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Climate change and plastic pollution are major threats to all marine life, from minuscule crustaceans to gigantic whales. Although many experiments have examined these threats, few have looked at what happens when they both strike at once. At least for the sea anemone, new research from a team at the Carnegie Institution for Science in Stanford, California, suggests that the combined threat is worse than the sum of its parts.
Under normal conditions, sea anemones derive energy from two main sources: the symbiotic algae that live within them, and food they grab from the sea. “Because the anemones with the symbiotic algae are getting nutrients from the algae, they can be more selective about what they eat,” says marine scientist Manoela Romanó de Orte, the lead researcher on this project.
But when anemones are exposed to rising water temperatures, they can expel their symbiotic algae, an event known as bleaching. When this happens, the sea anemone’s sole source of energy is its food. Scientists think these already stressed animals might be less selective about what they eat, and are slower to realize that they’ve ingested microplastic, not food. Indeed, the researchers found that bleached anemones retained ingested microplastics longer than healthy sea anemones.
The finding has worrisome implications for sea anemones, as well as their close relatives, corals. Aside from contributing to nutritional stress, de Orte says that microplastics are carriers for pollutants, viruses, and bacteria.
In her own research, Cornell University marine ecologist Drew Harvell, who was not involved in the new study, has found a strong link between plastic pollution and coral disease. Harvell and her colleagues surveyed more than 150 reefs across the Asia-Pacific region and found that the presence of plastic waste is associated with a substantially higher rate of coral disease. Plastics, along with warming water and excessive nutrients, can directly damage organisms and make them more susceptible to disease, Harvell says.
Harvell believes that many current policies aren’t taking into account the synergistic nature of both threats. “Certainly given the onslaught of warming events and the fact that we know things are going to become sicker, we should be doing better with things like plastics and land-based pollution,” she says.
De Orte says plastic microfibers from synthetic clothing are a major contributor to plastic pollution in the ocean. In fact, a 2017 report estimated that almost 35 percent of the microplastics entering the ocean come from laundering synthetic textiles.
Improving microplastic filtration systems in wastewater treatment plants could have a major impact on marine pollution, but individuals have a role to play as well, says de Orte. She says that buying clothing made from natural fibers, like wool or cotton, and washing synthetic garments less frequently could help stem the tide of microfiber pollution and help keep marine animals healthier.