Copepod Interactions with Harmful Algal Blooms

Copepods, a diverse group of planktonic crustaceans, play a pivotal role in the dynamics of harmful algal blooms (HABs) by grazing on toxin-producing microalgae and, conversely, by triggering algal defence mechanisms. These interactions encompass direct ingestion, avoidance behaviours and chemically mediated responses that influence bloom development and persistence. Through selective feeding, copepods can suppress or maintain algal populations, thereby modulating nutrient cycling and energy transfer in marine and freshwater ecosystems. Simultaneously, certain phytoplankton species detect waterborne cues from copepods—such as copepodamides—and respond by altering morphology, chain length or toxin production, creating a feedback loop that shapes community structure and trophic interactions.

The global significance of these processes extends to fisheries, aquaculture and public health, as copepod grazing can mitigate toxin accumulation in food webs, while induced algal defences may exacerbate bloom severity. By integrating field observations, laboratory experiments and molecular approaches, recent research has advanced our understanding of how environmental factors, predator cues and algal physiology interact to determine the outcome of copepod–algal encounters. These findings inform management strategies aimed at predicting bloom trajectories and harnessing natural grazer pressures to reduce HAB impacts.

Research from Nature Portfolio

Mass spectrometry analyses have recently detailed the chemical composition of copepodamides across marine and freshwater species, revealing conserved signalling compounds that trigger defensive traits—such as toxin synthesis and size plasticity—in diverse phytoplankton taxa. This work highlights how species-specific copepodamide signatures mediate grazer–prey interactions across aquatic realms. In parallel, transcriptomic profiling of a widespread calanoid copepod feeding on a saxitoxin-producing dinoflagellate has uncovered shifts in gene expression related to energy metabolism and digestive enzymes, indicating sublethal effects of toxin exposure on grazer physiology and potential consequences for lipid reserve formation.

Copepod Interactions with Harmful Algal Blooms publication trend

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

Technical terms

Harmful Algal Bloom (HAB): A dense aggregation of toxin-producing microalgae that poses ecological, economic and health risks.

Copepodamide: A chemical cue exuded by copepods that induces defensive responses, including toxin production, in phytoplankton.

Grazing Coefficient: A rate constant reflecting the proportion of prey biomass removed by grazers per unit time.

Saxitoxin: A potent neurotoxin synthesised by certain dinoflagellates, responsible for paralytic shellfish poisoning.

Paralytic Shellfish Toxin (PST): A group of neurotoxic compounds produced by dinoflagellates and accumulated in shellfish, affecting consumer safety.

References

1. Grazing impact of the calanoid copepods Acartia spp. on the toxic dinoflagellate Alexandrium pseudogonyaulax in the western coastal waters of Korea. Frontiers in Microbiology (2024).
2. Mass spectroscopy reveals compositional differences in copepodamides from limnic and marine copepods. Scientific Reports (2024).
3. The Influence of the Toxic Dinoflagellate Alexandrium minutum, Grown under Different N:P Ratios, on the Marine Copepod Acartia tonsa. Toxins (2023).
4. Induction of defensive traits in marine plankton—new copepodamide structures. Limnology and Oceanography (2018).
5. Transcriptomic responses of the calanoid copepod Calanus finmarchicus to the saxitoxin producing dinoflagellate Alexandrium fundyense. Scientific Reports (2016).
6. Algal Toxins Alter Copepod Feeding Behavior. PLOS ONE (2012).