Present address: Daniel H. Doctor, U.S. Geological Survey, Reston, Virginia, 20192, U.S.A.
Sources and transport of algae and nutrients in a Californian river in a semi-arid climate
Article first published online: 8 AUG 2007
Volume 52, Issue 12, pages 2476–2493, December 2007
How to Cite
OHTE, N., DAHLGREN, R. A., SILVA, S. R., KENDALL, C., KRATZER, C. R. and DOCTOR, D. H. (2007), Sources and transport of algae and nutrients in a Californian river in a semi-arid climate. Freshwater Biology, 52: 2476–2493. doi: 10.1111/j.1365-2427.2007.01849.x
- Issue published online: 8 AUG 2007
- Article first published online: 8 AUG 2007
- (Manuscript accepted 13 June 2007)
- algal load;
- hydrological condition;
- nutrient load;
- San Joaquin River
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.