Description: In this paper, we present two innovative optical systems dedicated to deep sea observation. The instrumentation and associated methodology are developed in the context of European project EXOCET/D (FP6-GOCE-CT-2003-505342, http://w3.ifremer.fr/exocetd) [SAR04]. The general objective of the project focuses on the design, the implementation and the test of specific instruments to explore, study and quantify biodiversity in the deep sea. The relationship between habitats and environmental dynamics is also an important issue of the project. The presented development takes benefit of work carried out at Ifremer for several years in the field of underwater imaging and measurement [CAD04].One specific target is to set up a complete methodology to make a 3D reconstruction of small scale scenes using stereovision techniques. To meet this scientific requirement, a new system, called IRIS (Invariant 3D Reconstruction by Instrumented Stereovision), has been specified and is under development. It includes the design of a stereovision head and the associated methods for data processing.For an operational use in an underwater environment, the stereovision head will be operated by Ifremers deep scientific Remotely Operated Vehicle victor 6000. The ROV is landed on the seafloor to keep a fixed and stable attitude, a small region of interest (around 1m3) is investigated by the stereovision rig mounted at the tip of victor 6000s instrumented robotic arm MAESTRO.

Description: The deep sea represents the largest ecosystem on earth. Due to its enormous dimensions and inaccessibility, the deep-sea realm is the worlds least known habitat. To understand ecological ties, the assessment of temporal variabilities is essential. Only long-term investigations at selected sites, describing seasonal and interannual variations, can help to identify changes in environmental settings determining the structure, the complexity, and the development of deep-sea communities. The opportunity to measure processes at sufficient time scales will also help to differentiate between natural variabilities and environmental changes due to anthropogenic impacts.High latitudes are amongst the most sensitive environments in respect to climate change, a fact urgently demanding the assessment of time-series in Polar Regions. The deep-sea long-term station Hausgarten of the Alfred Wegener Institute for Polar and Marine Research, Germany, was established in summer 1999 in the eastern Fram Strait off Spitsbergen. Beside a central experimental area at 2500 m water depth, we defined 9 stations along a depth transect between 1000-5500 m, and additional 6 stations along a latitudinal transect crossing the central Hausgarten station, which will be revisited yearly to analyse seasonal and interannual variations in biological, geochemical and sedimentological parameters.Moorings carrying current meters and sedimentation traps are used to assess hydrographic conditions in the area and to characterise and quantify organic matter fluxes to the seafloor. The exchange of solutes between the sediments and the overlaying waters are studied to investigate major processes at the sediment-water-interface. Vertical gradients of nutrients, organic carbon contents, C/N ratios, porosity and other geochemical parameters are determined to characterize the geochemical milieu of the upper sediment layers. Biogenic sediment compounds are analysed to estimate activities and total biomass of the smallest sediment-inhabiting organisms. The quantification of benthic organisms from bacteria to megafauna is a major goal in biological investigations.

Description: The deep sea is the largest and yet least explored ecosystem on Earth. Even less is known about the more remote deep-sea beyond the polar circle. Until recently, deep-sea research has predominantly encompassed single sampling campaigns or measurements. Such data, however, represent only snap shots in time and space so that ecological conclusions are of restricted applicability. Long-term studies offer the opportunity to identify environmental settings determining the structure, complexity and the development of deep-sea communities.Following a pre-site study using the French Remotely Operated Vehicle "VICTOR 6000" in summer 1999, we established the first long-term station in polar deep-sea regions in the western Fram Strait off Spitsbergen. The AWI-Hausgarten consists of nine stations along a depth gradient from 1000 to 5500m and a latitudinal transect of seven stations starting in the north at the margin of the sea ice. There is also an experimental area at the central station (2500m) for long-term experiments to study the effect of different substrates, nutrient enrichment and predator exclusion on benthic activity and diversity. Here, we present the methods used during our annual visits to study seasonal and interannual variations in biological, geochemical and sedimentological parameters.

Description: Fishers have often complained that standard United Kingdom groundfish survey data do notadequately reflect the grounds targeted by commercial fishers, and hence, scientists tend to make overcautiousestimates of fish abundance. Such criticisms are of particular importance if we are to make acreditable attempt to classify potential essential fish habitat (EFH) using existing data from groundfishsurveys. Nevertheless, these data sets provide a powerful tool to examine temporal abundance of fishon a large spatial scale. Here, we report a questionnaire-type survey of fishers (20012002) that invitedthem to plot the location of grounds of key importance in the Irish Sea and to comment on key habitatfeatures that might constitute EFH for Atlantic cod Gadus morhua, haddock Melanogrammus aeglefinus,and European whiting Merlangius merlangus. Plotted grounds were cross-checked using records ofvessel sightings by fishery protection aircraft (19851999). A comparison of the areas of seabedhighlighted by fishers and the observations made on groundfish surveys were broadly compatible forall three species of gadoids examined. Both methods indicated important grounds for cod and Europeanwhiting off northern Wales, the Ribble estuary, Solway Firth, north of Dublin, and Belfast Lough. Themajority of vessel sightings by aircraft did not match the areas plotted by fishers. However, fishingrestrictions, adverse weather conditions, and seasonal variation of fish stocks may have forced fishersto operate outside their favored areas on the (few) occasions that they had been recorded by aircraft.Fishers provided biological observations that were consistent among several independent sources (e.g.,the occurrence of haddock over brittle star [ophiuroid] beds). We conclude that fishers knowledge isa useful supplement to existing data sets that can better focus more detailed EFH studies.

Description: Patches of a very dense tube mat biotope were found during fish habitat studies in the eastern English Channel. At three locations in the lows between linear sand banks off the French coast an un-described small Chaetopterus sp. occurred with small Lanice conchilega as an enriched sediment stabilizing biotope. This biotope was distinct though having similarities to other tide swept sub-tidal biotopes dominated by L. conchilega. Using cameras and side-scan sonar it was seen to overlay heterogeneous cobbles and shell hash with intermittent rippled sand veneer. The patchiness of this enriching biogenic feature contributed to the variability in trawl catches of fish.

Description: In 1999, the AWI deep-sea research group established the first and only long-term deep-sea observatory beyond the polar circle, the AWI-Hausgarten (Fram Strait, west off Svalbard). It consists of nine regularly sampled stations along a depth gradient from 1200 to 5500m, a latitudinal transect and an experimental area at the centre for long-term experiments. Footage from underwater camera transects has shown that demersal fish which belong largely to the eelpout family constitute an important fraction of the benthic megafauna. Despite their numerical abundance little is known to date about their biology and functional ecological role. First evidence suggests that the abundance of fish decreases with increasing depth while the mean size of fish increases. Samples taken by trawls and baited traps at two stations complement camera observations and facilitated a direct identification of the species present: Lycodes squamiventer dominated at the shallow station (1200m) while Lycodonus flagellicauda, Gaidropsaris argentatus and the ray Raja hyperborea occurred in low numbers. The larger-sized congeneric Lycodes frigidus was most abundant at the central station (2400m), with a few individuals of the rare species Lycenchelys platyrhina. The biology and functional ecological role of these fishes is discussed with particular emphasis on their trophic status.