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Riverine input of macronutrients, iron, and organic matter to the coastal ocean off Oregon, U.S.A., during the winter

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Title Riverine input of macronutrients, iron, and organic matter to the coastal ocean off Oregon, U.S.A., during the winter
Names Wetz, Michael S. (creator)
Hales, Burke (creator)
Chase, Zanna (creator)
Wheeler, Patricia A. (creator)
Whitney, Michael M. (creator)
Date Issued 2006-08-30 (iso8601)
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Abstract Three cross-shelf transects were conducted off northern Oregon in February, 2003, coincident with flooding of
Coast Range rivers, to assess the riverine impact on coastal ocean biogeochemistry. During downwelling
conditions, low salinity river-influenced water was located in a narrow band near the coast and contained elevated
macronutrient, iron, and organic carbon concentrations. Wind relaxation allowed the river-influenced water to
spread out at the surface across the shelf. Nutrients supplied by the rivers could result in winter carbon fixation
equating to ~20% of the summer upwelling carbon fixation if conditions are suitable for phytoplankton growth,
which is likely on the basis of recent studies. This implies that wintertime production may be significant and
requires further study. Iron supplied by the rivers is sufficient to support the entire summer upwelling production
and because downwelling conditions prevail during the winter and minimize cross-shelf transport, this iron may
be retained on the shelf to support the summer phytoplankton blooms. Of the major eastern boundary current
systems, the northern California Current (including Oregon) and Portugal Current (i.e., Iberian Peninsula) have
the highest riverine discharge rates normalized to coastline length. In contrast, riverine inputs to the central
California, Canary (i.e., northwest Africa), Benguela and Peruvian Current systems averaged only 3–35% of that
in Oregon. This patchy riverine input (and narrower shelves) might explain why iron limitation is more
widespread off California and Peru than Oregon. These results show that small coastal rivers, characteristic of the
U.S. Pacific Northwest, can significantly alter coastal biogeochemical cycles and influence ecosystem structure.
Genre Article
Identifier Wetz, M.S., Hales, B., Wheeler, P.A., Chase, Z. and Whitney, M.,Riverine input of macronutrients, iron and organic matter to the coastal ocean off Oregon, USA, during winter. Limnology and Oceanography, 51:2221-2231, 2006.

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