Investigations of benthic macrofauna, in particular from soft sediments, have a long tradition, with the first quantitative studies in Scandinavian waters performed over 100 years ago. Benthic macrofauna is important as food for demersal fish, the cycling of organic matter and also play a role in carbon sequestration, and not the least as an indicator of environmental quality. Benthic macrofauna is normally defined as organisms retained on 1 mm (European standard) or 0.5 mm sieves. It includes invertebrates over a wide size spectrum; from large crustaceans like Norway Lobster and large bivalves like the Ocean Quahog, to small worms like polychaetes and oligochaetes. Benthic macrofauna also forms a substantial part of marine biodiversity, with more than 500 species in the soft sediments of Kattegat and the Danish estuaries. The typical data format is species specific abundance (number of individuals per species) and biomass (wet weight or dry weight per species) information and the sampling area are either 1/70 m-2 (0,0143 cm2) or 1/10 m-2 (10.000 cm2)