Whale poop links toxic algal blooms to ocean warming
By Heather McFarland | UAF on Comments Off on Whale poop links toxic algal blooms to ocean warming
Photo courtesy of Amelia Brower/NOAA Fisheries, NMFS Permit # 14245AFSC A bowhead whale and calf swim in an ice lead.
Analysis of bowhead whale poop shows that more toxins from typically warm-water toxic algae species are entering Arctic food webs as northern oceans warm and lose sea ice.
The findings are based on nearly 20 years of feces samples collected from bowhead whales harvested for subsistence purposes by Alaska Native people living on the Beaufort Sea coast.
The study, conducted by an interdisciplinary team led by the National Oceanic and Atmospheric Administration, was published this week in the journal Nature. University of Alaska Fairbanks co-authors included Rick Thoman and Gay Sheffield.
“The results of this long-term project underscore the level and quality of novel, impactful information that results when peoples, coastal Alaskans and urban-based scientists, work as a team to share their diverse backgrounds and expertise toward a common goal — in this case, harmful algae in the Arctic food web,” said Sheffield, a UAF Alaska Sea Grant Marine Advisory Program agent based in Nome.
“We had the biology and whale experts, algae and toxin experts, physical oceanographers, climate experts and community level representatives,” added Thoman, a climate specialist at the UAF Alaska Center for Climate Assessment and Preparedness. “It enabled questions to be answered that were no one’s speciality.”
The team took advantage of 205 feces samples collected by hunters during the fall as part of a monitoring program led by the North Slope Borough and the Alaska Eskimo Whaling Commission, in collaboration with 11 bowhead whaling communities. The program tracks baseline data on the whales’ life history and natural diseases, as well as other threats in Arctic waters.
Bowhead whales are considered excellent indicators of the health and structure of marine food webs. They feed mostly on tiny aquatic animals called zooplankton. Since zooplankton ingest algae, bowhead whales are an ideal species for tracking the presence of algal toxins.
Harmful algal blooms occur when certain species of algae are high in abundance and produce toxins that have harmful effects on wildlife and humans. Increasing algal toxin concentrations could threaten food safety for coastal communities in northern and western Alaska that rely on bowhead whales for their nutritional, cultural and economic well-being.
Until now, little data existed on the changing exposure to harmful algal toxins in the Arctic. The use of archived whale feces allowed scientists to go back in time to better understand harmful algal concentrations over the past 19 years.
The study showed that higher algal toxin concentrations in the whale poop were strongly correlated with larger areas of ice-free waters and the resulting warmer ocean temperatures. This is presumably because algae can germinate four to eight times more quickly in the increasingly warmer waters of the Beaufort Sea.
Wind speed and atmospheric pressure also influenced toxin levels in the zooplankton eaten by the bowhead whales. Stronger northeasterly winds were shown to decrease ocean heat in the Beaufort Sea, which lowered algal bloom densities and thus toxin levels. These winds also reduced the algae transported into the region from the more southern Chukchi and Bering seas.
As Arctic waters continue to warm and lose sea ice, more warm-water harmful algal species will enter the northern marine food web, the authors warn. They recommend establishing monitoring of marine wildlife for harmful algal toxic bloom exposure to protect Arctic communities that depend on these resources. Such monitoring would also enhance understanding of the conservation concerns associated with toxic bloom exposure in marine wildlife populations.
“This study serves as a baseline for communities where bowhead whales are culturally and calorically important,” explained Thoman. “The upshot of the paper is there are detectable [algal toxin] levels at this point which we attribute to more open water and sea surface temperatures that are contributing to growth of Alexandrium [algae].”
The increase in harmful algal blooms is one of many examples of how declining sea ice and the resulting warming oceans around Alaska are impacting climate, weather and marine ecosystems.
“The continuing reduction in sea ice quality, quantity and extent are having a profound effect on the marine ecosystems of the northern Bering, Chukchi and Beaufort seas,” emphasized Sheffield.
