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For the latest forecasts and critical weather information, visit weather.gov.

When Algae’s Past Predation Haunts Future Blooms

Harmful algal blooms caused by Alexandrium catenella pose significant threats to marine ecosystems, aquaculture, and human health. A study funded by NOAA’s National Centers for Coastal Ocean Science investigated how both top-down (predator cues) and bottom-up (nutrient availability) factors influenced predator-induced toxin production and cell growth in A. catenella. Recent findings show that when A. catenella is exposed to copepod predators, toxin retention increases and cell growth decreases. These effects can persist for generations, even after the predators are removed. 

The following key findings were recently published in the journal, Toxins:

  • Increases in toxin production that are associated with predation may compromise cell growth
  • Defense-related toxin production may shorten the duration of A. catenella blooms
  • Nutrient availability influences these effects, but past predator exposure is a more dominant factor in determining toxin content and growth rate
  • Predator exposure impacts are consistent across different nutrient regimes and bloom phases
Microscopic view of a copepod with a small inset of an algae
Copepod Acartia hudsonica (larger image) is a common predator of dinoflagellate Alexandrium catenella (insert). Photo by Gihong Park, UCONN Avery Point.

These findings suggest that predation and its legacy effects play a crucial role in the toxicity and duration of toxic algal blooms. Understanding these long-lasting effects is essential to improve harmful algal bloom predictions and related management strategies. 

This study was supported by the NCCOS Ecology & Oceanography of Harmful Algal Blooms (ECOHAB) project Are Growth and Toxicity of the Dinoflagellate Alexandrium Controlled by Grazer-induced Defense?, led by Hans Dam of the University of Connecticut. 

ECOHAB is a peer-reviewed, national, competitive program that funds research to advance understanding of the causes and impacts of HABs. ECOHAB research informs management of coastal resources to reduce HAB impacts and future threats.

This work is authorized under the Harmful Algal Bloom and Hypoxia Research and Control Act (33 U.S.C. §§ 4001 et seq.) and the NOAA Authorization Act of 1992.

Citation: 

Park, G., Batoh, C., and Dam, H.G. (2025). The Ghost of Predator Past: Interaction of Past Predator Exposure and Resource Availability on Toxin Retention and Cell Growth in a Dinoflagellate. Toxins, 17, 290. https://doi.org/10.3390/toxins17060290

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