Long-term monitoring of a seagrass meadow using wideband acoustic measurements

Abstract

Seagrasses are sentinel species whose sensitivity to changing water conditions makes them an indicator for sea level rise and climate change. The biological processes and physical characteristics associated with seagrass are known to affect acoustic propagation due to gas bodies contained within the seagrass tissue as well as photosynthesis-driven bubble production that results in free gas bubbles in the water. In this work, acoustical methods are applied to monitor seagrass biomass and gas ebullition with an autonomous field-deployed system using broadband acoustic measurements. Supporting environmental measurements including water temperature and salinity, dissolved oxygen, and photosynthetically active radiation (PAR) were also collected and used to interpret the acoustic data. A ray-based propagation model that includes losses due to the dispersion, absorption, and scattering of sound is applied to relate the measured acoustic signals to the gas bodies in the seagrass tissue and free bubbles in the water. This talk will present preliminary results from the first six months of a year-long deployment of the acoustic system in a dense seagrass meadow dominated by Thalassia testudinum (turtle grass) in Corpus Christi Bay, Texas (Gulf of Mexico). [Work supported by NSF.]