Arctic Coastal Lagoons: Watching Fish, Ice and a Changing Coast

Along Alaska's Chukchi Sea coast, hundreds of miles from any road, a chain of shallow coastal lagoons sits behind gravel berms. They are some of the richest places in the Arctic for fish and waterbirds, and for thousands of years they have fed the Iñupiat people of the region. Since 2012, the National Park Service and its partners have been watching how they change.

The Arctic Network's five parks: Bering Land Bridge National Preserve, Cape Krusenstern National Monument, Noatak National Preserve, Kobuk Valley National Park, and Gates of the Arctic National Park and Preserve. NPS

The lagoons

Most lagoons open to the sea only when spring runoff or a storm breaches the gravel berm; a few stay connected all the time, and some do not open at all in a given year. That on-and-off link with the ocean decides almost everything about them.

Why they matter

• Habitat. Their mix of sizes, depths, salinities and connections makes a mosaic used by migratory fish, waterfowl, furbearers and the prey fish and invertebrates that feed them.
• Food. Dolly Varden, sheefish, chum salmon and least cisco are netted, dried or smoked and eaten all year; waterfowl and gull eggs are prized; hides from the area become clothing and household goods. Iñupiat communities rely on these wild foods for food security.
• History. Archaeological sites in the beach ridges near Krusenstern Lagoon show people living off the lagoons for thousands of years.
• Visitors. Birders, anglers and wildlife watchers come from around the world.

A subsistence fisher catches whitefish at a channel trap dug into the beach at the Tukrok River mouth near Anigaaq, Cape Krusenstern National Monument. USFWS / Susan Georgette

What is changing

People who have lived by the lagoons have recorded changes since the 1980s — among them Bob Uhl, whose journals cover more than five decades of subsistence life at Sissualik. Shifting seasons, runoff and storms alter when a lagoon connects to the sea. No breach means fish cannot get in or out. A hard winter can freeze a lagoon almost to the bottom, killing trapped fish, cutting invertebrates and reshaping the food web. Climate change, coastal erosion and possible industrial development in the Chukchi region could all push further.

How they are monitored

A partnership of the NPS, the Wildlife Conservation Society and the Native Village of Kotzebue Environmental Program:

Kotlik Lagoon open to the Chukchi Sea in June (top) and closed in August (bottom), 2021. Contains modified Copernicus Sentinel-2 data (2021)

Who lives there

Freshwater fish like Arctic grayling and Alaska blackfish; fish that move between sea and river, like least cisco and sheefish; and sea fish like saffron cod ("tomcod") and starry flounder. Also humpback whitefish, Pacific herring, Dolly Varden (locally "trout"), sticklebacks, pond smelt and sculpins. They come in spring through autumn to feed, grow and spawn, and most leave for winter, because the lagoons freeze nearly solid; they overwinter in deeper rivers, lakes or the sea.

Open questions

• Where do the migrants come from and go? Sheefish are being fitted with GPS pop-up tags, and the ear stones (otoliths) of 60 whitefish analysed at the University of Alaska Fairbanks to trace their moves between fresh, brackish and salt water.
• Can any fish overwinter? Aukulak Lagoon freezes to the bottom and holds nothing if it does not open; Kotlik and Krusenstern connect to rivers that flow all winter, and hold grayling.
• How many grayling, and where do they go? Almost nothing is known.
• Are the fish safe to eat? Dolly Varden, saffron cod, flounder and whitefish were tested for PFAS and mercury — levels were very low; the results are being prepared for publication.
• Are the seasons shifting? The satellite record of opening and freeze-up is being analysed.
• Mysid shrimp, a key food for lagoon fish — which species, how many? Samples are being collected.
• Algal blooms — how often, and with what effect? A local concern, for future study.

Why park managers care

Warmer water holds less oxygen and breeds harmful algae; changed storms and runoff change when lagoons connect, and so which fish get in and survive the winter; longer open seasons could let in non-native or boreal species. Any of these would reach the people who depend on the lagoons for food, and the visitors who come for their wildness — which is why the partners keep watching, and keep sharing what they find.

Read more

The Wildlife Conservation Society's studies of the lagoons: Caspian terns breeding in the Arctic (2017) · what lagoon fish eat (2018) · winter habitat from remote sensing (2018) · zooplankton (2020) · freshwater input and fish (2021) · the food value of lagoon fish (2021).

Sources

Written from "Coastal Lagoons Resource Brief for the Arctic Network," by Kevin Fraley, Michael Lunde, Martin Robards, Tahzay Jones and Alex Whiting, Arctic Inventory and Monitoring Network, National Park Service; a work of the United States government in the public domain.