Coral Damage Research Articles

Possible effects of human impacts on epibenthic communities and coral rubble features in the marine Park of Bunaken (Indonesia)

Indo-Pacific coral reefs are considered among the most complex and biodiversified ecosystems in the world. Their existence is threatened by both natural and anthropogenic factors. Therefore, the assessment of anthropogenic disturbances is necessary to protect and manage these marine natural resources. In Bunaken Marine Park (North Sulawesi, Indonesia) epibenthic assemblages and coral rubble features at four impacted sites (each of them located close to villages and frequently exploited as recreational diving spots), and four well preserved sites (far from villages and scarcely frequented by divers), were investigated at 6, 12 and 18 m depth, in order to identify possible reef modifications. The assemblages were sampled by way of photographs. Coral rubble cover was estimated both by way of photographs and along belt transects, while grain size and the living fraction of the coral rubble were assessed by direct samples. The data showed significant differences between the study sites and between depths with regard to human activity. The hard coral cover and the assemblage heterogeneity are higher in control sites than in the impacted site where, especially in shallow water, the mechanical damage can strongly affect the assemblage structure. The mean percentage of coral rubble cover was significantly higher in the impacted sites, while its living portion was higher in the controls. The fine fraction (0.1–0.5 cm) of coral rubble was more abundant in the impacted sites, coarse fraction (4–8 cm) prevailed at the control sites while intermediate fractions did not show any differences. The three-dimensional structural complexity of the assemblages was reduced in the sites affected by physical disturbances. These results are strongly independent of depth. Human activities, which damage corals and increase coral rubble production, are mainly performed on the reef flat and reef edge but their effects are transferred along the reef wall in depth.

Quantification of coral heat shock proteins from individual coral polyps

The induction and regulation of heat shock proteins (hsps) is a significant defense mechanism that can preserve metabolic function and foster recovery from short-term stress events. Present coral sampling methodologies that involve hsp analysis often require the harvesting of large samples of live coral colonies that may already be stressed or in poor health. In the present study, 3 novel protocols were developed to: (1) extract single coral polyps, minimizing colony trauma; (2) purify protein from single coral polyps (approximately 12 mm 3 ); and (3) develop a more sensitive protein quantification method. The preliminary testing of 5 separate protein preparation methods resulted in a range of total protein yields from 47 to 77 µg coral polyp -1 . The optimized methods were able to recover, on average, 44 ± 12 µg protein polyp -1 (n = 20). Subsequent SDS-PAGE and immunoblotting analysis of single coral polyps resolved as little as 87 pg hsp70 coral polyp -1 . This minimally invasive sampling protocol reduces coral damage and, thus, reduces stress and diseases caused by sampling.

Local changes in community diversity after coral transplantation

Over several decades, coral transplantation has been developed as a tool to rehabilitate damaged coral reef habitats. This investigation aimed to determine whether this form of intervention would result in a significant improvement in diversity and abundance of associated reef species. The experiment consisted of 4 treatments: undisturbed sites (which also served as sources of the trans- plants), degraded plots to which corals were transplanted, empty plots that received no transplants, and control plots that were empty and situated at least 100 m away from the transplant and empty plots. The latter 3 treatments were replicated at 4 different sites. The establishment or movement of fish and invertebrates, as well as the abundance of algae, were recorded on a quarterly basis. Both non-metric multidimensional scaling and repeated measures ANOVA detected significant differ- ences among treatments, with transplant plots having higher numbers and abundances of taxa than the empty plots and the empty controls. The 2 latter treatments did not differ significantly from each other. The source sites had higher abundances of coral recruits (Poritidae) than all the other treat- ments and of sea urchins (Diadematidae) than the empty plots and empty controls. The transplant plots harbored greater numbers of damselfish (Pomacentridae) and sea urchins than the empty plots and empty controls. Thus, coral transplantation resulted in higher diversity and greater abundance of fish and invertebrates and has the potential to help re-establish degraded reef communities.

