科研之友
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摘要
Near-coastal retention of larvae affects the ecology of many marine species. In coastal upwelling ecosystems having strong offshore transport, larval ecology is greatly influenced by nearshore retention in bays and in the lee of headlands. Further, frontal dynamics along the periphery of retention zones can drive larval accumulation and transport. The purpose of this study is to examine larval distributions and associated processes across a retention zone and its peripheral front in the coastal upwelling environment of Monterey Bay, California, USA. During fall 2009 an autonomous underwater vehicle (AUV) was used to observe environmental variability at high resolution and acquire targeted water samples. Invertebrate larvae in samples were subsequently identified and quantified using molecular methods. To infer ecological processes we examine larval distributions in relation to environmental processes revealed by the AUV data and the greater regional observing system. As a window into biological-physical interactions that may concentrate motile larvae in convergence zones, we examine more extensive in situ and remote sensing observations that describe distribution patterns of motile phytoplankton. During the 10-day study intensification of upwelling caused flow of cold water into the bay and formation of an upwelling front. Drifter and satellite observations showed retention of near-surface water within the bay inshore of the front, where a bloom of motile phytoplankton intensified. Larval distributions were related to processes inferred at a range of scales. At the scale of the retention zone, dense phytoplankton accumulations indicated concentration of motile plankton in a convergence zone created by flow toward the coast, as well as nutritional support for larvae. At the scale of the front, velocity and water property measurements indicated convergence between cold deep-shelf water transported shoreward along shoaling bathymetry and the overlying warm surface water, influencing plankton accumulation and vertical transport. At the finest scales resolved, aerial photography revealed banded accumulations of dense phytoplankton bloom patches and narrow foam lines, common indicators of small-scale convergence zones and consistent with internal wave processes. Exceptionally high larval concentrations were detected in samples from locations affected by frontal and internal wave dynamics. This study illustrates how autonomous feature recognition and targeted sampling with an AUV, applied within the greater context of multidisciplinary observation across regional to small scales, can advance plankton ecology research.
- 出版日期2014-10
