ATLANTA (August 29, 2025) – Dr. Patrick Charapata, a research scientist at Georgia Aquarium, led a study that was just published in the journal Harmful Algae investigating the implications of harmful algal blooms in the Arctic, and what that means for the health of walrus who consume the nerve toxins while eating shellfish. This wasn’t an issue of concern decades ago, but as waters warm and harmful algae move into Arctic waters, researchers are working to uncover what this means for the health of wildlife, and also the food system that Indigenous people depend upon.

Why Ocean Warming Matters for Walruses

As Arctic waters warm, harmful algal blooms are appearing more often and in new places. Some algae—such as Alexandrium catenella—produce paralytic shellfish toxins (PSTs), a powerful nerve toxin. Think of the toxin’s path like a relay: tiny algae make it, clams and worms on the seafloor eat the algae and can hold onto it, and when walruses eat those invertebrates, they may take in the toxin along with their meal. Dr. Charapata spent three years building an easy-to-use way to estimate how much toxin could reach walruses during a bloom and where exposure might be higher depending on where walruses eat/forage.

How the Study Worked and What it Revealed

Using data from two confirmed Arctic bloom years (2019 and 2022), researchers modeled a typical day of feeding for a walrus. This approach produced estimates of daily toxin ingestion and mapped places and times where exposure was likely to be elevated.

Results indicate that during bloom periods, walruses are likely to ingest enough toxin to potentially affect their health. One important caveat remains: the exact dose that harms walruses has not yet been established, so these findings characterize exposure rather than a confirmed health threshold.

“These models give us our clearest picture yet of how a microscopic algae can become a potential macro-level health threat for walruses,” said Dr. Charapata. “They help us identify where risks may spike as Arctic conditions shift and where monitoring can protect both wildlife and the food-security and food-safety of people.”

For People and Communities: What Comes Next

This work reflects a One Health perspective, where animal, human, and environmental health are connected. The same modeling framework can help assess toxin risks for marine subsistence foods important to Native Alaskan communities and can support more informed decisions during future blooms.

Researchers plan to refine estimates as new toxicity data become available, especially walrus-specific thresholds, and to apply the approach to additional bloom scenarios so partners can use it for planning and early warning.

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