Scientists have documented an increase in harmful algal blooms in northern waters


An algal bloom discolored a strip of the Gastineau Canal north of the Douglas Bridge in Juneau on Monday, July 30, 2018. Scientists have documented an increase in harmful algal blooms in the northern Bering and Chukchi Seas. (Jeremy Hsieh / KTOO)

Scientists have documented an increase in harmful algal blooms in the northern Bering and Chukchi Seas. The flowers have toxins in them, but scientists aren’t sure what effects they will have on marine mammals.

“We don’t yet know whether toxin levels in arctic food webs are high enough to have health effects on marine mammals in this (arctic) region,” said Don Anderson.

Anderson, a senior scientist at the Woods Hole Oceanographic Institute (WHOI), has been studying algae cysts in the Bering and Chukchi Seas for several years. He showcased his data and the work of other researchers in the area during a virtual Strait Science event hosted on October 14th from the University of Alaska’s Fairbanks Northwest campus.

Map of harmful algal blooms in the northern Bering and Chukchi Seas. (Courtesy Don Anderson / WHOI)

Not all types of algal blooms are harmful, stressed Anderson. In fact, there are thousands of them scattered across the oceans. But in the northern Bering and Chukchi Seas there is a growing presence of alexandrium cysts, an algal bloom that produces harmful saxitoxin.

The previously accepted explanation for how they got this far north is known as the “trail of death” hypothesis, Anderson said.

“That (says) it is carried from the south in these relatively warm surface waters and that in the Chukchi region it would form cysts that fall on bottom sediments where temperatures would be too cold to support significant germination,” said Anderson . “I call this cyst seedbed a sleeping giant.”

As bottom water temperatures in the northern Bering and Chukchi Seas have warmed dramatically in recent years, cysts are now growing locally in arctic waters. In other words, the sleeping giant has awakened.

“So what you have is a dramatic increase in the potential for what we would call local flower initiation. In other words, not just transport, but flowers that are inoculated from this region, from the seedbeds of both Ledyard Bay and Barrow cysts, ”said Anderson.

Ocean currents on a map in the northern Bering and Chukchi Seas. (Courtesy Don Anderson / WHOI)

Recently, the United States Geological Survey concluded that the recurrent seabird extinctions in the Bering Strait were not related to harmful algal blooms. However, USGS scientists found low levels of toxin in many of the bird species they sampled.

Anderson emphasized that since 2016, low biotoxin levels have been documented in all different species of marine mammals, seabirds and different fish species in the Bering Sea.

Even so, Anderson said the consumption of various forage fish or salmon in the area still poses a low risk to human health.

“Based on current knowledge of these toxins in many other parts of the world, we believe that muscle and fat are unlikely to accumulate saxitoxin in concentrations that pose a threat to human health. These tissues have not yet been fully tested, but there are reasons to believe they will not accumulate toxins, ”said Anderson.

This baseline is based on the only metric that exists by the FDA regarding the safe food consumption of shellfish. It determines the degree to which mussels or other shellfish become too poisonous to eat and then cause paralytic shellfish poisoning. However, it is not the best way to measure how high levels of algae toxins can be in marine mammals before they harm the people who eat themsaid Anderson.

Alaska marine mammal map showing toxin levels found in different species, from Kathi Lefebvre’s 2016 report of algae toxins in the waters of Alaska, used with permission. (Courtesy Kathi Lefebvre)

Although Anderson believes that the health risks to livelihoods for Bering street consumers are fairly small, he nevertheless stressed that caution and safe practices should be used as usual when consuming shellfish or marine mammals. He also highlighted that other parts of the world live under the same conditions.

“Many regions of the world are exposed to similar risks and yet are able to maintain healthy communities and ecosystems. But it does this through good management, good communication, and understanding of the threats, ”said Anderson.

Overall, there is an increasing potential to harm human and ecosystem health in northern Alaskan waters as cysts spread and cause more harmful algal blooms.

An observation by Edgar Ningeulook, cited in 2013, indicated an algal bloom near a historic site called Ipnauraq.

“This was the site of a red tide that caused many deaths at once. And it doesn’t say what, what did you eat? I find that this is a place that is fished a lot, especially for herring, one of those forage fish I was talking about. This is how herring was eaten, mussels, who knows. But note its location, it is in this way of transported flowers from the south. So long ago there was this threat and it got to the point where a lot of people died, ”said Anderson.

Research in the Chukchi Sea is ongoing. Anderson’s team will work with scientists on the Russian side of the Strait in 2022 to learn the full extent of the other changes in the Bering Sea ecosystem.


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