Acoustic monitoring in the Bering Strait

The lives of marine mammals are coming under increasing challenges with a changing climate and industrial activity in the Arctic, including potential for expanding shipping and oil exploration activities. The Bering Strait is one of the regions where shipping activity is expected to increase the most. This passage is also used by a vast number of several marine mammal species that make seasonal migrations in and out of the Arctic. This overlap between marine mammals and increasing ship activity has the potential to impact the lives of these animals by increasing the risk of collision and increasing underwater noise levels.

The fluke of a grey whale as it plunges back into the waters of the Bering Strait. Photo Ricardo Antunes.

The Northern Bering Sea waters are typically covered with ice during the winter, and are prone to extreme weather conditions. This makes monitoring for the presence of marine mammals and assessing impacts of climate change and industrial activities quite challenging. Since the summer of 2013 when our team worked with a local hunter from Savoonga to deploy our first sound recording instruments off St. Lawrence Island, we have been deploying sound recording instruments around the entire Island to detect the vocalizations of marine mammals and noise levels in the Northern Bering Sea and leading into the Bering Strait. This information will constitute an important baseline from which to assess changes in ambient noise and patterns of marine mammal presence, and will allow us to anticipate future impacts associated with increasing shipping.

One of the sound recording instruments lays on the deck of the boat prior to deployment. This is one of five we deployed in June 2015. Photo Ricardo Antunes

During June 2015 our team, led by Dr. Ricardo Antunes, went on the next expedition to the waters of the Bering Strait. The goal was to recover two recorders deployed in October 2014 and deploy five others for monitoring marine mammals and anthropogenic noise throughout the summer. Instrument recoveries are always exciting as our team tries to find them after months underwater, wondering if they had been dragged along the bottom by drifting ice, if their waterproof housings have leaked or if the batteries kept working in cold Arctic waters. Luckily our team managed to find both recorders and was exhilarated to discover that they had worked perfectly, recording throughout the whole period. This means that they probably recorded vocalizations made by bowhead whales during both their Southward and Northward migration, as they pass off St. Lawrence. In the coming months, we will be analyzing these recordings for the presence of vocalizations of bowhead whales, walrus, bearded seals and other marine mammals, as well as measuring the noise levels generated by vessels steaming through the Bering Strait.

Retrieving sound recording instruments deployed in October 2014. We were able to locate both of the instruments and will analyze the recordings in the coming months.

Deployment of additional instruments was also quite successful, helped by extremely good weather and support from captain Adem Boeckman and the remainder of the Anchor Point’s crew. We have been using a larger vessel recently due to the dangers of working offshore with heavy anchors for our equipment. The analysis of the winter recordings has started in the lab and when finished will provide insight into the migration patterns of marine mammals and into the assessment of baseline noise levels in the area—this will help us as noise levels potentially increase so we can determine if they are having an impact on these amazing animals and this important area.

Captain Adem Boeckman of the Anchor Point. We have been using a larger vessel recently due to the dangers of working offshore with heavy anchors for our equipment.

Eider duck research at Icy Cape

Our field research sites, by nature of the boundaries of Arctic Beringia, are in remote and wild places. The barrier islands of Kasegaluk Lagoon are no exception to this.  A thin strip of land a couple of miles offshore in the Chukchi Sea, Solivik Island is at first glance wind-swept and barren. There are no trees, no shrubs, and no animals in sight. There’s a lot of sand and bones, and yet these islands soon reveal themselves to be teeming with life.

Camp on the barrier islands of the Chukchi Sea coast. Tents are encircled by both an electrified fence and a trip-wire fence in case a polar bear wanders into camp.

Arctic tern colonies are the most obvious terrestrial life, as the birds attack to defend their nests with loud cries of “kak, kak, kak” and dive bombing that isn’t always a bluff. The tern colonies we encountered had up to ten nests in a small area, just bare scrapes on the ground, with two eggs each. Common eiders and long-tail ducks use the aggressive terns as cover and often site their nests among or on the edges of these colonies. The ducks benefit from the terns as they chase off ravens, jaegers, gulls, and biologists.

Arctic tern nest

Common eiders are the most at-risk waterbird species on Alaska’s North Slope due to the susceptibility of their nest sites to potential overwash and erosion from storm surges. The birds often hide their nests among driftwood, which provides cover from nest predators as well as protection from the elements.

Female eider duck captured for genetic sampling prior to release

Our work is to assess the ecological importance of, and risk to, the poorly understood barrier island ecosystems in northern Alaska, and assess which islands are, or will continue to be, the most critical for nesting birds. This is critical information for managers as the area is developed, both for avoiding disturbance and for disaster preparedness. We are assessing the physical health of the ducks, as well as collecting genetic, and population size information. Our sites in the Chukchi Sea will be compared with sites at Prudhoe Bay and further east to the Canada border in the Arctic National Wildlife Refuge.

Determining approximate age of embryos by candling eggs with a makeshift egg-candler, a field notebook. Photo Sally Andersen

Written by Sally Andersen, WCS Arctic Beringia Program Conservation Coordinator, June 2015.