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Abstract

The Antarctic Peninsula experiences a fast retreat of glaciers, which
results in an increased release of particles and sedimentation and,
thus, a decrease in the available photosynthetic active radiation (PAR,
400-700 nm) for benthic primary production. In this study, we
investigated how changes in the general sedimentation and shading
patterns affect the primary production by benthic microalgae, the
microphytobenthos. In order to determine potential net primary
production and respiration of the microphytobenthic community, sediment
cores from locations exposed to different sedimentation rates and
shading were exposed to PAR of 0-70 mu.mol photons m(-2)s(-1). Total
oxygen exchange rates and microphytobenthic diatom community structure,
density, and biomass were determined. Our study revealed that while the
microphytobenthic diatom density and composition remained similar, the
net primary production of the microphytobenthos decreased with
increasing sedimentation and shading. By comparing our experimental
results with in situ measured PAR intensities, we furthermore identified
microphytobenthic primary production as an important carbon source
within Potter Cove's benthic ecosystem. We propose that the
microphytobenthic contribution to the total primary production may drop
drastically due to Antarctic glacial retreat and related sedimentation
and shading, with yet unknown consequences for the benthic heterotrophic
community, its structure, and diversity.