Benthic foraminifera in Hornsund, Svalbard: Implications for paleoenvironmental reconstructions

Abstract

Modern hydrology of a typical Arctic fjord (Hornsund, SW Spitsbergen, Sval− bard) was investigated and compared with commonly used in paleoceanography proxies: benthic foraminiferal assemblages and their stable isotope (d 18 O and d 13 C) composition. The benthic foraminifera from Hornsund comprised 45 species and 28 genera. Their spatial variations follow the zonation pattern, resulting from the influence of Atlantic water at the fjord mouth and glacial meltwaters at the fjord head. At the mouth of the fjord, the total number of species and the contribution of agglutinating species were the highest. In the in− ner part of fjord, the foraminiferal faunas were poor in species and individuals, and aggluti− nating species were absent. "Living" (stained) foraminifera were found to be common throughout the short sediment cores (~10 cm long) studied. The stable isotope values of d 18 O and d 13 C were measured on tests of four species: Elphidium excavatum forma clavata, Cassidulina reniforme, Nonionellina labradorica and Cibicides lobatulus. The results con− firmed the importance of species−specific vital effects, particularly in the case of C. loba− tulus. The variability in the isotopic composition measured on different individuals within a single sample are comparable to isotopic composition of the same species test between sam− pling stations. The temperatures and bottom water salinities calculated from d18 O values in different foraminifera tests mirrored those recorded for bottom waters in the central and outer fjords relatively well. However, in the case of the inner fjord, where winter−cooled bottom waters were present, the calculated values from d 18 O were systematically higher by about 2°C. The obtained results imply that particular caution must be taken in interpretation of fjord benthic foraminifera assemblages in high resolution studies and in selection of ma− terial for isotope analyses and their interpretation in cores from inner fjords or silled fjords, where winter−cooled waters may be present.Key wo r d s: Arctic, Spitsbergen, benthic foraminifera, oxygen and carbon stable isotopes, paleotemperature, fjords.

Contemporary sedimentation in the forefield of Hornbreen,Hornsund

“…5 km from glaciers' fronts showed salinity increase from less than 28 PSU (Practical Salinity Units) at surface to 34.68 PSU close to the bottom (ca. 138 m below sea level) [24]. Moreover, similar results have been obtained in the fore eld of Kongsbreen (Kongsfjorden, Svalbard), where the measured thickness of surface layer of brackish water, at the distance of ca.…”

“…Existence of four main water layers has been stated: surface layer of cool brackish water at depth 0-11 m originating from glacier melting (1), layer of water mixing (depth 11-25 m), where rapid changes of temperature and salinity occur (2), layer of fjord water (depth 25-50 m) with a regular increase of density and salinity, and decrease of temperature in term of depth (3), layer of over-cooled dense water (depth 50-55 m) remained from winter mixing (4). Existence of the latter even during late summer seasons in 1999, 2000 and 2002 has also been proved [24]. Similar summer water column salinity strati cation was observed in Brepollen in July 2002.…”

Atlantic Water advection vs. glacier dynamics in northern Spitsbergen since early deglaciation

“…8g), as suggested by Rasmussen et al (2012) for the Isfjord. Indeed, C. lobatulus calcifies in summer, whereas N. labradorica calcifies in spring or early summer (Zajączkowski et al, 2010). Rising δ 13 C and lower δ 13 C values in N. labradorica (Figs.…”

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

“…the higher concentration of ∑Chlns-a in deeper than in surface sediment layer. The high percentage of pyropheophorbides-a at station H2 suggests that benthic activity is responsible for sediment mixing at this site, which tallies with the information that mixing in the surface sediment layers of Hornsund is caused mainly by bioturbation (Zajączkowski et al 2010;Włodarska-Kowalczuk et al 2013).…”