Nutrient cycling in the Columbia River Basin involves the transport of nutrients through the system, as well as transformations from among dissolved, solid, and gaseous phases, depending on the element. The elements that constitute important nutrient cycles include macronutrients such as nitrogen (as ammonium, nitrite, and nitrate), silicate, phosphorus, and micronutrients, which are found in trace amounts, such as iron. Their cycling within a system is controlled by many biological, chemical, and physical processes.
The Columbia River Basin is the largest freshwater system of the Pacific Northwest, and due to its complexity, size, and modification by humans, nutrient cycling within the system is affected by many different components. Both natural and anthropogenic processes are involved in the cycling of nutrients. Natural processes in the system include estuarine mixing of fresh and ocean waters, and climate variability patterns such as the Pacific Decadal Oscillation and the El Nino Southern Oscillation (both climatic cycles that affect the amount of regional snowpack and river discharge).[1][2] Natural sources of nutrients in the Columbia River include weathering, leaf litter, salmon carcasses, runoff from its tributaries, and ocean estuary exchange. Major anthropogenic impacts to nutrients in the basin are due to fertilizers from agriculture, sewage systems, logging, and the construction of dams.[3][4]
Nutrients dynamics vary in the river basin from the headwaters to the main river and dams, to finally reaching the Columbia River estuary and ocean. Upstream in the headwaters, salmon runs are the main source of nutrients.[5] Dams along the river impact nutrient cycling by increasing residence time of nutrients, and reducing the transport of silicate to the estuary, which directly impacts diatoms, a type of phytoplankton.[6] The dams are also a barrier to salmon migration, and can increase the amount of methane locally produced.[6] The Columbia River estuary exports high rates of nutrients into the Pacific Ocean;[7] with the exception of nitrogen, which is delivered into the estuary by ocean upwelling sources.[8]
- ^ "Fate and Transport of Nitrogen | Environmental Assessment Program | Washington State Department of Ecology, Puget Sound". www.ecy.wa.gov. Archived from the original on 2017-12-08. Retrieved 2017-11-07.
- ^ Hamlet, Alan F.; Lettenmaier, Dennis P. (1999-11-01). "Columbia River Streamflow Forecasting Based on ENSO and PDO Climate Signals". Journal of Water Resources Planning and Management. 125 (6): 333–341. doi:10.1061/(ASCE)0733-9496(1999)125:6(333).
- ^ "Natural Sources of Nitrogen | Sources and Pathways | Environmental Assessment Program | Washington State Department of Ecology". www.ecy.wa.gov. Archived from the original on 2017-12-08. Retrieved 2017-11-04.
- ^ Hileman, James (July 1975). "Columbia River Nutrient Study". Environmental Protection Agency.
- ^ "Why Protect Salmon - Wild Salmon Center". Wild Salmon Center. Retrieved 2017-11-27.
- ^ a b Friedl, Gabriela; Wüest, Alfred (2002-04-01). "Disrupting biogeochemical cycles - Consequences of damming". Aquatic Sciences. 64 (1): 55–65. doi:10.1007/s00027-002-8054-0. ISSN 1015-1621. S2CID 44859140.
- ^ Gilbert, Melissa; Needoba, Joseph; Koch, Corey; Barnard, Andrew; Baptista, Antonio (2013-07-01). "Nutrient Loading and Transformations in the Columbia River Estuary Determined by High-Resolution In Situ Sensors". Estuaries and Coasts. 36 (4): 708–727. doi:10.1007/s12237-013-9597-0. ISSN 1559-2723. S2CID 85414307.
- ^ Lohan, Maeve C.; Bruland, Kenneth W. (2006-02-01). "Importance of vertical mixing for additional sources of nitrate and iron to surface waters of the Columbia River plume: Implications for biology". Marine Chemistry. 98 (2): 260–273. Bibcode:2006MarCh..98..260L. doi:10.1016/j.marchem.2005.10.003.
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