CHARACTERIZATION OF SOFT-BOTTOM BENTHIC HABITATS OF THE ALAND ISLANDS, NORTHERN BALTIC SEA

Sediment surface and profile imaging (SPI) was used in combination wit h grab sampling of sediment (sediment type, organic content, benthic i nfauna) and hydrography (temperature, oxygen saturation of bottom wate r) to analyze and describe the soft-bottom benthic habitats of the Ala nd archipelago (60 degrees 00' to 60 degrees 30' N, 19 degrees 30' to 20 degrees 30' E) in the northern Baltic Sea. The SPI analysis covered 42 stations (5 to 263 m depth), from inner sheltered bays to open coa stal waters, with varying sediment types (soft mud with high organic c ontent to sandy substrates with low organic content; loss on ignition: 0.5 to 12.4%). Clustering of the sampled stations (sediment propertie s) yielded 3 distinct categories of sedimentary habitats: (1) inner ar chipelago areas and bays with high organic content of the sediment and reduced oxygen saturation in the bottom water, (2) archipelago waters with intermediate values of all analyzed parameters, and (3) open coa stal sediments with low organic content and high oxygen saturation (2 deep offshore stations formed an additional group based primarily on d epth). Visual analysis of the images provided information on several a dditional abiotic and biotic characteristics of the sediment, and sign ificant correlations were found mainly between oxygen saturation, orga nic content, sediment type, shear strength (penetration of gear), surf ace relief and the depth of the redox potential discontinuity layer in the sediment. The sediment properties were also reflected in the zoob enthos. The correlations between parameters measured are discussed in relation to applicability of the SPI method, monitoring demands, and b asic understanding of the sediment-animal relationships.