This is a Preprint and has not been peer reviewed. The published version of this Preprint is available: https://doi.org/10.1371/journal.pwat.0000051. This is version 1 of this Preprint.
Worldwide moderate-resolution mapping of lake surface chl-a reveals variable responses to global change (1997-2020)
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Authors
Benjamin M Kraemer,
Karan Kakouei,
Catalina Munteanu,
Michael W. Thayne 
,
Rita Adrian
Abstract
Anthropogenic activity is leading to widespread changes in lake water quality--a key contributor to socio-ecological health. But, the anthropogenic forces affecting lake water quality (climate change, land use change, and invasive species) are unevenly distributed across lakes, across the seasonal cycle, and across space within lakes, potentially leading to highly variable water quality responses that are poorly documented at the global scale. Here, we used 742 million chlorophyll-a (chl-a) observations merged over 6 satellite sensors (daily, 1 to 4 km resolution) to quantify water quality changes from 1997 to 2020 in 345 globally-distributed large lakes. Chl-a decreased across 56% of the cumulative total lake area, challenging the putative widespread increase in chl-a that is expected due to human activity. 18% of lakes exhibited both significant positive and significant negative chl-a trends across different locations or times of the year. This spatiotemporal complexity demonstrates the value of moderate resolution mapping of lake chl-a to inform water management decision-making and to determine the local ecological consequences of human activity.
DOI
https://doi.org/10.31223/X54G9W
Subjects
Fresh Water Studies
Keywords
lake, chlorophyll-a
Dates
Published: 2021-09-01 21:38
Last Updated: 2021-09-02 04:38
License
CC0 1.0 Universal - Public Domain Dedication
Additional Metadata
Conflict of interest statement:
None.
Data Availability:
GlobColour data (http://globcolour.info) used in this study has been developed, validated, and distributed by ACRI-ST, France. Geospatial and morphometric data for each lake is available from the previously published HydroLAKES database under the identifier doi: 10.1038/ncomms13603 and can be found at http://www.hydrosheds.org.
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Comment #51 Daniel Odermatt @ 2021-10-12 21:55
Dear colleagues,
congratulations on this interesting study and thanks for sharing the manuscript.
I noticed that you observed striking shifts in chl-a for Lake Nicaragua, and we identified with a different algorithm a few years ago that the lake shifted from cyano to green algae dominance between 2008 and 2011 (https://essd.copernicus.org/articles/10/1527/2018/, Figure 15). We used however only MERIS data, which was advantageous to identify cyanobacteria, but not so much concerning temporal coverage in exactly these years.
You mention in your manuscript that nutrient pollution in the lake peaked in the mid 2000's, and refer to a paper in Spanish from 2006. I'm not fluent in Spanish but found only 2002 and 2003 data in that paper. This seems unsuitable to support your interpretation. Furthermore, I'm wondering if your BRT adjustment can compensate the differences between the optical properties of cyanobacteria and green algae, which is necessary to obtain comparable chlorophyll-a concentrations across both fractions.
Best regards,
Daniel