A Cold, Dark Desert
For up to ten months of the year, the Gulf of Anadyr is a frozen desert. Sea ice blankets the 200,000-square-kilometer bay, blocking sunlight and halting nearly all biological production in the water column. Below this ice shield, however, a powerful force gathers. The Anadyr Current, a nutrient-rich tongue of Pacific Ocean water, flows north into the gulf. This water, chilled to sub-freezing temperatures, carries high concentrations of nitrates, phosphates, and silicates—the important fertilizers for marine plant life. All winter, these nutrients accumulate under the ice, creating a reservoir of potential energy, waiting for the sun.
The Great Bloom
When the sea ice retreats between May and June, the Gulf of Anadyr transforms. Sunlight penetrates the nutrient-laden surface waters, triggering one of the most intense phytoplankton blooms on the planet. The production is so immense that it is visible from space. Diatoms, a type of single-celled algae, are the primary actors in this explosion of life. This bloom forms the base of a highly efficient and compressed food web.
The sudden abundance of phytoplankton is consumed by massive swarms of zooplankton, such as copepods and krill. This secondary production supports immense populations of forage fish, which in turn feed larger predators. The region is a significant feeding ground for seabirds and marine mammals. Eastern North Pacific gray whales (Eschrichtius robustus) undertake one of the longest migrations of any mammal, traveling up to 14,000 miles from their calving lagoons in Baja California, Mexico, to feast in the Bering and Chukchi Seas. They are bottom-feeders, sucking up sediment from the seafloor to filter out invertebrates like amphipods that have grown fat on the rain of dead plankton. Bowhead whales and Pacific walruses also rely heavily on the productivity of this region. The entire ecosystem's annual energy budget is largely determined by the intensity and timing of this brief, explosive spring bloom.