NATURAL AND ANTHROPOGENIC INFLUENCE ON THE DISTRIBUTION OF SALT MARSH FORAMINIFERA IN THE BAY OF TÜMLAU, GERMAN NORTH SEA

Abstract

We studied the distribution and ecology of modern foraminifera in a salt marsh in the Bay of Tumlau, Eiderstedt peninsula at the German North Sea coast; this marsh is influenced by human activities. To encompass the full range of environments, we sampled natural and grazed salt marshes, and adjacent tidal flats for foraminiferal and environmental parameters, including salinity, pH, grain size, and elevation relative to the tidal frame. Agglutinated taxa Jadammina macrescens , Trochammina inflata , and Miliammina fusca , and the miliolid Quinqueloculina sp. dominate the vegetated salt marshes, however their distribution patterns lack a clear separation between low, middle and high marsh faunas. Tidal flats, tidal channels, marsh ponds and drainage ditches are characterized by hyaline species, among which Elphidium williamsoni is dominant in ponds, while Elphidium excavatum, Haynesina germanica , and Ammonia batava dominate tidal flats and ditches. The different marsh species occupy specific niches linked to ecosystem stability and the combined influence of submergence frequency, substrate (i.e., grain size), pH, and likely food sources. The observed lack of salt marsh foraminiferal subzones and the small-scale spatial variability of species distributions reflect the various impacts of diking, ditching, sheep grazing and sediment compaction on the morphology, hydrology and vegetation in the studied salt marsh. The faunas lack a consistent relation to elevation above sea-level, restricting the applicability of foraminiferal reference data sets from human-interfered salt marshes for past sea-level reconstructions.