Anthropogenic Sound in the Sea: Are Ascidians Affected?

Abstract

Sound pollution in the marine environment has been increasing largely due to anthropogenic sources such as vessel traffic, coastal development, fossil fuel extraction, and military exercises. Studies determining the effects of anthropogenic sound on marine organisms have mostly focused on vertebrates, namely fish and marine mammals; however, less research has been done to study the effects of sound on marine invertebrates. The goal of this research is to examine the effect of anthropogenic sound on the ascidian Styela plicata (Lesueur, 1823) in Tampa Bay, FL. A total of 48 ascidians were collected from 2 sites with differing amounts of boat traffic and thus different anthropogenic soundscapes. Ascidians were individually exposed to 3 separate stimuli: a recording of a boat motor, a song recording, and a water current to simulate turbulence. Ascidian reactions were recorded as the frequency of siphon closing events and the length of time the siphons remained closed after disturbance. Ascidians from both sites increased the frequency and longevity of siphon closure events in response to anthropogenic stimuli but showed only a minor difference in response between sample sites. Research into the effect of anthropogenic sound on invertebrates such as ascidians and their symbionts may provide a better understanding of larger scale ecological impacts from such disturbances.