Effects of the coexisting Baltic amphipodsMonoporeia affinisandPontoporeia femorataon the fate of a simulated spring diatom bloom

• Published in: Marine ecology. Progress series (Halstenbek) 2001-03, Vol.212, p.107-115
• Main Authors: van de Bund, Wouter J., Ólafsson, Emil, Modig, Helene, Elmgren, Ragnar
• Format: Article
• Language: English
• Subjects: Algal blooms; Animals; Bunds; Diatoms; Microcosms; Mortality; Oxygen; Radioactive decay; Radiocarbon; Sediments
• ISSN: 0171-8630; 1616-1599

A laboratory experiment was performed to quantify the fate of diatom phytodetritus and how this is affected by the presence of benthic amphipods. A Baltic Sea spring bloom sedimentation event was simulated by adding14C-labeled diatoms (Skeletonema costatum) to microcosms with varying densities of the amphipodsMonoporeia affinisandPontoporeia femorata, as well as to microcosms without amphipods, where the sediment was disturbed mechanically. After 1 mo of incubation, 51 to 77% of the added diatom carbon was still in the sediment; 2 mo later 49 to 66% remained. The effect of amphipods on the fate of the phytodetritus differed between species. At near-field density,M. affinisincorporated 6 to 11% of the added14C,P. femorataonly 1.2%. The results indicate that burrowing slows mineralization, presumably by mixing organic material to anoxic depths in the sediment. The effect ofP. femorataon mineralization could not be distinguished from the effect of mechanical stirring.M. affinisfeeding and respiration resulted in a significant increase in mineralization; at low densities this compensated for the mixing effect, at high densitiesM. affinisfeeding resulted in enhanced net mineralization.