Food web studies based on stable C and N isotope ratios usually assume isotopic equilibrium between a consumer and its diet. In the Arctic, strong seasonality in food availability often leads to diet switching, resulting in a consumer's isotopic composition to be in flux between different food sources. Experimental work investigating the time course and dynamics of isotopic change in Arctic fauna has been lacking, although these data are crucial for accurate interpretation of food web relationships. We investigated seasonal (ice-covered spring vs. ice-free summer) and temperature (1 vs. 4 degrees C) effects on growth and stable C and N isotopic change in the common nearshore Arctic amphipod Onisimus litoralis following a diet switch and while fasting in the laboratory. In spring we found no significant temperature effect on N turnover [half-life (HL) estimates: HL-N = 20.4 at 4 degrees C, 22.4 days at 1 degrees C] and a nonsignificant trend for faster growth and C turnover at the higher temperature (HL-C = 13.9 at 4 degrees C, 18.7 days at 1 degrees C). A strong seasonal effect was found, with significantly slower growth and C and N turnover in the ice-free summer period (HL-N = 115.5 days, HL-C = 77.0 days). Contrary to previous studies, metabolic processes rather than growth accounted for most of the change in C and N isotopic composition (84-89 and 67-77%, respectively). This study provides the first isotopic change and metabolic turnover rates for an Arctic marine invertebrate and demonstrates the risk of generalizing turnover rates based on taxon, physiology, and environment. Our results highlight the importance of experimental work to determine turnover rates for species of interest.

(2014) A framework and database for community sea ice observations in a changing Arctic: an Alaskan prototype for multiple users, Polar Geography, 37:1, 5-27To link to this article: http://dx

) under both clean and sediment-laden ice. With increasing ice algal biomass, the δ 13 C ratio of sea ice particulate organic matter (POM) in clean ice increased from -25 ‰ in February to -16 ‰ in May, while no and little enrichment was observed in sediment-laden ice and pelagic POM, respectively. The abundance of ice metazoans in clean ice increased with progressing season from 17 700 (Feb) to 276 200 ind. m -2 (May), dominated by nematodes and ice-associated polychaete juveniles. In sediment-laden ice, maximum abundance was 16 600 ind. m -2 (May). Abundances of meroplanktic polychaete juveniles were at least one order of magnitude below abundances in the ice, suggesting sea ice is an important feeding habitat for these young life stages. Sediment within the ice had a profound impact on sea ice biota, and delayed or inhibited the spring bloom development.KEY WORDS: Arctic sea ice · Sea ice sediments · Ice algae · Ice fauna · Particulate organic carbon · POC · Particulate organic nitrogen · PON · Stable isotope ratio Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 394: [49][50][51][52][53][54][55][56][57][58][59][60][61][62][63] 2009 The dominance of the light regime in regulating primary production in sea ice is well documented from field and laboratory experiments (e.g. Gradinger et al. 1991, Arrigo 2003, Gradinger 2009). For ice algal growth, major abiotic modifiers of available light are seasonality, ice thickness and snow cover (Maykut 1985). Only recently has sediment, incorporated within the ice, been studied with regard to its ability to modify the albedo and attenuation properties of sea ice (Light et al. 1998). Sediment occurs in concentrations above 100 g m -2 in Arctic sea ice (e.g. Nürnberg et al. 1994), and such sediment-rich patches are particularly common in the Chukchi and Beaufort Seas (Barnes et al. 1982, Osterkamp & Gosink 1984, Eicken et al. 2005, forming so-called 'dirty ice' or 'sediment-laden ice'. Up to 50% of the entire Arctic ice cover can contain visually detectable amounts of sediment (Pfirman et al. 1989, Reimnitz et al. 1993, Nürnberg et al. 1994, which is transported across the offshore Arctic with the ice drift.Sea ice sediments located in the top 20 to 30 cm of the ice alter the spectral albedo, whereas total sediment load affects light transmission (Light et al. 1998). Osterkamp and Gosink (1984) observed, for example, about 10-fold higher attenuation coefficients for sediment-laden fast ice compared to clean ice. Previous studies have demonstrated that modulation of light by snow cover is a major factor responsible for horizontal patchiness in sea ice physical and biological variables (e.g. Gosselin et al. 1986, Grossi et al. 1987, Steffens et al. 2006. In this study, we hypothesized that sea ice sediment load should also have a pronounced effect on the seasonal development of sea ice biota due to its alteration of the light regime. We expected significantly higher maximum biomass values for ice algae and higher sea ice meiof...

The motivation for this report was a request from the Nuclear Regulatory Commission (NRC) for NBS to analyze the hardware, software, and file structure that would be required to automate selected types of data for a specific application. This problem was analyzed at the NBS, in the context of the constraint that the recommended hardware and software would have to be compatible with that in use at the NRC.Using primarily vendor literature and the experience of NBS workers, several commercially available database management systems (DBMSs) were examined. The DBMS that was found to be most suitable in relation to the requirements was tested to verify its adequacy. This report identifies various hardware and DBMSs by trade names, as necessary to provide a descriptive characterization of their features and to answer a specific request on costs of the recommended hardware and software. Neither the recommendations nor the inclusion of any item of hardware or software in this report implies a recommendation or endorsement by the National Bureau of Standards for applications other that for which this study was undertaken. Further, the vendors were not asked to verify information for accuracy and clarity, and the recommendations are based on the technical judgement of the authors.Due to the changing nature of the systems features and the user application environment, the information presented is current only to January 1986. DISTRIBUTIONThis document has been prepared for the use of the Nuclear Regulatory Commission. Responsibility for its further use rests with that agency. NBS requests that if release to the public is contemplated, such action be taken only after consultation with the Technical Information

<p>Arctic coastal sea-ice environments are undergoing some of the most rapid changes anywhere in the Arctic, with implications for coastal communities’ food security and infrastructure, marine ecosystems, and permafrost. We argue that responses to such rapid change are most effective when informed by Indigenous and local knowledge and local observations to provide understanding of relevant processes, their impacts, and potential adaptation options. Community-based observations in particular can help create an interface across which different forms of knowledge, scientific research, and formal and informal education can co-develop meaningful responses. Through a broader literature review and a series of workshops, we have identified principles that can aid in this process, which include matching observing program and community priorities, creating sufficient organizational support structures, and ensuring sustained community members’ commitment. Drawing on a set of interconnected examples from Arctic Alaska focused on changing sea-ice environments and their impacts on coastal communities, we illustrate how these approaches can be implemented to provide knowledge sharing resources and tools. Specifically, in the context of the Alaska Arctic Observatory and Knowledge Hub (A-OK), a group of Iñupiat ice and coastal marine ecosystem experts is working with sea-ice geophysicists, marine biologists, and others to track changes in coastal environments as well as the services that the ice cover provides to coastal communities. The co-development of an observing framework and a web-based searchable database of observations has provided an interface for exchange and an education resource. An annual survey of hunting trails across the shorefast ice cover in the community of Utqiaġvik serves to further illustrate how different, response-focused activities such as the tracking of ice hazards – increasingly a concern with loss of ice stability and shortening of the ice season – can be embedded within a community-based monitoring framework.</p>