Acoustic characterization of submerged aquatic vegetation: military and environmental monitoring applications

McCarthy, Elena; Sabol, Bruce M.

doi:10.1109/oceans.2000.882226

Cited by 24 publications

(17 citation statements)

References 3 publications

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“…Similarly, a hand-held mine hunting sonar deployed by divers and operating in the 115-140 kHz frequency range was unable to detect the target. 1 Backscatter from the seagrass was sufficiently strong to completely obscure reflections from the Manta target simulator.…”

Section: Introductionmentioning

confidence: 99%

Laboratory investigation of the acoustic response of seagrass tissue in the frequency band 0.5–2.5 kHz

Wilson

Dunton

2009

The Journal of the Acoustical Society of America

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Previous in situ investigations of seagrass have revealed acoustic phenomena that depend on plant density, tissue gas content, and free bubbles produced by photosynthetic activity, but corresponding predictive models that could be used to optimize acoustic remote sensing, shallow water sonar, and mine hunting applications have not appeared. To begin to address this deficiency, low frequency (0.5-2.5 kHz) acoustic laboratory experiments were conducted on three freshly collected Texas Gulf Coast seagrass species. A one-dimensional acoustic resonator technique was used to assess the biomass and effective acoustic properties of the leaves and rhizomes of Thalassia testudinum (turtle grass), Syringodium filiforme (manatee grass), and Halodule wrightii (shoal grass). Independent biomass and gas content estimates were obtained via microscopic cross-section imagery. The acoustic results were compared to model predictions based on Wood's equation for a two-phase medium. The effective sound speed in the plant-filled resonator was strongly dependent on plant biomass, but the Wood's equation model (based on tissue gas content alone) could not predict the effective sound speed for the low irradiance conditions of the experiment, in which no free bubbles were generated by photosynthesis. The results corroborate previously published results obtained in situ for another seagrass species, Posidonia oceanica.

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Section: Introductionmentioning

confidence: 99%

Laboratory investigation of the acoustic response of seagrass tissue in the frequency band 0.5–2.5 kHz

Wilson

Dunton

2009

The Journal of the Acoustical Society of America

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“…Since the diffraction hyperbolas in our sonar profiles are constrained only to a narrow zone in the uppermost part of the Quaternary sequence (Figures 3 and 4), we propose that the gas (probably methane) originates from a degradation of organic matter contained in the Holocene paralic and marine sediments and/or Late Pleistocene terrestrial sequences [62,97,99]. Gas production related to biological processes in seagrass meadows can also greatly hinder the propagation of acoustic signals [100][101][102]; however, the contribution of this effect is difficult to determine from our dataset since only a single borehole (V-5/95) is located within a meadow (Figure 3a). Nevertheless, significant signal attenuation below the meadows can be observed in the geophysical data (Section 3.2, Figures 3a and 4d).…”

Section: Influence Of Gas Presencementioning

confidence: 95%

Sound Velocity in a Thin Shallowly Submerged Terrestrial-Marine Quaternary Succession (Northern Adriatic Sea)

Novak

Šmuc

Poglajen³

et al. 2020

Water

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Estimating sound velocity in seabed sediment of shallow near-shore areas submerged after the Last Glacial Maximum is often difficult due to the heterogeneous sedimentary composition resulting from sea-level changes affecting the sedimentary environments. The complex sedimentary architecture and heterogeneity greatly impact lateral and horizontal velocity variations. Existing sound velocity studies are mainly focused on the surficial parts of the seabed sediments, whereas the deeper and often more heterogeneous sections are usually neglected. We present an example of a submerged alluvial plain in the northern Adriatic where we were able to investigate the entire Quaternary sedimentary succession from the seafloor down to the sediment base on the bedrock. We used an extensive dataset of vintage borehole litho-sedimentological descriptions covering the entire thickness of the Quaternary sedimentary succession. We correlated the dataset with sub-bottom sonar profiles in order to determine the average sound velocities through various sediment types. The sound velocities of clay-dominated successions average around 1530 m/s, while the values of silt-dominated successions extend between 1550 and 1590 m/s. The maximum sound velocity of approximately 1730 m/s was determined at a location containing sandy sediment, while the minimum sound velocity of approximately 1250 m/s was calculated for gas-charged sediments. We show that, in shallow areas with thin Quaternary successions, the main factor influencing average sound velocity is the predominant sediment type (i.e. grain size), whereas the overburden influence is negligible. Where present in the sedimentary column, gas substantially reduces sound velocity. Our work provides a reference for sound velocities in submerged, thin (less than 20 m thick), terrestrial-marine Quaternary successions located in shallow (a few tens of meters deep) near-shore settings, which represent a large part of the present-day coastal environments.

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“…An important acoustical effect is due to bubble production by the plants, which can have a significant impact on both object detection and bottom mapping sonars by increasing clutter through reflection, absorption, and scattering of sound. 1,2 Remote sensing techniques have been demonstrated to monitor biological markers, such as photosynthetic activity from seagrass, as an assessment of marine ecosystem health. 3,4 Additionally, seismo-acoustic survey tools have been investigated to obtain carbon sink estimates for the sediment underneath seagrass beds.…”

Section: Introductionmentioning

confidence: 99%

Sound speed and attenuation measurements within a seagrass meadow from the water column into the seabed

Lee¹,

Ballard²,

McNeese³

et al. 2017

The Journal of the Acoustical Society of America

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In situ measurements of sound speed and attenuation at 50 kHz were conducted in a Thalassia testudium meadow. Measurements were obtained at discrete depths in the water column, in the seagrass canopy, and in the sediment beneath the seagrass. Measurements were also obtained in bare sediment located a few meters away. Sediment biomass abundance was measured from cores collected at each site. Even though the measurements were obtained in the dormant season (winter), significant differences in sound speed and attenuation were observed in the sediment beneath the seagrass bed compared to the bare sediment.

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Acoustic characterization of submerged aquatic vegetation: military and environmental monitoring applications

Cited by 24 publications

References 3 publications

Laboratory investigation of the acoustic response of seagrass tissue in the frequency band 0.5–2.5 kHz

Laboratory investigation of the acoustic response of seagrass tissue in the frequency band 0.5–2.5 kHz

Sound Velocity in a Thin Shallowly Submerged Terrestrial-Marine Quaternary Succession (Northern Adriatic Sea)

Sound speed and attenuation measurements within a seagrass meadow from the water column into the seabed

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