Microphytobenthic biomass along gradients of physical conditions in Arctic Kongsfjorden, Svalbard

Abstract

In contrast to numerous studies on the biomass of marine microphytobenthos from temperate coastal ecosystems, little is known from polar regions. Therefore, microphytobenthos biomass was measured at several coastal sites in Arctic Kongsfjorden (Spitsbergen) during the polar summer (June-August 2006). On sandy sediments, chla varied between 8 and 200 mg m -2 and was related to water depth, current/wave exposure and geographical location. Biomass was rather independent of abiotic parameters such as sediment properties, salinity, temperature or light availability. At three stations, sediments at water depths of 3-4, 10, 15, 20 and 30 m were investigated to evaluate the effect of light availability on microalgae. Significant differences in distribution patterns of biomass in relation to deeper waters )10 m were found. The productive periods were not as distinct as phytoplankton blooms. Only at 3-4 m water depth at all three stations were two-to threefold increases of biomass measured during the investigation period. Hydrodynamic conditions seemed to be the driving force for differences in sediment colonisation by benthic microalgae. In spite of the extreme Arctic environmental conditions for algal growth, microphytobenthos biomass was comparable to marine temperate waters.

Microphytobenthos of Arctic Kongsfjorden (Svalbard, Norway): biomass and potential primary production along the shore line

“…A halogen lamp (fibre optics of Leica MZ 6 binocular) was used as the light source. Studies of Glud et al (2002), Leu (2006) and Woelfel et al (2009a) as well as our values (Table 1) reported an average photon fluence density (PFD) of PAR of about 100 lmol photons m -2 s -1 at 5 m water depth in Kongsfjorden. Since most samples were taken at approximately 5 m water depth, our samples were equally irradiated with ca.…”

“…Decreasing in water transparency was observed in early June. In July, small changes in the vertical attenuation coefficients and PAR data (0.2-0.3; (Woelfel et al 2009a). Thus, light availability was rather similar at all sites down to 5 m water depth throughout the study period, except in the near vicinity of glaciers, where more turbid water was observed but not analysed.…”

“…W3, W4, NW5) were dominated by rocky substrates and thus not easy to sample, at these stations sandy areas (sediment traps) were chosen. All stations were sampled once and a detailed description of geographical locations (longitude, latitude) is given in Woelfel et al (2009a). In addition, at two stations (Brandal (BRL) and London (LON)) further sediment samples were taken in transect order at water depths of 5, 10, 15, 20 and 30 m (BRL at 26th and 28th July and LON at 3th and 8th August 2007).…”

“…1). Both stations are representative of Kongfjorden's rare sandy areas and were chosen because of their good accessibility for diving as well as for comparison to a former study of Woelfel et al (2009a). Due to high patchiness of microphytobenthic biomass, three replicate cores were taken from each sampling location (sampled from within a 1 m 2 area).…”

“…Bottom substrata from echo sounding Sediment grain sizes at BRL and LON were only determined in 2006 (Woelfel et al 2009a). However, for comparison in the present study water content was measured as weight loss after drying pre-weighed sediment samples for 24 h at 105°C in an oven.…”