OLIGOTREND, a global database of multi-decadal chlorophyll a and water quality time series for rivers, lakes, and estuaries

Reversed eutrophication, called oligotrophication, has been widely documented globally over the last 30 years in rivers, lakes, and estuaries. However, the absence of a comprehensive and harmonized dataset has hindered a deeper understanding of its ecological consequences. To address this data gap, we developed the OLIGOTREND database, which contains multi-decadal time series of chlorophyll a, nutrients (nitrogen and phosphorus), and related physicochemical parameters, totalling 4.3 million observations. These data originate from 1894 unique monitoring locations across estuaries (n = 238), lakes (687), and rivers (969). Most time series cover the period from 1986–2022 and comprise at least 15 years of chlorophyll a observations. Each location is associated with catchment and hydroclimatic attributes. Trend and breakpoint analyses were applied to all time series. Chlorophyll a showed temporally variable and ecosystem-specific responses to nutrient declines with an overall declining trend for 18 % of the time series, contrasting greatly with a majority of declining trends for nutrient concentrations. We harmonized the database to ensure reproducibility and ease of access and support future updates and contributions. Available at https://doi.org/10.6073/pasta/a7ad060a4dbc4e7dfcb763a794506524 (Minaudo and Benito, 2024), the OLIGOTREND database supports collaborative efforts aimed at further advancing our understanding of biogeochemical and biological mechanisms underlining oligotrophication and ecological impacts of global long-term environmental change.

This study was funded by the Iberian Association of Ecology (SIBECOL) through the 2022 early-career advanced grant to Camille Minaudo and Xavier Benito. Both Camille Minaudo and Xavier Benito have received funding from the postdoctoral fellowships programme Beatriu de Pinós funded by the Secretary of Universities and Research (Government of Catalonia) and by the Horizon 2020 programme of research and innovation of the European Union under the Marie Skłodowska-Curie grant agreement no. 801370. Andras Abonyi was supported by the National Research, Development and Innovation Office, Hungary (project FK 142485), and by the János Bolyai Research Scholarship of the Hungarian Academy of Sciences. Estela Romero acknowledges the support of the Grant “Severo Ochoa Centres of Excellence” (CEX2018-000828-S) funded by grant no. MCIN/AEI/10.13039/50110001103 and the project KALORET (PID2021-128778OA-I00) funded by grant no. MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe”.

info:eu-repo/semantics/publishedVersion