RESPONSE OF DEEP-SEA BENTHIC FORAMINIFERA FROM THE MEDITERRANEAN SEA TO SIMULATED PHYTOPLANKTON PULSES UNDER LABORATORY CONDITIONS

Abstract

Food and oxygen concentrations have been identified as environmental constraints influencing the vertical distribution of benthic foraminifera. Field studies, however, have been largely inconclusive as to which degree each factor regulates the observed distribution pattern. For this reason, different experiments were performed to investigate the response of deep-sea benthic foraminifera to simulated phytodetritus pulses under laboratory conditions, where oxygen concentrations can be influenced separately. In the laboratory, deep-sea foraminifera developed a normal vertical distribution pattern, and the habitats of single species reflected the results obtained from field investigations. Therefore, conclusions from the data produced in the laboratory can be transferred to nature. A mainly epifaunal life style was shown for Adercotryma glomerata and Spiroplectinella earlandi, but also indicated for Uvigerina peregrina. Hippocrepina sp. was spread over the entire sediment column with a shallow infaunal maximum. Epistominella pusilla, Seabrookia earlandi and Alveolophragmium wiesneri showed an epifaunal to shallow infaunal distribution. Ceratobulimina arctica, Trochammina inflata and Melonis barleeanum preferred an infaunal habitat. No suspension feeders were observed in the experiments. The addition of algae as food material resulted in elevated population densities. Under the influence of high oxygen contents with no or only short-term fluctuations, no migration to the upper layers was recorded after the addition of food. However, more specimens were found in deeper layers, because more organic material was transported downward into the sediment after the food pulse. The experimental laboratory results support the theoretical scenarios outlined in the TROX-model.