Ingo Schewe

Our ability to understand the complex interactions of biological, chemical, physical, and geological processes in the ocean and on land is still limited by the lack of integrative and interdisciplinary observation infrastructures. The main purpose of the planned open-ocean infrastructure FRAM (FRontiers in Arctic marine Monitoring) is permanent presence at sea, from surface to depth, for the provision of near real-time data on climate variability and ecosystem change in a marine Arctic system. The Alfred-Wegener-Institut - Helmholtz-Zentrum für Polar- und Meeresforschung (AWI), together with partner institutes in Germany and Europe, aims at providing such infrastructure for the polar ocean as a major contribution to the grand challenges of Earth observation and environmental status. The FRAM Ocean Observing System targets the gateway between the North Atlantic and the Central Arctic, representing a highly climate-sensitive and rapidly changing region of the Earth system. It will serve national and international tasks towards a better understanding of the effects of change in ocean circulation, water mass properties and sea-ice retreat on Arctic marine ecosystems and their main functions and services. FRAM will implement existing and nextgeneration sensors and observatory platforms, allowing synchronous observation of relevant ocean variables, as well as the study of physical, chemical and biological processes in the water column and at the seafloor. Experimental and event-triggered platforms will complement observational platforms. Products of the infrastructure are continuous long-term data with appropriate resolution in space and time, as well as ground-truthing information for ocean models and remote sensing. FRAM will integrate and develop already existing observatories, i.e. the oceanographic mooring array HAFOS (Hybrid Arctic/Antarctic Float Observing System) and the Long-Term Ecological Research (LTER) site HAUSGARTEN.

During an expedition to the deep-sea long-term observatory HAUSGARTEN in the eastern Fram Strait in summer 2003, the availability of a Remotely Operated Vehicle allowed a targeted sampling of surface sediments around a relatively large dropstone (0.9 m²) to determine suspected differences in community structure and dynamics of nematode assemblages in relation to the confined flow regime and patchy food availability in the immediate vicinity of the stone. The almost rectangular dropstone was about 150 cm in length, 60 cm in width, and up to 15 cm in height. Small-scale current measurements around the dropstone using a MAVS-3 acoustic current meter exhibited a rather complex pattern. A computational fluid dynamics simulation revealed areas of constantly flowing near-bottom currents as well as the generation of vortices in certain areas around the dropstone. Concentrations of biogenic compounds in the sediments surrounding the dropstone generally followed the complex flow pattern. The differences in physical and biochemical conditions around the dropstone were reflected in species composition and diversity, trophic structure and life-history traits of the nematode communities, and to a lesser extent in their total abundance and biomass.

Megafauna plays an important role in benthic ecosystems and contributes significantly to benthic biomass in the Arctic. The distribution is mostly studied using towed cameras. Here, we compare the megafauna from two sites located at different distances from the Kongsfjord: one station at the entrance to the fjord, another on the outer shelf. Although they are only located 25 km apart and at comparable depth, there were significant differences in their species composition. While the inshore station was characterized by shrimps (2.57±2.18 ind. m⁻²) and brittlestars (3.21± 3.21 ind. m⁻²), the offshore site harboured even higher brittlestar densities (15.23±9.32 ind. m⁻²) and high numbers of the sea urchin Strongylocentrotus pallidus (1.23±1.09 ind. m⁻²). Phytodetrital concentrations of the upper sediment centimetres were significantly higher inshore compared with offshore. At a smaller scale, there were also differences in the composition of different transect sections. Several taxa were characterized by a patchy distribution along transects. We conclude that these differences were caused primarily by habitat characteristics. The seafloor inshore was characterized by glacial soft sediments, whereas the station offshore harboured large quantities of stones. Although the use of a new web-2.0-based tool, BIIGLE (http://www.BIIGLE.de), allowed us to analyse more images (∼90) than could have been achieved by hand, taxon area curves indicated that the number of images analysed was not sufficient to capture the species inventory fully. New automated image analysis tools would enable a rapid analysis of larger quantities of camera footage.