Acoustic assessment of sound scattering zooplankton in warm- and cold-core eddies in the Gulf of Mexico /
Zooplankton and micronekton which cause a density
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| Format: | Thesis Book |
| Language: | English |
| Published: |
[Place of publication not identified] :
[publisher not identified] ;
1997.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=736584791&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Zooplankton and micronekton which cause a density discontinuity with the surrounding seawater reflect acoustic energy. This acoustic backscatter intensity (ABI) was measured using a vessel mounted 153 kHz acoustic Doppler current profiler. The ABI was used to describe vertical migration and distribution of sound scatterers in several mesoscale hydrographic features commonly found in the Gulf of Mexico: cold-core rings (CCRs), warm-core Loop Current eddies (LCES) and the Loop Current (LC). The present paradigm contends that cold-core (cyclonic) features are mesoscale areas of enhanced production due to an influx of new nitrogen to surface waters as a result of divergent flow. The null hypothesis which was tested in this study was that the acoustic signatures of these features were not significantly different from one another. Clear diel differences in all of the features and a robust, positive correlation between ABI and plankton and micronekton wet displacement volume collected in MOCNESS tows in the upper 100 m of the water column were observed. During the day, ABI in CCRs was significantly greater than in LCEs and in the LC with regards to the upper 200 m. However, ABI in the LCEs and LC were not significantly different from each other. During the night, the ABI in the upper 50 m of the CCRs was significantly greater than that in the LCEs and the LC. However, there were no differences between features when ABI at night was summed for the entire upper 200 m, due to organisms into the upper 200 m of the water column at night. Two LCEs were revisited at an age of 8-9 months after their initial acoustic transacts. The null hypothesis that there would be no significant difference in integrated ABI when the LCEs were resampled was rejected: both LCEs showed a reduction in integrated ABI over the upper 200 m. Further investigations into the faunal changes of these features are warranted, but the ADCP should continue to be a useful tool in the examination of the distribution of sound scatterers in mesoscale features in the Gulf of Mexico. |
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| Item Description: | Vita. "Major Subject: Zoology". |
| Physical Description: | xii, 154 leaves : illustrations, maps ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references: pages 125-130. |