Die Sedimentkernanalyse der kanadischen Seen zeigt, dass die Algen seit Mitte des 19. Jahrhunderts in den meisten von ihnen zugenommen haben Die weit verbreitete Erhöhung der Primärproduktion des kanadischen Sees des 20. Jahrhunderts und die Rolle der Klimaerwärmung, Sonneneinstrahlung und menschlichen Auswirkungen

A key section of the news article:

>A team led by researchers at McGill University in Montreal and Université Laval analyzed sediment cores taken from 80 lakes across the country and found that algae has been increasing in the majority of them since the mid-1800s.
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>For lead author Hamid Ghanbari, the most interesting finding was a spike in the rate of the increase in algal growth: since the 1960s, it increased sevenfold.
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>“This was something very surprising for us and when we compared our data with other historical records, we found out that rising temperature is a major factor,“ Ghanbari said.
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>Aside from climate change, excess nitrogen and phosphorus can also contribute to algal growth when they are carried into waterways through runoff from animal manure and chemical fertilizers, stormwater and wastewater.
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>Algae, along with bacteria and phytoplankton, are essential for the aquatic food web. But too much algae can be a bad thing.
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>The recently published peer-reviewed study looked at algal growth overall and didn’t analyze for blooms.
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>While some lakes see some algae as a part of their cycle, Ghanbari said the concern is what will happen if the increase in algae leads to growth outside of what’s normal.
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>“That’s where the problem starts,“ he said. „We don’t know at the moment what that threshold is, but we know the increasing chlorophyll or algae levels in the lakes could lead to several problems.“

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Research link:

[Widespread 20th-century increases in Canadian lake primary production and the roles of climate warming, solar irradiance and human impacts](https://www.nature.com/articles/s43247-025-02569-7)

Abstract:

>Lakes provide many vital ecosystem services but are highly sensitive to human impacts and climate change. While data needed to assess their long-term trajectories are generally unavailable, lake responses to such perturbations can be inferred from sediment archives, including records of chlorophyll, a proxy for primary production. However, few if any datasets exist to test hypotheses at large spatial scales about the drivers of long-term change. Here, we apply rapid hyperspectral imaging to produce high-resolution records of sediment chlorophyll (defined as the sum of chlorophyll a and b and their degradation products) in dated cores from 80 lakes across Canada and identify an overall increase since the mid-19th-century. Breakpoint analysis detected a shift whereby the average rate of chlorophyll increase was seven times greater after 1966 than before. We then compared spatiotemporal chlorophyll trends to climate variables, solar irradiance, and land-use data to assess their relationships to past changes in primary production. We identified robust correlations between chlorophyll and climate variables (temperature and ice cover) that were especially strong after 1966, suggesting continental-scale alterations to lake primary production in response to recent accelerated warming. We also detected significant associations with incident solar radiation and catchment human impacts, and show that both had the potential to influence past primary production at the continental scale.