Arctic Sea Ice Ecology by unknow

Author:unknow
Language: eng
Format: epub
ISBN: 9783030374723
Publisher: Springer International Publishing

4.8 Sea Ice Meiofauna: Unknown Diversity and Food Web Interactions – Case Study 3

This case study addresses the importance of meiofauna in the sea ice through the sea ice season with a focus on their changing composition and food web contribution during the ice algal bloom season. The small animal fauna within sea ice (Fig. 1.​2) are often overlooked, potentially due to methodological challenges. Sea ice algae can relatively easily be quantified by bulk parameters like Chl a or particulate organic carbon. No such bulk variable is available for meiofauna. They are microscopically small, occur often in low abundances and their taxonomy is challenging. It requires therefore the sampling of many ice cores at the same site and skilled biologists to estimate their abundance and composition in the field, often entangled and hidden between hundreds of small ice algal cells and aggregates (Fig. 4.29a). We conducted several studies on meiofauna abundance in the nearshore Alaskan Arctic and contrasted those results with data from expeditions into the central Arctic Ocean (e.g. Gradinger et al. 2009). All these efforts combined with work from other colleagues led to the recent and first ever synopsis of meiofauna occurrences on a pan-Arctic scale (Bluhm et al. 2017). These studies demonstrated the complexity in the composition and seasonal changes of the ice meiofauna communities and provided new insights into their role in the food web dynamics. The following paragraphs highlight some of the challenges and advances made but also the many open questions still remaining in terms of basic biology and climate change challenges. One of the most basic questions addressed by field biologists is: Who lives where? To approach this question, sea ice biologists have to deal with methodological challenges, as melting of ice causes sudden changes in environmental properties that some taxa might not survive, or may cause shifts in their physiology (relevant for experimental work). Current standard approaches for sea ice meiofauna (Gradinger and Bluhm 2009) include melting of the ice in sea water to reduce salinity effects such as osmotic stress. As most sea ice meiofauna taxa are found in the bottom 10 cm of the sea ice, most of our studies focused on this small part of the ice column. This can underestimate the true meiofauna abundance, especially in summer in the central Arctic (Friedrich 1997), when meiofauna (and algae) are found throughout the entire ice thickness. Given the complexity of collecting ice, melting it in buffered sea water, concentrating the animals over a 20 μm sieve and counting them alive or fixed in a microscope, it does not really come as a surprise that the current inventory of species is far from complete and new additions have occurred and will occur in the future. The following short examples illustrate the exciting discoveries and ongoing research questions related to the existence of meiofauna in Arctic sea ice. The focus will be on studies in the nearshore Alaskan Arctic, where coastal fast ice occurs over shallow water depths of less than 20 m.

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