Broadband Characteristics of Zooplankton Sound Scattering Layer in the Kuroshio–Oyashio Confluence Region of the Northwest Pacific Ocean in Summer of 2019
Acoustic technology, as an important investigation method for fishery resources, has been widely used in zooplankton surveys. Since the Kuroshio–Oyashio confluence region has an extensive distribution of zooplankton, describing and analyzing the characteristic of the zooplankton sound scattering lay...
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| Format: | Article |
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MDPI AG
2021-08-01
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| Series: | Journal of Marine Science and Engineering |
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| Online Access: | https://www.mdpi.com/2077-1312/9/9/938 |
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| author | Minghua Xue Jianfeng Tong Siquan Tian Xuefang Wang |
| author_facet | Minghua Xue Jianfeng Tong Siquan Tian Xuefang Wang |
| author_sort | Minghua Xue |
| collection | DOAJ |
| description | Acoustic technology, as an important investigation method for fishery resources, has been widely used in zooplankton surveys. Since the Kuroshio–Oyashio confluence region has an extensive distribution of zooplankton, describing and analyzing the characteristic of the zooplankton sound scattering layer (SSL) in this area is essential for marine ecology research. To understand its spatial–temporal distribution, acoustic data of the Kuroshio–Oyashio confluence region at the Northwest Pacific Ocean, obtained by a Simrad EK80 broadband scientific echosounder in 2019, were used on board the research vessel (RV) Songhang. After noise removal, the volume backscattering strength (<i>S<sub>V</sub></i>) was measured to plot the broadband scattering spectrogram of each water layer and to exhibit zooplankton distribution. The results show that the main sound scattering within 0–200 m originate from the zooplankton, and the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>S</mi><mi>V</mi></msub></mrow></semantics></math></inline-formula> of each layer increases with the rise of the transducer frequency. The magnitude of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>S</mi><mi>V</mi></msub></mrow></semantics></math></inline-formula> was closely synchronized with the solar altitude angle, which gets smaller when the angle is positive, then larger when the angle is negative. It means that the SSL has a diel vertical migration (DVM) behavior with the variation of solar height. Meanwhile, scattering strength was positively correlated with temperature in the vertical direction and showed a maximum of −54.31 dB at 20–40 m under the influence of the thermocline. The Kuroshio and Oyashio currents had an obvious influence on the scattering strengths in this study, indicating a low value when next to the Oyashio side and a high value on the Kuroshio side. The scattering strength near the warm vortex center was higher than that at the vortex edge. The results of this study could provide references for a long-term study on ecological environment variation and its impacts on zooplankton distribution. |
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| institution | Directory Open Access Journal |
| issn | 2077-1312 |
| language | English |
| last_indexed | 2024-03-10T07:32:32Z |
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| spelling | doaj.art-0f215742b3a146abb41542fc9b2421a72023-11-22T13:45:37ZengMDPI AGJournal of Marine Science and Engineering2077-13122021-08-019993810.3390/jmse9090938Broadband Characteristics of Zooplankton Sound Scattering Layer in the Kuroshio–Oyashio Confluence Region of the Northwest Pacific Ocean in Summer of 2019Minghua Xue0Jianfeng Tong1Siquan Tian2Xuefang Wang3College of Marine Sciences, Shanghai Ocean University, Shanghai 201306, ChinaCollege of Marine Sciences, Shanghai Ocean University, Shanghai 201306, ChinaCollege of Marine Sciences, Shanghai Ocean University, Shanghai 201306, ChinaCollege of Marine Sciences, Shanghai Ocean University, Shanghai 201306, ChinaAcoustic technology, as an important investigation method for fishery resources, has been widely used in zooplankton surveys. Since the Kuroshio–Oyashio confluence region has an extensive distribution of zooplankton, describing and analyzing the characteristic of the zooplankton sound scattering layer (SSL) in this area is essential for marine ecology research. To understand its spatial–temporal distribution, acoustic data of the Kuroshio–Oyashio confluence region at the Northwest Pacific Ocean, obtained by a Simrad EK80 broadband scientific echosounder in 2019, were used on board the research vessel (RV) Songhang. After noise removal, the volume backscattering strength (<i>S<sub>V</sub></i>) was measured to plot the broadband scattering spectrogram of each water layer and to exhibit zooplankton distribution. The results show that the main sound scattering within 0–200 m originate from the zooplankton, and the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>S</mi><mi>V</mi></msub></mrow></semantics></math></inline-formula> of each layer increases with the rise of the transducer frequency. The magnitude of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>S</mi><mi>V</mi></msub></mrow></semantics></math></inline-formula> was closely synchronized with the solar altitude angle, which gets smaller when the angle is positive, then larger when the angle is negative. It means that the SSL has a diel vertical migration (DVM) behavior with the variation of solar height. Meanwhile, scattering strength was positively correlated with temperature in the vertical direction and showed a maximum of −54.31 dB at 20–40 m under the influence of the thermocline. The Kuroshio and Oyashio currents had an obvious influence on the scattering strengths in this study, indicating a low value when next to the Oyashio side and a high value on the Kuroshio side. The scattering strength near the warm vortex center was higher than that at the vortex edge. The results of this study could provide references for a long-term study on ecological environment variation and its impacts on zooplankton distribution.https://www.mdpi.com/2077-1312/9/9/938Northwest Pacific OceanKuroshio–Oyashiosound scattering layerzooplanktonvolume backscattering strength |
| spellingShingle | Minghua Xue Jianfeng Tong Siquan Tian Xuefang Wang Broadband Characteristics of Zooplankton Sound Scattering Layer in the Kuroshio–Oyashio Confluence Region of the Northwest Pacific Ocean in Summer of 2019 Journal of Marine Science and Engineering Northwest Pacific Ocean Kuroshio–Oyashio sound scattering layer zooplankton volume backscattering strength |
| title | Broadband Characteristics of Zooplankton Sound Scattering Layer in the Kuroshio–Oyashio Confluence Region of the Northwest Pacific Ocean in Summer of 2019 |
| title_full | Broadband Characteristics of Zooplankton Sound Scattering Layer in the Kuroshio–Oyashio Confluence Region of the Northwest Pacific Ocean in Summer of 2019 |
| title_fullStr | Broadband Characteristics of Zooplankton Sound Scattering Layer in the Kuroshio–Oyashio Confluence Region of the Northwest Pacific Ocean in Summer of 2019 |
| title_full_unstemmed | Broadband Characteristics of Zooplankton Sound Scattering Layer in the Kuroshio–Oyashio Confluence Region of the Northwest Pacific Ocean in Summer of 2019 |
| title_short | Broadband Characteristics of Zooplankton Sound Scattering Layer in the Kuroshio–Oyashio Confluence Region of the Northwest Pacific Ocean in Summer of 2019 |
| title_sort | broadband characteristics of zooplankton sound scattering layer in the kuroshio oyashio confluence region of the northwest pacific ocean in summer of 2019 |
| topic | Northwest Pacific Ocean Kuroshio–Oyashio sound scattering layer zooplankton volume backscattering strength |
| url | https://www.mdpi.com/2077-1312/9/9/938 |
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