Allelopathy in Harmful Algal Blooms and Shellfish Interactions

Harmful algal blooms (HABs) are proliferations of toxin-producing phytoplankton that exert allelopathic pressure through the release of bioactive compounds. These allelochemicals mediate interactions within planktonic communities and can compromise the health of commercially important shellfish by altering physiological processes, accumulating toxins and inducing oxidative stress. Allelopathy in HABs thus encompasses both the suppression of competing microalgae and the modulation of shellfish metabolism, immunity and feeding behaviour. In bivalves such as oysters and mussels, exposure to allelochemical-rich waters can lead to reduced growth rates, impaired cellular antioxidant defences and elevated concentrations of paralytic shellfish toxins, with subsequent risks to aquaculture productivity and human health. Understanding the chemical ecology of these interactions is pivotal for the development of early warning systems, selective breeding for resistant shellfish strains and targeted mitigation strategies that preserve ecosystem function and seafood safety.

Research from Nature Portfolio

Studies have illuminated the mechanistic basis of allelopathy in a model HAB organism, revealing that exuded compounds can profoundly remodel the lipid profile and membrane integrity of co-occurring microalgae. In these experiments, competitor species showed differential susceptibility: one maintained homeostatic lipid metabolism and photosynthetic capacity, while another experienced compromised membrane lipids, increased permeability and inhibited photosynthesis. This work underscores the targeted nature of allelochemicals that confer a competitive edge to bloom-forming species and suggests parallels with the vulnerability of shellfish tissues to such bioactive metabolites.

Allelopathy in Harmful Algal Blooms and Shellfish Interactions publication trend

The graph below shows the total number of articles in allelopathy in harmful algal blooms and shellfish interactions across all publications each year (not limited to Nature Index journals).

Technical terms

Allelopathy: The biochemical interaction in which an organism releases compounds that influence the growth or survival of other organisms.

Allelochemical: A bioactive chemical produced by one organism that affects the physiology or development of another.

Harmful algal bloom (HAB): A rapid increase in phytoplankton density that produces toxins or causes ecological harm.

Paralytic shellfish toxins (PSTs): A group of neurotoxins that block sodium channels and can accumulate in shellfish tissue, posing risks to human consumers.

Reactive oxygen species (ROS): Chemically reactive molecules containing oxygen that can indicate oxidative stress within cells.

Lipidome: The complete set of lipids in a cell or organism, relevant to membrane structure and energy storage.

Photosynthetic efficiency (Fv/Fm): A parameter measuring the maximum potential quantum efficiency of photosystem II in photosynthetic organisms.

References

1. Immediate and delayed effects of a heatwave and Prorocentrum lima ((Ehrenberg) Stein 1878) bloom on the toxin accumulation, physiology, and survival of the oyster Magallana gigas (Thunberg, 1793). The Science of The Total Environment (2023).
2. Allelopathic Effect of a Chilean Strain of Karenia selliformis (Gymnodiniales, Dinoflagellata) on Phytoplankton Species. Microorganisms (2024).
3. Effects of Harmful Algal Blooms on Fish and Shellfish Species: A Case Study of New Zealand in a Changing Environment. Toxins (2022).
4. Karenia brevis allelopathy compromises the lipidome, membrane integrity, and photosynthesis of competitors. Scientific Reports (2018).