Clarifying the trophic state concept to advance macroscale freshwater science and management

Abstract For over a century, ecologists have used the concept of trophic state (TS) to characterize an aquatic ecosystem's biological productivity. However, multiple TS classification schemes, each relying on a variety of measurable parameters as proxies for productivity, have emerged to meet use‐specific needs. Frequently, chlorophyll a, phosphorus, and Secchi depth are used to classify TS based on autotrophic production, whereas phosphorus, dissolved organic carbon, and true color are used to classify TS based on both autotrophic and heterotrophic production. Both classification approaches aim to characterize an ecosystem's function broadly, but with varying degrees of autotrophic and heterotrophic processes considered in those characterizations. Moreover, differing classification schemes can create inconsistent interpretations of ecosystem integrity. For example, the US Clean Water Act focuses exclusively on algal threats to water quality, framed in terms of eutrophication in response to nutrient loading. This usage lacks information about non‐algal threats to water quality, such as dystrophication in response to dissolved organic carbon loading. Consequently, the TS classification schemes used to identify eutrophication and dystrophication may refer to ecosystems similarly (e.g., oligotrophic and eutrophic), yet these categories are derived from different proxies. These inconsistencies in TS classification schemes may be compounded when interdisciplinary projects employ varied TS frameworks. Even with these shortcomings, TS can still be used to distill information on complex aquatic ecosystem function into a set of generalizable expectations. The usefulness of distilling complex information into a TS index is substantial such that usage inconsistencies should be explicitly addressed and resolved. To emphasize the consequences of diverging TS classification schemes, we present three case studies for which an improved understanding of the TS concept advances freshwater research, management efforts, and interdisciplinary collaboration. To increase clarity in TS, the aquatic sciences could benefit from including information about the proxy variables, ecosystem type, as well as the spatiotemporal domains used to classify TS. As the field of aquatic sciences expands and climatic irregularity increases, we highlight the importance of re‐evaluating fundamental concepts, such as TS, to ensure their compatibility with evolving science.

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Publication Details

Journal
Ecosphere
Published
2025-09-01
DOI
https://doi.org/10.1002/ecs2.70392
Citations
3
Primary Topic
Fish Ecology and Management Studies
Type
article
Field-Weighted Citation Impact
6.94

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article

Clarifying the trophic state concept to advance macroscale freshwater science and management

Kate C. Fickas, Benjamin M. Kraemer, Robert Ladwig, Walter K. Dodds et al.
3 citations
Ecosphere
Fish Ecology and Management Studies
6.94
article

Clarifying the trophic state concept to advance macroscale freshwater science and management

Kate C. Fickas, Benjamin M. Kraemer, Robert Ladwig, Walter K. Dodds, Rachel M. Pilla, Daví Gasparini Fernandes Cunha, Tyler V. King, Richard Iestyn Woolway, Michael F. Meyer, Simon Topp, Isabella A. Oleksy, Ludmila Silva Brighenti, Joshua Culpepper, Mortimer Werther, Amina I. Pollard, Brian P. Lanouette, César Ordóñez, Shin‐ichiro S. Matsuzaki, Dina M. Leech, Stephanie E. Hampton, Carolina C. Barbosa, Jianning Ren, Alexander K. Fremier, Xiao Yang
article en
3 citations

Abstract

Abstract For over a century, ecologists have used the concept of trophic state (TS) to characterize an aquatic ecosystem's biological productivity. However, multiple TS classification schemes, each relying on a variety of measurable parameters as proxies for productivity, have emerged to meet use‐specific needs. Frequently, chlorophyll a, phosphorus, and Secchi depth are used to classify TS based on autotrophic production, whereas phosphorus, dissolved organic carbon, and true color are used to classify TS based on both autotrophic and heterotrophic production. Both classification approaches aim to characterize an ecosystem's function broadly, but with varying degrees of autotrophic and heterotrophic processes considered in those characterizations. Moreover, differing classification schemes can create inconsistent interpretations of ecosystem integrity. For example, the US Clean Water Act focuses exclusively on algal threats to water quality, framed in terms of eutrophication in response to nutrient loading. This usage lacks information about non‐algal threats to water quality, such as dystrophication in response to dissolved organic carbon loading. Consequently, the TS classification schemes used to identify eutrophication and dystrophication may refer to ecosystems similarly (e.g., oligotrophic and eutrophic), yet these categories are derived from different proxies. These inconsistencies in TS classification schemes may be compounded when interdisciplinary projects employ varied TS frameworks. Even with these shortcomings, TS can still be used to distill information on complex aquatic ecosystem function into a set of generalizable expectations. The usefulness of distilling complex information into a TS index is substantial such that usage inconsistencies should be explicitly addressed and resolved. To emphasize the consequences of diverging TS classification schemes, we present three case studies for which an improved understanding of the TS concept advances freshwater research, management efforts, and interdisciplinary collaboration. To increase clarity in TS, the aquatic sciences could benefit from including information about the proxy variables, ecosystem type, as well as the spatiotemporal domains used to classify TS. As the field of aquatic sciences expands and climatic irregularity increases, we highlight the importance of re‐evaluating fundamental concepts, such as TS, to ensure their compatibility with evolving science.

EcosphereVol. 16(9)
University of Geneva (CH), United States Geological Survey (US), Oak Ridge National Laboratory (US), Environmental Systems Research Institute (United States) (US), Environmental Protection Agency (US), University of Wisconsin System (US), University of Wisconsin–Madison (US), Longwood University (US), University of California, Santa Barbara (US), University of Freiburg (DE), Bangor University (GB), National University of Singapore (SG), Southern Methodist University (US), Universidade de São Paulo (BR), Institute of Arctic and Alpine Research (US), Kansas State University (US), York University (CA), National Institute for Environmental Studies (JP), Aarhus University (DK), Universidade do Estado de Minas Gerais (BR), Janicki Bioenergy (United States) (US), Environmental Protection Agency (IE), Oregon Water Science Center, Swiss Federal Institute of Aquatic Science and Technology (CH), Washington State University (US), University of California, Davis (US), University of Puerto Rico at Carolina (PR), Colorado State University (US)
National Science Foundation, Conselho Nacional de Desenvolvimento Científico e Tecnológico, U.S. Geological Survey, Natural Environment Research Council, Oak Ridge National Laboratory
Openalex Percentile: Top 3%
Fish Ecology and Management Studies
6.94
DOIOpen Access PDFOpenAlex
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