World's Coral Reefs Research Articles

Marine biodiversity hotspots and conservation priorities for tropical reefs.

Coral reefs are the most biologically diverse of shallow water marine ecosystems but are being degraded worldwide by human activities and climate warming. Analyses of the geographic ranges of 3235 species of reef fish, corals, snails, and lobsters revealed that between 7.2% and 53.6% of each taxon have highly restricted ranges, rendering them vulnerable to extinction. Restricted-range species are clustered into centers of endemism, like those described for terrestrial taxa. The 10 richest centers of endemism cover 15.8% of the world's coral reefs (0.012% of the oceans) but include between 44.8 and 54.2% of the restricted-range species. Many occur in regions where reefs are being severely affected by people, potentially leading to numerous extinctions. Threatened centers of endemism are major biodiversity hotspots, and conservation efforts targeted toward them could help avert the loss of tropical reef biodiversity.

Spectrographic imaging. A bird's-eye view of the health of coral reefs.

Almost three-quarters of the world's coral reefs are thought to be deteriorating as a consequence of environmental stress. Until now, it has been possible to evaluate reef health only by field survey, which is labour-intensive and time-consuming. Here we map live coral cover from the air by remote imaging, a technique that will enable the state of shallow reefs to be monitored swiftly and over large areas.

1997–98: Unprecedented thermal stress to coral reefs?

Mass bleaching is a stress response of corals subjected to warmer‐than‐normal seawater temperatures during the warm season. During 1997–98 there were unprecedented numbers of reports of bleaching on many of the world's coral reefs. Observational evidence suggests an increase in frequency of mass coral bleaching events since the late 1970s. Two indices of warm season sea surface temperatures (SSTs; SST maximum anomaly and degree‐months) are presented for 47 reef sites where bleaching occurred during 1997–98. The level of thermal stress at the vast majority of these coral reef sites during 1997–98 was unmatched in the period 1903–99. Warm season SSTs at these coral reef sites have significantly warmed over this period and the frequency of warm season SST extremes has increased since the late 1970s. Continued warming of tropical SSTs, as is likely due to the enhanced greenhouse effect, will increase the level of thermal stress to coral reefs. Increased frequency of bleaching events will reduce corals' capacity to recover and may significantly alter the make‐up of present day coral reef ecosystems.

The health and future of coral reef systems

Coral reefs are among the most productive and diverse ecosystems on earth and provide a multitude of valuable ecosystem services. Moreover, the resources derived from coral reefs are essential to the food security of millions of people living within tropical coastal communities. Unfortunately, burgeoning human populations in coastal regions are placing an unsustainable burden on these resources such that degradation of coral reefs is common. In addition, during 1998, El Niño driven increases in sea temperature caused a mass bleaching event that further degraded many of the world's coral reefs. This article provides a brief review of the status of the world's coral reefs and highlights their value to society. Also, the anthropogenic and natural disturbances that threaten the future of coral reefs are discussed and finally, this article offers some potential remedies that promote sustainable use of coral reef resources thus ensuring their future survival.

Global climate change and the thermal tolerance of corals

The thermal environment of reef-building corals is critical to their distribution and survival. Recent evidence has revealed that the mean global temperature has increased by 1 degree Celsius over the past century. Examination of tropical sea temperatures reveal that they have also increased by almost 1°C over the past 100 years and are currently increasing at the rate of approximately 1-2°C per century. Japanese waters are no exception. Waters off Okinawa have increased by 1.4°C since 1930 and are currently increasing at the rate of 2.3°C per century (95% confidence interval, 1.4-3.1°C). Coral bleaching occurs when the thermal tolerance of corals and their zooxanthellae are exceeded, probably due to an increased sensitivity of the zooxanthellae to chronic photoinhibition. The consequences of bleaching can be devastating, with corals dying in vast numbers and such aspects as coral reproduction being severely curtailed. In 1998, the world's coral reefs experienced the worst bleaching on record. Japanese reefs were severely effected, with bleaching coinciding with a massive temperature anomaly in July-August 1998. Vast numbers of corals died. The intention of this paper is collect what we know about coral bleaching from biochemical, physiological and ecological perspectives and to discuss to how reefs (especially around Okinawa) might change in the next century. A single important issue surfaces in these deliberations. If temperatures continue to increase, then corals will experience greater incidences of bleaching and mortality unless they can acclimate physiologically or adapt genetically. The conclusions that stem from this issue are of great concern. Firstly, available evidence suggests that corals are not acclimating physiologically to any really extent to the sporadic and seasonal changes in sea temperature. Secondly, the rate of change in sea temperature arguably exceeds the capacity of coral populations to genetically adapt fast enough. The third conclusion is the most worrying. If corals are not changing fast enough, then coral reefs will experience more frequent and more intense bleaching. Given the outcome for many coral reefs across the planet during the 1998 episodes of bleaching, this has to be of great concern to coral reef users and managers everywhere.

