Ducks nesting on the Yukon-Kuskokwim Delta may be the latest species at risk on the front lines of climate change.
Researchers reported at last week’s Alaska Marine Science Symposium in Anchorage that in a laboratory test, two varieties of sea-ducks, already listed as threatened, almost died when exposed to saline water at levels already found where they nest.
Researcher Tuula Hollmén with the University of Alaska Fairbanks College of Fisheries and Ocean Sciences was clearly moved, along with audience members, when she showed video of ducklings exposed to what is called “brackish” water, with a salinity of six parts of salt per 1,000.
“Again, I want to emphasize that the response was unexpected,” said Hollmén.
Six parts of salt per 1,000 is a salinity level below that already present in the mixed waters where two species of sea-ducks, the threatened spectacled and Steller’s eiders, nest.
In the Alaska SeaLife Center lab in Seward, three ducklings could be seen reacting after just three or four days of exposure. They hunched over, unable to lift their heads, eat, preen or stay afloat in water.
“At this point the ducklings could not forage or swim normally,” explained Hollmén, “and we considered them to not have survived in the wild.”
Seabirds have a special gland located between their eyes to process the salt in sea water, but that gland isn’t fully functioning when they hatch. The time it takes to kick in varies by species, as does how vulnerable each species may be to salinity. For example, common eiders don’t show any effect until the water is much saltier.
Hollmén’s study was the first conducted on spectacled and Steller’s eiders. Because they migrate to the sea later than their cousins, she already expected them to be more sensitive. She thought she was being conservative when she designed the study to test at six parts of salt per 1,000, because she had found those levels present in the environment when she first started work in the Y-K Delta. She said that with the loss of sea ice and more storm surges, the levels now in the nesting grounds are up to 10 parts of salt per 1,000.
The question is, what does the lab experiment mean for ducklings in the wild?
“These ducklings were reared in ideal conditions with unrestricted food,” said Hollmén. “And if there are some other factors, maybe even lesser-degree effects could have some impact in the wild.”
Those wild conditions could also be better because salinity levels vary.
After witnessing the ducklings struggling during the test, Hollmén reacted quickly and stopped the experiment to bathe her subjects in fresh water. There was a palpable sense of relief in the audience when she showed a video of the same three tiny ducklings, now paddling and frolicking in the water.
“This is the ducklings a couple of days later. They are busy and happy with good waterproofing again,” she said.
Hollmén went on to document that at just a week into their lives, spectacled and Steller’s eider ducklings can tolerate higher salinity. At eight days of age, her subjects showed no effects in salty water with eight parts per 1,000.
Hollmén is working with her federal colleagues and the U.S. Fish and Wildlife Service to produce maps of the Y-K Delta with salinity levels going back to 2013. The idea is to assess the habitat not just for eiders, but for other water birds. There’s a lot of work ahead.
“We know very little about salinity sensitivity in these other species,” said Hollmén.
According to the USFWS, the Yukon-Kuskokwim Delta has one of the world’s largest populations of waterbirds.