Role of microphytobenthos and denitrification for nutrient turnover in embayments with floating macroalgal mats: a spring situation

Aquatic Microbial Ecology

Kristina Sundbäck¹  Alison Miles¹ 

DOI  :  10.3354/ame030091

学科分类：生物科学（综合）

来源: Inter-Research

【 摘 要 】

ABSTRACT: The importance of the microphytobenthos (MPB) for nutrient turnover was studied in 2 shallow bays on the west coast of Sweden, during the period that floating green macroalgal mats generally become established in the area. Sediment-waternutrient fluxes (N, P and Si) and oxygen fluxes and denitrification were measured in light and dark laboratory incubations prior to and during the early growth of green-algal mats (April to June). The importance of microphytobenthic activity and hence,trophic status of the sediment system, magnitude of sediment fluxes and presence of macroalgal mats were shown to differ between the 2 bays. On a daily basis, the MPB decreased the efflux of inorganic N by 30 to 100%, P by 70 to 100% and Si by 10 to 95%.Thus, the MPB appears to efficiently control the availability of sediment-derived nutrients to ephemeral green algae during the period that is critical for the onset of the macroalgal growth. The MPB may even depress the development of green-algal mats,providing that these depend on the sediment nutrient efflux. Microphytobenthic N assimilation was compared with other N-consuming processes, such as denitrification and green-macroalgal N-assimilation. In autotrophic sediments, the MPB was the dominatingN-consuming component (1 to 5.3 mmolN m^-2 d^-1), denitrification (0.1 to 0.7 mmolN m^-2 d^-1) being a minor N-sink. In the net heterotrophic sediments, however (with no or little net MPB productivity, higherinfaunal biomass and hence larger nutrient effluxes), green macroalgal growth was the main N-incorporating process (mean 2.3 mmolN m^-2 d^-1). This was followed by denitrification (0.3 to 1.4 mmolN m^-2 d^-1), whichremoved roughly 20% of the remineralised N. Thus, denitrification may be a significant N-sink in bays harbouring green-algal mats on the west coast of Sweden.

【 授权许可】

Unknown