Northern North Sea benthic Ostracoda: modern distribution and palaeoenvironmental significance

Abstract

The ostracod faunas of the northern North Sea exhibit a depth-related distribution that is controlled by substrate and hydrographic conditions. Four biofacies are defined on the basis of total (live + dead) counts. Sandy substrates shallower than 110 m are characterized by Robertsonites tuberculatus and Cytheropteron latissimum. These species are replaced by Acanthocythereis dunelmensis and Palmenella limicola on sandy muds in the Fladen Ground (110-150 m). Muellerina abyssicola dominates from 175-250 m in the Norwegian Channel, giving way to Krithe praetexta at greater depths on soft-bottom substrates. The results are compared with data from the Skagerrak and the western European shelf area. Temperature ranges for the commonest taxa show that North Sea faunas contain endemic western European species (temperature range on average 2-20 °C), some southern species (5-26 °C) and taxa that range to high latitudes (-2 to +14 °C). Southern species are confined to the southern and western margins of the North Sea due to low summer bottom temperatures (<6 °C) in the central North Sea and low winter bottom temperatures (<4 °C) in the shallow waters off Germany and Denmark. The applicability of species temperature ranges and of sublittoral faunal provinces in palaeoenvironmental studies in the eastern Atlantic is assessed.