Long-term acoustic monitoring of marine mammal response to the 2010 oil spill in the Northern Gulf of Mexico

Abstract

The 2010 deep water horizon (DWH) oil spill in the Northern Gulf of Mexico brought a need for assessing spill impact and recovery timeline for the deepwater ecosystem, including marine mammals. Passive acoustics is emerging as a viable technology to monitor short-term and long-term abundance dynamics and to assess different factors that may cause an observed response. Multi-year pre-spill and post-spill acoustic data collected at different distances from the DWH incident site by the Littoral Acoustic Demonstration Center (LADC) are used to compare first-year oil spill response by three different groups of marine mammals: sperm whales, beaked whales, and dolphins. Densities of acoustic phonations by these animals are extracted from collected data and used for point estimates of the resident population density. As an example, a regional abundance estimate shows a decrease in the number of sperm whales at the site nearest to the DWH (9 mi away) which exceeds statistical uncertainties and can be accepted as an existing trend. The use of acoustic data to extract information about environmental factors, such as anthropogenic noise level or food call densities, that may contribute to the explanation of existing trends is also discussed. [Work is partially supported by NSF.]