The biogeography and ecology of common diatom species in the northern North Atlantic, and their implications for paleoceanographic reconstructions

Abstract

Sound knowledge of present-day diatom species and their environments is crucial when attempting to reconstruct past climate and environmental changes based on fossil assemblages. For the North Atlantic region, the biogeography and ecology of many diatom taxa that are used as indicator-species in paleoceanographic studies are still not well known. Using information contained in large diatomenvironment calibration datasets can greatly increase our knowledge on diatom taxa and improve the accuracy of paleoenvironmental reconstructions. A diatom calibration dataset including 183 surface sediment samples from the northern North Atlantic was used to explore the distribution and ecology of 21 common Northern Hemisphere diatom taxa. We define the ecological responses of these species to April sea ice concentrations and August sea surface temperatures (aSSTs) using Huisman-Olff-Fresco (HOF)-response curves, provide distribution maps, temperature optima and ranges, and high-quality light microscope images. Based on the results, we find species clearly associated with cold, warm and temperate waters. All species have a statistically significant relationship with aSST, and 15 species with sea ice. Of these, Actinocyclus curvatulus, Fragilariopsis oceanica and Porosira glacialis are most abundant at high sea ice concentrations, whereas Coscinodiscus radiatus, Shionodiscus oestrupii, Thalassionema nitzschioides, Thalassiosira angulata, Thalassiosira nordenskioeldii and Thalassiosira pacifica are associated with low sea ice concentrations/icefree conditions. Interestingly, some species frequently used as sea ice indicators, such as Fragilariopsis cylindrus, show similar abundances at high and low sea ice concentrations with no statistically significant relationship to sea ice.present the geographical distribution of the common diatom species in the northern North Atlantic, (2) discuss the relationship between diatom species and two important environmental variables (SST and sea ice) and (3) present good-quality light-microscopy images of these species to aid with species identification. Materials and methodsA diatom calibration dataset (Andersen et al., 2004a(Andersen et al., , 2004bMiettinen et al., 2015) including 183 surface sediment samples (prepared for analysis using standard methodology, see Koç Karpuz and Schrader, 1990;Koç et al., 1993) and measured environmental data (SSTs and sea ice concentrations) around the North Atlantic, the Labrador Sea, the Nordic Seas and Baffin Bay (Fig. 1) was used in this study to examine the biogeography and ecology of common North Atlantic diatom taxa. The calibration dataset consists of 52 diatom species in total, of which we selected the 21 most common species based on their wide-ranging occurrence at high latitudes and their frequent use as paleoceanographic indicators in the northern North Atlantic and Arctic regions. However, some common North Atlantic taxa, such as Chaetoceros resting spores, Paralia sulcata, Fossula arctica and Fragilariopsis reginae-jahniae were not included in ...

Response of biological productivity to North Atlantic marine front migration during the Holocene

“…Although we lack information on diatom sources in our study, the distribution of some HBI III-producing diatoms (i.e. Rhizosolenia hebetata f. semispina) do trace the AF's modern position (Oksman et al, 2019), and are important members of Arctic Water assemblages in the North Atlantic (Koç Karpuz & Schrader, 1990;Oksman et al, 2019). Collectively, this evidence indicates that HBI III and T. quinqueloba track the migration of the AF along the NIS.…”

Changes in the composition of marine and sea-ice diatoms derived from sedimentary ancient DNA of the eastern Fram Strait over the past 30,000 years

“…In particular, the sample is dominated by sequences assigned to Skeletonema, Thalassiosira and Pseudo-nitzschia granii. Thalassiosira angulata, a species associated with low sea-ice concentrations (Oksman et al, 2019) and temperate water masses (Weckström et al, 2014), displays peak proportions in this sample. Lower proportions of sympagic diatoms in this sample are in accordance with the sea-ice retreat reconstructed from low IP25 and high brassicasterol concentrations (Müller and Stein, 2014) and high proportions of the subpolar planktic foraminifers…”

“…from the Fram Strait in modern surveys (Karpuz and Schrader, 1990;Oksman et al, 2019;von Quillfeldt, 2000) and micropaleontological records (Oksman et al, 2017;Stabell, 1986). We detect typical ice-associated (sympagic) and/or coldwater diatoms (e.g.…”

“…Their dominance is likely the result of high paleoproductivity or of differential overrepresentation caused by preservation and/or technical biases. Indeed, in the Fram Strait especially Chaetoceros and Thalassiosira species have high productivity in different hydrographical regimes (Gradinger and Baumann, 1991;Lalande et al, 2013) as well as at Kongsfjorden, a major outlet of western Svalbard potentially influencing the coring site (Hodal et al, 2012), and even in micropaleontological studies they are often dominant (Birks and Koç, 2002;Bylinskaya et al, 2016;Oksman et al, 2017Oksman et al, , 2019. Next to high paleo-productivity, the preservation of sedaDNA could be biased by differential degradation.…”

Changes in the composition of marine and sea-ice diatoms derived from sedimentary ancient DNA of the eastern Fram Strait over the past 30 000 years

“…frigida, whereas samples characterised by moderate to high (> 0.8 µg g −1 total organic carbon) concentrations of IP 25 display highly variable proportions without a clear relationship. Nitzschia frigida (Grunow) forms arborescent colonies (Medlin and Hasle, 1990) and is often abundant from late winter in the bottom layer of nearshore first-year ice and in multi-year ice in the Arctic pack-ice zones (Krawczyk et al, 2017;Melnikov et al, 2002;Olsen et al, 2017;Poulin et al, 2011;von Quillfeldt et al, 2003), but it can also be found in the water column during vernal under-ice or ice-edge blooms (Hasle and Heimdal, 1998;Olsen et al, 2017). Recently, De Schepper et al (2019) used sedaDNA metabarcoding on a core from the East Greenland Sea and identified the Mediophyceae OTU_5051 which was significantly correlated to the IP 25 concentrations.…”