Impact on the copepod community structure in a coastal region after a mining dam disaster in the Southwestern Atlantic Ocean

Zooplankton plays an important role in marine ecosystems by controlling the phytoplankton population, regenerating nutrients and exporting biogenic matter. Their distribution is limited by the environmental characteristics of the pelagic realm, and potential changes in the environment may promote several levels of responses. Zooplankton was sampled in the Southwestern Atlantic Ocean in a coastal region near the Doce River after the worst mining dam disaster ever recorded in Brazilian waters. Samples were collected using a WP2 plankton net fitted with a 200-micron mesh and a mechanical flowmeter, and preserved in a 4% buffered formaldehyde. Results showed an increase in abundance right after the disaster with more than 222.959 ind.m-3 at the river mouth, a two-hundred-fold increase over the past year, with two copepod species, Parvocalanus scotti and Oithona nana, making up to 80% of this total abundance. A decrease in species richness and diversity was also observed in the sampling area along the year as well as a shift in species composition. A significant impact on the zooplankton community was observed due to the mining residues that reached the coastal area of the Doce River in the Southwestern Atlantic Ocean, with negative consequences for the entire local food web.