Data from: Vertical distribution of marine invertebrate larvae in response to thermal stratification in the laboratory

We investigated the effect of the presence of an experimentally generated thermocline on the vertical distribution of larval Strongylocentrotus droebachiensis, Asterias rubens and Argopecten irradians. Vertical distributions were recorded over 90 min in rectangular plexiglass thermocline chambers designed to regulate the temperature of a central observation compartment to the desired values. The temperature in the bottom water layer (B) and the temperature difference between layers (ΔT) were manipulated in an orthogonal design. We used, for S. droebachiensis: 4 levels of ΔT (0, 3, 6 and 12 °C) and 3 levels of B (3, 6 and 9 °C); for A. rubens: 3 levels ΔT (0, 6 and 12 °C) and 2 levels of B (6 and 12 °C); and for A. irradians: 3 levels of ΔT (0, 5 and 11 °C) and 2 levels of B (5 and 11 °C). The difference in temperature between water layers did not affect the vertical distribution of echinoderms consistently, while the distribution of A. irradians was limited to the bottom layer when any thermal stratification was present regardless of strength. Our results suggest that the vertical position of larvae of S. droebachiensis and A. rubens is related to the temperatures of the surface layer and that the presence alone or the steepness of the thermocline has less influence on their distribution. Consequently, in the field, echinoderm larvae would aggregate at the surface unless temperature extremes were encountered. In contrast, the position of A. irradians was limited to the bottom layer in the presence of a thermocline of at least 5 °C (the shallowest used in our study). Such thermoclines are common in a natural setting and could affect the vertical distribution and horizontal dispersal of larvae by acting as a barrier to vertical migration.本研究探究了实验构建的温跃层（thermocline）对光棘球海胆（Strongylocentrotus droebachiensis）、多棘海盘车（Asterias rubens）以及海湾扇贝（Argopecten irradians）幼体垂直分布的影响。研究人员在矩形有机玻璃（plexiglass）温跃层舱内记录了90分钟内的幼体垂直分布情况，该舱体可将中央观测舱的温度调控至预设值。本实验采用正交设计，对底层水体温差（记为B）以及各水层间的温度差（记为ΔT）进行调控。针对光棘球海胆，我们设置了4个ΔT梯度（0、3、6和12 ℃）与3个B梯度（3、6和9 ℃）；针对多棘海盘车，设置了3个ΔT梯度（0、6和12 ℃）与2个B梯度（6和12 ℃）；针对海湾扇贝，则设置了3个ΔT梯度（0、5和11 ℃）与2个B梯度（5和11 ℃）。水层温差并未对棘皮动物的垂直分布产生一致影响，但当存在任何强度的热分层时，海湾扇贝的分布均被限制在底层水体中。研究结果表明，光棘球海胆与多棘海盘车的幼体垂直分布位置与表层水体温度相关，而温跃层的存在与否及其陡峭程度对其分布的影响相对较弱。因此，在自然环境中，棘皮动物幼体通常会聚集于表层水体，除非遭遇极端温度条件。与之相反，当温跃层温差至少达到5 ℃（即本实验中使用的最小温差梯度）时，海湾扇贝幼体的分布始终被限制在底层水体中。此类温跃层在自然环境中较为常见，可通过阻碍垂直迁移行为，对幼体的垂直分布与水平扩散产生影响。