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.

Algal pigments in Southern Ocean abyssal foraminiferans indicate pelagobenthic coupling

“…Niche separation between different surface-sediment feeding foraminiferans is demonstrated by the composition of algal pigments in the cytoplasm, confirming previous experimental results (Heinz et al, 2001;Nomaki et al, 2005Nomaki et al, , 2009Witte et al, 2003). The high ratios of chlorophyll a and Pheo a pigments in Miliolinella 1 and Miliolinella 2 shows that they were feeding on fresh phytodetritus.…”

“…But it has also been shown that many deep-sea foraminiferans are associated with phytodetrital aggregates (Cornelius and Gooday, 2004) and can give a fast response to pulses of phytodetritus (Gooday, 1988(Gooday, , 2002. The response of foraminiferans to phytodetritus exposure has been extensively documented both in situ and experimentally (Enge et al, 2011;Heinz et al, 2001;Nomaki et al, 2005Nomaki et al, , 2009Witte et al, 2003). Indirectly, the distribution of benthic foraminiferal faunas, e.g., dominated by Epistominella exigua (Brady, 1884) in various Southern Ocean environments are a reflection of the importance of phytodetritus pulses (Mackensen et al, 1993(Mackensen et al, , 1995.…”

Response of the benthic foraminiferal community to a simulated short-term phytodetritus pulse in the abyssal North Pacific

“…The agglutinated species Adercotryma glomerata also demonstrated algal uptake. This species prefers the epifaunal habitat (Gooday 1993, Heinz et al 2001, 2002, occurring in high abundances when phytodetritus is present (Thiel et al 1988) and showing elevated growth and reproduction (Gooday & Hughes 2002). Cribrostomoides subglobosum showed elevated feeding rates in our experiment and may be an important species for the cycling of organic matter in the deep-sea.…”

Technical Note: Determination of the metabolically active fraction of benthic foraminifera by means of Fluorescent In Situ Hybridization (FISH)

“…Cultures were fed, every two weeks, with a mixture of algae (Dunaliella parva, Chlorella sp. and Isochrysis sp., Heinz, 2001;Heinz et al, 2001). Prior to injection in the cultures, the algae were treated in an ultrasound bath.…”