bleaching episode in 1998 prior to any major changes in the reef fish communities. Repeat surveys were undertaken in 1999 one year after the coral mortality. Over 250 fish species were sampled from 35 families. Results suggest that changes in the overall fish community structures are not great, despite massive changes in the benthic cover. Significant changes have been observed in a number of individual species. These include those most heavily dependent on live coral cover for shelter or sustenance. Future potential changes are discussed, and potential management interventions are considered. 相似文献
8.
This paper presents initial results from a study of factors that inhibit or enhance hard coral recovery in rubble fields created by blast fishing in Komodo National Park and Bunaken National Park, Indonesia. Within nine sites monitored since 1998, there was no significant natural recovery. Levels of potential source coral larvae were assessed with settlement tiles in the rubble fields and in nearby high coral cover sites. Rubble movement was measured and shown to be detrimental to small scleractinians, especially in high current areas. In shallow water (2-6 m deep), rubble is often overgrown by soft corals and corallimorpharians, which inhibit hard coral survival. There is increased scleractinian recruitment in quadrats cleared of soft coral, and Acropora nubbins transplanted into soft coral fields suffer greater mortality than those transplanted above the soft coral canopy. Gaining an understanding of the prognosis for coral recovery is essential not only in order to assess the long-term impacts of blast fishing, but also to improve management decisions about protection of intact reefs and potential restoration of damaged areas. 相似文献
9.
Many studies have assessed in unison specific biological attributes and certain environmental impacts but few studies have analyzed multiple biological variables and pressures from multiple sites at the same time. Our study’s goal was to quantify the major potential human pressures in the shallow subtidal rocky reefs along a tropical Atlantic coast; propose a relative environmental pressure index and investigate the relationships between environmental pressures, the benthic community and coral population attributes. The analysis of human pressures suggests that one-third of sites were under high or very high proportional stress. Sites with high human pressure had lower live cover, higher percent of recent mortality and density of Siderastrea stellata. These relations were species specific. The coral species S.stellata seemed to be the best indicator of present environmental stress. These findings demonstrate the need to include multiple species and stressors in monitoring programs designed to contribute to coastal management initiatives. 相似文献
10.
Differential survival of coral transplants on various substrates under elevated water temperatures 总被引：1，自引：0，他引：1
Yap HT 《Marine pollution bulletin》2004,49(4):306-312
Closely related scleractinian coral species that exhibited similar survival patterns under relatively normal field conditions responded very differently to the occurrence of an environmental disturbance. The two species studied were Porites cylindrica and Porites rus which occur in the same reef zones in shallow reef flats. Transplants of both species were evenly distributed and attached to three different types of substrate: live coral colonies of P. cylindrica, dead coral colonies (also of P. cylindrica), and epoxy coated metal grids that were raised above the sandy substrate. With the onset of above-normal water temperatures due to the El Ni?o episode of 1998, P. cylindrica transplants immediately showed signs of bleaching stress and tissue necrosis, followed by algal overgrowth and mortality soon afterwards. In contrast, transplants of P. rus bleached more slowly and suffered less mortality, with a few actually showing signs of recovery at the end of the experimental period which covered a total of 14 weeks. These differences in responses could be attributed to properties of the symbiotic zooxanthellae, of the host coral tissue itself, or both. Over-all, survival was good on the metal grids (average of 35%), and on the live coral (average of 22%). It was poor on the dead coral (average of 6%). The metal grids as well as live coral tissue apparently provided a favorable substrate for the attached coral fragments, even for those of a different species. Under the conditions of this particular study, attachment of live coral fragments on already dead colonies for the purpose of increasing live coral cover on the reef did not yield favorable results. This is an area that requires further investigation. 相似文献
11.
This field study aims to determine whether increased levels of organically enriched particulate matter released by net pen fish farms (Eilat, Red Sea) would affect the growth of nubbins taken from the branching coral Stylophora pistillata. We followed the survival and growth of 1322 nubbins pruned from five colonies that were transplanted at a depth of 6 m in the vicinity of the fish cages and in a reference site, in front of the Interuniversity Institute (IUI). Nubbins were attached on U-shaped PVC plates in three orientations (up, vertical and down positions). After 50 days, survival was high in both localities and no difference was recorded between the spatial orientations. At the fish farm, however, burial of the nubbin's lateral growths and partial coverage of nubbins by settled particulate matter resulted in significant reduction of the lateral growth rates of nubbins settled in the up position as compared to the reference site. On the other hand, faster growth rates were recorded in the vertical set of nubbins at the fish farm when compared with the IUI site. These results strengthen the conclusion that physical effects, rather than nutrient enrichment, may constitute the main cause of stress for minute coral fragments (resembling coral recruits) growing near the vicinity of a fish farm. 相似文献
12.
