Modeling the low-frequency response of seagrass in a resonator tube

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2022-05-04

Authors

Torres, Nicholas Antonio

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Abstract

Seagrasses are a vital part of coastal ecosystems. They serve a number of important environmental functions, but are currently declining at rapid rates. A necessary requirement to preserving these resources is an ability to monitor them. Seagrass can strongly affect acoustic propagation in seawater, and this effect can be exploited to monitor these resources. Seagrass impacts the acoustic propagation through the release of bubbles from photosynthesis as well as gas contained within the seagrass tissue itself. Previous mathematical models that treat the seagrass tissue as a fluid have not sufficiently explained acoustic propagation through seagrass. In the present work, a Finite Element Method (FEM) model was used alongside data from the literature to determine if an elastic model for seagrass captures the effects it has on acoustic propagation. The results of this model were then compared against a recently-published measurement of the shear modulus of Thalassia testudinum. Additional resonator experiments were then used to inform refinements of the FEM model. The improved FEM model resolved a number of discrepancies in the initial model. Finally, the improved model was used with resonator measurements to infer the shear modulus of the two different types of tissue present in seagrass, the epidermis and aerenchyma tissue in T. testudinum.

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