Naturally occurring neurotoxin associated with killing marine mammals found in Indian River Lagoon dolphins, scientists say

A new study led by Florida Tech shows a naturally occurring neurotoxin may be present in the Indian River Lagoon, even when potentially harmful algae blooms aren’t.

Researchers were able to detect the toxin in bottlenose dolphins. It is the first report of this particular neurotoxin being detected in marine mammals during non-bloom conditions, and researchers must determine if it is negatively affecting marine animals.

“Large mammals like bottlenose dolphins are sort of the canary in the coal mine for ecosystems," said Dr. Spencer Fire, assistant professor of Biological Sciences at Florida Tech. "That’s why we call them a marine sentinel species.”

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The neurotoxin, called saxitoxin, is produced by a species of glowing, or bioluminescent, algae. Researchers found evidence of saxitoxin in liver samples from dead dolphins even when there were no algae blooms present.

“Once we know it’s in the animals’ bodies, the next step is to look for what kind of impact (it has),” Fire said.

The next step is to observe the dolphins’ behavior and see if they are exhibiting behaviors that are consistent with neurological dysfunction, Fire said.

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Researchers have been taking a closer look at the dolphin’s diet and also found trace levels of saxitoxin over a three-year period throughout the Indian River Lagoon.

Saxitoxin poisoning has been associated with puffer fish, and led to a ban on their harvesting in the lagoon since the early 2000s.

“Our marine ecosystems are changing rapidly, and I think this may be one of the harmful ways our marine system can change, whether it’s due to climate change, or nutrient input, human impacts from coastal development,” Fire said. “These are all things that, in some way, have been influencing harmful algal blooms.”

Adam Poulisse,

Adam Poulisse joined WFTV in November 2019.