Seasonal dynamics of sub-ice fauna below pack ice in the Arctic (Fram Strait) |
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| Institution: | 1. Antarctic Climate & Ecosystems Cooperative Research Centre, University of Tasmania, Hobart, Tasmania, Australia;2. Department of Oceanography, Dalhousie University, Halifax, Nova Scotia, Canada;1. Faculty of Biosciences and Aquaculture, Nord University, 8049 Bodø, Norway;2. Plymouth Marine Laboratory, Prospect Place, West Hoe, Plymouth PL13DH, UK;1. Laboratorio de Ecología, Comportamiento y Mamíferos Marinos, División Mastozoología, Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”, Av. Ángel Gallardo 470 (C1405DJR), Buenos Aires, Argentina;2. Museo Acatushún de Aves y Mamíferos Marinos Australes, Sarmiento 44 (9410), Ushuaia, Tierra del Fuego, Argentina;3. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina;4. Toxicología Ambiental, Instituto de Investigaciones Marinas y Costeras (IIMyC), Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, Funes 3350, (CP 7600) Mar del Plata, Argentina;5. Centro Austral de Investigaciones Científicas, Bernardo Houssay 200, (CP 9410), Ushuaia, Tierra del Fuego, Argentina;6. Laboratorio de Análisis por Activación Neutrónica, Centro Atómico Bariloche, Comisión Nacional de Energía Atómica, Av. E. Bustillo 9.500, (CP8400), Bariloche, Argentina;7. Centro de Estudios Biomédicos, Biotecnológicos, Ambientales y Diagnóstico (CEBBAD), Universidad Maimónides, Hidalgo 775 piso 7, (C1405BDB), Buenos Aires, Argentina;1. Norwegian Polar Institute, Fram Centre, N-9296 Tromsø, Norway;2. Department of Arctic and Marine Biology, University of Tromsø, N-9037 Tromsø, Norway;3. Institute of Oceanology, PAN, Powstancow Warszawy 55, Sopot 81-712, Poland;1. Institute of Oceanology, Polish Academy of Sciences, Powstańców Warszawy 55, 81–712 Sopot, Poland;2. Institute of Oceanography, University of Gdańsk, al. Marsza?ka J. Pi?sudskiego 46, 81-378 Gdynia, Poland |
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| Abstract: | Pronounced seasonality is a characteristic feature of polar ecosystems, but seasonal studies in the high-Arctic pack-ice zone are still scarce because of logistical constraints. During six expeditions (1994–2003) to the Fram Strait area between Greenland and Svalbard in winter, spring, early summer, late summer and autumn, the sub-ice habitat and fauna below the pack ice (0–1 m depth) were analyzed for seasonal patterns. Both environmental variables such as ice cover, temperature, salinity and chlorophyll a (chl a), as well as species composition, abundance and biomass of the sub-ice fauna showed distinct seasonal dynamics. Most species of the sub-ice fauna were found in early summer, followed by autumn, spring and late summer; the lowest number occurred in winter. The sub-ice fauna was dominated by copepod nauplii during all seasons. Next numerous was the small pelagic copepod Oithona similis, followed by occassional swarms of Pseudocalanus minutus and Calanus spp. Abundances of the sympagic fauna in the sub-ice water layer were much lower, with ectinosomatid copepods being usually the most numerous sympagic group. In the course of the year, total abundances of the sub-ice fauna showed a steep increase from the earliest sampling dates towards the end of winter/beginning of spring reaching maximum numbers then, and a decrease to minimum numbers in early summer. A second peak occurred in late summer, followed by a decrease towards autumn. This significant trend was due to the abundances of copepod nauplii and Oithona similis. Sympagic species were virtually absent during winter, and increased significantly in spring and early and late summer. A factor analysis revealed the variables ice cover and thickness, water temperature and salinity, as well as chl a as the major controlling factors for the seasonal patterns in different groups and species of the sub-ice fauna. Because of the special environmental conditions in the sub-ice habitat, and the unique species composition characterized by small taxa, young stages, and sympagic species, the seasonal dynamics of the Arctic sub-ice fauna differ substantially from those of the epipelagic zooplankton community in the Arctic Ocean. |
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