Managing the Impacts of SCUBA Divers on Thailand's Coral Reefs

While dive tourism enjoys continued growth worldwide, concern exists that it is contributing to the degradation of coral communities, biologically and aesthetically. This study examined the effect of SCUBA diver contacts with coral and other substrates. Ninety-three percent of divers made contact with substrata during a 10-minute observation period with an average of 97 contacts per hour of diving. Two-thirds of the divers caused some coral damage by breaking fragments from fragile coral forms with an average of 19 breakages per hour of diving. Fin damage was the major type of damage. Underwater photographers caused less damage per contact than non-photographers; as did male divers, compared with females. Diver-induced damage decreases with increasing number of logged dives and attendance at pre-dive briefings. Park managers can help reduce impact by identifying and directing use to sites that are resistant to damage, matching diver competence and site preferences, and alerting operators to dive conditions. Minimising impact requires dive operators to be proactive in promoting minimal impact diving behaviour. This includes selecting sites that match diver expectations and experience, and providing pre-dive briefings in the context of diver activities and physical capacity, and site susceptibility to impact and current strength.

The influence of protected area management on the status of coral reefs at Misali Island, Tanzania following the 1998 bleaching event in the western Indian Ocean

AbstractThe reefs of Misali Island, Tanzania suffered serious coral mortality as a result of the 1998 coral bleaching event in the western Indian Ocean. Four years after this event, Frontier‐Tanzania assessed reef substrate in Misali Island Marine Conservation Area (MIMCA) using scuba surveys. Substrate cover was compared between sites within and outside the nonextraction zone (NEZ) of MIMCA and recovery rates were estimated through reference to previous studies. Coral recovery at Misali Island following the bleaching event has generally been slow, but nonextractive management of MIMCA has enhanced coral recovery within the NEZ. The absence of fishing activities in the NEZ has sustained herbivorous fish populations and thus reduced algal overgrowth; however, outside the NEZ, diving and anchoring activities have caused further coral damage and led to increased levels of debris. Awareness‐raising programmes could lessen these problems and the NEZ appeared to be well‐placed to capitalize on nonmanageable factors that are thought to mitigate the effects of coral bleaching. In addition, the implementation of flexible zoning schemes could improve recovery rates after future bleaching events.

High zooxanthella density shortens the survival time of coral cell aggregates under thermal stress

To investigate bleaching mechanisms in coral–zooxanthella symbiotic systems, it is important to study the cellular- or tissue-level responses of corals to stress. We established an experimental system to study the stress responses of coral cells using coral cell aggregates. Dissociated coral cells aggregate to form spherical bodies, which rotate by ciliary movement. These spherical bodies (tissue balls) stop rotating and disintegrate when exposed to a thermal stress. Tissue balls prepared from dissociated cells of Fungia sp. and Pavona divaricata were exposed to either elevated temperature (31 °C, with 25 °C as the control) or elevated temperature in the presence of exogenous antioxidants (ascorbic acid and catalase, or mannitol). The survival curves of tissue balls were markedly different between 31 and 25 °C. At 31 °C, most tissue balls disintegrated within 24 h, whereas at 25 °C, most tissue balls survived for more than 24 h. There was a negative correlation between survival time and the zooxanthella density of tissue balls at 31 °C, but no significant relationship was found at 25 °C. Antioxidants extended the survival time of tissue balls at high temperature, suggesting that zooxanthellae produce reactive oxygen species under stress. These results indicate that zooxanthellae produce harmful substances and damage coral cells under high-temperature stress. Tissue balls provide a good experimental system with which to study the effects of stress and various chemical reagents on corals cells.

Managing the Impacts of SCUBA Divers on Thailand's Coral Reefs

While dive tourism enjoys continued growth worldwide, concern exists that it is contributing to the degradation of coral communities, biologically and aesthetically. This study examined the effect of SCUBA diver contacts with coral and other substrates. Ninety-three percent of divers made contact with substrata during a 10-minute observation period with an average of 97 contacts per hour of diving. Two-thirds of the divers caused some coral damage by breaking fragments from fragile coral forms with an average of 19 breakages per hour of diving. Fin damage was the major type of damage. Underwater photographers caused less damage per contact than non-photographers; as did male divers, compared with females. Diver-induced damage decreases with increasing number of logged dives and attendance at pre-dive briefings. Park managers can help reduce impact by identifying and directing use to sites that are resistant to damage, matching diver competence and site preferences, and alerting operators to dive conditions. Minimising impact requires dive operators to be proactive in promoting minimal impact diving behaviour. This includes selecting sites that match diver expectations and experience, and providing pre-dive briefings in the context of diver activities and physical capacity, and site susceptibility to impact and current strength.

