From the worm’s point of view. I: Environmental settings of benthic ecosystems in Arctic fjord (Hornsund, Spitsbergen)

Abstract

As a consequence of ongoing climate warming, nearly all tidal glaciers in Arctic are retreating; hence, the seascape of glacial fjords is changing in many aspects. We took the example of Hornsund, the well-studied Svalbard fjord, with over 30 years of almost continuous observations of marine system. Recent data were collected during summer oceanographic surveys between 2001 and 2013 and compared with archival data from 1980s. As most of the phenomena connected with the warming happen at the sea surface (ice, wind, waves, surface currents, brackish water), we were interested, how the presumably stable, near-bottom waters in fjords behave, what are the environmental changes that are experienced directly by the worms living in the sediment. We have found that both the inner fjord basins (usually regarded as stable) and the outer fjord parts (exposed to the direct influence of shelf waters) has changed. Warming was documented in the inner basins, while cooling and warming episodes were recorded in the outer parts of the fjord. We demonstrate that following the increase melting and retreat of the glaciers, the area of shallows increased, salinity decreased and temperature increased-partly due to the advection of Atlantic waters from the shelf. Observed changes are in accordance with the model of arctic fjords evolution towards boreal ones associated with increased organic matter turnover. The observed changes are most likely typical for all cold water, glaciated fjords that are exposed to climate warming.

Recent distribution of Echinodermata species in Spitsbergen coastal waters

“…Species having pelagic larvae, as is the case for most of our echinoderms, are expected to expand their occurrence ranges with the ongoing borealisation of the Svalbard area (Berge et al 2005). West Spitsbergen fjords and coastal waters that were previously exposed to regular freezing and maintained local cold water pools are now often washed by Atlantic waters from the shelf and represent an ecotone type of area with mixed subarctic/boreal conditions (Drewnik et al 2016a). This may explain the lack of zonation among the Echinodermata species found in this study.…”

“…In the winter, the water column cools to an isothermic -1.5°C in the fjords and coastal waters (Węsławski et al 1994). In the summer, the maximum temperatures did not exceed 8°C at the surface and 5°C in the near-bottom waters (Swerpel 1985;Drewnik et al 2016a). Most of the sediments in fjordic and coastal waters are glaciomarine and occur from numerous tidal glaciers that discharge turbid freshwaters and cause heavy mineral sedimentation in the fjords Lydersen et al 2014).…”

Algal pigments in Hornsund (Svalbard) sediments as biomarkers of Arctic productivity and environmental conditions

“…The dominant sediments, mostly silt, in Hornsund are very fine-grained and rather homogeneous (Grzelak and Kotwicki 2012;Drewnik et al 2016). The organic carbon content was estimated from 0.8 to 1.8% (Drewnik et al 2016). …”

Trace element accumulation in the shell of the Arctic cirriped Balanus balanus

“…The average depth of the fjord is 90 m, with the maximum depth at 260 m. The fjord floor is diverse, but it is more homogenous compared to Kongsfjorden (Drewnik et al, 2016). The bottom along the coastline has a steep slope, although patches of flat bottom are also observed (Drewnik et al, 2016).…”

“…The average depth of the fjord is 90 m, with the maximum depth at 260 m. The fjord floor is diverse, but it is more homogenous compared to Kongsfjorden (Drewnik et al, 2016). The bottom along the coastline has a steep slope, although patches of flat bottom are also observed (Drewnik et al, 2016). In the deeper parts of the fjord, the seabed is covered mostly with finegrained and homogenous sediment with a variable content of sand (Grzelak & Kotwicki, 2012).…”