Evaluation of the budget for silicic acid in Cascadia Basin deep water

• Published in: Deep-sea research. Part I, Oceanographic research papers Vol. 57; no. 5; pp. 677 - 686
• Main Authors: Esther, Tabitha A., Hammond, Douglas E., Hautala, Susan L., Paul Johnson, H., Schwartz, Richard J., Paukert, Amelia N.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.05.2010; Elsevier; Pergamon Press Inc
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Basins; Biological and medical sciences; Budgeting; Cascadia Basin; Coastal environments; Deep sea; Deep water; Earth, ocean, space; Exact sciences and technology; External geophysics; Fluxes; Fundamental and applied biological sciences. Psychology; Germanium; Marine; North Pacific deep-water chemistry; Oceanography; Physical and chemical properties of sea water; Physics of the oceans; Plumes; Sea water ecosystems; Sediments; Si remineralization; Silica cycle; Silicon; Synecology; Pacific Ocean; Cascadia Basin; North Pacific; Cascadia; INW, Pacific, North Pacific Deep Water; INE, USA, Oregon; INE, Pacific, Cascadia Basin; IN, North Pacific; INE, USA, Washington; North Pacific deep-water chemistry; Germanium; Si remineralization; Cascadia Basin; Silica cycle; sea water; remineralization; Silicic acid; plumes; inorganic acids; Silicon compound; Deep water; Hydrothermal vent; enrichment; Biogenic factor; Flux density; hydrochemistry; ocean floors; Box model; Observation data; marine sediments
• ISSN: 0967-0637; 1879-0119
• DOI: 10.1016/j.dsr.2010.02.002

Between 2 and 3 km depth, North Pacific deep waters contain a plume of water with high silicic acid concentrations. The plume extends outward from Cascadia Basin (the Washington Margin), where waters can contain in excess of 200 μM off the coast of Oregon and Washington. To identify the source of the high Si concentrations in Cascadia Basin, we measured silicic acid and germanium concentrations in deep waters, and their fluxes from sediments using incubated cores. The mean flux of silicic acid into bottom waters is 0.81±0.05 mmol/m 2-day, and the Ge/Si ratio of this flux is 0.7±0.1 μmol/mol. A box model, incorporating these results with hydrographic data, indicates that (1) no more than 5% of the silicic acid added to Basin deep waters can have a hydrothermal source (either hot or warm seeps), and (2) the total input of silicic acid to Basin deep waters is 0.06±0.02 Tmol/y. This input is nearly all from remineralized biogenic debris and should contribute about 0.5% of the 14 Tmol/y that are estimated to be necessary to maintain the North Pacific plume.