Response Of Coral Reefs Research Articles

Potentialities, uncertainties and complexities in the response of coral reefs to future sea‐level rise

AbstractCoral islands formed of largely unconsolidated sands only a few metres above sea level are thought to be particularly vulnerable to sea‐level rise consequent upon global warming. However, scenarios which predict catastrophic flooding and loss of island area need reassessment, particularly in the light of the continued downwards revision of projected rates of future sea‐level rise. Revised questions concern the interactions between reef growth and sea‐level change, biophysical constraints on coral growth, and the importance to reef systems of potential changes in the magnitude, frequency and location of tropical cyclones and hurricanes. It is clear that most reefs have the growth potential to meet even the highest of future sea‐level rise scenarios, but too little is known about physiological and physical constraints to reef growth to adequately evaluate the importance of these two factors in constraining this potential at the present time. Future sea‐level rise in the tropical oceans, and coral reef responses, will take place against a backdrop of inter‐regional differences in Holocene sea levels, resulting from the varying interaction of eustatic and hydro‐isostatic processes. These differences have generated varying constraints on the development of modern reefs and varying inherited topographies upon which future sea‐level changes will be superimposed. These controls are particularly important in assessing differences in vulnerability to future sea‐level rise for reef islands in the Pacific Ocean and the Caribbean Sea.

完新世の記録に基づいて推定する将来の地球環境変動に対するサンゴ礁の応答

完新世の記録に基づいて推定する将来の地球環境変動に対するサンゴ礁の応答

ENCORE: The effect of nutrient enrichment on coral reefs. 1. Experimental design and research programme

An in situ reef fertilization experiment is being undertaken on the Australian Great Barrier Reef, to investigate the response of coral reefs to nutrient enrichment. This experiment, known as ENCORE, is designed to quantify the fate of nitrogen and phosphorus within a coral reef, and compare their impact on a variety of coral reef organisms. Co-ordinated by the Great Barrier Reef Marine Park Authority (GBRMPA), 30 scientists from eight Australian and three overseas organizations are undertaking research encompassing cellular through to community level responses. This research will provide a scientific basis for developing appropriate water quality management strategies in coral reef environments, and may identify a number of sub-lethal indicators of nutrient stress.

Responses of coral reefs and reef organisms to sedimentation

Unprecedented development along tropical shorelines is causing severe degradation of coral reefs primarily from increases in sedimentation. Sediment particles smother reef organisms and reduce light available for photosynthesis. Excessive sedmentation can adversely affect the structure and function of the coral reef ecosystem by altering both physical and biological processes. Mean sediment rates and suspended sediment concentrations for reefs not subject to stresses from human activities are < 1 to ca 10 mg cm-* d-' and < 10 mg I-', respectively. Chronic rates and concentrations above these values are 'hlgh'. Heavy sedmentation is associated with fewer coral species, less live coral, lower coral growth rates, greater abundance of branching forms, reduced coral recruitment, decreased calcification, decreased net productivity of corals, and slower rates of reef accretion. Coral species have different capabilities of clearing themselves of sediment particles or surviving lower light levels. Sedlment rejection is a function of morphology, orientation, growth habit, and behavior; and of the amount and type of se lment . Coral growth rates are not simple indicators of sediment levels. Decline of tropical fisheries is partially attributable to deterioration of coral reefs, seagrass beds, and mangroves from sedimentation. Sedimentation can alter the complex interactions between fish and their reef habitat. For example, sedimentation can lull major reef-building corals, leading to eventual collapse of the reef framework. A decline in the amount of shelter the reef provides leads to reductions in both number of individuals and number of species of fish. Currently, we are unable to rigorously predict the responses of coral reefs and reef organisms to excessive sedimentation from coastal development and other sources. Given information on the amount of sediment which will be introduced into the reef environment, the coral community composition, the depth of the reef, the percent coral cover, and the current patterns, we should be able to predict the consequences of a particular activity. Models of physical processes (e.g. sediment transport) must be complemented with better understanding of organism and ecosystem responses to sediment stress. Specifically, we need data on the threshold levels for reef orgarusms and for the reef ecosystem as a whole the levels above which sedimentation has lethal effects for particular species and above which normal functioning of the reef ceases. Additional field studies on the responses of reef organisms to both temgenous and calcium carbonate sediments are necessary. To effectively assess trends on coral reefs, e.g. changes in abundance and spatial arrangement of dominant benthic organisms, scientists must start using standardized monitoring methods. Long-term data sets are critical for tracking these complex ecosystems.