Acoustic Characterization of the Mesopelagic Boundary Sound Scattering Layer

中层边界声散射层的声学特征

• 批准号: 0434078
• 负责人: Whitlow Au
• 金额: --
• 依托单位: University of Hawaii
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-08-15 至 2008-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0434078&HistoricalAwards=false
• 关键词: Acoustic; Characterization; Mesopelagic; Boundary; Sound

The acoustic properties of mid-water biologically induced sound scattering layers in coastal environment is poorly understood, especially around sub-tropical and tropical islands in the Pacific, where the bottom slope can very steep. The sound scattering layer can represent a large acoustic target and can easily be mistakenly as a false bottom and can interfere with sonar systems. The sound scattering layer around the Hawaiian Islands is known as the mesopelagic boundary community (MBC) of micronekton comprising of small fishes, shrimps, and squids. This layer, like most deep-scattering layers, undergoes vertical migration. However, the Hawaiian boundary's migration also has a large horizontal component that is predictable along some coastlines. The project team will characterize the acoustic environment of the mesopelagic boundary community by performing 1) multi-frequency acoustic backscatter measurements at multiple grazing angles at different portions of the layer to account for differences in density and layer thickness, 2) acoustic, video and oceanographic measurements to estimate density and species and the relationship of oceanographic conditions at the same locations of the backscatter measurements, 3) acoustic and chlorophyll a measurements to estimate zooplankton and phytoplankton abundance and density at the locations of the backscatter measurements, 4) island scale spatial and temporal distribution of the mesopelagic boundary sound scattering layer at various locations around an island, with Oahu serving as a model for other islands in temperate and tropical Pacific. This research will increase our understanding of the environment and the characteristics of the mesopelagic boundary community. The mesopelagic boundary community is an important part of the coastal ecosystem associated with Pacific and other islands that have steep bottom slopes and increase understanding of its ecology is important for preserving, managing and operating in this environment. This community of micronekton also serves as an important food resource for many commercially important species including billfish, tunas, and bottomfish and also spinner dolphins.

人们对沿海环境中层水生物诱导声散射层的声学特性知之甚少，特别是在太平洋的亚热带和热带岛屿周围，那里的底坡可能非常陡峭。 声散射层可以代表一个大的声学目标，很容易被误认为是假底，并可能干扰声纳系统。 夏威夷群岛周围的声音散射层被称为微浮游生物的中层边界群落（MBC），由小鱼、虾和鱿鱼组成。 这一层，像大多数深散射层，经历垂直迁移。 然而，夏威夷边界的迁移也有很大的水平分量，这是可以预测的沿着一些海岸线。项目小组将通过以下方式确定中层边界群落声学环境的特征：1）在层的不同部分以多个掠射角进行多频声学后向散射测量，以考虑密度和层厚的差异，2）进行声学、视频和海洋学测量，以估计在后向散射测量的同一地点的密度和物种以及海洋学条件之间的关系，3）声学和叶绿素a测量，以估计后向散射测量地点的浮游动物和浮游植物丰度和密度， 在岛屿周围不同位置的海洋中层边界声散射层的岛屿尺度空间和时间分布，Oakland作为温带和热带太平洋其他岛屿的模式。这项研究将增加我们对中远洋边界群落的环境和特征的了解。 中层界线生物群落是与太平洋和其他具有陡峭底坡的岛屿有关的沿海生态系统的重要组成部分，增加对其生态的了解对于在这一环境中进行养护、管理和运作十分重要。 这个微浮游生物群落也是许多重要商业物种的重要食物资源，包括长嘴鱼、金枪鱼、底鱼和飞旋海豚。