Researchers discover lack of ice and unusually active ecosystem in Bering and Chukchi seas

Researchers on the Norseman II research vessel typically conduct observations in the Bering and Chukchi seas from June through September. This year, however, the COVID-19 pandemic delayed the cruise until October. As it turned out, the later timing yielded an important discovery of its own: Scientists were surprised to find no ice and an unusually active ecosystem for the mid-fall Arctic.

According to Seth Danielson, a professor at the University of Alaska Fairbanks, the most surprising finding of the three-week cruise was the high concentration of phytoplankton in the water. “For a time of year in which the sunlight is disappearing there were quite a lot of these plants,” he said. Danielson said that this signals that there is plenty of light and nutrients. This is unusual because nutrients are used up by the end of the summer in many ecosystems. For instance, the Bering and Chukchi sea ecosystems historically transition into lower activity levels as sea ice forms. However, this year sea ice formation was delayed, in part due to unseasonably warm ocean temperatures.

This, in turn, leads to unusually high levels of activity such as the “fall bloom” of newly growing phytoplankton. While the plankton bloom is only one component of the ecosystem, it points toward a larger trend. “By extension we know that any consumers up the food chain that depend on this bloom will be able to benefit from some new meals,” said Danielson.

The lack of ice points toward warming water temperatures, which Danielson said could have mixed implications for the marine ecosystem. A benefit is that the growing season can start earlier and extend later into the fall. Because plankton are blooming later, they will also die and drop

to the seafloor later. This could be good for animals, such as clams and walrus, that rely on an active seafloor ecosystem. Due to the later influx of plankton bodies, Danielson explained that seafloor organisms might not have to “fast” through the winter months when there is typically little food.

However, the warmer water temperatures could have negative ramifications, as well. Warmer water raises metabolic rates, which will increase the food requirements of the ecosystem, Danielson said. This could result in heightened competition for resources. Moreover, warmer waters are causing sub-Arctic fishes to travel further north. Danielson said that this phenomenon is likely already exerting predation pressure on the ecosystem.

Given the variety of different factors at play, it is impossible to say what the overall implications will be.

“Hence, the net impact on the ecosystem is unclear - there are factors pulling the marine ecosystem in multiple directions at once,” Danielson explained, “These are the types of relations that we are trying to better understand with our research.”

The Norseman II has been collecting data in the Arctic for several years. Danielson said that the vessel takes samples from specific locations, including a station south of St. Lawrence Island and another set between St. Lawrence Island and Diomede. Researchers take samples of “as much of the marine ecosystem as we can,” Danielson said.

This includes water samples and “grabs” of seafloor mud. Researchers on the cruise come from the University of Alaska Fairbanks as well as the University of Maryland Center for Environmental Science and Clark University.