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

<p>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 d...

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Main Authors: C. Minaudo, A. Abonyi, C. Alcaraz, J. Diamond, N. J. K. Howden, M. Rode, E. Romero, V. Thieu, F. Worrall, Q. Zhang, X. Benito
Format: Article
Language:English
Published: Copernicus Publications 2025-07-01
Series:Earth System Science Data
Online Access:https://essd.copernicus.org/articles/17/3411/2025/essd-17-3411-2025.pdf
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Summary:<p>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 <span class="inline-formula"><i>a</i></span>, nutrients (nitrogen and phosphorus), and related physicochemical parameters, totalling 4.3 million observations. These data originate from 1894 unique monitoring locations across estuaries (<span class="inline-formula"><i>n</i></span> <span class="inline-formula">=</span> 238), lakes (687), and rivers (969). Most time series cover the period from 1986–2022 and comprise at least 15 years of chlorophyll <span class="inline-formula"><i>a</i></span> observations. Each location is associated with catchment and hydroclimatic attributes. Trend and breakpoint analyses were applied to all time series. Chlorophyll <span class="inline-formula"><i>a</i></span> 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<span id="page3412"/> nutrient concentrations. We harmonized the database to ensure reproducibility and ease of access and support future updates and contributions. Available at <a href="https://doi.org/10.6073/pasta/a7ad060a4dbc4e7dfcb763a794506524">https://doi.org/10.6073/pasta/a7ad060a4dbc4e7dfcb763a794506524</a> (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.</p>
ISSN:1866-3508
1866-3516