Diving down the reefs? Intensive diving tourism threatens the reefs of the northern Red Sea

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.

Bleached, But Not by the Sun: Sunscreen Linked to Coral Damage

Warm, shallow, sun-drenched seas sparkling with brilliantly colored fish and coral species—we’ve all seen dazzling images of tropical reefs. Coral reefs are among the most biologically productive and diverse ecosystems in the world, providing food protein for half a billion people. But tropical reefs have begun dying from bleaching, with the frequency and spatial extent of such bleaching increasing dramatically over the past 20 years. Now a study finds that chemical compounds in sunscreen products can cause abrupt and complete bleaching of hard corals, even at extremely low concentrations [EHP 116:441–447; Danovaro et al.]. Zooxanthellae, symbiotic algae that live in healthy coral tissue, provide nutrients to corals through photosynthesis. The algae also help make the spectacular colors for which corals are known. The corals lose their color when zooxanthellae die or leave the reef; the protective skeletons of the corals are thus exposed, and the corals die. Rising seawater temperatures, bacterial and viral diseases, ultraviolet light or other radiation, and pollution have been blamed for coral bleaching. Scientists at the Polytechnic University of the Marche Region in Ancona, Italy, studied the effects of sunscreen exposure on samples from tropical reefs. The researchers collected branches of hard coral from sites in the Red Sea, the Caribbean Sea, the Indian Ocean off Thailand, and the Pacific Ocean near Indonesia. Coral branches were immersed in bags of virus-free seawater supplemented with various quantities of sunscreen, then incubated in situ. These samples were compared with controls also incubated in situ in virus-free seawater. The researchers found that among the several brands of sunscreen tested, four commonly found ingredients—paraben, cinnamate, benzophenone, and camphor derivatives—can stimulate dormant viral infections in zooxanthellae. The sunscreen chemicals caused viruses within zooxanthellae to replicate until their algal hosts exploded, spilling viruses into the surrounding seawater, which could then spread infection to nearby coral communities. Coral bleaching occurred, often within a few hours, but always within 4 days, at sunscreen quantities as small as 10 μL/L. Controls remained healthy. The researchers estimate that approximately 10% of the world’s coral reefs are potentially threatened by sunscreen that washes off swimmers in reef waters. The study suggests that, as tourism continues to increase in tropical reef areas, the impact of sunscreens on coral bleaching could rise significantly in the future.

Reef walking on Red Sea reef flats – Quantifying impacts and identifying motives

Reef walking on the shallow reef flats of fringing reefs is an activity commonly observed on Red Sea coral reefs. Of the 137 in-water observations of reef walkers made at Ras Um Sidd, Sharm El Sheikh, South Sinai, 12.4% caused coral damage. Eighteen incidents of coral damage were recorded, 44.4% being breakages of branching corals, 39.8% abrasions of various growth forms and 16.7% detachments of soft coral colonies. Sediment was stirred-up on 31.4% of observations. Tramplers broke 0.1 branches per minute and raised 1.5 sediment clouds, thereby causing more damage than reported from divers. Damage caused depended on coral community structure and past trampling history, with communities dominated by fragile branching corals being most susceptible to mechanical damage and communities heavily trampled in the past being less susceptible. Given that main motives for reef walking included crossing the reef flat, adjusting gear or communicating, management interventions, such as the construction of a walkway combined with a public awareness campaign, could reduce the numbers of reef walkers by up to 39%.

Patterns of coral damage associated with the 2004 Indian Ocean tsunami at Mu Ko Similan Marine National Park, Thailand

On 26 December 2004, a severe earthquake in Sumatra caused a series of tsunami waves to strike southwestern coastal areas of Thailand. In this study, we investigated the patterns of tsunami‐related damage to coral reefs at Mu Ko Similan Marine National Park. The results showed that the percent of damaged corals ranged from 7.2% to 39.7% of the total live coral cover, and the intensity of the coral damage was high at depths deeper than 10 metres at most study sites. In addition, massive and tabulate coral forms were the most susceptible to tsunami damage. The surveys also revealed that a high degree of coral damage occurred where the reef slope gradually dropped away from the shoreline. Therefore, coral communities and coastal profiles can be major factors influencing the movement of the currents generated by the tsunami and consequently may affect the pattern of coral damage by the tsunami.

