Subtidal benthic marine litter off the coast of Rio de Janeiro, Brazil

Several studies have reported on the presence of litter on beaches and in the oceans, but this represents the smallest part of the litter that ends up in the sea. Little is known about the litter that settles on the ocean floor, especially near coastal regions. Thus, this study quantified, classified and determined possible sources of subtidal benthic marine litter input off the coast of Rio de Janeiro, Brazil. Different sites were selected in Guanabara Bay, an area with the greatest industrial and population concentration in the state of Rio de Janeiro, and on the coasts of Costa do Sol and Costa Verde, where tourism represents the main economic activity. Material was collected by scuba diving at depths of between 5 and 15 meters at 31 sites distributed among the study areas. A total of 1,209 items was found, with Guanabara Bay having the highest average concentration (92.40 items/km2), followed by Costa do Sol and Costa Verde (14.15 items/km2 and 9.91 items/km2, respectively). Plastic materials are the most representative solid waste (55.08%), followed by metals (14.97%) and fishing gear (12.48%). Results indicated that local activities affected the composition of the marine litter on Costa do Sol and Costa Verde, whereas in Guanabara Bay, anthropogenic material carried by rivers influenced the marine litter composition at certain locations in addition to local activities. Environmental education actions associated with tourism and fishing activities and better waste management are necessary to minimize the presence of litter in subtidal benthic environments.