A yearlong record of acoustic propagation and ambient sound in a seagrass meadow

Abstract

Seagrasses are sentinel species whose structures are sensitive to variations in environmental conditions and thus reliable indicators of long-term changes in sea level and regional climate. The biological and physical characteristics of seagrasses are known to affect acoustic propagation. Gas bodies contained within the seagrass tissue as well as photosynthetic-driven bubble production result in free gas bubbles attached to the plants and in the water. The detachment of gas bubbles from the plants is also a source of ambient sound. In this work, we deployed a measurement system in a shallow (1.3 m deep) seagrass meadow that included an acoustic projector, a set of receiving hydrophones, an instrumentation pressure vessel that housed the electronics controlling the acoustic data acquisition and data storage, and a suite of environmental sensor loggers. Acoustic propagation and ambient sound were collected every ten minutes for a period of one year. Coincident measurements of water temperature, salinity, dissolved oxygen, and photosynthetically active radiation were also collected and used to interpret the acoustic data. We present preliminary results from the yearlong deployment of the acoustic system in a moderately dense seagrass bed dominated by Thalassia testudinum (turtle grass) in Corpus Christi Bay, Texas. [Work supported by NSF.]