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

[00:22 . 24]海冰是北极海洋生态系统的主要特征。它的存在影响着北极海洋生态系统，特别是在底栖和远洋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），这将潜在地影响底栖动物的食物需求。一些证据表明，两种类型的冰藻（以北极Melosira arctic为主的冰下冰藻和以Nitzchia frigida为主的冰内冰藻）目前都大量到达底栖动物。本研究将探讨北极大型底栖动物对冰藻和浮游植物衍生有机物的消化率。从大型动物的角度来看，消化率包括三个独立的组成部分：1)选择（遇到的有机物质是被摄入还是被拒绝？）2)吸收（是被摄入的有机物质通过肠道被吸收，还是随粪便排出？）3)同化（被吸收的有机物被同化成生物量吗？）对各种藻类（冰内冰藻、冰下冰藻和浮游植物）长期同化的评估将通过测定脂质生物标志物及其同位素比率，以及测定在挪威和阿拉斯加Kotzebue工作的各个方面收集的生物的CHN和蛋白质特征来进行。短期吸收的评估将首先在全岩心输送实验中使用灰比法。在整个核心实验之后，将确定每个营养组的优势分类群，并将其用于比较用灰分比法计算的吸收效率和用脉冲追踪放射性示踪剂方法计算的碳保持效率。最后，该小组计划在挪威的斯瓦尔巴群岛的新奥勒松实验室和阿拉斯加的Kotzebue海湾重复占优势的分类群吸收效率实验。这个拟议的项目是对挪威研究委员会在挪威资助的两个项目的补充，并将从两个项目中获得协同效益。

0222410CloughSea 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.