This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: A team of marine scientists led by researchers at the University of California, Santa Cruz, has developed a new approach to predicting harmful algal blooms (HABs), changing how oceanographers track these hazardous marine events. In a study published this week in the Proceedings of the National Academy of Sciences, the researchers demonstrated that passively measuring chemical "alarm cues" produced by microscopic ocean predators—a group of polar lipids known as copepodamides—allows scientists to forecast toxic algal blooms up to seven weeks in advance.
This "top-down" biological monitoring technique extends predictive lead time by more than a month compared with conventional toxin-tracking methods, giving coastal agencies and shellfish fisheries critical advance warning before toxins reach dangerous levels. For decades, ocean forecast models have focused almost exclusively on "bottom-up" physical and environmental drivers, such as ocean currents, water temperature and nutrient upwelling, according to the study's senior author, distinguished ocean sciences professor Raphael Kudela. "By capturing the chemical signals of biological predators, we've opened up a vital top-down window into ecosystem dynamics," Kudela said.
"By 'listening' to chemical interactions between marine grazers and algae, we can add a new and reliable monitoring technique to our early-warning toolbox." Harmful algal blooms in the California Current System are primarily driven by Pseudo-nitzschia, a genus of microscopic marine diatoms capable of producing the potent neurotoxin domoic acid. When tiny herbivorous crustaceans called copepods graze on phytoplankton, they release trace chemical compounds known as copepodamides. These lipids act as an aquatic "predator scent," or alarm signal.
Diatoms like Pseudo-nitzschia detect these grazer cues and respond by activating defensive mechanisms, including a dramatic increase in domoic acid production to potentially deter grazers. "Globally, researchers are continuing to find new instances of predator-induced toxin production in different species of harmful algae," said Aubrey Trapp, the study's corresponding author. Trapp finished her Ph.D. dissertation in Kudela's lab and is now a postdoctoral scholar at Northwest Indian College in Bellingham, Washington.
In marine environments, ambient copepodamides are dilute and degrade rapidly, making them historically difficult to measure in open seawater. To overcome this challenge, the research team adapted "solid-phase adsorption toxin tracking" (SPATT)—a passive sampling technology that uses porous resin beads suspended in mesh rings to continuously absorb dissolved compounds directly from ocean water over days or weeks. Over a 28-month monitoring campaign at the Santa Cruz Municipal Wharf—a recognized hot spot in Monterey Bay for toxic bloom activity—the team showed that SPATT samplers reliably captured copepodamide concentrations, which correlated directly with zooplankton net counts.
Subsequent lab experiments at UC Santa Cruz confirmed that exposing local Pacific strains of Pseudo-nitzschia to copepodamides triggered a tenfold surge in cellular toxin production. Discover the latest in science, tech, and space with over 100,000 subscribers who rely on Phys.org for daily insights. d research that matter—daily or weekly. Current public health monitoring relies on measuring toxin levels in seawater or shellfish tissue, which often provides coastal managers with only days to a week of notice before harvesting closures must be enforced.
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