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）对多棘海胆（Strongylocentrotus droebachiensis）、海星（Asterias rubens）以及海湾扇贝（Argopecten irradians）幼体垂直分布的影响。研究采用定制的矩形有机玻璃温跃层实验舱，将中央观测舱的温度调控至预设值，并在90分钟内记录受试生物的垂直分布情况。本实验采用正交设计，调控底层水层温度（B）以及水层间温差（ΔT）两个变量。针对不同受试物种，设置的变量梯度如下：多棘海胆的ΔT设为0、3、6、12℃四个水平，B设为3、6、9℃三个水平；海星的ΔT设为0、6、12℃三个水平，B设为6、12℃两个水平；海湾扇贝的ΔT设为0、5、11℃三个水平，B设为5、11℃两个水平。水层温差并未对棘皮动物的垂直分布产生一致影响；但无论热分层强度如何，只要存在热分层，海湾扇贝的分布便会被限制在底层水层中。研究结果显示，多棘海胆与海星幼体的垂直分布与表层水温相关，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，除非遭遇极端水温，棘皮动物幼体通常会聚集于表层水域。与之相反，当实验中出现至少5℃（本研究设置的最低温跃层强度）的温跃层时，海湾扇贝幼体的分布便会被限制在底层水层中。这类温跃层在自然环境中十分常见，可通过阻碍垂直迁移，进而影响幼体的垂直分布与水平扩散过程。