Foraminiferal species responses to in situ, experimentally induced anoxia in the Adriatic Sea

[摘要] Anoxia was successfully induced in four benthic chambers installed at 24 mdepth in the northern Adriatic Sea for periods varying from 9 days to 10months. During the 10-month period, species richness significantly decreased.Although no significant change in Shannon diversity and evenness wasobserved, the composition of the foraminiferal assemblages changed with time.This change is due to interspecific differences in tolerance to anoxia.Reophax nanus, Textularia agglutinans andQuinqueloculina stelligera all showed a significantdecrease with time, strongly suggesting they are sensitive to anoxia.Conversely, Eggerella scabra, Bulimina marginata,Lagenammina atlantica, Hopkinsina pacifica andBolivina pseudoplicata appeared to be resistant to the experimentalconditions. Quinqueloculina seminula was apparently sensitive toanoxia but showed a clear standing stock increase during the first month ofthe experiment, which we interpret as an opportunistic response to increasingorganic matter availability due to the degradation of the dead macrofaunalorganisms. None of the anoxia-sensitive species is able to accumulateintracellular nitrates. Nitrate accumulation could be shown for some testedspecimens of the dominant anoxia-tolerant species E. scabra andB. marginata. However, tests on the denitrification capacity ofthese taxa yielded negative results, suggesting that their resistance tolong-term anoxia is not due to their ability to denitrify.

[学科分类] 地球化学与岩石