Marine animal forests as useful indicators of entanglement by marine litter.

Entanglement of marine fauna is one of the principal impacts of marine litter, with an incidence that can vary strongly according to regions, the type and the quantity of marine litter. On the seafloor, areas dominated by sessile suspension feeders, such as tropical coral reefs or deep-sea coral and sponge aggregations, have been termed "animal forests" and have a strong potential to monitor the temporal and spatial trends of entanglement by marine litter, especially fishing gears. Several characteristics of these organisms represent advantages while avoiding constraints and bias. Biological constraints and logistical aspects, including tools, are discussed to better define a strategy for supporting long-term evaluation of accumulation and entanglement of marine litter.