A seafloor crater in the German Bight and its effects on the benthos

In 1963 a deep crater was formed about 65 m below sea level in the western part of the German Eight, due to a gas eruption caused by drilling carried out from the platform 'Mr. Louie'. The study area is situated in a sandy to muddy bottom area inhabited by an Amphiura filiformis association (sensu Salzwedel et al. 1985). The crater. sometimes called 'Figge-Maar'. functions as a sediment trap, concentrating particles and organisms from the water column, thus leading to extreme sedimentation rates of about 50 cm, on average, per year. Crater stations, compared with stations situated in the vicinity, show enrichments of juveniles. Echinoderms, especially the subsurface-dwelling heart urchin Echinoderms cordatum and ophiuroids are responsive to enrichment. Other species that are typical of the Amphiura filiformis association are shown to be unable to cope with the special conditions in the crater.