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Iron links river runoff and shelf width to phytoplankton biomass along the U.S. West Coast
Author(s) -
Chase Zanna,
Strutton Peter G.,
Hales Burke
Publication year - 2007
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2006gl028069
Subject(s) - streamflow , environmental science , oceanography , phytoplankton , estuary , upwelling , biomass (ecology) , surface runoff , chlorophyll a , hydrology (agriculture) , geology , nutrient , drainage basin , ecology , geography , biology , botany , cartography , geotechnical engineering
A poleward increase in phytoplankton biomass along the West Coast of North America has been attributed to increasing river runoff towards the north. We combine streamflow and shelf width data with satellite‐derived estimates of phytoplankton biomass to quantify the relationship between these variables. We find that a combination of winter streamflow and shelf width can account for over 80% of the spatial variance in summer chlorophyll within 50 km of the coast. At a given location, interannual variability in streamflow is not associated with interannual variability in chlorophyll. We attribute these relationships to the role of rivers as suppliers of the micronutrient iron, and the role of the shelf as a ‘capacitor’ for riverine iron, charging during the high‐flow winter season and discharging during the upwelling season. Data from the Oregon shelf confirm that, during winter, a significant fraction of riverine iron escapes the estuary and reaches the coastal ocean.