Digestibility of Ice Algae and Phytoplankton: The Potential Impacts of Changing Food Supply to the Arctic Benthos

安布罗斯海冰是北极海洋生态系统的主要特征。它的存在影响北极海洋生态系统，特别是在海底和中上层系统广泛耦合的大陆架上。如果海冰的范围和厚度继续下降，预计到达底栖动物的藻类物质类型将发生变化(从冰藻到浮游植物)，这可能会影响底栖动物的食物需求。一些证据表明，这两种类型的冰藻(以北极直链杆菌为主的冰下冰藻和以冷尼茨藻为主的冰内冰藻)目前都大量到达底栖生物。这项研究工作将调查北极大型底栖动物对冰藻和浮游植物衍生的有机物的消化能力。从大型动物的角度来看，可消化率包括三个独立的组成部分：1)选择(被摄取或拒绝的有机物质？)；2)吸收(被摄取的有机物质在通过肠道的过程中被吸收，还是从粪便中排出？)；以及3)同化(被吸收的有机物质被同化成生物量？)。对各种藻类(冰内冰藻、冰下冰藻和浮游植物)的长期同化进行评估，方法是确定脂质生物标记物及其同位素比率，并确定在挪威和阿拉斯加科策布埃开展工作的所有方面收集的生物体的CHN和蛋白质特征。短期吸收的评估将首先在全岩心输送实验中使用灰比方法。在全核心实验之后，将确定每个营养类群的优势类群，并将其用于比较通过灰比方法计算的吸收效率和使用脉冲追逐放射性示踪剂方法计算的碳保持效率。最后，该小组计划在挪威斯瓦尔巴特群岛的NY Aalesund实验室和阿拉斯加的Kotzebue Sound重复主要的分类群吸收效率实验。这一拟议项目是对挪威研究理事会资助的两个项目的补充，并将产生协同效益。

0222423AmbroseSea ice is a dominant feature of marine ecosystems in the Arctic. Its presence impacts Arctic marine ecosystems, especially on the shelves where benthic and pelagic systems are extensively coupled. If the extent and thickness of sea ice continue to decline, a shift is predicted in the type of algal material reaching the benthos (from ice algae to phytoplankton), which will potentially impact the food requirements of the benthos. Several pieces of evidence show that both types of ice algae (below-ice ice algae dominated by Melosira arctica and within-ice ice algae dominated by Nitzchia frigida) presently reach the benthos in significant quantities. This research effort will investigate the digestibility of ice algae and phytoplankton-derived organic matter by the Arctic macrobenthos. From the perspective of a macrofaunal organism, digestibility includes three separate components: 1) selection (is encountered organic material ingested or rejected?); 2) absorption (is ingested organic material absorbed during passage through the gut, or does it get egested in the feces?); and 3) assimilation (is absorbed organic material assimilated into biomass?). Assessment of long-term assimilation of the various types of algae (within-ice ice algae; below-ice ice algae; and phytoplankton) will be conducted by determining lipid biomarkers and their isotopic ratios, and by determining CHN and protein signatures of organisms collected during all aspects of the work in both Norway and Kotzebue, Alaska. Assessment of short-term absorption will first use the ash-ratio method in a whole-core delivery experiment. Following the whole-core experiments, dominant taxa from each trophic group will be identified and used in a comparison of absorption efficiencies as calculated by the ash-ratio method, and carbon retention efficiencies as calculated using a pulse-chase radiotracer approach. Finally, the group plans to repeat the dominant taxa absorption efficiency experiments in both Svalbard, Norway at the Ny Aalesund lab and in Kotzebue Sound, Alaska. This proposed project compliments, and will derive synergistic benefits from two projects funded by the Norwegian Research Council in Norway.