Development of acoustic remote sensing of seagrass ecosystems and understanding of their climate impacts

Seagrasses provide a multitude of ecosystem services and act as important carbon sinks. However, seagrass habitats are declining globally, and they are among the most threatened ecosystems on earth. For these reasons, long-term and continuous measurements of seagrass parameters are of primary importance for ecosystem health assessment and sustainable management. This talk will present results from both active and passive acoustical methods for ecosystem monitoring in seagrass meadows. Examples of both techniques will be presented based on data collected as part of a two-year continuous deployment of an acoustical measurement system operating in a seagrass bed dominated by Thalassia testudinum (turtle grass) in Corpus Christi Bay, Texas. From a propagation perspective using a broadband acoustic source, gas bodies contained within the seagrass tissue as well as photosynthetic-driven bubble production results in attenuation and scattering of sound that produces increased transmission loss. For the passive approach, the detachment of gas bubbles from the plants is an important component of the ambient soundscape. The data show annual trends related to the seasonal growth pattern of Thalassia as well as diurnal trends correlated with photosynthetically active radiation. [Work supported by ONR, NSF, ARPA-E.]