Digestibility of ice algae and phytoplankton: The potential impacts of changing food supply to the arctic benthos

0222500 Lopez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，特别是在海底和水层系统广泛耦合的大陆架上。如果海冰的范围和厚度继续减少，预计到达底栖生物的藻类物质类型将发生变化（从冰藻到浮游植物），这将可能影响底栖生物的食物需求。若干证据表明，这两种冰藻（以北极直链藻为主的冰下冰藻和以冷菱形藻为主的冰内冰藻）目前都大量进入底栖生物。这项研究工作将调查北极大型底栖动物对冰藻和植物毒素衍生的有机物的消化率。从大型底栖生物的角度来看，消化率包括三个独立的组成部分：1）选择（遇到的有机材料摄入或拒绝？）; 2)吸收（摄入的有机物质在通过肠道时被吸收，还是在粪便中排出？）同化作用（被吸收的有机物质是否被同化为生物量？）将通过确定脂质生物标志物及其同位素比率，并通过确定在挪威和阿拉斯加Kotzebue开展的各方面工作期间收集的生物体的CHN和蛋白质特征，对各种藻类（冰内冰藻、冰下冰藻和浮游植物）的长期同化作用进行评估。短期吸收的评估将首先在全堆芯输送实验中使用灰比法。在全岩心实验之后，将确定每个营养组的优势类群，并将其用于比较灰分比法计算的吸收效率和使用脉冲追踪放射性示踪剂方法计算的碳保留效率。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重复进行主要类群的吸收效率实验。这一拟议项目是对挪威研究理事会在挪威资助的两个项目的补充，并将从这两个项目中获得协同效益。

0222500LopezSea 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.