Spatial and temporal variability of chlorophyll-a and particulate organic matter in the sediments and the water column of Potter Cove (Antarctica)

ADRIÁN GONZALO ATENCIO, MARÍA LILA BERTOLIN, LORENA LONGHI, GUSTAVO ADOLFO FERREYRA, MARTHA ELBA FERRARIO & IRENE RUTH SCHLOSS

Berichte zur Polar und Meeresforschung - Reports on Polar and Marine Research

Alfred-Wegener-Institut

Año: 2008 p. 154 - 161

1618-3193

Sunlight fuels marine primary production. Light reaching the seafloor sustains benthic primary production that contributes to the total primary production of coastal ecosystems and consequently to the organic matter availability for the consumers in the system. Benthic diatoms can retain photosynthetic capacity in the dark and even inside sediments, thus potentially forming an important pool of primary producers, which can resume photosynthesis if exposed to light again. Several authors showed that total phytoplankton biomass in the South Shetlands is very low. This is also the case in Potter Cove, where the combination of mixing processes and low water transparency due to the input of suspended particulate matter from freshwater runoff could be responsible for the low phytoplankton biomass. The pulses of organic matter derived fromphytoplankton production in the water column have long been considered to be one of the main sources of particulate organic matter (POM) for zoobenthos nourishment. Benthic consumers are usuallydependent on productivity in the water column. Phytoplankton, and especially diatoms,constitute an important food source for benthic organisms such as suspension and deposit feeders. However, the low phytoplankton production found in Potter Cove would not be sufficient to fulfil the nutritional requirements of the high densities of benthic filter feeders. We therefore hypothesize that microphytobenthos biomass represents a significant fraction of the POM pool in this environment, contributing to satisfy benthic suspension and deposit feeders energy needs. The aim of this paper was to investigate the temporal and spatial variability of chlorophyll-a (Chl-a) and organic matter in surface sediments of Potter Cove (Antarctica) in a year-round study. To address the importance of water columnderived material for the sedimentary organic matter pool, we also analysed the seasonal variation of pelagic total particulate matter (TPM), suspended POM, Chl-a, as well as light penetration in the water column. Fluctuations of wind speed and direction were registered and analysed throughout the year in order to understand their influence on the dynamics of these parameters.