Collaborative Research: Do Crustacean Zooplankton Play a Pivotal Role in Structuring Heterotrophic Plankton Communities?

最近对海洋生态系统的研究表明，关于营养级联的证据相互矛盾，特别是甲壳类浮游动物-浮游植物之间的联系的相对强度。罗斯海是研究这一明显冲突的天然实验室。它是一个季节性浮游植物丰度较高的地点，以不同的浮游植物类群区域为特点；南极洲中南部的多尼亚主要是形成群落的准单胞藻南极洲，而这片海域的沿海地区通常是硅藻或鞭毛物种。最近的研究表明，虽然南极洲中南部的波利尼亚呈现出大规模的浮游植物水华，但南极洲对许多甲壳类浮游动物来说，糟糕的食物质量阻碍了对这种浮游植物水华的直接利用。相反，有证据表明，间接利用这种产物可能是那些较高营养水平的人获得碳和能量的主要机制。具体地说，我们假设，在罗斯海夏季期间，纳米和微型浮游动物是甲壳类浮游动物(主要是桡足类和幼年浮游动物)的重要食物来源，那里的浮游植物组合以裸藻为主。反过来，我们还假设，桡足类(和其他甲壳类)的捕食控制和结构这些原生生物组合的物种组成。我们将在南半球夏季在罗斯海中南部的波利尼亚(RSP)和Terra Nova Bay(TNB)驻扎站点来验证这些假设。我们推测，在TNB的浮游植物组合中占主导地位的硅藻物种是草食性/杂食性浮游动物的直接营养来源(相对于RSP中南部的情况)。也就是说，在TNB中，异养原生动物对甲壳类饲料的贡献将会减少。我们的研究将解决我们在食物网络结构和营养级联知识方面的根本空白，并更好地了解这片常年寒冷的海洋生物群落内的碳和能量流动。PIS将通过课程开发(南极生物学)和海洋科学教育卓越中心(COSEE-WEST)的教师培训员活动，在公共教育(K-12)中发挥积极作用，COSEE-WEST是一个由NSF资助的创新项目，以南加州大学和加州大学洛杉矶分校为中心。

Recent studies of marine ecosystems show conflicting evidence for trophic cascades, and in particular the relative strength of the crustacean zooplankton-phytoplankton link. The Ross Sea is a natural laboratory for investigating this apparent conflict. It is a site of seasonally high abundances of phytoplankton, characterized by regions of distinct phytoplankton taxa; the southcentral polynya is strongly dominated by the colony-forming prymnesiophyte Phaeocystis antarctica, while coastal regions of this sea are typically dominated by diatoms or flagellate species. Recent studies indicate that, while the south-central polynya exhibits a massive phytoplankton bloom, the poor food quality of P. antarctica for many crustacean zooplankton prevents direct utilization of much of this phytoplankton bloom. Rather, evidence suggests that indirect utilization of this production may be the primary mechanism by which carbon and energy become available to those higher trophic levels. Specifically, we hypothesize that nano and microzooplankton constitute an important food source for crustacean zooplankton (largely copepods and juvenile euphausiids) during the summer period in the Ross Sea where the phytoplankton assemblage is dominated by the prymnesiophyte. In turn, we also hypothesize that predation by copepods (and other Crustacea) controls and structures the species composition of these protistan assemblages. We will occupy stations in the south-central Ross Sea Polynya (RSP) and Terra Nova Bay (TNB) during austral summer to test these hypotheses. We hypothesize that the diatom species that dominate the phytoplankton assemblage in TNB constitute a direct source of nutrition to herbivorous/omnivorous zooplankton (relative to the situation in the south-central RSP). That is, the contribution of heterotrophic protists to crustacean diets will be reduced in TNB. Our research will address fundamental gaps in our knowledge of food web structure and trophic cascades, and provide better understanding of the flow of carbon and energy within the biological community of this perennially cold sea. The PIs will play active roles in public education (K-12) via curriculum development (on Antarctic biology) and teacher trainer activities in the Centers for Ocean Science Education Excellence (COSEE-West), an innovative, NSF-funded program centered at USC and UCLA.