Freshwater Ecology

Freshwater ecosystems—encompassing rivers, streams, lakes, wetlands and groundwater—occupy less than one per cent of Earth’s surface yet sustain roughly one third of all vertebrate species and a similar proportion of global biodiversity. These environments are shaped by hydrological regimes, geomorphology, water chemistry and biological interactions. Flow variability governs sediment transport, nutrient fluxes and habitat structure, while temperature, light and oxygen concentrations regulate metabolic rates and community composition. Primary producers fix carbon and form the base of aquatic food webs, supporting invertebrates and fish whose feeding, reproduction and movement create feedbacks that influence water quality and ecosystem resilience. Human pressures—dams, abstraction, pollution, land‐use change and climate warming—alter natural flow patterns and water chemistry, fragment habitats and compromise ecological function. Contemporary freshwater ecology seeks to understand these processes at multiple scales, to reveal how species and communities respond to environmental change, and to inform management aimed at conserving biodiversity and securing critical ecosystem services such as water purification, flood regulation, fisheries production and carbon storage.

Research from Nature Portfolio

Field studies in Arctic lakes have documented marked increases in juvenile growth rates of cold-water fish under recent warming. Analyses of otolith growth rings in a high-latitude char population over four decades reveal that longer ice-free seasons and higher summer temperatures enhance somatic growth, although density-dependent effects moderate these gains. These insights highlight how climate warming drives size-structured shifts in fish communities and may alter predator–prey dynamics in freshwater lakes.

Integrating palaeolimnological and modern food-web methods has uncovered gradual ecological reorganisation in a regulated floodplain wetland following flow regulation and sediment inputs. Subfossil invertebrate assemblages and stable-isotope records trace a transition from a clear-water, macrophyte-dominated state to a more eutrophic, turbid regime. Mixing-model reconstructions of δ13C and δ15N in subfossil and contemporary biota reveal shifts in trophic relationships, indicating altered resource pathways and a slow but persistent change in ecosystem structure over the past two centuries.

Freshwater Ecology publication trend

The graph below shows the total number of articles in freshwater ecology across all publications each year (not limited to Nature Index journals).

Technical terms

Hydrological regime: The pattern of flow variability in freshwater systems, including magnitude, frequency and seasonality of discharge.

Palaeolimnology: The reconstruction of past lake or wetland conditions using biological (e.g., diatoms, invertebrate remains) and geochemical (e.g., isotopes, organic matter) proxies.

Otolith sclerochronology: The study of incremental growth rings in fish ear stones to infer age and past environmental influences on growth.

Endozoochory: Dispersal of organisms or propagules via ingestion and subsequent excretion by animals.

Food-web mixing model: An analytical framework using stable-isotope ratios to quantify the proportional contributions of different sources and prey to consumer diets.

References

1. The Aquatic Habitat.
2. Climate warming accelerates somatic growth of an Arctic fish species in high-latitude lakes. Scientific Reports (2023).
3. Integration of palaeo-and-modern food webs reveal slow changes in a river floodplain wetland ecosystem. Scientific Reports (2020).
4. Bird‐mediated endozoochory as a potential dispersal mechanism of bony fishes. Ecography (2024).
5. Undesirable river biofilms: The composition, environmental drivers, and occurrence of sewage fungus. Ecological Indicators (2024).
6. Trophic plasticity of omnivorous fishes in natural and human‐dominated landscapes. Limnology and Oceanography (2023).