Upwelling, downwelling, and cross-shelf transport of bivalve larvae: test of a hypothesis
Upwelling, downwelling, and cross-shelf transport of bivalve larvae: test of a hypothesis
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双壳类幼虫的上升流、下降流和跨架运输：假设检验
DOI：
10.3354/meps302001
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发表时间：
2005
影响因子：
2.5
通讯作者：
L. Brink
中科院分区：
文献类型：
--
作者：
A. Shanks;L. Brink
幼虫的供应影响海洋群落的结构。通过上升流和下升流进行幼虫的跨陆架运输可能会导致幼虫供应的变化。我们测试了一种假说，即缓慢游动的双壳类幼虫在上升流期间被冲到岸边，在下流期间被冲到岸边。我们在北卡罗来纳州达克的一条横断面上采样，当时洋流从上升流转变为下降流，然后又回到上升流。在每次换班期间，近岸的水与离岸的水交换，水流的速度比幼虫的游泳速度快10到100倍。在温跃层以下发现了幼虫Spisula solidissima和Ensis Directus，与预测相反，它们在上升流时被扫到岸上，在下流期被冲到离岸。当在温跃层上方发现S.solidissima幼虫时，正如预测的那样，跨陆架运输。幼虫Tellina spp.尽管有跨陆架洋流和近岸水域与近岸水域的交换，但侧边木立线虫仍在距海岸5公里的范围内。它们并不表现为被动粒子；它们既不会被上升流冲离海岸，也不会被下流冲到岸上。对于这些分类群，这一假设被拒绝了。这些幼虫可能通过使用与集中在汇聚前锋的动物所表现出的类似的行为而保持在靠近海岸的位置。鉴于双壳类幼虫的游动速度相对较慢，没有理由预计任何一种幼虫会被上升流席卷近岸。上升流和下升流对幼虫分布的影响因幼虫的行为和垂直分布而异。如果没有仔细的采样，就不能通过上升流引起幼虫定居的变化，从而引发幼虫的离岸运输。
Larval supply affects the structure of marine communities. Cross-shelf transport of larvae by upwelling and downwelling may cause variation in larval supply. We tested the hypothesis that slow- swimming bivalve larvae are swept offshore during upwelling and shoreward during downwelling. We sampled a transect at Duck, North Carolina during a period when currents shifted from upwelling to down- welling and back to upwelling. During each shift, nearshore water was exchanged with offshore water and currents were 10 to 100 times faster than larval swimming speeds. Larval Spisula solidissima and Ensis directus were found below the thermocline and, con- trary to prediction, were swept onshore during up- welling and offshore during downwelling. When S. solidissima larvae were found above the thermocline, cross-shelf transport was as predicted. Larval Tellina spp. and Mulinia lateralis remained within 5 km of shore despite cross-shelf currents and the exchange of nearshore waters with offshore waters. They did not behave as passive particles; they were not swept off- shore by upwelling or onshore by downwelling. For these taxa the hypothesis was rejected. These larvae may have remained close to shore by using behaviors analogous to those displayed by animals concentrated at convergent fronts. Given the relatively slow swim- ming speed of bivalve larvae, there is no reason to expect that any larval type is swept offshore by up- welling. The effect of upwelling and downwelling on larval distributions varies with larval behavior and ver- tical distribution. Without careful sampling, one cannot invoke offshore transport of larvae by upwelling as a cause of variations in larval settlement.