Recent studies report conflicting results concerning the effects of eutrophication on coral reproduction. The present study examines reproductive effort in the brooding coral Stylophora pistillata exposed to chronic eutrophication caused by in situ fish cages (FC) in the northern Gulf of Eilat (Aqaba). Histological studies of 20 S. pistillata colonies transplanted to each of two study sites, one close to the nutrient enriched FC site and the other at a reference site (IUI), 8 km southwest of the FC site, show that, overall, corals from the FC site have a significantly higher percentage of polyps containing oocytes and testes than corals from the IUI site. However, average oocyte size and the percentage of oocytes reaching the size at which fertilization occurs (i.e., >200 microm) were both significantly greater in colonies at the IUI site compared to the FC site. As the reproductive season progressed, colonies at the IUI site exhibited a decrease in the percentage of polyps containing oocytes, concomitant with an increase in the number of polyps containing planulae, indicating successful development of oocytes into planulae. In contrast, in colonies at the FC site oocyte numbers were greatest at the end of the reproductive season, and overall, numbers of planulae were significantly lower compared with the IUI colonies, suggesting relative failure of oocyte maturation, fertilization and ensuing larval development. The significantly higher lipid content found during the reproduction season in IUI colonies compared with FC colonies corroborates this assertion. This data strongly suggest that nutrients released from the fish farms have adverse effects on successful production of larvae of S. pistillata. In view of the recent severe deterioration of the coral reefs of Eilat and their present critical state of health, the only chance for their renewal is the use of immediate, prudent and rational protection measures against all man-made perturbations. 相似文献
13.
Intensive recreational SCUBA diving threatens coral reef ecosystems. The reefs at Dahab, South Sinai, Egypt, are among the world’s most dived (>30,000 dives y−1). We compared frequently dived sites to sites with no or little diving. Benthic communities and condition of corals were examined by the point intercept sampling method in the reef crest zone (3 m) and reef slope zone (12 m). Additionally, the abundance of corallivorous and herbivorous fish was estimated based on the visual census method. Sediments traps recorded the sedimentation rates caused by SCUBA divers. Zones subject to intensive SCUBA diving showed a significantly higher number of broken and damaged corals and significantly lower coral cover. Reef crest coral communities were significantly more affected than those of the reef slope: 95% of the broken colonies were branching ones. No effect of diving on the abundance of corallivorous and herbivorous fish was evident. At heavily used dive sites, diver-related sedimentation rates significantly decreased with increasing distance from the entrance, indicating poor buoyancy regulation at the initial phase of the dive. The results show a high negative impact of current SCUBA diving intensities on coral communities and coral condition. Corallivorous and herbivorous fishes are apparently not yet affected, but are endangered if coral cover decline continues. Reducing the number of dives per year, ecologically sustainable dive plans for individual sites, and reinforcing the environmental education of both dive guides and recreational divers are essential to conserve the ecological and the aesthetic qualities of these dive sites. 相似文献
14.
Karnit Bahartan Mohammad Zibdah Alvaro Israel Avigdor Abelson 《Marine pollution bulletin》2010,60(5):759-764
The current state of health of the coral reefs in the northern Gulf of Aqaba (Red Sea), notably the Eilat reefs, is under debate regarding both their exact condition and the causes of degradation. A dearth of earlier data and unequivocal reliable indices are the major problems hinder a clear understanding of the reef state. Our research objective was to examine coral-algal dynamics as a potential cause and an indication of reef degradation. The community structure of stony corals and algae along the northern Gulf of Aqaba reveal non-seasonal turf algae dominancy in the shallow Eilat reefs (up to 72%), while the proximate Aqaba reefs present negligible turf cover (<6%). We believe that turf dominancy can indicate degradation in these reefs, based on the reduction in essential reef components followed by proliferation of perennial turf algae. Our findings provide further evidence for the severe state of the Eilat coral reefs. 相似文献
15.
Smith TB Nemeth RS Blondeau J Calnan JM Kadison E Herzlieb S 《Marine pollution bulletin》2008,56(12):1983-1991
Managing the effects of anthropogenic disturbance on coral reefs is highly dependant on effective strategies to assess degradation and recovery. We used five years of field data in the US Virgin Islands to investigate coral reef response to a potential gradient of stress. We found that the prevalence of old partial mortality, bleaching, and all forms of coral health impairment (a novel category) increased with nearshore anthropogenic processes, such as a five-fold higher rate of clay and silt sedimentation. Other patterns of coral health, such as recent partial mortality, other diseases, and benthic cover, did not respond to this potential gradient of stress or their response could not be resolved at the frequency or scale of monitoring. We suggest that persistent signs of disturbance are more useful to short-term, non-intensive (annual) coral reef assessments, but more intensive (semi-annual) assessments are necessary to resolve patterns of transient signs of coral health impairment. 相似文献
16.