Quantifying acceptable levels of visitor use on Red Sea reef flats

Abstract The effects of trampling by visitors walking over the reef flat to snorkel or swim along the reef edge were studied at Ras Um Sidd, a popular fringing reef site at Sharm El Sheikh, and in the Ras Mohammed National Park, South Sinai, Egypt. Twelve stations showed a sequence of events linked to increased frequency and extent of trampling, with the intensities of trampling ranging from 0.1 to 324 tramplers m−2 yr−1. Heavily trampled stations had a reduced coral cover (in particular branching corals), higher amounts of coral damage, less old dead coral, less obligate corallivorous fishes and more herbivores. Wave exposure was crucial in determining the susceptibility of coral communities to trampling. Exposed communities were dominated by branching corals and were mechanically more resistant, since wave stress had favoured stockier growth forms. The applicability of the ‘carrying capacity concept’ was investigated as a management tool for determining how much use is sustainable. Examination of the relationship between hard coral cover and intensity of trampling suggested that carrying capacity could be set at approximately 50 tramplers m−2 yr−1. The actual amount of damage caused by trampling showed a linear increase with increasing trampling intensities, so that the carrying capacity concept, as defined in this study, was not applicable to the relationship since no threshold existed. Instead, the ‘limits of acceptable change’ approach would be more practicable, with managers deciding what amount of coral damage they permit before limiting access. To establish meaningful limits of change, more knowledge is required about ecological as well as social consequences (e.g. visitor satisfaction) of such limits. Copyright © 2007 John Wiley & Sons, Ltd.

Coral Reefs Still in Danger from Tourism Head

As a diver since 1985 with over 500 dive hours logged on tropical reefs and now a coral reef conservationist working directly with the marine tourism sector, I have to wonder if Norman Karin is talking about the same dive community I know (“A diver's perspective on coral damage,” Letters, 13 July, p. [196][1]). I'm not about to pretend that recreational use and overuse ranks with climate change, coastal development, and unsustainable and destructive fishing practices as the most significant global threats to coral health. And I've had the honor to dive with stellar dive businesses who are ambassadors for sustainability. But to suggest that the dive community as a whole has had some sort of collective epiphany around sustainable behavior and best practices is just uninformed. According to a 2002 report ([1][2]), marine tourism is a major factor contributing to reef decline at no-take Marine Protected Areas (MPAs) in Hawaii. In 2003, between 28,000 and 100,000 people per year visited just four sites, with diving and snorkeling being the most popular marine recreation activity ([2][3]). Tourism numbers have increased steadily over the years. In 1999, tiny Honolua Bay on Maui averaged 250 tourists per day and up to 700 per day during peak season ([3][4]). This volume has certainly increased. Research also shows that 45% of certified SCUBA divers who visit dive sites break coral colonies. Most of this damage appears to be from fin kicks ([4][5]). Finally, Karin points to Bonaire Marine Park as evidence of diver awareness. I agree that Bonaire is spectacular and a model that should be emulated and exported worldwide. But to hold up the well-funded, relatively affluent, politically stable, and uncorrupt Netherlands Antilles as somehow representative of most coral reef destinations and MPA systems is disingenuous. Most MPAs are not reaching their conservation goals. Crushing poverty and competing resource use often derail the best conservation efforts. Denial or special pleading to displace tourism's contribution and responsibility certainly doesn't help. 1. 1.[↵][6] 1. D. Turgeon, 2. R. Asch , The state of coral reef ecosystems of the United States and Pacific Freely Associated States (U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Ocean Service, Silver Spring, MD, 2002). 2. 2.[↵][7] 1. K. N. Holland, 2. C. G. Meyer , Human Activities in Marine Protected Areas–Impact on Substrates (Hawaii Institute of Marine Biology, Kaneohe, HI, 2003). 3. 3.[↵][8] 1. E. K. Brown, 2. Dynamics Sediment , Water Motion Characteristics, and Human Use Patterns Within Honolua Bay MLCD, (1999) Submitted to State of Hawaii Department of Land and Natural Resources in partial fulfillment of Conservation District Use Permit Number: MA-2772. 4. 4.[↵][9] 1. N.H.L. Baker, 2. C. M. Roberts , Biol. Conserv. 120, 481 (2004). [OpenUrl][10] [1]: /lookup/doi/10.1126/science.317.5835.196b [2]: #ref-1 [3]: #ref-2 [4]: #ref-3 [5]: #ref-4 [6]: #xref-ref-1-1 View reference 1. in text [7]: #xref-ref-2-1 View reference 2. in text [8]: #xref-ref-3-1 View reference 3. in text [9]: #xref-ref-4-1 View reference 4. in text [10]: {openurl}?query=rft.jtitle%253DBiol.%2BConserv.%26rft.volume%253D120%26rft.spage%253D481%26rft.atitle%253DBIOL%2BCONSERV%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx

