Seabird deaths, warm oceans, algal blooms puzzle scientists
A series of unusual ocean events in Kachemak Bay, Alaska and the Pacific Northwest has scientists wondering if warming oceans are causing everything from harmful algal blooms to seabird die-offs. So far, though, marine biologists have not yet made a direct connection between all these incidents:
• Reports of dead seabirds in Kachemak Bay that are at least twice normal numbers;
• Warmer oceans in the bay and along the Pacific Ocean coast;
• A harmful algal bloom that has spread from southern California to Homer; and
• An increase in domoic acid from the algal bloom that has shut down some fisheries in Washington and Oregon.
“It’s an interesting time to be a marine biologist — and a scary one,” said Julia Parrish, a fisheries professor at the University of Washington, Seattle, and executive director of COASST, or Coastal Observation and Seabird Survey Training, which instructs citizen scientists in monitoring seabirds along the Pacific Ocean coast.
While Kachemak Bay has seen a die-off
of common murres and other seabirds, warmer oceans and an increase in algae called pseudo-nitzschia, scientists have not detected more than trace amounts of domoic acid caused by harmful algal blooms in local marine life — good news for local oyster farmers. At high levels of domoic acid, sea food becomes unsafe to eat.
Parrish called the die-off of seabirds “elevated,” but nowhere near the size of a historical die-off on Wingham Island north of Kayak Island in Prince William Sound. In that die-off, surveyors reported 1,000 dead birds per kilometer. In Homer, reports in July were of two-to-three dead birds per kilometer. Normal reports are of one bird per kilometer. This week, two COASST groups reported even higher numbers of dead birds of about 10 per kilometer at the end of the Homer Spit and at Anchor Point.
In July, reports from COASST observers in Homer started to come in of unusual numbers of dead birds on local beaches, mostly common murres, the black birds with white bellies that fly low across the water. Naturalists doing tours of Kachemak Bay also reported large rafts of murres off rookeries like Gull Island, with birds staying in the water and not attempting to mate and nest on rocks.
Last Friday, COASST volunteers Carol Harding and Janet Klein reported finding dead 11 common murres, three sooty shearwaters, a glaucous winged gull and a marbled murrelet, all in a 1.7-kilometer stretch on the Spit beach from the mouth of the harbor to the Seafarers Memorial. Harding also said they saw three dying murres struggling in the surf.
In a 2.4-kilometer stretch of the Anchor Point beach, on Saturday, Michael Mungoven and Lisa Climo reported finding dead 27 common murres, one sooty shearwater and one glaucous winged gull. Two murres also were dying in the surf, Mungoven said.
COASST walkers mark dead birds with yellow tags but don’t collect the birds. People seeing dead birds should leave them alone so that COASST volunteers can track them, said Leslie Slater, a wildlife biologist with the Alaska Maritime National Wildlife Refuge.
From a public health standpoint, Slater said, “It’s always prudent not to handle dead, decaying tissues, nor should one let their dogs gnaw on them as well.”
Dead birds washing up most likely have come from Kachemak Bay and nearby populations and not washed up as flotsam from further away, Parrish said. An increase in birds washing up isn’t necessarily a sign of increased mortality in general.
“It could also mean compression of birds closer to the shoreline,” Parrish said.
Tests done on seabirds found dead on Homer beaches show they died of starvation, but what caused them to starve is not yet known, Slater said.
“Why are they starving? It’s not that there’s no food, because if there was no food, we’d be knee deep in birds,” Parrish said.
Slater said warmer water could affect the vertical migration of forage fish — how deep or shallow they swim — and make fish deeper and harder for seabirds to catch. She noted that commercial fishermen have reported salmon are deeper this year. That’s all speculation, though.
“Unfortunately, it could be that they’re only able to determine the cause of death is starvation,” Slater said.
In 2014 and 2015, water temperatures in Kachemak Bay have been above average, said Angela Doroff, Kachemak Bay Research Reserve research coordinator. KBRR analyst Steve Baird said the 15-year average ocean temperature for July was 8.5 degrees Celsius or 47.4 degrees Fahrenheit. In July 2014, the average temperature was 9.27 C or 48.7 F and for July 2015 even higher, 10.33 C or 50.6 F.
Warmer ocean temperatures raise concerns about harmful algal blooms, which tend to go up in warmer temperatures. In July, scientists monitoring algal blooms in the bay with the Kachemak Bay Research Reserve saw a decline in concentrations of one plankton of concern, Pseudo-nitszchia, which sometimes produces domoic acid.
High amounts of domoic acid can make sea life unsafe to eat. Plankton numbers increased in late July and early August, with Pseudo-nitszchia present everywhere in the bay except Halibut Cove and Bear Cove and blooming in Sadie Cove.
In the Aleutians, one bloom was so thick divers had to cancel a planned research trip because they couldn’t see, Doroff said.
The good news with the Pseudo-nitszchia bloom is that scientists measured only trace amounts of domoic acid.
Domoic acid has been seen in higher amounts associated with harmful algal blooms off California, Oregon and Washington. The U.S. Food and Drug Administration considers unsafe domoic acid concentrations to be 20 parts per million or 20,000,000 nanograms per liter.
In Kachemak Bay, tests done by the National Oceanic and Atmospheric Administration, National Ocean Service Marine Biotoxins Program in Charleston, S.C., found domoic acid in trace amounts of 7 to 13 nanograms per liter in test of Pseudo-nitszchia samples. Tests were negative for samples of mussels and sand lances.
“That’s an important message for all our shellfish growers,” Doroff said.
How warm ocean water, algal blooms and seabird die-offs connect remains a big question for scientists.
“I would say nobody knows, but I would also say there’s a preponderance of evidence at global and regional levers that the climate is changing, and the cause is increased greenhouse gases,” Parrish said.
COASST is a sentinel program, she said, a broad look at one event.
“You can capture a little bit of what’s going on, but hey, it’s different, it’s higher than normal,” Parrish said.
The birds are showing scientists something is wrong with the ecosystem, Doroff said.
“When you start thinking about things as a whole system, there’s very rarely a smoking gun,” she said. “There are levels of shifts that make it unpalatable for one reason or another.”
Michael Armstrong can be reached at firstname.lastname@example.org.
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