Pervasive changes in algal indicators since pre-industrial times: A paleolimnological study of changes in primary production and diatom assemblages from ~200 Canadian lakes

Griffiths, Kate; Jeziorski, Adam; Antoniades, Dermot; Beaulieu, Marieke; Smol, John P.; Gregory‐Eaves, Irene

doi:10.1016/j.scitotenv.2022.155938

Cited by 14 publications

(25 citation statements)

References 55 publications

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“…There are multiple factors that might contribute to this regional discrepancy in the response of lakes to LULC development. For one, the region’s flat catchment topography (Bharath and Elshorbagy 2018), naturally nutrient-rich geology (Taranu and Gregory-Eaves 2008; Griffiths et al 2022) and its changing hydrology (i.e., declining river flows due to a reduction in yearly persistence and maximum depth of local snowpacks; Schindler and Donahue 2006) may further modulate the effect of agricultural development (Bunting et al 2016) and urban expansion (Leavitt et al 2006). Indeed, the combined effects of increasing agricultural and urban development and the Prairie region’s flat, nutrient-rich landscape on lake water quality were supported by our variation partitioning analysis, where LULC explained a considerable amount of the variation (15%) in water quality alongside lake physiography (11%) and their interaction (9%; Fig.…”

Section: Discussionmentioning

confidence: 99%

“…There is a growing body of evidence that has identified that long-term anthropogenic impacts may have disproportionately altered the productivity and water physiochemistry of Prairie lakes relative to other ecozones, leading to the present-day dichotomy in baseline nutrient levels and water quality. For example, time-series analyses revealed widespread increases in algal biomass since pre-industrial times (Taranu et al 2015; Ho et al 2019; Griffiths et al 2022), and indicate that in highly developed and economically important ecozones, such as the Prairies and the Mixedwood Plains, these trends have accentuated. Furthermore, analyses of bioindicators preserved in lake sediment records have shown that the highest degree of taxonomic turnover since pre-industrial conditions have been localized in ecozones that currently have the more intense land uses, with agriculture and urbanization being key stressors to those lakes (Griffiths et al 2021; Griffiths et al 2022).…”

Section: Discussionmentioning

confidence: 99%

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Agricultural land use and lake morphology explain substantial variation in water quality across Canada

Schacht

MacKeigan

Taranu

et al. 2022

Preprint

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Despite decades of research and mitigation efforts, declines in freshwater quality resulting from anthropogenic nutrient input remain a persistent issue worldwide. Canada has the greatest number of freshwater lakes in the world, yet we have a limited understanding of the magnitude and scale at which most lakes have been affected by human activities, namely Land Use/Land Cover (LULC) alterations. In response, the NSERC Canadian Lake Pulse Network has compiled the first nationwide systematic database of Canadian lake quality metrics by surveying 664 lakes across 12 ecozones over three years. To assess the influence of human impact on water quality and its spatial variation across this lake set, we built models quantifying the association between watershed LULC and physiochemical water parameters. We found that agricultural and urban land use explained the greatest proportion of variation in water quality among LULC categories (R2 = 0.20–0.29), although threshold values of water quality metrics (i.e., concentrations of major ions, total phosphorus [TP], total nitrogen [TN], dissolved organic carbon [DOC], and Chlorophyll a [Chl-a]) differed among ecozones. Generally, when the percentage of catchment agricultural land use exceeded 30–35%, we noted significant increases in TP, TN, DOC, and Chl-a concentrations. Similarly, when urban land use surpassed 1–6%, we observed significant increases in ion concentrations and specific conductance. Overall, our study highlights that while drivers of water quality may be similar across regions, management strategies for freshwater ecosystems must consider their geographic context to better predict when and where threshold responses will occur.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Agricultural land use and lake morphology explain substantial variation in water quality across Canada

Schacht

MacKeigan

Taranu

et al. 2022

Preprint

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“…Instead of the ecozone-specific HI classes of the original survey (see Huot et al, 2019), sites were re-classified into high (HI ≥ 0.15) and low (HI < 0.15) HI classes (described in Griffiths et al, 2022).…”

Section: Study Area and Samplingmentioning

confidence: 99%

“…Interesting trends in water quality and ecosystem change across Canada have already emerged from LakePulse. For example, trends in water chemistry as a function of ecozone and land use distinguished the Prairies and Boreal Plains ecozones, where the former has extensive agricultural and pastural development, as indicated by enriched total nitrogen (TN), total phosphorus (TP), dissolved organic carbon (DOC), chlorophyll-a (Chl-a), major ions and specific conductance (Griffiths et al, 2022;Sánchez Schacht et al, 2023).…”

