Growing potential for toxic algal blooms in the Alaskan Arctic
A warming Arctic presents potential new threats to humans and marine
wildlife in the fast-changing region

Date:
October 5, 2021
Source:
Woods Hole Oceanographic Institution
Summary:
Changes in the northern Alaskan Arctic ocean environment have
reached a point at which a previously rare phenomenon -- widespread
blooms of toxic algae -- could become more commonplace, potentially
threatening a wide range of marine wildlife and the people who
rely on local marine resources for food. That is the conclusion of
a new study about harmful algal blooms (HABs) of the toxic algae
Alexandrium catenella.



FULL STORY ========================================================================== Changes in the northern Alaskan Arctic ocean environment have reached
a point at which a previously rare phenomenon -- widespread blooms of
toxic algae - - could become more commonplace, potentially threatening
a wide range of marine wildlife and the people who rely on local marine resources for food. That is the conclusion of a new study about harmful
algal blooms (HABs) of the toxic algae Alexandrium catenella being
published in the journal Proceedings of the National Academy of Science.


==========================================================================
The study, led by scientists at the Woods Hole Oceanographic Institution
(WHOI) in collaboration with colleagues from the National Oceanic and Atmospheric Administration (NOAA) and other researchers in the U.S, Japan,
and China, looked at samples from seafloor sediments and surface waters collected during 2018 and 2019 in the region extending from the Northern
Bering Sea to the Chukchi and Beaufort Seas north of Alaska. The sediment samples allowed the researchers to count and map Alexandrium cysts --
a seed-like resting stage that lies dormant in the seafloor for much of
the year, germinating or hatching only when conditions are suitable. The
newly germinated cells swim to the surface and multiply using the sun's
energy, producing a "bloom" that can be dangerous due to the family of
potent neurotoxins called saxitoxins that the free-swimming cells produce.

Although microscopic algae in the ocean are most often beneficial
and serve as the base of the marine food web, some species produce
potent neurotoxins that can directly and indirectly affect humans and
wildlife. When the Alexandriumcells are consumed by shellfish and some
fish, those toxins can accumulate to levels that can be dangerous to
humans and wildlife, resulting in the human syndrome called paralytic
shellfish poisoning, with symptoms ranging from tingling lips, to
respiratory distress, to death. In fish, toxin levels can be highest
in digestive and excretory organs, such as the stomach, kidney, liver,
but are very low in muscle and roe. The toxin can also cause illness
and mortality of marine wildlife such as larger fish, marine mammals,
and seabirds.

This is of particular concern for members of coastal communities in
northern and western Alaska who rely on a variety of marine resources
for food.

"We've known about human and marine wildlife health risks associated
with Alexandrium and its toxins in Alaskan waters for a long time,
including occasional events north of Bering Strait, but these results show increased potential for large and recurrent blooms of this species as a
new hazard for Alaska's Arctic," said Don Anderson, WHOI senior scientist
and Director of the U.S. National Office for Harmful Algal Blooms,
who led the study. "The rapid warming that we're seeing all across the
Arctic is setting the stage for dangerous bloom events in the waters of
western and northern Alaska that we formerly thought were too cold for significant germination and growth." Alexandrium are part of a group
of single-celled organisms found in oceans and lakes worldwide known as dinoflagellates, named for their flagella -- whip-like appendages that
cells use to swim through the water. In their cyst stage, Alexandrium
cells settle on the seafloor where they can remain inactive for decades, waiting for water temperatures to become favorable for them to germinate
and take on their free-swimming form.

"As the climate has warmed, the significant and ongoing reduction in
extent and duration of seasonal ice cover along the coast of western and northern Alaska has resulted in dramatic changes" said Bob Pickart, a WHOI physical oceanographer and co-leader of the project with Anderson. "These include warming temperatures due to local heating of ice-free waters,
as well as an increased influx of warmer, fresher water from the Pacific flowing north through the Bering Strait region into the Chukchi Sea."
In addition, atmospheric conditions and less seasonal sea ice means
organisms that rely on sunlight to grow, including Alexandrium, are able
to thrive and multiply. As a result of this and related changes, the
authors write in their paper, the Arctic Ocean ecosystem is witnessing an "unprecedented regime shift."


