Fine-scale distribution of hydrolytic activity associated with foraminiferans and bacteria in deep-sea sediments of the Norwegian-Greenland Sea

Pronounced fine-scale gradients of enzymatic degradation of organic material were observed in the uppermost horizons of deep-sea sediments of the Norwegian-Greenland Sea. Since these gradients coincided with the occurrence of dense populations of epibenthic agglutinated foraminiferans, it was hypothesized that the foraminiferans were the main contributors to the large pool of hydrolytic enzymes observed. Parallel analyses of the enzymatic activity associated with individual foraminiferans selected from the sediments confirmed this hypothesis. Measurements of bacterial biomass (by epifluorescence microscopy) and production (incorporation of tritiated leucine) suggest that in the specific ecological situation analysed, bacteria benefit from the metabolism of foraminiferans rather than being the main decomposers. The immediate degradation at the sediment surface without incorporation of the sedimented particles into the sediment may have an impact on the early diagenesis of organic material and its sedimentary record in these deep-sea sediments