Contribution of Nutrients from Sediments and Interstitial Water to Colville River System, Alaska.

摘要

Arctic regions differ from temperate areas in the extreme seasonality of climatic conditions. In 1971, water samples and bottom sediments were taken from the Colville River system in Arctic Alaska prior to breakup, during breakup, and during summer for nutrient study. Although sediments are primarily sandy, some silt and clay are also present especially in the oceanic portion of the delta. Clay minerals are primarily kaolinite and illite. Montmorillonite and small amounts of a chlorite-like mineral are also present. The organic content in the sediments was higher in the upper river channel than in the ocean, whereas interstitial nitrogen components showed the opposite trend. These interstitial components are the products of organic decomposition in sediments. Once flooding begins, river water, which consists of snowmelt from mudflats, sand dunes, and the tundra surface, moves under the sea ice as a wedge. It contains more nutrients than does the seawater beneath. This floodwater, rich in inorganic-N (N/P ratio = 23:1 in 1971), is significant in contributing to the nitrogen-deficient seawater (N/P ratio = 3:1), and provides a basic ingredient for phytoplankton production. During summer, depletion of nutrients prevails as a result of phytoplankton uptake and dilution by seawater. Such nutrient input is significant in the primary productivity of this nearshore zone, helping account for the abundance of fish found in the area.