Do benthic meiofaunal and macrofaunal communities respond to seasonality in pelagial processes in an Arctic fjord (Kongsfjorden, Spitsbergen)?

Abstract

This study explores whether the marked seasonality in pelagic productivity and phytodetritus fluxes to the sea bottom in an Arctic fjord is reflected in variability of benthic communities in terms of taxonomic composition and standing stocks. Three stations located along the Kongsfjorden (west Spitsbergen) axis were visited in four seasons (May, August, October and January), and meiofauna and macrofauna was sampled. The elusive seasonal variability in benthic attributes contrasted with the clear seasonal effects in organic matter productivity and vertical fluxes (with diatom bloom-related peak in spring). No consistent differences in meiofaunal and macrofaunal density, diversity or composition among the four seasons were detected by PERMANOVA tests. Possible responses to spring food supply in meiofaunal reproduction timing were demonstrated in variability in individual size of Nematoda (decline in October after the maximum in August), Harpacticoida (decline in May and increase till October) and macrobenthic Crustacea (minimum in May). The spatial patterns shaped by the environmental gradients related to glacial inputs, the faunal impoverishment in inner basin and a shift in dominants along the fjord axis, were clearly designated and stable throughout the year. The resilience of Arctic fjordic benthic community to marked seasonality in pelagic phytodetritus fluxes may be related to organic matter reserves in sediments (large enough to sustain the detritus feeders on a year-round basis), inclusion of macroalgal carbon into the diet and common employment of lecithotrophic larva or direct development by polar benthos.

Seasonal constancy (summer vs. winter) of benthic size spectra in an Arctic fjord

“…It is possible that in those regions detectable seasonal variation in size structure of benthic communities can also occur, but further studies are needed to test it. Lack of seasonal patterns in benthic size spectra is consistent with the study of Włodarska-Kowalczuk et al (2016), who did not found a clear response of Kongsfjorden benthic standing stocks or diversity to changes of organic matter supply during four seasons. Their findings and the present study support the hypothesis of the sediment 'food bank' existence in the polar sediments that was first formulated for the West Antarctic Peninsula by Mincks et al (2005).…”

“…For meiofaunal nematodes and Prionospio cirrifera, the individual biomass was lower at stations KB1 and KB2, but higher at KB3. Włodarska-Kowalczuk et al (2016) showed no difference in mean individual biomass of Nematoda between winter and summer in the outer basin of Kongsfjorden, but higher individual biomass in spring. This was explained by the effect of the seasonal recruitment following the spring bloom.…”

Ecosystem Kongsfjorden: new views after more than a decade of research

“…However, environmental changes, such as rising temperatures coupled with enhanced food availability due to an increasing frequency of sea ice-free days per year, may have a stronger effect on succession than exposure time of disturbance. Wlodarska-Kowalczuk et al (2016) investigated relations between the marked seasonality in pelagic productivity and phytodetritus fluxes to the sea bottom on taxonomic composition and standing stocks of benthic communities. They detected no consistent differences in meio-and macrofaunal density, diversity or composition during the year, although possible responses to spring food supply in meiofaunal reproduction were observed in Nematoda, Harpacticoida and macrobenthic Crustacea.…”

Limited congruence exhibited across microbial, meiofaunal and macrofaunal benthic assemblages in a heterogeneous coastal environment

“…Nematode and macrofaunal samples have been seen to have congruent patterns of assemblage structure in Araçá Bay, Brazil 11 . The environmental gradients associated with glacial meltwater in a fjord were associated with congruence of foraminifera and macrofauna 21 .…”