With the world’s coral reefs threatened by coastal development, pollution, rising sea temperatures and other factors, scientists have developed a new method to monitor the health of these underwater ecosystems.

Chris Langdon, associate professor of marine biology and fisheries at the University of Miami, and colleagues, tested two new methods to monitor biological productivity at Cayo Enrique Reef in Puerto Rico.

They compared a technique that measures changes in dissolved oxygen within a chamber that encloses an area of water above the reef with one that measures the flux of dissolved oxygen across the turbulent boundary layer above an unconfined portion of the seafloor.

They found that both these methods worked well. The boundary layer technique can be used to monitor metabolic activity of reefs in remote locations, at any depth over long time periods. The enclosure method can be used for in-situ disturbed environment experiments.

By measuring dissolved oxygen production and consumption rates, the researchers were able to monitor the balance between the production of new organic matter by the reef’s coral and algae, and the consumption of that organic matter by animals of the reef. This is essential to assessing the health of coral reef ecosystems. A combination of these methods is a valuable tool for assessing and studying the effects of climate change on coral reef health, according to the authors.

Measurements of biological productivity have typically been made by tracing changes in dissolved oxygen in seawater as it passes over a reef. However, this is a labor-intensive and difficult method, requiring repeated measurements. The new method opens up the possibility of making long-term, unattended, time-stamped measurements of photosynthesis and respiration of coral reefs and any other benthic ecosystems.

According to a recent analysis by the World Resources Institute, nearly 75 percent of the world’s coral reefs are currently threatened by human activities and ecological disturbances, such as rising ocean temperatures, increased pollution, overfishing, and ocean acidification

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