A Holocene record of aquatic bio-optics in subarctic fennoscandia

Nevalainen, Liisa; Rantala, Marttiina V.; Meyer-Jacob, Carsten; Kivilä, E. Henriikka; Ojala, Antti E. K.; Smol, John P.; Luoto, Tomi P.

doi:10.1016/j.quascirev.2020.106491

Cited by 2 publications

(6 citation statements)

References 51 publications

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“…Consistently, previous research from subarctic lakes in northern Sweden indicated more conspicuous declines in lake-water TOC near and below the treeline compared to lakes situated at higher altitudes (Rosén 2005). Notwithstanding, the treeline advance during the warm and dry climate period preceding the Neoglacial may still have promoted plant growth and increased soil organic carbon stocks subsequently mobilized during the early Neoglacial (Nevalainen et al 2020b). Similar transient increases in the inwash of organic matter at the onset of climate deterioration have been observed from other northern tundra lakes (Liversidge 2012).…”

Section: Tundra Lake: Biogeochemical Evidence Of Ecosystem Changes Un...supporting

confidence: 82%

“…Sediment chronologies were constructed based on radiometric dating combining radiolead ( 210 Pb) and radiocesium ( 137 Cs) analyses for the recent (~ past century) and radiocarbon ( 14 C) analysis for the older sediments. Details on the sediment dating for the tundra lake were presented in a previous study investigating the development of underwater UV regimes in the lake during the Holocene (Nevalainen et al 2020b). Following similar procedures, 210 Pb and 137 Cs dates for the woodland lake sediment core were analyzed at the Paleoecological Environmental Assessment and Research Lab (Queens University, Kingston, Ontario, Canada) using the constant rate of supply (CRS) model.…”

Section: Sediment Sampling and Datingmentioning

confidence: 99%

“…An array of biogeochemical techniques was used in combination to track changes in lake-water and sediment organic matter origin and content. The biogeochemical analyses were carried out following standard procedures as detailed in Nevalainen et al (2020b). Before analysis, the sediments were freeze dried and homogenized and further sieved (125 µm mesh) for the spectroscopic analyses.…”

Section: Biogeochemical Analysesmentioning

confidence: 99%

“…The synchronous decline in lake-water TOC implies that the lakewater organic carbon pool had a comparatively large autochthonous component, which is supported by the modern water chemistry and the surrounding landscape providing relatively few sources of allochthonous organic matter. Notwithstanding, some part of the lake-water TOC shift is likely related to a decline in land carbon input as the sharpest TOC decline around ~ 1000-500 BCE was followed by a stepwise ncrease in benthic macroinvertebrates (Cladocera) with intense pigmentation and affinity to clear waters suggesting increased underwater UV transparency (Nevalainen et al 2020b). In the tundra lake overall, sediment δ 13 C and especially C/N values, indicative of relative changes in organic matter source, did not show as clear cut a connection to the CHLa and lake-water TOC trends as recorded in the woodland lake.…”

Section: Tundra Lake: Biogeochemical Evidence Of Ecosystem Changes Un...mentioning

confidence: 99%

“…As in the woodland lake, the above biogeochemical changes occurred most likely in response to the progressing Neoglacial climate regime, and marked a clear transition in the status of the tundra lake following one and a half millenium of comparatively stable and elevated CHLa and lake-water TOC (Nevalainen et al 2020b). The timing and magnitude of the transition differs from that observed in the woodland lake where the decline in lake-water and sediment organic content was sharper and initiated much later.…”

