Spatial dynamics of a nearshore, micronekton sound-scattering layer

被引:20
作者
Benoit-Bird, KJ
Au, WWL
机构
[1] Univ Hawaii, Hawaii Inst Marine Biol, Kailua, HI 96734 USA
[2] Univ Hawaii, Dept Zool, Kailua, HI 96734 USA
基金
美国海洋和大气管理局;
关键词
mesopelagic boundary community; acoustic sampling; patchiness; heterogeneity; vertical structure; biological forcing; Hawaiian islands;
D O I
10.1016/S1054-3139(03)00092-4
中图分类号
S9 [水产、渔业];
学科分类号
0908 ;
摘要
In the Hawaiian Islands, there is a distinct resident community of micronekton, distributed along a narrow band where the upper underwater slopes of the islands meet the oceanic, mesopelagic environment. This mesopelagic boundary community serves as an important food resource to many animals. The goal of this work was to examine spatial heterogeneity of the Hawaiian mesopelagic boundary biomass at a range of scales, in the context of its diel vertical and horizontal migrations. A modified echosounder was used to sample the coasts of three Hawaiian Islands, permitting a range of scales from several meters to several kilometers to be assessed rapidly. The Hawaiian mesopelagic boundary community fits the hierarchical model of patch structure with patches within patches that are part of a larger-scale matrix of patches. Large differences in the overall distribution patterns of the mesopelagic boundary community exist along with a wide range of overall mesopelagic-animal densities. High animal-density locations have boundary-community layers with a large (kilometers) horizontal extent, and low animal-density locations have small (tens of meters), discrete patches. Higher animal-density locations are also more complex than low-density sites, with more levels of patchiness within the same range of spatial scales, Both time of day and distance from shore significantly affected the geometric and density characteristics as well as the distribution of aggregations within the boundary layer. Horizontal and vertical structures of the mesopelagic boundary community are also coupled. In high-density sites, there is strong vertical layering in acoustic-scattering strength while in low-density sites vertical acoustic structure is absent. The differences observed in the distribution of the mesopelagic boundary community at different levels of overall mesopelagic-animal density suggest biological forcing as the dominant mechanism. A description of heterogeneity in the mesopelagic boundary community in Hawaii is the first step in understanding its importance to both neritic and oceanic ecosystems and its potential for linking these two systems. (C) 2003 International Council for the Exploration of the Sea. Published by Elsevier Ltd. All rights reserved.
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页码:899 / 913
页数:15
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