Mixotrophic Strategies in Aquatic Ecosystems

Mixotrophy encompasses a spectrum of nutritional modes in which single-celled and multicellular aquatic organisms combine photosynthesis with prey ingestion. By circumventing the traditional dichotomy of phytoplankton and microzooplankton, mixotrophs exert a pivotal influence on carbon and nutrient cycling across freshwater and marine systems. Constitutive mixotrophs possess intrinsic photosynthetic and heterotrophic machinery, while non-constitutive mixotrophs acquire phototrophic capacity through ingestion of specific prey. These versatile organisms modulate food-web structure, enhance nutrient retention under oligotrophic conditions and form efficient conduits between microbial loops and higher trophic levels. Environmental drivers such as light availability, temperature, nutrient limitation and prey abundance orchestrate shifts between phototrophy and phagotrophy, with implications for biogeochemical modelling, biological carbon pump efficacy and resilience of aquatic ecosystems under climate change.

Research from Nature Portfolio

Recent studies have demonstrated that light availability can act as a regulatory switch in mixotrophic bacterivory, with eukaryotic phototrophic flagellates exerting top-down control on heterotrophic bacteria in oligotrophic seawater. Under increasing irradiance, predator-prey dynamics intensify, leading to reduced bacterial abundances despite unchanged bacterial growth rates. This light-mediated top-down regulation alters nutrient remineralisation pathways and shortens the microbial food chain, highlighting a mode by which mixotrophs can streamline energy transfer and reshape nutrient cycles in ultra-oligotrophic environments.

Mixotrophic Strategies in Aquatic Ecosystems publication trend

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

Technical terms

Mixotrophy: Combination of phototrophic and heterotrophic nutrition within a single organism.

Photoautotrophy: Energy acquisition exclusively through photosynthesis.

Phagotrophy: Ingestion of particulate organic matter or prey cells for nutrition.

Constitutive mixotrophs: Organisms with inherent capacity for both photosynthesis and phagotrophy.

Non-constitutive mixotrophs: Organisms that obtain phototrophic function by ingesting phototrophic prey.

Chlorophagy: Autophagic degradation of chloroplast fragments within specialised vacuoles.

References

1. Choanoflagellates alongside diverse uncultured predatory protists consume the abundant open-ocean cyanobacterium Prochlorococcus. Proceedings of the National Academy of Sciences of the United States of America (2023).
2. A multifunctional organelle coordinates phagocytosis and chlorophagy in a marine eukaryote phytoplankton Scyphosphaera apsteinii. New Phytologist (2025).
3. Transcriptomic insights into the shift of trophic strategies in mixotrophic dinoflagellate Lepidodinium in the warming ocean. ISME Communications (2024).
4. A light-induced shortcut in the planktonic microbial loop. Scientific Reports (2016).
5. Defining Planktonic Protist Functional Groups on Mechanisms for Energy and Nutrient Acquisition: Incorporation of Diverse Mixotrophic Strategies. Protist (2016).
6. The role of mixotrophic protists in the biological carbon pump. Biogeosciences (2014).