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Sources and transport of algae and nutrients in a Californian river in a semi‐arid climate
Author(s) -
OHTE NOBUHITO,
DAHLGREN RANDY A.,
SILVA STEVEN R.,
KENDALL CAROL,
KRATZER CHARLES R.,
DOCTOR DANIEL H.
Publication year - 2007
Publication title -
freshwater biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.297
H-Index - 156
eISSN - 1365-2427
pISSN - 0046-5070
DOI - 10.1111/j.1365-2427.2007.01849.x
Subject(s) - nutrient , environmental science , nitrate , tributary , algae , algal bloom , biomass (ecology) , phosphorus , hydrology (agriculture) , environmental chemistry , agronomy , ecology , phytoplankton , chemistry , biology , geology , cartography , geotechnical engineering , organic chemistry , geography
Summary 1. To elucidate factors contributing to dissolved oxygen (DO) depletion in the Stockton Deep Water Ship Channel in the lower San Joaquin River, spatial and temporal changes in algae and nutrient concentrations were investigated in relation to flow regime under the semiarid climate conditions. 2. Chlorophyll‐ a (chl‐ a ) concentration and loads indicated that most algal biomass was generated by in‐stream growth in the main stem of the river. The addition of algae from tributaries and drains was small ( c .15% of total chl‐ a load), even though high concentrations of chl‐ a were measured in some source waters. 3. Nitrate and soluble‐reactive phosphorus (SRP) were available in excess as a nutrient source for algae. Although nitrate and SRP from upstream tributaries contributed (16.9% of total nitrate load and 10.8% of total SRP load), nutrients derived from agriculture and other sources in the middle and lower river reaches were mostly responsible (20.2% for nitrate and 48.0% for SRP) for maintaining high nitrate and SRP concentrations in the main stem. 4. A reduction in nutrient discharge would attenuate the algal blooms that accelerate DO depletion in the Stockton Deep Water Ship Channel. The N : P ratio, in the main stem suggests that SRP reduction would be a more viable option for algae reduction than nitrogen reduction. 5. Very high algal growth rates in the main stem suggest that reducing the algal seed source in upstream areas would also be an effective strategy.