Late Winter Biogeochemical Conditions Under Sea Ice in the Canadian High Arctic

With the Arctic summer sea-ice extent in decline, questions are arising as to how changes in sea-ice dynamics might affect biogeochemical cycling and phenomena such as carbon dioxide (CO2) uptake and ocean acidification. Recent field research in these areas has concentrated on biogeochemical and CO2 measurements during spring, summer or autumn, but there are few data for the winter or winter–spring transition, particularly in the High Arctic. Here, we present carbon and nutrient data within and under sea ice measured during the Catlin Arctic Survey, over 40 days in March and April 2010, off Ellef Ringnes Island (78° 43.11′ N, 104° 47.44′ W) in the Canadian High Arctic. Results show relatively low surface water (1–10 m) nitrate (<1.3 µM) and total inorganic carbon concentrations (mean±SD=2015±5.83 µmol kg−1), total alkalinity (mean±SD=2134±11.09 µmol kg−1) and under-ice pCO2sw (mean±SD=286±17 µatm). These surprisingly low wintertime carbon and nutrient conditions suggest that the outer Canadian Arctic Archipelago region is nitrate-limited on account of sluggish mixing among the multi-year ice regions of the High Arctic, which could temper the potential of widespread under-ice and open-water phytoplankton blooms later in the season

Species sensitivity distributions for suspended clays, sediment burial and grain size change in the marine environment

Assessment of the environmental risk of discharges, containing both chemicals and suspended solids (e.g., drilling discharges to the marine environment), requires an evaluation of the effects of both toxic and nontoxic pollutants. To date, a structured evaluation scheme that can be used for prognostic risk assessments for nontoxic stress is lacking. In the present study we challenge this lack of information by the development of marine species sensitivity distributions (SSDs) for three nontoxic stressors: suspended clays, burial by sediment, and change in sediment grain size. Through a literature study, effect levels were obtained for suspended clays, as well as for burial of biota. Information on the species preference range for median grain size was used to assess the sensitivity of marine species to changes in grain size. The 50% hazardous concentrations (HC50) for suspended barite and bentonite based on 50% effect concentrations (EC50s) were 3,010 and 1,830 mg/L, respectively. For burial the 50% hazardous level (HL50) was 5.4 cm. For change in median grain size, two SSDs were constructed; one for reducing and one for increasing the median grain size. The HL50 for reducing the median grain size was 17.8 ¿m. For increasing the median grain size this value was 305 ¿m. The SSDs have been constructed by using information related to offshore oil- and gas-related activities. Nevertheless, the results of the present study may have broader implications. The hypothesis of the present study is that the SSD methodology developed for the evaluation of toxic stress can also be applied to evaluate nontoxic stressors, facilitating the incorporation of nontoxic stressors in prognostic risk assessment tools

Ecological Drivers of and Responses by Arctic Benthic Communities, with an Emphasis on Kongsfjorden, Svalbard

Knowledge on the causes and consequences that structure benthic communities is essential to understand and conserve Arctic ecosystems. This review aims to summarize the current knowledge on the effects of abiotic and biotic factors on species interactions and community traits, i.e. diversity, structure, and functioning of Arctic coastal hard- and soft-bottom habitats, with emphasis on Kongsfjorden (Svalbard). Current evidence indicates that descriptive and mensurative studies on the distribution of species prevail and few studies allow inferences on the underlying processes generating observed patterns. Furthermore, Arctic hard- and soft-bottom communities show some fundamental differences in their ecology. The recovery in hard-bottom communities from disturbance, for instance, takes exceptionally long (i.e. > decadal) due to slow growth and/or sporadic recruitment, while it is considerably shorter in soft-bottom communities. Also, Arctic hard-bottom communities display strong competitive hierarchies that appear negligible in communities populating sedimentary shores. This review concludes with a suggestion to shift the focus in Arctic benthos research from pattern to processes and the identification of major research gaps. These include (i) the apparent demarcation of studies being devoted to either rocky or to sedimentary shores, which hamper studies on habitat connectivity, (ii) the lack of studies addressing the effects of pathogens and diseases on community ecology, and (iii) the incomplete assessment of potentially significant drivers of community ecology, such as trophic interactions, recruitment success, and competition