A climate factor causes mass mortalities among Arctic birds
Climate change in the Arctic is not only causing the disappearance of sea ice or the thawing of the permafrost. With warmer water masses, new organisms also find their way into the Arctic Ocean regions. This includes types of algae that are potentially poisonous for the animals such as seabirds there and causing massive die-offs. So far known mainly from the Alaska area, mass die-offs also affect the abundant bird life on the coasts of Chukotka, as Dr. Katya Uryupova shows in her guest article exclusively for PolarJournal.
The Chukotka Peninsula is very well known for its bird communities. In summer it houses massive breeding colonies of sea birds which are supported by significant productivity of the water column ecosystem in the north-western Bering Sea and the Bering Strait. Planktonic organisms and fish form a vital basis of the bird’s diet there. The Russian Far East provides nesting opportunities for 40 species of seabird, about 3.5 million seabirds nest along the Bering Sea coast of the Chukotka Peninsula, with colonies becoming more numerous and larger as one moves south.
In late summer 2021, biologists witnessed massive bird die-offs along the Chukotka Peninsula, the Pacific Coast of Russia. The findings were reported from a few sites near Cape Dezhnev in the Bering Strait, in particular, in Pouten Bay. Scientists have found hundreds of dead and dying birds ashore, some of the birds swam/walked very slow and looked vigourless. Only certain species of birds were affected, among them auklets and murres. These bird species eat zooplanktonic prey and small schooling forage fish respectively.
Recently, similar trends have been described in the Northeast Pacific area: seabird die-off has been reported from the Bering Strait region, Aleutian Islands, and the Gulf of Alaska (including Middleton Island) in May-September 2021. Shearwaters were affected the most, although kittiwakes, murres, gulls, and puffins were reported dead and dying seabirds as well. In the Gulf of Alaska, Middleton Island a few birds were tested positive for Avian Botulism Type C, a natural toxin produced by a bacterium (Clostridium botulinum) and concentrated in aquatic invertebrates that filter feed sediments or water. All collected carcasses were examined and tested: results for other avian diseases were either negative, or pending.
Historically, mass mortality of some species of seabirds was described in the north Pacific, where it occurred sporadically. For instance, dead birds were found on the coasts of Kamchatka in 1973, 1981, and 1983. The cause of such mass mortality of seabirds was not clear at that time. One of the recent mass mortality of sea birds happened on Wrangel Island in 2017, and die-off of short-tailed shearwater occurred in the western part of Chukotka in 2018, and in 2019. The diet of short-tailed shearwaters is primarily crustaceans. Researchers did an examination of birds and concluded that the ocean surface temperature anomaly was a key reason for the significant seabird deaths in the region.
Over the last several years, masses of dead birds have been turning up on Alaska shorelines. Scientists are getting more and more confident that dramatic changes in the ecosystem are caused by the warming climate in the region. And one of the threats causing dramatic changes in the ecosystem are algal blooms that have proliferated in the warm conditions. Toxins being released by those blooms may affect bird colonies in the north. The U.S. scientists have revealed that seabird die-offs occurred at the same time as marine heatwaves in the North Pacific and Bering and Chukchi seas. High Northern Hemisphere latitudes are undergoing rapid and significant change associated with climate warming, as a result harmful algal blooms can produce toxins that poison fish, mammals and birds, and even non-toxic blooms can consume all the oxygen in the water resulting in fish kill and a long-term starvation in birds.
Scientists link these mass seabird die-offs to climate change and a warming ocean. It causes a decrease in the number of zooplankton organisms, and as a result, less fish are available. Birds then have to cover long distances to find food, often ineffectively. In fact, a recent study has shown that harmful algal blooms of the toxic dinoflagellate algae Alexandrium catenella often stretch from the Northern Bering Sea to the Chukchi and Beaufort Seas north of Alaska, and these blooms are likely to be large and frequent. When the bacterial cells are consumed by shellfish and some fish, those toxins can accumulate to levels that can be dangerous to humans and wildlife such as larger fish, marine mammals, and seabirds. The current observations along the coast of Chukotka clearly point to a sad new reality: The Arctic Ocean ecosystem undergoes an unprecedented, unusual regime shift with severe changes in its biodiversity and an uncertain future for the inhabitants.
Dr. Ekaterina Uryupova is a Visiting Fellow at the Arctic Institute. She has been working in the polar regions as a researcher and a polar guide. Her areas of expertise revolve around climate change, marine ecosystems, fisheries, and environmental policy.
