Utilization of Nutrients Entering Through the Bering Strait to the Southwestern Chukchi Sea with the Example of Mineral Phosphorus

Abstract

Spatial variations of the nutrient concentration along the northwestward stream from the Bering Sea to the Chukchi Sea are considered for dissolved inorganic phosphorus (DIP) based on data from two surveys conducted in early September 2010 and 2020. The water mass from the Bering Sea has higher DIP than Chukchi Sea water, but in the upper layer its phosphorus is gradually lost due to both mixing with local water and consumption for photosynthesis. In the subsurface layer, the decrease in DIP is prevented by its recycling from degraded organic matter. The fluxes of phosphorus are estimated separately using the balance model with TS analysis, previously used in estuarial studies. Successive DIP utilization along the stream is traced, which forms in the Chukchi Sea two zones of high productivity divided by a wide low-productive zone. Nutrients from the upper layer are utilized within the southwestern Chukchi Sea, resulting in primary production 0.1–0.2 gC m^–3 day^–1, but the main stock of allochthonous nutrients from the subsurface layer is utilized further downstream (at Wrangel Island or in the northern Chukchi Sea) and results in production of 0.3–0.4 gC m^–3 day^–1. Localization of high-productive zones is determined by density stratification, which possibly depends on the stream strength: the stronger the advection through Bering Strait, the farther from the strait both zones are located. The recent tendency of strengthening of the stream tends to remove the zones of utilization the nutrients of Pacific origin from the southwestern Chukchi Sea.