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The MAREANO (Marine AREA database for NOrwegian coast and sea areas) mapping programme includes acquisition of multibeam bathymetry and backscatter data together with a comprehensive, integrated biological and geological sampling programme. Equipment used includes underwater video, box corer, grab, epibenthic sled and beam trawl. Habitat maps are produced by combining information on landscapes, landscape elements, sediment types and biological communities. Video observations provide information about the megafauna diversity of large ([1 cm) epifauna and bottom types, whilst bottom samples describe the composition of epifauna, hyperfauna (crustaceans living in the upper part of the sediment and/or swimming just above the substratum) and infauna, and sediment composition. In this study, two biological data sets are used to study fauna response to environmental heterogeneity at two different spatial scales: (1) broad scale, megahabitat (1-10s km), based on information about megafauna taxa observed during video surveys in the Nordland/ Troms area, (2) fine scale, mesohabitat (10s m-1 km), based on information about species composition documented with video records and bottom sampling gear from the bank ''Tromsøflaket''. In general, the highest diversity is found on bottoms with mixed substrates indicating that substratum heterogeneity is very important for the biodiversity at both scales. The number of taxa shows a maximum at depths between 200 and 700 m followed by a gradual decrease down to 2,200 m. At the broad scale, multibeam data provides a variety of terrain variables that indicate environmental variation (e.g. exposure to currents, interpreted substrates). This analysis identifies six fauna groups associated to specific landscape elements. Diversity of megafauna shows a strong correlation with number of bottom types occurring along video transects. It is highest at the shelf break and decreased with depth on the slope in parallel with a decrease in habitat heterogeneity and temperature. At a fine scale, six biotopes are identified based on megafauna composition with habitat characteristics ranging from homogenous muddy bottom, biotope 1, to the most heterogeneous bottom with [20% rocks and several bottom types present in biotope 6. The macrofauna 123Hydrobiologia ( ) 685:191-219 DOI 10.1007 sampled is used for description of the whole benthic community, including diversity, biomass and production, related to these six biotopes. The variation in percentage cover of substrate types and in particular the cover of hard substrates demonstrate to be a good proxy for the benthic community composition (megaand macrofauna) and its diversity.

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A large and diverse dataset has been compiled and analysed in the Barents Sea and Finnmark fjords in northern Norway in order to map and characterise pockmarks. The main data sources are regional side-scan sonar and deep-towed boomer lines and extensive bathymetric datasets of multibeam echo sounding. Small to medium-sized pockmark fields occur in several basins west of Nordkappbanken. The most extensive is in Ingøydjupet, where the largest pockmarks are nearly 100 m wide and up to 8 m deep. Small to medium-sized pockmarks are, however, more common (20-50 m wide, 2-5 m deep). The pockmark density is typically 150-200 per km 2 . North of the Finnmark coast, from Magerøya/Nordkapp to the Russian border, pockmark distribution is nearly continuous. The density varies mainly between 300 and 600 per km 2 , and most pockmarks are small (15-40 m wide, 1.5-4 m deep). Recent studies suggest that the pockmarks in the southwestern Barents Sea were formed from seabed expulsion of gas due to dissociation of gas hydrates during the last deglaciation. Locally, gas has been observed to leak from the Barents Sea floor, but not from pockmarks, suggesting recent inactivity. We further explore the possibility that the pockmarks were formed during a short-lived event and that their shapes have been preserved due to low sedimentation rates and turbulent ocean currents. Numerous small pockmarks also occur in four studied Finnmark fjords. They are most common in Varangerfjorden and Porsangerfjorden where non-gas generating Proterozoic rocks subcrop. The origin of these pockmarks is most likely related to groundwater seepage.

Maps of surficial sediment distribution and benthic habitats or biotopes provide invaluable information for ocean management and are at the core of many seabed mapping initiatives, including Norway's national offshore mapping programme MAREANO (www.mareano.no). Access to high-quality multibeam echosounder data (bathymetry and backscatter) has been central to many of MAREANO's mapping activities, but in order to maximize the cost-effectiveness of future mapping and ensure timely delivery of scientific information, seabed mappers worldwide may increasingly need to look to existing bathymetry data as a basis for thematic maps. This study examines the potential of compiled single-beam bathymetry data for sediment and biotope mapping. We simulate a mapping scenario where full coverage multibeam data are not available, but where existing bathymetry datasets are supplemented by limited multibeam data to provide the basis for thematic map interpretation and modelling. Encouraging results of sediment interpretation from the compiled bathymetry dataset suggest that production of sediment grain size distribution maps is feasible at a 1:250 000 scale or coarser, depending on the quality of available data. Biotope modelling made use of full-coverage predictor variables based on (i) multibeam data, and (ii) compiled single-beam data supplemented by limited multibeam data. Using the same response variable (biotope point observations obtained from video data), the performance of the respective models could be assessed. Biotope distribution maps based on the two datasets are visually similar, and performance statistics also indicate there is little difference between the models, providing a comparable level of information for regional management purposes. However, whilst our results suggest that using compiled bathymetry data with limited multibeam is viable as a basis for regional sediment and biotope mapping, it is not a substitute. Backscatter data and the better feature resolution provided by multibeam data remain of great value for these and other purposes.