All of that material pouring into the ocean
has resulted in a heightened supply of nutrients.
The extra nutrients plus the warmer waters and
more sunlight shining through — thanks to the
missing or thinner sea ice — add up to larger
phytoplankton blooms, Frey says. Some of that
algal biomass — scientists don’t yet know how
much — is toxic, akin to the deadly red tides blossoming along Florida’s coasts in recent years
(SN: 9/29/18, p. 14). Such toxins can kill fish, as
well as produce neurological damage in humans.
Paralytic shellfish poisoning has increased
sevenfold among Alaskans over the last 40 years,
with the rise possibly caused by an increase in
harmful algal blooms, Frey says. The state now has
one of the highest incidences of shellfish poisoning in the world. The frequency and distribution
of harmful algal blooms have both increased dramatically in recent years, prompting the first
special section on harmful algal blooms included
in the 2018 Arctic Report Card.
The culprit algae may have “been present in many
areas at low levels that wouldn’t be harmful. But
the minute you start warming seawater … and
removing sea ice, they adjust,” Frey says. “We are
just starting to make measurements of harmful
algal blooms and starting to understand how those
species in the Arctic respond to light. It’s a very
new question that has yet to be answered.”
Frey, as part of the Distributed Biological
Observatory program, visited the Bering Sea last
July to measure how less sea ice, as well as thinner
sea ice, changes the amount of light that reaches
the waters to encourage blooms. Even the thinner
ice — often covered with small melt ponds — could
have a big effect on how much light penetrates,
The melt ponds “are basically skylights” for
the waters below, she says. Having melt ponds
on the surface of the sea ice can increase transmission of light into the water from perhaps
10 percent to as much as 60 or even 70 percent,
Frey reported at the December meeting.
The increase in phytoplankton blooms was particularly dramatic in 2018, the report card notes.
Less sea ice and more melt ponds meant more light
penetrated the Arctic’s waters earlier in the year,
prompting blooms in the northern Bering Sea even
as the south bloomed later. The northern waters,
which normally see blooms in May, bloomed as
early as March. The amount of algal biomass in
March was about 275 percent higher than the average March biomass for 2003 to 2017.
Scientists are still studying how much the
harmful algal blooms may have contributed to
excess seabird deaths. Bloom-related toxins have
been implicated in other wildlife mass mortality
events in the last few years, from walrus to seals
to whales — animals that probably ate contaminated fish and shellfish, just like humans, the
Arctic Report Card notes. As warming waters
and decreasing ice cover create ever more favorable conditions for all algal blooms, the threat of
harmful toxins will almost certainly contribute
to economic losses for two of the region’s biggest
industries: fishing and tourism.
“Historically we shouldn’t be seeing another
year like , but under that argument, this
year shouldn’t have happened,” Stabeno said in
December. “What we saw this year was predicted
to happen in 2050,” she added. “This gives us a
view of the future.” s
s NOAA Arctic Report Card. December 2018.
April usually means ice in the Bering Sea. But satellite maps from April 2013 through
2018 (top) show a basically ice-free sea last year. Warming waters and decreasing sea
ice cover encourage harmful algal blooms, which can hurt tourism and fishing (bottom,
a native Alaskan fishes with a drop line on the Bering Sea in Nome, Alaska).
2013 2014 2015
2016 2017 2018