What the study found
Phycotoxins in two marine harmful algal genera are induced by both relative nitrogen enrichment and elevated grazing risk. The authors report that grazing risk may rival, and perhaps exceed, the toxin-inducing effect of nitrogen enrichment.
Why the authors say this matters
The authors conclude that understanding phycotoxin production requires considering both nutrient availability and selective pressure from grazers. They suggest that future work on the evolution and variable production of phycotoxins should integrate these bottom-up and top-down factors.
What the researchers tested
The researchers conducted a meta-analysis of 113 control-treatment contrasts from 37 peer-reviewed experimental studies. They compared the effects of relative nitrogen enrichment, defined as a higher nitrogen-to-phosphorus ratio than the control, and elevated grazing risk, defined as exposure to zooplankton grazers or their chemical cues, on phycotoxin induction in Alexandrium dinoflagellates and Pseudo-nitzschia diatoms.
What worked and what didn't
Both relative nitrogen enrichment and elevated grazing risk increased phycotoxin production. The two genera responded similarly to relative nitrogen enrichment, but Pseudo-nitzschia toxins increased 10 times more than Alexandrium toxins in response to grazers.
What to keep in mind
The analysis is limited to the two most-studied marine harmful algal bloom genera. The abstract does not describe other limitations beyond that scope.
Key points
- A meta-analysis found that phycotoxins increase in response to both relative nitrogen enrichment and grazing risk.
- Grazing risk may rival or exceed the toxin-inducing effect of relative nitrogen enrichment.
- The comparison used 113 control-treatment contrasts from 37 experimental studies.
- The study focused on Alexandrium dinoflagellates and Pseudo-nitzschia diatoms.
- Pseudo-nitzschia toxins increased 10 times more than Alexandrium toxins in response to grazers.
Disclosure
- Research title:
- Grazing risk can induce toxins as strongly as nitrogen enrichment
- Authors:
- Milad Pourdanandeh, Erik Selander
- Institutions:
- University of Gothenburg, Lund University
- Publication date:
- 2026-03-08
- OpenAlex record:
- View
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