2019_programme: TEXGRASS-2018: A SEAGRASS EXPERIMENT ON THE TEXAS GULF OF MEXICO COAST

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  • Session: 01. Memorial Session for Jean-Pierre Hermand
    Organiser(s): Chapman Ross
  • Lecture: TEXGRASS-2018: A SEAGRASS EXPERIMENT ON THE TEXAS GULF OF MEXICO COAST [invited]
    Paper ID: 839
    Author(s): Lee Kevin, Johnson Jay, Ballard Megan, Venegas Gabriel, Sagers Jason, Mcneese Andrew, Rahman Abdullah, Wilson Preston
    Presenter: Lee Kevin
    Presentation type: oral
    Abstract: One of Jean Pierre Hermand’s beloved research topics was seagrass acoustics. A thrust of his research was the use of acoustics as a remote sensing tool for monitoring seagrass ecosystem health by exploiting the sensitivity of acoustic propagation to bubbles from photosynthetic activity and respiration. Because the oxygen production cycle is largely driven by sunlight, these acoustical effects have a diurnal dependence. At the 5th Underwater Acoustics Conference and Exhibition held in Skiathos, J.P. and some of the current authors began planning a new collaborative seagrass experiment to take place in 2018, with the goal of combining J.P.’s remote sensing methods above the seabed and our in situ techniques for making acoustic measurements in the rhizosphere. Circumstances lead us locate the experiment in a Thalassia testudinum meadow in the Lower Laguna Madre, a shallow bay on the southern Texas Gulf of Mexico coast. Weeks before the experiment was to take place, J.P. unexpectedly and tragically passed away. In this paper, we discuss the experiment, TEXGRASS-2018, for which J.P. was an inspiring presence. As part of the experiment, an omnidirectional source transmitted frequency-modulated chirps every 10 minutes for a 24-hour period, during which oceanographic probes measured water temperature, salinity, and dissolved oxygen. The received acoustic signals were match-filtered to obtain band-limited impulse responses, enabling identification of various propagation paths within the waveguide. During part of the diurnal cycle, the below-sediment measurements were conducted to observe temporal changes in the rhizosphere. Dependence of the received acoustic amplitude and frequency content on time-of-day, dissolved oxygen, and other environmental parameters will be discussed with the goal of furthering the use of acoustics to study seagrass photosynthesis and productivity. [Work supported by ARL:UT IR&D and ONR.]\n\nNOTE TO ORGANIZER: This abstract is for Memorial Session for Jean Pierre Hermand. the session organizer Ross Chapman has approved it.
  • Corresponding author: Dr Lee Kevin
    Affiliation: Applied Research Laboratories,University of Texas at Austin
    Country: United States
    e-mail:

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