Climate change, coral bleaching and the future of the world's coral reefs

Sea temperatures in many tropical regions have increased by almost 1°C over the past 100 years, and are currently increasing at ~1–2°C per century. Coral bleaching occurs when the thermal tolerance of corals and their photosynthetic symbionts (zooxanthellae) is exceeded. Mass coral bleaching has occurred in association with episodes of elevated sea temperatures over the past 20 years and involves the loss of the zooxanthellae following chronic photoinhibition. Mass bleaching has resulted in significant losses of live coral in many parts of the world. This paper considers the biochemical, physiological and ecological perspectives of coral bleaching. It also uses the outputs of four runs from three models of global climate change which simulate changes in sea temperature and hence how the frequency and intensity of bleaching events will change over the next 100 years. The results suggest that the thermal tolerances of reef-building corals are likely to be exceeded every year within the next few decades. Events as severe as the 1998 event, the worst on record, are likely to become commonplace within 20 years. Most information suggests that the capacity for acclimation by corals has already been exceeded, and that adaptation will be too slow to avert a decline in the quality of the world’s reefs. The rapidity of the changes that are predicted indicates a major problem for tropical marine ecosystems and suggests that unrestrained warming cannot occur without the loss and degradation of coral reefs on a global scale.

Paradise lost: how marine science failed the world's coral reefs

The response of the coral reef scientific community to the present global crisis in coral reefs is here compared with response times and response patterns of scientists in two previous international environmental crises: eutrophication of the Great Lakes and acid rain in the Northen Hemisphere. In both these previous crises, less than a decade passed from first appreciation of the problem to development of identification/evaluation/mitigation frameworks that were useful in a policy context. Key elements were avoidance of arguments over methods, genuinely multidisciplinary teams, and the presence of respected, technically trained managers. By contrast, twenty years after identification of the major stresses on reefs and description of the major monitoring strategies, there is no process–response model in place, in any country, equivalent to those produced in response to eutrophication of the Great Lakes or acid rain. Reasons for this failure include, but are not limited to: dominance by one field of science, biology; lack of competent scientific managers; and emphasis on monitoring programmes, with no clear idea how the results will be used.

World's coral reefs said to be at high risk

More than one‐quarter of the world's coral reefs are at high risk and another one‐third are at medium risk because of threats caused by human activities, according to a new report that may be the first systematic and data‐driven global assessment of coral reefs.The report, “Reefs at Risk: A Map‐Based Indicator of Threats to the World's Coral Reefs,” indicates that these threats place much of the world's marine biodiversity at risk, because coral reefs are highly productive, species‐rich habitats that are home to more than one quarter of all known marine fish species.

Brighter Prospects for the World's Coral Reefs?

Just a few years ago, scientists sounded the alarm that coral reefs around the world were seriously ailing. But now, some coral reef biologists are beginning to suspect that reefs may not be quite as widely imperiled as they once thought. Increasingly, researchers think that the decline may be local or regional rather than global in scope. Although reefs in Southeast Asia and the Caribbean are crumbling, for instance, most in the Pacific and Indian Ocean appear to be in good health.

Chronicling coral death

How would a geologist approach an assessment of the health of coral reefs? Readers of the June 1997 issue of Geotimes learn the answer by following the thoughts of George, a fictional geologist attending an international conference on global reef decline.In “Gauging the Health of the World's Coral Reefs: Monitoring vs. Mapping,” University of Miami marine geologist Robert N. Ginsburg, using the voice of George, suggests that mapping dead and dying corals would document the history and extent of reef decline and provide more clues about the relationship between coral health and such factors as location and ocean circulation than would monitoring. By some estimates, as many as 10% of the world's reefs have been seriously damaged by over‐exploitation, pollution, disease, ocean warming, and predators. Twenty years ago, 50% of the sea floor near Jamaica was covered by living coral; today, that coverage has decreased to 5%. In response to this decline, an international coalition has designated 1997 as the International Year of the Reef.

Science management of the world's fragile coral reefs

Science management of the world's fragile coral reefs

Reef: a safari through the coral world

Featuring more than 100 of the renowned author's dazzling photographs, this companion to Shark is the first work to capture the extraordinary underwater landscape of the world's coral reefs. The stunning images, accompanied by detailed captions, convey the full range of incredible inhabitants of coral reefs from Australia to the Bahamas to the Red Sea. 115 color photographs; 5 color drawings; 4 maps.

The genus Codium (Codiales, Chlorophyta) at Lord Howe Island (NSW).

Five species of Codium have been found on the world's southernmost coral reef at Lord Howe Island, New South Wales (31�33'S.,159�03'E.). The genus forms, along with the brown algal order Dictyotales, a dominant marine algal group on the island. One species, the South African C. extricatum Silva, is a new record for the Australian region. Codium platydados is newly described based on Lord Howe, Great Barrier Reef and Philippine collections. Codium bulbopilum Setchell and C spongiosum Harvey have previously been recorded from the island and are major cover species in shallow lagoon waters. Codium arabicum is reported from the island and adjacent Australian mainland for the first time at what appear to be the species' southernmost limits of distribution. Anatomical variability and taxonomic relationships of the species are considered, and the geographical and local distributions discussed.

Algae and grazing in coral reef ecosystems

In many parts of the world coral reefs are an economically important part of the environment, both as a source of fish and as an attraction for tourists. Their proper management and preservation is, therefore, of great practical importance, and this demands a clear understanding of the very complex ecosystem involved. This article reviews the significance of the grazing of coral reef algae by a variety of herbivores, especially fish.

Torres Strait and the Inner Route

The north-east coast of Australia is fronted by the world's longest coral reef system, which stretches in a north/south direction between latitudes 9° and 24° South. Although its outer limit is at distances of between 20 and 120 miles from the coast the enclosed waters are relatively shallow and contain many islands, detached reefs and shoals. The shipping lane between the coast and the Great Barrier Reef is known as the Inner Route. Torres Strait, its northern entrance, although extensive is shallow throughout and encumbered by reefs and islands to such an extent that only one route through it has been lit. The alternative routes are shallow or tortuous.