Abstract
We quantified benthic diatom diversity in streams in the Miellajokka catchment, about 200 km north of the Arctic circle in Sweden. Beta diversity among sites was related to local-scale environmental heterogeneity (occurring on the order of 1 km or less), and its magnitude was equal (Sørensen Index = 0.62) to levels previously reported for rivers on regional environmental gradients across hundreds of kilometres of Arctic Fennoscandia. Species turnover was the dominant (77%) component of beta diversity in the Miellajokka catchment. Small, stress-tolerant taxa dominated the assemblages, and there were no clear patterns of functional class among sites. Site ordinates from non-metric dimensional scaling were most strongly correlated with flood frequency (r = 0.83) and water temperature (r = 0.89), which was higher in harsh tundra sites than below treeline. Additionally, site ordinates were correlated (r = 0.83) with ecosystem-scale gross primary production — indicative of a link between diatom diversity and ecosystem function. Our results advance understanding of patterns diatom diversity in Arctic streams by quantifying local-scale variation that is understudied in this region, and by identifying the consequences of this local-scale diversity for an ecosystem-scale process.
Highlights
Arctic streams and rivers are among the most sensitive ecosystems to climate change, and are subject to widespread shifts in the composition of their biological communities (Lento et al 2019; Heino et al 2020)
Navicula Navicula Navicula cryptocephala Nitzschia Nitzschia frustulum Nitzschia perminuta Pinnularia Psammothidium Psammothidium cf. marginulatum Reimeria sinuata Rossithidium petersenii Rossithidium pusillum Stauroforma exiguiformis Stauroneis Staurosira venter Tabellaria flocculosa Ulnaria danica Other Bacillariophyta observed with light microscopy overlap among taxa within this species complex, and (2) our study region does not contain the dramatic contrasts in nutrient concentrations or pH necessary to distinguish among these taxa based on their relationship to environmental
Beta diversity was dominated by the turnover component, which is often thought to reflect environmental patterns based on the reasoning that diatoms have relatively narrow environmental preferences and only well-adapted species survive in each site’s specific conditions
Summary
Arctic streams and rivers are among the most sensitive ecosystems to climate change, and are subject to widespread shifts in the composition of their biological communities (Lento et al 2019; Heino et al 2020). Benthic diatom monitoring is strongly biased to eutrophic or otherwise human-impacted streams and rivers, with limited coverage in Arctic regions (Kahlert and Gottschalk 2014; Lindholm et al 2018). This is in part because the European Water Framework Directive requires the calculation of quantitative metrics based on aquatic organism groups to evaluate water quality and to enforce environmental legislation (Kelly et al 1998; Kahlert and Gottschalk 2014). Evidence suggests that detailed sampling is needed to understand Arctic stream diatom assemblages, but the small number of existing records do not reflect local (occurring on the order of ∼1 km or less) heterogeneity in land cover and stream conditions
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