Golbuu Y van Woesik R Richmond RH Harrison P Fabricius KE 《Marine pollution bulletin》2011,62(4):824-831
Coral community structure is often governed by a suite of processes that are becoming increasingly influenced by land-use changes and related terrestrial discharges. We studied sites along a watershed gradient to examine both the physical environment and the associated biological communities. Transplanted corals showed no differences in growth rates and mortality along the watershed gradient. However, coral cover, coral richness, and coral colony density increased with increasing distance from the mouth of the bay. There was a negative relationship between coral cover and mean suspended solids concentration. Negative relationships were also found between terrigenous sedimentation rates and the richness of adult and juvenile corals. These results have major implications not only for Pacific islands but for all countries with reef systems downstream of rivers. Land development very often leads to increases in river runoff and suspended solids concentrations that reduce coral cover and coral diversity on adjacent reefs. 相似文献
17.
Yvonne Sawall Jamaluddin Jompa Magdalena Litaay Andi Maddusila Claudio Richter 《Marine pollution bulletin》2013
Coral recruitment was assessed in highly diverse and economically important Spermonde Archipelago, a reef system subjected to land-based sources of siltation/pollution and destructive fishing, over a period of 2 years. Recruitment on settlement tiles reached up to 705 spat m−2 yr−1 and was strongest in the dry season (July–October), except off-shore, where larvae settled earlier. Pocilloporidae dominated near-shore, while a more diverse community of Acroporidae, Poritidae and others settled in the less polluted mid-shelf and off-shore reefs. Non-coral fouling community appeared to hardly influence initial coral settlement on the tiles, although, this does not necessarily infer low coral post-settlement mortality, which may be enhanced at the near- and off-shore reefs as indicated by increased abundances of potential space competitors on natural substrate. Blast fishing showed no local reduction in coral recruitment and live hard coral cover increased in oligotrophic reefs, indicating potential for coral recovery, if managed effectively. 相似文献
18.
The extensive deterioration of coral reefs worldwide highlights the importance of creating efficient monitoring methods to best assess their state of health. At present, several suggested parameters serve such indicators. None of these, however, is well accepted as reliably representing reef community health. In the present study we examine a new approach based on the ratio between mortality and recruitment rates of branching corals, which we term 'Deterioration Index' (DI). It aims at providing a quantitative indication of the state of health of reef-building coral communities. The method was developed and tested on 16 coral communities on artificially laid rocks along the coast of Eilat, Red Sea (Gulf of Aqaba). In contrast to frequently used indices (i.e. mortality rate, abundance and species richness), which did not demonstrate a consistent result in comparing disturbed vs. undisturbed coral communities, the DI revealed significant differences between these communities. Our results suggest that the use of the DI may enable the detection of disturbed coral communities in one instance monitoring, where the other parameters had failed. The DI, therefore, may provide a comparable quantitative assessment of the deterioration process and its intensity in a coral community. We propose the DI approach as an efficient and applicable tool for coral reef monitoring. 相似文献
19.
Coral bleaching and mortality on artificial and natural reefs in Maldives in 1998, sea surface temperature anomalies and initial recovery 总被引：8，自引：0，他引：8
Edwards AJ Clark S Zahir H Rajasuriya A Naseer A Rubens J 《Marine pollution bulletin》2001,42(1):7-15
The bleaching and subsequent mortality of branching and massive corals on artificial and natural reefs in the central atolls of Maldives in 1998 are examined with respect to sea surface temperature (SST) anomalies. SST normally peaks in April-May in Maldives. The UK Meteorological Office's Global sea-Ice and SST data set version 2.3 b shows that in 1998 monthly mean SST was 1.2-4 S.D. above the 1950-1999 average during the warmest months (March-June), with the greatest anomaly in May of +2.1 degrees C. Bleaching was first reported in mid-April and was severe from late April to mid-May with some recovery evident by late-May. At least 98% of branching corals (Acroporidae, Pocilloporidae) on artificial structures deployed on a reef flat in 1990 died whereas the majority of massive corals (Poritidae, Faviidae, Agariciidae) survived the bleaching. The pre-bleaching coral community on the artificial reefs in 1994 was 95% branching corals and 5% massives (n = 1589); the post-bleaching community was 3% branching corals and 97% massives (n = 248). Significant reductions in live coral cover were seen at all natural reefs surveyed in the central atolls, with average live coral cover decreasing from about 42% to 2%, a 20-fold reduction from pre-bleaching levels. A survey of recruitment of juvenile corals to the artificial structures 10 months after the bleaching event showed that 67% of recruits (> or = 0.5 cm diameter) were acroporids and pocilloporids and 33% were from massive families (n = 202) compared to 94% and 6%, respectively, in 1990-1994 (n = 3136). Similar post-bleaching dominance of recruitment by branching corals was seen on nearby natural reef (78% acroporids and pocilloporids; 22% massives). A linear regression of April mean monthly SST against year was highly significant (p < 0.001) and suggests a rise of 0.16 degree C per decade. If this trend continues, by 2030 mean April SST in the central atolls will normally exceed the anomaly level at which corals appear there are susceptible to mass bleaching. 相似文献