CORVALLIS, Ore. Researchers at Oregon State University for the first time have confirmed some of the mechanisms by which overfishing and nitrate pollution can help destroy coral reefs it appears they allow an overgrowth of algae that can bring with it unwanted pathogens, choke off oxygen and disrupt helpful bacteria.
These "macroalgae," or large algal species, are big enough to essentially smother corals. They can get out of control when sewage increases nitrate levels, feeds the algae, and some of the large fish that are most effective at reducing the algal buildup are removed by fishing.
Scientists found that macroalgal competition decreased coral growth rates by about 37 percent and had other detrimental effects. Other research has documented some persistent states of hypoxia.
Researchers call this process "the slippery slope to slime."
Findings on the research were just published in PLoS One, a professional journal. The work was supported by the National Science Foundation.
"There is evidence that coral reefs around the world are becoming more and more dominated by algae," said Rebecca Vega-Thurber, an OSU assistant professor of microbiology. "Some reefs are literally covered up in green slime, and we wanted to determine more precisely how this can affect coral health."
The new study found that higher levels of algae cause both a decrease in coral growth rate and an altered bacterial community. The algae can introduce some detrimental pathogens to the coral and at the same time reduce levels of helpful bacteria. The useful bacteria are needed to feed the corals in a symbiotic relationship, and also produce antibiotics that can help protect the corals from other pathogens.
One algae in particular, Sargassum, was found to vector, or introduce a microbe to corals, a direct mechanism that might allow introduction of foreign pathogens.
There are thousands of species of algae, and co
|Contact: Rebecca Vega-Thurber|
Oregon State University