A Diver's Perspective on Coral Damage

I must take exception to a comment and its implications in Richard Stone's otherwise excellent article “A world without corals?” (News Focus, 4 May, p. [678][1]). Stone introduces the human toll on reefs by citing damage inflicted by “divers clumsily breaking off chunks of coral.” It is undeniable that recreational divers will, on occasion, inadvertently injure corals. However, I have been a certified SCUBA diver since 1992 and have logged over 150 ocean dives all over the world, and in that time I have seen only sporadic instances of divers impacting corals. Formal dive training by all major certification agencies includes instruction on reef protection, and the vast majority of dive tour operators repeatedly lecture divers about avoiding contact with coral and other marine life. It is undeniable that our coral reefs are threatened by human activities, but it is unfair to imply that sport divers at all popular reefs contribute significantly to this plight. Rather than a threat, I would argue that the growth of recreational diving is a major benefit to the future of our reefs: Divers are among the most environmentally conscious individuals I have met (note the “army of snorkeling and diving volunteers” described in the article), and this pastime depends on having beautiful, healthy corals to explore. As proof of this view, one need only visit Bonaire, a popular dive destination and the site of some of the world's healthiest coral reefs. Bonaire instituted strong legislation, including laws enacted in 1975 that made it illegal to break or sell coral. Subsequent efforts in cooperation with the World Wildlife Fund established a vast marine park that completely encompasses the island. [1]: /lookup/doi/10.1126/science.316.5825.678

The formation of policy for protection of cold-water coral off the coast of Norway

Abstract This paper presents the implementation of conservation measures, especially bottom trawl free areas, for the protection of cold-water coral off the Norwegian coast. The protection measures became effective less than 9 months after the managers were informed and the public became aware of damaged coral on nationwide television. Behind this quick reaction were a number of agents such as the oil industry, fishers, biologists, NGOs as well as policy-makers. The implementation of the protected areas was remarkably free of contention. This work attempts to outline the reasons for this, and determine whether there are lessons to be learned with regard to conservation measures elsewhere.

Quantifying the environmental impacts of artisanal fishing gear on Kenya’s coral reef ecosystems

The environmental impacts of artisanal fishing gear on coral reef ecosystems were studied in the multi-gear fishery of southern Kenya to evaluate which types of gear have the greatest impact on coral reef biodiversity. The gear types studied were large and small traps, gill nets, beach seines, hand lines and spear guns. Levels of coral damage, proportion of juvenile fish and discards, size and maturity stage at first capture were quantified and compared amongst the gear types. Results indicate that fishers using beach seines, spears and gill nets cause the most direct physical damage to corals. Spear fishers showed the highest number of contacts to live corals per unit catch followed by fishers using gill nets (12.6 ± 1.8 and 5.9 ± 2.0 coral contacts per kg fish caught per trip respectively). Apart from discarding 6.5% of their daily catch in the sea, as it was too small, beach seine fishers also landed the highest percentage of juvenile fish (68.4 ± 15.7%), a proportion significantly higher ( p < 0.001) than in any other gear. The size and maturity stage at first capture for 150 of 195 species caught by all gear types was well below the lengths at which they mature. For example, 100% of Lethrinus xanthochilus, 99% of Lethrinus nebulosus and 94% of Lethrinus harak caught were juveniles. Across all gear types, 50.1 ± 22.7% of the catch consisted of juvenile fish, indicating serious growth overfishing. Field assessment of levels of coral density showed that fishing grounds where beach seines were still in use had a significantly lower density than where beach seining was not used. This correlation is likely to arise in part because seines cannot be used in the most coral rich areas, and in part because coral loss is a consequence of seine use. On a per gear basis therefore, beach seines had the most impact on coral reef biodiversity. This study emphasizes the need to enforce restrictions on destructive gear and mesh sizes.

