Evidence of eutrophication in Arctic lakes

Ayala-Borda, Paola; Lovejoy, Connie; Power, Michael; Rautio, Milla

doi:10.1139/as-2020-0033

Cited by 14 publications

(11 citation statements)

References 59 publications

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“…The timing of these events varies noticeably between studies and agedepth models always contain an element of uncertainty; however, evidence of warmer temperatures has been previously recognized during the first millennium CE in northern Finland (Korhola et al 2000;Luoto and Nevalainen 2018) and the circumpolar Arctic more broadly (Kaufman et al 2009). The most recent increase in CHLa corroborates the growing evidence of increasingly productive northern lakes (Michelutti et al 2005;Ayala-Borda et al 2021) and is most likely related to anthropogenic warming. For the lake flora, these productive periods were likely characterized by generally improved resource availability, especially as the record provides no evidence of increases in allochthonous (shading) lake-water TOC, and increased organic substrata but possibly also changes in water chemistry, habitats and predation (Smol and Stoermer 2010).…”

Section: Woodland Lake: Biogeochemical Evidence Of Ecosystem Changes ...supporting

confidence: 73%

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: Woodland Lake: Biogeochemical Evidence Of Ecosystem Changes ...supporting

confidence: 73%

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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“…Continuous PAR recordings under the ice of Ward Hunt Lake have shown that the PAR often reaches levels as high as 100-200 μmol m −2 s −1 in summer (Bégin, Tanabe, Kumagai, et al, 2021). The under ice Chl-a concentrations in Arctic CB lakes were also almost two times higher than values in these lakes in summer (Ayala Borda et al, 2021), further indicating the importance of winter for northern aquatic ecosystems despite the overall low light levels. IMBEAU ET AL.…”

Section: Discussionmentioning

confidence: 99%

Hidden Stores of Organic Matter in Northern Lake Ice: Selective Retention of Terrestrial Particles, Phytoplankton and Labile Carbon

et al. 2021

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Over the last few decades, global warming has led to widespread shrinking of the cryosphere and has brought a sense of urgency toward the study of ice habitats. One of the most heavily impacted cryospheric habitats is freshwater ice. Climate change is leading to substantial reductions in the thickness and duration of lake and river ice cover worldwide (Sharma et al., 2019;Wrona et al., 2016). In the northern hemisphere, ice in lakes and rivers freezes an average of 5.8 days later and melts 6.5 days earlier than 100 years ago, based on the measurements taken between the years 1846and 1995(Magnuson, et al., 2000. Global air temperatures increased 1.2°C during this period. The majority of boreal and Arctic lakes are still ice-covered for six to ten months a year, and the potential importance of this cold and dark period on ecosystem structure and function is increasingly recognized (Grosbois & Rautio, 2018;Hampton et al., 2017;Schneider et al., 2017). Considering that ice-covered lakes include nearly 50% of the world's lakes, there is a pressing Abstract Around 50% of the world's lakes freeze seasonally, but the duration of ice-cover is shortening each year and this is likely to have broad limnological consequences. We sampled freshwater ice and the underlying water in 19 boreal and polar lakes to evaluate whether lake ice contains an inoculum of algae, nutrients, and carbon that may contribute to lake ecosystem productivity. Boreal and Arctic lakes differed in ice duration (6 vs. >10 months), thickness (70 vs. 190 cm), and quality (predominantly snow ice vs. black ice), but in all lakes, there were consistent differences in biological and biogeochemical composition between ice and water. Particulate fractions were often more retained while most dissolved compounds were excluded from the ice; for example, the ice had more terrestrial particulate carbon, measured as fatty acid biomarkers (averages of 1.1 vs. 0.3 µg L −1 ) but lower dissolved organic carbon (2.2 vs. 5.7 mg C L −1 ) and inorganic phosphorus concentrations (4.0 vs. 7.5 µg C L −1 ) than the underlying water. The boreal ice further had three times higher chlorophyll-a, than the water (0.9 vs. 0.3 µg L −1 ). Of the dissolved fractions, the contribution of protein-like compounds was higher in the ice, and this in all lakes. These labile compounds would become available to planktonic microbes when the ice melts. Our results show that freshwater ice has an underestimated role in storage and transformation in the biogeochemical carbon cycle of ice-covered lake ecosystems.Plain Language Summary Winter ice cover of 1-2 m thickness can comprise 20%-70% of the total lake depth in boreal and Arctic lakes. While sea ice is known to contain substantial quantities of carbon and organisms that at ice melt contribute to biological production in the underlying water column, little is known about the composition of lake ice and its role in storage of organic carbon. Our analyses of 19 boreal and Arctic lakes revealed large but different stores of organic material in lake ...

