Seagrass plays major role in pollution reduction

James Cook University researchers were involved in a joint international study, which will be featured on Friday, 17 February 2017 on the cover of the prestigious Science journal.

Researchers used genetic sampling to show there was a 50% reduction in bacterial pathogens capable of causing disease in humans and marine organisms when seagrass meadows were present.

Lead author Dr Joleah Lamb, from Cornell University and a PhD graduate of JCU, said surveys of corals next to seagrass meadows also showed twofold reductions in disease levels compared to corals without adjacent seagrass meadows.

“The results showed clearly that seagrass meadows significantly reduce bacterial loads and can benefit both humans and other organisms in the environment, particularly corals, which are under pressure globally.”

Dr Lamb became focused on the problem of water pollution when an entire research team became ill in Indonesia.

“I stumbled across a time-lapse video of clams rapidly removing algae from aquariums. We immediately contemplated whether the vast seagrass ecosystems around the islands we worked on could perform this same service.”

Testing showed seagrass meadows had a huge effect, but the scientists don’t quite know why yet. Plants can inactivate pathogens using natural biocides, biofilm interactions, via nutrient removal, and by altering soil or water chemistry.

“We don't fully understand the exact mechanisms that are driving the reductions in bacterial load. An intact seagrass ecosystem also comprises a diversity of bivalves, sponges, and tunicates that could further remove bacteria from the water column,” said Dr Lamb.

JCU’s Dr David Bourne was part of the team working on the project. “This study suggests that seagrass meadows alleviate a range of factors that lead to diseases of reef-building corals, such as reducing the abundance of pathogenic microorganisms and enhancing water quality,” he said.

Dr Lamb said seagrass ecosystems could also play an important role in sustaining the rapid increase in aquaculture as a response to global food shortages.

“This industry is highly susceptible to disease outbreaks from bacterial infections. Integrating seagrass treatment systems with aquaculture could lower the economic and environmental costs of marine disease outbreaks,” she said.

Dr Bourne said seagrass systems are under pressure globally.

“Rehabilitation of these ecosystems could offer a low cost way to benefit the marine environment, including corals reefs being impacted by human activities,” he said.

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