On sulphide and the distribution of Arenicola marina in a tidal mud flat in the Dutch Wadden Sea

Abstract

The concentrations of free sulphide in the upper 30 cm of the sediment of a tidal mud flat in the Dutch Wadden Sea were measured periodically during one and a half year. Also grain size composition and iron sulphide content were determined. In sandy sediments free sulphide values were as a rule below 5 mg S·l −1 pore water throughout the year; at stations with fine sediment much higher values were found. The depth to which Arenicola marina burrowed in the sandy sediments was 22 cm at maximum. Generally sulphide concentrations at this depth were below 0.1 mg S·l −1 but local contact of the animals to concentrations of 50 mg S·l −1 may occur. The density of the lugworms was found to be inversely related to the free sulphide concentration at the depth of the burrows. Whether the sulphide was responsible for this distribution or other parallel changes in sediment characteristics is not clear. Iron sulphide appeared to be of no importance for the distribution of Arenicola marina although the worms were often found in contact with concentrations as high as 450 mg S·l −1 sediment.