Section: Tundra Lake: Biogeochemical Evidence Of Ecosystem Changes Un...mentioning

confidence: 99%

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Neoglacial lake-ecosystem changes above and below the subarctic Fennoscandian treeline inferred from changes in diatom functional groups

et al. 2022

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Algal communities act as sensitive indicators of past and present climate effects on northern lakes, but their responses can vary considerably between ecosystems. Functional trait-based approaches may help us better understand the nature of the diverse biotic responses and their underlying ecosystem changes. We explored patterns in diatom (Bacillariophyceae) growth forms and species composition during the Neoglacial in two shallow lakes typical of subarctic regions, including a dark-colored woodland lake and a clear tundra lake. Sediment carbon and nitrogen elemental and isotope biogeochemistry and spectral indices were used to track broadscale changes in lake productivity, the inflow of organic carbon from land, and benthic substratum over the past three millennia. The biogeochemical indices tracked declines in land-lake connectivity as well as lake-water and sediment organic enrichment above and below the subarctic treeline driven by Neoglacial cooling. This broadscale environmental transition was intercepted by periods of elevated primary production associated with transient Neoglacial warm anomalies and, in particular, the twentieth century warming. Although the Neoglacial development of the lakes showed conspicuous similarities, diatom functional and taxonomic responses were not uniform between the lakes pointing to intrinsic differences in the development of benthic habitats and underwater-light regimes. Many of the observed biotic shifts aligned with expectations based on earlier research linking diatom functional traits to changing light and organic levels but the results also point to further research needs, particularly to better differentiate the individual and interactive effects of substratum and light. Despite distinct anthropogenic imprints in the biogeochemical record, the scale of human impact on the lakes’ biota has not, as yet, been profound, but the changes are nonetheless clear when compared to the previous three millennia of natural lake development.

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Section: Tundra Lake: Biogeochemical Evidence Of Ecosystem Changes Un...supporting

confidence: 82%

Section: Sediment Sampling and Datingmentioning

confidence: 99%

Section: Biogeochemical Analysesmentioning

confidence: 99%

Section: Tundra Lake: Biogeochemical Evidence Of Ecosystem Changes Un...mentioning

confidence: 99%

Section: Tundra Lake: Biogeochemical Evidence Of Ecosystem Changes Un...mentioning

confidence: 99%

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Neoglacial lake-ecosystem changes above and below the subarctic Fennoscandian treeline inferred from changes in diatom functional groups

et al. 2022

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Traces of sunlight in the organic matter biogeochemistry of two shallow subarctic lakes

et al. 2021

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Global environmental change alters the production, terrestrial export, and photodegradation of organic carbon in northern lakes. Sedimentary biogeochemical records can provide a unique means to understand the nature of these changes over long time scales, where observational data fall short. We deployed in situ experiments on two shallow subarctic lakes with contrasting light regimes; a clear tundra lake and a dark woodland lake, to first investigate the photochemical transformation of carbon and nitrogen elemental (C/N ratio) and isotope (δ13C, δ15N) composition in lake water particulate organic matter (POM) for downcore inferences. We then explored elemental, isotopic, and spectral (inferred lake water total organic carbon [TOC] and sediment chlorophyll a [CHLa]) fingerprints in the lake sediments to trace changes in aquatic production, terrestrial inputs and photodegradation before and after profound human impacts on the global carbon cycle prompted by industrialization. POM pool in both lakes displayed tentative evidence of UV photoreactivity, reflected as increasing δ13C and decreasing C/N values. Through time, the tundra lake sediments traced subtle shifts in primary production, while the woodland lake carried signals of changing terrestrial contributions, indicating shifts in terrestrial carbon export but possibly also photodegradation rates. Under global human impact, both lakes irrespective of their distinct carbon regimes displayed evidence of increased productivity but no conspicuous signs of increased terrestrial influence. Overall, sediment biogeochemistry can integrate a wealth of information on carbon regulation in northern lakes, while our results also point to the importance of considering the entire spectrum of photobiogeochemical fingerprints in sedimentary studies.

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A Holocene record of aquatic bio-optics in subarctic fennoscandia

Cited by 2 publications

References 51 publications

Neoglacial lake-ecosystem changes above and below the subarctic Fennoscandian treeline inferred from changes in diatom functional groups

Neoglacial lake-ecosystem changes above and below the subarctic Fennoscandian treeline inferred from changes in diatom functional groups

Traces of sunlight in the organic matter biogeochemistry of two shallow subarctic lakes

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