IMPACT OF WATER QUALITY DETERIORATION ON CORAL REEF COMMUNITY STRUCTURE IN THE NORTHERN RED SEA, EGYPT

Fifteen water quality parameters and nine coral community variables were assessed in eight reef sites along the Red Sea coast of Egypt. Coral reef environments are suffering of stress from increased anthropogenic activities, particularly in the vicinity of heavily populated and touristic areas such as Hurghada, Ain Al-Sukhna and Sharm ElSheikh. Increased terrestrial runoff of sediments, nutrients, organic matter and other pollutants are the main causes of water quality deterioration in the investigated reef sites. The results showed that bioerosion of corals by sea urchins, and enhanced abundance of macroalgae and consequent competitive overgrowth of corals were the major reasons of coral damage observed in the area of study. Population density of sea urchins exhibited significant and positive correlations with the majority of eutrophicatio n parameters. Salinity was significantly and negatively correlated with live hard coral cover. Exceeding levels of DIN and TSM above the threshold concentrations for eutrophication were reported to be indirectly and adversely affecting coral reefs through stimulating the growth of macroalgae, enhancing sea urchin density and reducing water transparency. The results support the predictions of bottom-up hypothesis that confirm the critical role of eutrophicatio n in structure of coral reef community.

Germ theory for ailing corals

Human activities damage coral reef ecosystems. Application of the 'germ theory', proposed more than a century ago for human diseases, could foster action on global environmental ailments such as this.

Precursors for resilience in coral communities in a warming climate: a belief network approach

This paper explores how successful management interventions might benefit coral reefs during the period of climate warming that is expected in coming decades. To aid this task we have developed a prototype decision-support tool, called ‘ReefState’, which integrates the outcomes of management interventions within a ‘belief network’ of connected variables that describe future warming, coral damage and coral recovery. In a case study applied to the inshore waters of the central Great Barrier Reef, Australia, our worst case scenarios, like several others, suggest that reefs will become devoid of significant coral cover and associated biodiversity by 2050. Even under more optimistic (low) rates of future warming, the persistence of hard coral dominated reefscapes beyond 2050 will be heavily reliant on 2 things, the ability of corals to increase their upper thermal bleaching limits by ~0.1°C per decade, and management that produces local conditions that constrain excessive algal biomass proliferation during inter-disturbance intervals. Despite being perturbed by a global warming process, management of local ecological factors will thus be of critical importance in shaping the future trajectories of coral reef ecosystems.

Oxygen consumption rate of the corals Goniastrea aspera, Porites lobata, and Pavona frondifera under red soil stress in the Ryukyu Islands, Okinawa, Japan

Effects of short-term sedimentation on common coastal coral species, Goniastrea aspera, Porites lobata and Pavona frondifera, from the reef flat southeast of the Ryukyu Islands, Okinawa, Japan were investigated in laboratory experiments using oxygen uptake respirometers. The O2 consumption rate was significantly different among species and between sediment treatments (20 and 200mg l-1 red soil suspension, P<0.05). In dark experiments, Goniastrea showed higher respiration rates (0.020±0.002ml O2 cm-2h-1) than did Pavona (0.017±0.003mL O2 cm-2h-1) and Porites (0.010±0.001ml O2 cm-2h-1). In light experiments, Goniastrea also showed higher O2 consumption rates (0.021±0.003ml O2 cm-2h-1) than did Porites (0.010±0.004ml O2 cm-2h-1) and Pavona (0.007±0.001ml O2 cm-2h-1). Zooxanthellae densities were 6.53±0.13, 3.12±0.05, and 4.37±0.07 (×106cells cm-2; mean±SE, n=8) in Goniastrea, Porites, and Pavona, respectively. Coral respiration rate increased proportionally with zooxanthellae density in Goniastrea and Pavona. High zooxanthellae density may increase the O2 production that contributes to colony respiration; however, in Porites, the relationship between zooxanthellae density and coral respiration rate was not clear. The massive corals, Goniastrea and Porites, are more resistant to sediment stress than is the plate-like coral, Pavona. Goniastrea showed high tolerance and adaptation to stress conditions in all experiments, at all times (12h), with similar trends in both dark and light conditions. Porites was affected only within the first 3h under light conditions, while Pavona was the most affected species. These results help us to understand coral damage caused by red soil sedimentation, as well as coral mortality and potential shifts in community structure related to prolonged or repeated elevated levels of sedimentation on coastal reefs.