========================================================================== Among these shifts is both the timing and favorability of ocean conditions
that promote the germination of Alexandrium cysts on the seafloor in the Ledyard Bay area of the northeast Chukchi Sea. Previously, Alexandrium
was known to exist in the Chukchi Sea as dormant cysts or as bloom cells thought to be carried north through the Bering Strait from populations
that originated in southeastern Alaska, the Aleutian Islands, or the east
coast of Russia. The fast north-flowing currents through the narrow Bering Strait slow near Ledyard Bay, allowing Alexandrium cysts to settle to the seafloor. Over time, exceptionally dense and large beds of Alexandrium
cysts have formed. Formerly, water temperatures on the seafloor were
thought to be too cold to allow significant germination to inoculate
local blooms. However, the authors demonstrate that warming over the
last two decades has increased bottom water temperatures in Ledyard Bay
and nearby waters by nearly 2DEGC, sufficient to nearly double the flux
of germinated cells from the seafloor and also speeding up the process,
thereby advancing bloom initiation by almost three weeks and lengthening
the window for favorable growth and bloom formation in surface waters. The swimming Alexandrium cells in surface waters can grow and multiply As a
result, they find increased potential for large blooms of Alexandrium
to produce dangerous levels of the PSP toxins that can enter the food
web and threaten the people and wildlife of the Arctic ecosystem during
warmer years.

"What we're seeing now are very different Arctic Ocean conditions
than anyone in living memory has known," said Anderson. "We've learned
from the Gulf of Maine in the Atlantic Ocean how to monitor and manage Alexandrium bloom events and how to sustain commercial and recreational fisheries in the face of HABs, but navigating this new Alaskan Arctic
HAB problem is going to take a great deal of targeted research and far
more attention to the food security of coastal residents and Alaska
Natives and the health of Arctic wildlife than we've paid so far."
"The threat is clear, but we don't yet know the extent to which these
toxins will ultimately lead to increased human exposure or to impacts
on the health of wildlife at all levels of the food web," said Kathi
Lefebvre, a research biologist at NOAA's Northwest Fisheries Science
Center who, in partnership with Anderson, is leading a parallel study in
close collaboration with Alaskan subsistence communities on the effects, concentrations, and movements of these toxins in food webs. "To complicate
the challenge, this is a new stress on northern marine ecosystems that
are already undergoing unprecedented change, adding yet another concern
for the food security of coastal peoples for whom the ocean is a primary
source of food and a central element of their identity.

??Alaskan coastal communities are now aware of this emerging issue
and have been active partners in the research process to protect their subsistence life as well as advance our understanding of the changing
Arctic and what it means for the future." Support for research was
provided by the U.S. National Science Foundation Office of Polar Programs
and Ocean Sciences Division, by the U.S. National Oceanic and Atmospheric Administration's Arctic Research Program and National Centers for Coastal
and Ocean Science ECOHAB Program, and by the National Institutes of
Health through the Woods Hole Center for Oceans and Human Health.

Key takeaways: -Changes in the northern Alaskan Arctic Ocean environment
have reached a point at which widespread blooms of the toxic algae
Alexandrium catenella could become more commonplace, potentially
threatening a wide range of marine wildlife and the people who rely on
local marine resources for food.



========================================================================== -Free-swimming Alexandrium cells produce saxitoxin, a family of
neurotoxins responsible for paralytic shellfish poisoning in wildlife
and in humans that consume affected animals.

-Field research showed extensive beds of Alexandrium cysts, a dormant,
seed- like life stage of the algae, in seafloor sediments north of
the Bering Strait, in the Chukchi Sea, and in the western Beaufort Sea
near Pt. Barrow -Conditions also favor germination of those cysts and
the growth of the germinated, free-swimming swimming cells in surface
waters, augmenting populations transported into the Arctic from waters
further south.

Authors: Donald M. Anderson1, Evangeline Fachon1, Robert S. Pickart2,
Peigen Lin2, Alexis D. Fischer11 Mindy L. Richlen1, Victoria Uva11,
Michael Brosnahan1, Leah McRaven2, Frank Bahr2, Kathi Lefebvre3,
Jacqueline M.

Grebmeier4, Seth Danielson5, Yihua Lyu6, Yuri Fukai7 ========================================================================== Story Source: Materials provided by
Woods_Hole_Oceanographic_Institution. Note: Content may be edited for
style and length.


========================================================================== Journal Reference:
1. Donald M. Anderson, Evangeline Fachon, Robert S. Pickart,
Peigen Lin,
Alexis D. Fischer, Mindy L. Richlen, Victoria Uva, Michael
L. Brosnahan, Leah McRaven, Frank Bahr, Kathi Lefebvre, Jacqueline
M. Grebmeier, Seth L. Danielson, Yihua Lyu, Yuri Fukai. Evidence
for massive and recurrent toxic blooms of Alexandrium catenella in
the Alaskan Arctic. Proceedings of the National Academy of Sciences,
2021; 118 (41): e2107387118 DOI: 10.1073/pnas.2107387118 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/10/211005124742.htm

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