Soft bottom macrobenthos in a Baltic archipelago: Spatial variation and optimal sampling strategy

Macrozoobenthos was surveyed in August 1982 close to Tvärminne Zoological Station on the SW coast of Finland. In a stratified random design 117 core samples were taken from 41 stations at a depth of 15 m to 47 m. Abundance was high (mean at 9 200 ind /m2) and biomass was low (mean at 69.1 g/m2). While the single remote corer used has a high sampling efficiency, the high abundance may indicate a community change in the Baltic Sea during the last 50 years or it may be related to the maximum abundances in the 6—7 year population fluctuation pattern. The depth gradient was the most important environmental variable affecting the faunal composition at the stations and within the geographical strata. In an optimal sampling design in the study area, the stations should be randomly distributed within strata defined by depth. Only one sample unit at each station is recommended, whereas the number of stations should be high, especially in shallow (< 20 m) areas.