Section: Introductionmentioning

confidence: 99%

Changes in midge assemblages reflect climate and trophic gradients across north temperate and boreal lakes since the pre‐industrial period

Griffiths,

Jeziorski,

Antoniades

et al. 2023

Freshwater Biology

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North temperate and boreal lakes are affected by a complex suite of anthropogenic stressors, yet little is known about how these ecosystems are faring across the most lake‐rich nation, Canada. The NSERC Canadian Lake Pulse Network is the first large‐scale national survey of its kind, with the aim of assessing the health of Canadian lakes, determined by the deviation of key variables from baseline pre‐industrial conditions (pre‐1880 CE). We examined midge remains (chironomids and Chaoborus) from modern and pre‐industrial sediment intervals in 67 lakes, spanning a range of sizes, ecozones, and degrees of catchment land‐use change. A marked northwest/southeast divide was evident in the modern chironomid assemblages, which was partially associated with water quality, physiographical and climatic variables, with a small portion of the variance explained by geography alone. Between the pre‐industrial and modern sediment intervals, taxa typically found in warmer waters increased across the country (p < 0.001); this pattern also was evident in the littoral assemblages (p = 0.01), providing additional support for the influence of warming. Turnover in chironomid assemblages varied across trophic classes. Mesotrophic lakes showed increases in macrophyte‐associated taxa, whereas eutrophic lakes showed declines in littoral taxa, perhaps reflecting increased turbidity, and the increase of low‐oxygen‐tolerant profundal taxa in eutrophic lakes with high human impacts. Overall, the distribution and dynamics of chironomid assemblages across Canadian lakes appear to be strongly linked to changes in climate and deep‐water oxygen conditions.

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“…Microfossil analysis is a widely used technique but is limited to organisms with well-preserved and morphologically distinct remains, such as diatom frustules (Hembrow et al ., 2014;Leira, 2005) and the resting cysts produced by some dinoflagellates (Drljepanet al ., 2014). Photosynthetic pigments can provide a record of eukaryotic algal and cyanobacterial community composition, abundance, and primary productivity (Griffiths et al ., 2022;Kpodonuet al ., 2016;Makri et al ., 2019;Watanabe et al ., 2012), but many pigments are not specific enough to enable taxonomic identification beyond the class level (Gong et al ., 2020). These limitations of traditional palaeolimnological techniques highlight the need for complementary and improved methods which can be applied to a wider diversity of organisms, such as sedimentary DNA (sedDNA).…”

Section: Introductionmentioning

confidence: 99%

Evaluating the use of lake sedimentary DNA in palaeolimnology: A comparison with long-term microscopy-based monitoring of the phytoplankton community

Thorpe

Mackay

Goodall

et al. 2023

Preprint

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Palaeolimnological records provide valuable information about how phytoplankton respond to long-term drivers of environmental change. Traditional palaeolimnological tools such as microfossils and pigments are restricted to taxa that leave sub-fossil remains, and a method that can be applied to the wider community is required. Sedimentary DNA (sedDNA), extracted from lake sediment cores, shows promise in palaeolimnology, but validation against data from long-term monitoring of lake water is necessary to enable its development as a reliable record of past phytoplankton communities. To address this need, 18S rRNA gene amplicon sequencing was carried out on lake sediments from a core collected from Esthwaite Water (English Lake District) spanning ~105 years. This sedDNA record was compared with concurrent long-term microscopy-based monitoring of phytoplankton in the surface water. Broadly comparable trends were observed between the datasets, with respect to the diversity and relative abundance and occurrence of chlorophytes, dinoflagellates, ochrophytes and bacillariophytes. Up to 20% of genera identified in the microscopy record were also detected using sedDNA, and sedDNA revealed a previously undetected community of phytoplankton. However, a substantial proportion of genera identified by microscopy were not detected using sedDNA, highlighting the current limitations of the technique that require further development such as reference database coverage. These results suggest that sedDNA can be used as an effective record of past phytoplankton communities, at least over timescales of less than 100 years, but the taphonomic processes which may affect its reliability, such as the extent and rate of deposition and DNA degradation, require further research.

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Pervasive changes in algal indicators since pre-industrial times: A paleolimnological study of changes in primary production and diatom assemblages from ~200 Canadian lakes

Cited by 14 publications

References 55 publications

Agricultural land use and lake morphology explain substantial variation in water quality across Canada

Agricultural land use and lake morphology explain substantial variation in water quality across Canada

Changes in midge assemblages reflect climate and trophic gradients across north temperate and boreal lakes since the pre‐industrial period

Evaluating the use of lake sedimentary DNA in palaeolimnology: A comparison with long-term microscopy-based monitoring of the phytoplankton community

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