What happens to marine life when oxygen is scarce?

Woods Hole, Mass. (July 26, 2021) — In September of 2017, Woods Hole Oceanographic Institution postdoctoral scholar Maggie Johnson was conducting an experiment with a colleague in Bocas del Toro off the Caribbean coast of Panama. After sitting on a quiet, warm open ocean, they snorkeled down to find a peculiar layer of murky, foul-smelling water about 10 feet below the surface, with brittle stars and sea urchins, which are usually in hiding, perching on the tops of coral.

Surge in Nitrogen Has Turned Sargassum into the World’s Largest Harmful Algal Bloom

Scientists have discovered dramatic changes in the chemistry and composition of Sargassum, floating brown seaweed, transforming this vibrant living organism into a toxic “dead zone.” Results suggest that increased nitrogen availability from natural and anthropogenic sources, including sewage, is supporting blooms of Sargassum and turning a critical nursery habitat into harmful algal blooms with catastrophic impacts on coastal ecosystems, economies, and human health. Globally, harmful algal blooms are related to increased nutrient pollution.