Collaborative Proposal: Optimizing Recruitment of Neocalanus copepods through Strategic Timing of Reproduction and Growth in the Gulf of Alaska

阿拉斯加湾支持着一个多样化和多产的海洋群落，其中包括许多具有重要商业价值的鱼类。在这个食物网的底部是小型浮游甲壳类动物，它们是许多此类鱼类以及海鸟和海洋哺乳动物的主要食物来源。尺足类Neocalanus flemingeri就是其中一种甲壳类动物，在每年春天的藻类或浮游植物水华期间，它的种群数量都会迅速增长。在初冬出现最年轻的桡足类，或称无节幼体，与几个月后春季浮游植物开花的不可预测的时间之间的明显不匹配，引发了关于雌性何时繁殖以及这与无节幼体的生存和生长有何关系的重要问题。成虫的滞育和无节幼体的生理休眠两种类型的休眠可能是这种桡足类物种成功的关键。成年雌性的产卵期的时间和持续时间与滞育的出现有关。此外，无节幼体可能在食物来源不足时进入生理静止状态，在浮游植物水平增加后恢复生长。这项研究将解决生物海洋学家的一个长期目标，即了解休眠及其在控制海洋桡足类种群周期中的作用。它将使用分子生物学中称为转录组的新技术来对细胞用来控制桡足类动物生命过程的信息进行分类，在这种情况下，这些信息与成年和无节幼体的休眠有关。本科生和博士后研究员将接受跨学科研究培训，来自夏威夷原住民和阿拉斯加原住民团体的学生将成为参与的目标。渔业是阿拉斯加湾的一项主要产业，外联活动将侧重于宣传桡足类在海洋生态系统中发挥的作用。将为现有网站生成包括图像在内的新内容：Seward Line长期观测计划、阿拉斯加海洋观测系统和海湾观察阿拉斯加计划。弗莱明格里新银鱼春季种群的补充依赖于成功地从滞育中羽化，然后是下一代的繁殖、存活和生长。基于个体的模型在使用食物、温度和平流作为关键环境因子来预测尺足类水蚤的种群增长方面取得了重大进展。然而，这些模型中几乎没有包含无节幼体招募的预测因子，因为考虑到采样困难和缺乏评估生理状态的生物标记物，对生命周期的这一部分知之甚少。这项研究将利用现有的监测工作来跟踪冬季和早春期间的弗莱明格里线虫种群。研究小组将结合实验室和现场的方法来确定新出现的雌性动物繁殖的持续时间和同步性，以及在低食物条件下无节幼体生存的策略。浮游动物样本将被处理，以计数无节幼体对物种的影响，并确定无节幼体和成年雌性无节幼体的生理状况。基因表达研究将开发雌性休眠和生殖准备以及无节幼树生长和可能的休眠的分子标记，这些标记将反过来用于评估野外采集的个体。这将是第一次将分子和传统工具相结合的综合研究，将滞育成虫、无节幼体生产和由此产生的桡足类春季种群联系起来。

The Gulf of Alaska supports a diverse and productive marine community that includes many commercially important fishes. Toward the base of this food web are small planktonic crustaceans that serve as the primary food source for many of these fish, as well as seabirds and marine mammals. The copepod Neocalanus flemingeri is one of these crustaceans, and it experiences rapid population growth during each spring's algal, or phytoplankton, bloom. An apparent mismatch between the presence of the youngest stages of the copepod, or nauplii, in early winter and the unpredictable timing of the spring phytoplankton bloom several months later raises important questions about when females reproduce and how this relates to survival and growth of nauplii. Two types of dormancy, diapause in adult females and physiological quiescence in nauplii, may be the key to the success of this copepod species. Timing and duration of the egg-laying period by adult females is linked to emergence from diapause. In addition, nauplii may enter a state of physiological quiescence while food resources are low, resuming growth after phytoplankton levels increase. This research will address a long-standing goal of biological oceanographers to understand dormancy and its role in controlling population cycles in marine copepods. It will use new technologies in molecular biology called transcriptomics to catalog the messages used by the cells to control copepod life processes, in this case those related to dormancy in adults and nauplii. Undergraduate students and a postdoctoral investigator will be trained in interdisciplinary research, and students from Native Hawaiian and Native Alaskan groups will be targeted for participation. Fishing is a major industry in the Gulf of Alaska, and outreach will focus on communicating the role copepods play in marine ecosystems. New content, including images, will be generated for existing websites: the Seward Line long-term observation program, the Alaska Ocean Observing System and the Gulf Watch Alaska Program. Recruitment to the Neocalanus flemingeri spring population is dependent on successful emergence from diapause followed by reproduction, survival, and growth of the next generation. Individual-based models have made significant progress in predicting population growth in calanoid copepods using food, temperature, and advection as key environmental factors. Few of these models include predictors for naupliar recruitment, however, because little is known about this part of the life cycle given sampling difficulties and the lack of biomarkers to evaluate physiological state. This study will leverage existing monitoring efforts to track the N. flemingeri population during the winter and early spring. The research team will combine laboratory and field approaches to determine duration and synchronization of reproduction in emerging females and strategies for naupliar survival during low food conditions. Zooplankton samples will be processed to enumerate nauplii to species and to determine physiological condition of both nauplii and adult females. Gene expression studies will develop molecular markers for female dormancy and reproductive readiness and for naupliar growth and possible dormancy, which in turn will be used to evaluate field collected individuals. This will be the first comprehensive study to combine molecular and traditional tools to connect diapausing adults, naupliar production, and the resulting spring population of copepodites.