Swimming and Vulnerability in Pelagic Development

浮游生物发育的早期游泳提供了一种系统，可以检验关于水柱而不是底栖动物在其生活史早期作为栖息地的好处的假设。不同的海洋动物将卵释放到水中，形成独立的浮游生物胚胎，这些胚胎很早就会游泳，通常还在胚胎阶段。早期游泳阶段的广泛存在表明水柱在早期和脆弱的生活史阶段作为栖息地的优势。单独的胚胎沉积在底部可能会有更大的风险。底栖动物的胚胎得到了更多的亲代保护，这进一步表明底栖动物对单独的胚胎来说是一个危险的地方。这个项目将回答三个问题。早期的游泳会使底栖动物的早期胚胎阶段消失吗？早期游泳会减少常见的远洋捕食者的捕获吗？动物在早期阶段是否比底栖动物更容易受到远洋动物的攻击？这些问题将通过实验室和现场研究的结合来解决，这些研究将分析湍流和非湍流条件下的下沉和游动速度。由于湍流使游泳者偏离垂直方向，实验还将比较湍流中的垂直偏置与静水中的垂直偏置，以估计在湍流中重新定向到垂直方向的有效性。温度通常随深度而变化，因此该项目还将测量温度对下沉和游泳速度的影响。游得比沉得快可能会增加与伏击捕食者的相遇，因此下沉和游泳的速度将与捕食者相对于水的速度进行比较，并与捕食者感知体积内预测的湍流产生的切变进行比较。与被动下沉者相比，游泳者在更短的距离上排水，从而对捕食者产生更小的信号，这一假设也将得到验证。在胚胎开始游泳之前和之后对它们的捕获和摄食进行量化，将检验游泳会减少每次捕获成功率的假设。捕食者包括鱼类幼虫、桡足类、水母和栉水母。关于游泳前和游泳阶段的脆弱性的结果将与已发表的关于远洋和底栖捕食者的丰度和清除率的数据相结合，以检验处于早期发育阶段的动物在水柱中比在靠近底部的地方更安全的假设。两名研究生将在其论文研究中参与拟研究，几名本科生将参与研究。

Early swimming in planktonic development provides a system for testing hypotheses on advantages of the water column rather than the benthos as a habitat for animals early in their life histories. Diverse marine animals release eggs into the water to develop as solitary planktonic embryos that swim early, often while still in embryonic stages. The widespread existence of early swimming stages suggests advantages of the water column as a habitat at early and vulnerable life history stages. Solitary embryos deposited on the bottom may be at greater risk. Benthic embryos receive greater parental protection, further indicating that the benthos is a risky place for solitary embryos. This project will answer three questions. Does early swimming remove early embryonic stages from benthic predators, despite turbulent mixing? Does early swimming reduce capture by common pelagic predators? Are animals at early stages less vulnerable to pelagic than to benthic predators?These questions will be addressed through a combination of lab and field studies that assay sinking and swimming velocities under turbulent and non-turbulent conditions. Because turbulence turns swimmers away from vertical orientation, experiments will also compare vertical bias in turbulence with vertical bias in still water to estimate effectiveness of reorientation to the vertical in turbulence. Temperature commonly varies with depth, so this project will also measure the effect of temperature on rates of sinking and swimming. Swimming faster than sinking could increase encounters with ambush predators, so velocities of sinking and swimming will be compared with those of predators relative to water, and to predicted turbulence generated shear within predators' perception volumes. The hypothesis that swimmers displace water at smaller distances, and thus produce a smaller signal to predators than do passive sinkers, will also be tested. Quantifying capture and ingestion of embryos before and after they begin to swim will test the hypothesis that swimming decreases successful captures per encounter. Predators will include fish larvae, copepods, medusae, and ctenophores. Results on vulnerability of preswimming and swimming stages will be combined with published data on abundance and clearance rates of pelagic and benthic predators to test the hypothesis that animals at early stages of development are safer from predation in the water column than near the bottom. Two graduate students will participate in the proposed research in their dissertation research, and several undergraduates will participate in the research.