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“…TP is a key lake health indicator since lakes are often phosphoruslimited, but excess phosphorus can result in eutrophication and suitable conditions for harmful algal bloom (HAB) events. Recently, a naturally eutrophic lake with high TP levels was reported from near the four ERA lakes sampled here (Ayala-Borda et al, 2021). The high TP load was thought to be due to the phosphorus-rich bedrock in the immediate area combined with high snow accumulation due to local lake morphology and orientation, which resulted in the increased water tracks in early spring maintaining summer phytoplankton production.…”

Section: General Microbial Diversitymentioning

confidence: 78%

Freshwater Microbial Eukaryotic Core Communities, Open-Water and Under-Ice Specialists in Southern Victoria Island Lakes (Ekaluktutiak, NU, Canada)

2022

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Across much of the Arctic, lakes and ponds dominate the landscape. Starting in late September, the lakes are covered in ice, with ice persisting well into June or early July. In summer, the lakes are highly productive, supporting waterfowl and fish populations. However, little is known about the diversity and ecology of microscopic life in the lakes that influence biogeochemical cycles and contribute to ecosystem services. Even less is known about the prevalence of species that are characteristic of the seasons or whether some species persist year-round under both ice cover and summer open-water conditions. To begin to address these knowledge gaps, we sampled 10 morphometrically diverse lakes in the region of Ekaluktutiak (Cambridge Bay), on southern Victoria Island (NU, Canada). We focused on Greiner Lake, the lakes connected to it, isolated ponds, and two nearby larger lakes outside the Greiner watershed. The largest lakes sampled were Tahiryuaq (Ferguson Lake) and the nearby Spawning Lake, which support commercial sea-run Arctic char (Salvelinus alpinus) fisheries. Samples for nucleic acids were collected from the lakes along with limnological metadata. Microbial eukaryotes were identified with high-throughput amplicon sequencing targeting the V4 region of the 18S rRNA gene. Ciliates, dinoflagellates, chrysophytes, and cryptophytes dominated the lake assemblages. A Bray–Curtis dissimilarity matrix separated communities into under-ice and open-water clusters, with additional separation by superficial lake area. In all, 133 operational taxonomic units (OTUs) occurred either in all under-ice or all open-water samples and were considered “core” microbial species or ecotypes. These were further characterized as seasonal indicators. Ten of the OTUs were characteristic of all lakes and all seasons sampled. Eight of these were cryptophytes, suggesting diverse functional capacity within the lineage. The core open-water indicators were mostly chrysophytes, with a few ciliates and uncharacterized Cercozoa, suggesting that summer communities are mixotrophic with contributions by heterotrophic taxa. The core under-ice indicators included a dozen ciliates along with chrysophytes, cryptomonads, and dinoflagellates, indicating a more heterotrophic community augmented by mixotrophic taxa in winter.

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Evidence of eutrophication in Arctic lakes

Cited by 14 publications

References 59 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

Hidden Stores of Organic Matter in Northern Lake Ice: Selective Retention of Terrestrial Particles, Phytoplankton and Labile Carbon

Freshwater Microbial Eukaryotic Core Communities, Open-Water and Under-Ice Specialists in Southern Victoria Island Lakes (Ekaluktutiak, NU, Canada)

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