Collaborative Proposal: Cross-Shelf Transport and Post-Bloom New Production Near the Pribilof Islands

提案提要：拟议的研究将检验一项假设，即富含营养物质和浮游动物的坡面水在架上流动会影响春季水华后的新生物产量和普里比利群岛附近的浮游动物种群，从而增强该区域支持幼鱼和食浮游海鸟的能力。该项目将调查坡水的架上运输，这些水提供的营养物质支持夏季的新初级生产，而夏季是一个陆架上新生产的可获得性受到层化限制的季节。第二个假设是，这种新的生产方式将由硅藻而不是鞭毛虫主导，基于硅藻的食物网将导致以硅藻为基础的食物网中的中型浮游动物的能量含量高于基于鞭毛虫的食物网中的中型浮游动物。与那些以脂肪含量较低的浮游植物为食的浮游动物相比，这些能量丰富的浮游动物对幼鱼和食浮性海鸟的价值预计更大。该项目还将在2004年至2007年的7/8月巡航期间测试这些假设。在这些巡航期间，PIS将比较夏季跨陆架平流较弱的中陆架区域(系泊2)、中陆架间歇性平流但垂直混合很少的区域(系泊4)和普里比洛夫群岛的产量及其命运，在那里，营养物质既有陆上输送，也有潮汐混合进入上层混合层。该项目将测量沿陆架和跨陆架流动(Stabeno，PMEL)、营养物浓度(Mordy，UW/PMEL)、浮游植物现存量(塞曼，U·新英格兰)、新的、再生的和总生产量(Zeeman，Sambrotto，Lamont-Doherty)、微型浮游动物的捕食率与浮游植物现存量和生产量的关系(Strom，西华盛顿大学)、浮游动物的生物量和组成(Coyle，U·Alaska，Fairbank)、浮游动物、幼鱼和海鸟的脂肪含量、脂肪酸组成和稳定的同位素特征(NAPP，NMFS)，以及海洋鸟类的觅食分布和食物习性(Hunt，West Washington University)加州，欧文)。此外，该项目将使用卫星跟踪的漂移器和系泊设备来测量海流。这项提案是白令海第一个涉及营养丰富的坡面水的架上流量对春季水华后新产量的影响，以及这一新产量如何影响幼鱼(即0龄大眼鳕鱼)和食浮性海鸟猎物的丰度和质量的问题。开花后的新产量对于提供高质量的猎物可能特别重要，因为此时幼鱼正在开发储备以携带它们度过冬天，而海鸟正在喂养逐渐长大的幼鸟。这项工作侧重于一个具有重大经济和社会意义的区域，并审查了影响普里比洛夫群岛水域生产力的生态过程及其养育幼鱼、依赖幼鱼的海鸟和海洋哺乳动物的能力。该地区最丰富的鱼类是幼鳕鱼，这是世界上最大的单一物种渔业的目标。拟议研究产生的信息将有助于评估全球气候变化影响春季后水华数量、新产量和上层营养水平可获得的猎物营养质量的机制。该项目将包括实地和实验室的本科生、研究生和博士后，以分析和整理数据，并将努力与圣保罗和圣乔治群岛的学校系统开展外联方案。这项工作将在参考文献和网站上传播。

ABSTRACTProposal #: 0327308PI/PD: Hunt (lead proposal)Submitted: 02/18/2003Requested Amount: $ 1,704,140Note: Collaborative with 0326415 (Zeeman) 0323150 (Strom) 0326561 (Coyle) 0326953 (Sambrotto) Synopsis of proposal:The proposed study will test the hypothesis that on-shelf flow of nutrient- and zooplankton-rich slope water influences post-spring-bloom new production and zooplankton populations in the vicinity of the Pribilof Islands, thereby enhancing the region's ability to support juvenile fish and planktivorous seabirds. The project will investigate on-shelf transport of slope water, which supplies nutrients that sustain new primary production in summer, a season when the availability of new production on the shelf is limited by stratification. A second hypothesis is that this new production will be dominated by diatoms rather than by flagellates, and a diatom-based food web will result in meso-zooplankton with a greater energy content than meso-zooplankton in a flagellate-based food web. These energy-rich zooplankton are expected to be of greater value to juvenile fish and planktivorous seabirds than those that have fed upon less lipid-rich phytoplankton. The project will also test these hypotheses during July/August cruises in 2004 to 2007. During these cruises, the PIs will compare production and its fate in an area on the middle shelf where summer-time cross-shelf advection is weak (Mooring 2), on the middle shelf in an area of episodic advection but little vertical mixing (Mooring 4) and at the Pribilof Islands where there is both on-shelf transport and tidal mixing of nutrients into the upper mixed layer. The project will measure along- and across-shelf flows (Stabeno, PMEL), nutrient concentrations (Mordy, UW/PMEL), standing stocks of phytoplankton (Zeeman, U. New England), new, regenerated and total production (Zeeman, Sambrotto, Lamont-Doherty), the grazing rates of micro-zooplankton in relation to phytoplankton standing stocks and production (Strom, Western Washington University), zooplankton biomass and composition (Coyle, U. Alaska, Fairbanks), lipid content, fatty-acid composition, and stable isotope signatures of zooplankton, juvenile fish and seabirds (Napp, NMFS), and the foraging distributions and food habits of marine birds (Hunt, U. California, Irvine). In addition, the project will use satellite-tracked drifters and moorings to measure currents. This proposal is the first in the Bering Sea to address the effect of on-shelf fluxes of nutrient-rich slope water on post-spring-bloom new production, and in turn, how this new production affects the abundance and quality of prey for juvenile fish (i.e., age-0 walleye pollock) and planktivorous seabirds. Post-bloom new production may be particularly important for providing high quality prey at a time when juvenile fish are developing the reserves to carry them through the winter and seabirds are feeding growing young. The work focuses on a region of great economic and societal importance, and examines the ecological processes that affect the productivity of Pribilof Islands' waters and their ability to support juvenile fish, and the seabirds and marine mammals that depend on them. The most abundant fish in the area are juvenile walleye pollock, the target of the world's largest single-species fishery. The information generated by the proposed research will be of value in assessing the mechanisms whereby global climate change can affect the amount of post- spring bloom new production and the nutritional quality of prey available to upper trophic levels. The project will include undergraduate, graduate and post-doctoral students in the field and in the laboratory for the analysis and workup of the data and will strive to develop outreach programs with the school systems on St Paul and St. George Islands. The work will be disseminated in the refereed literature and through web sites.