Submitted to: Journal of Freshwater Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 25, 2006
Publication Date: December 1, 2006
Citation: Spencer, D.F., Lembi, C., Blank, R.R. 2006. Spatial and temporal variation in the composition and biomass of algae present in California rice fields. Journal of Freshwater Ecology. 21:649-656. Interpretive Summary: Algae grow in California rice fields where they may smoother seedlings or cause them to dislodge, resulting in yield loss. A particular alga, known locally as “elephant hide” has been very difficult to control. At the request of the California Rice Research Board, we surveyed northern California rice fields with the express purposes of identifying this troublesome alga and trying to identify field characteristics that might be associated with its abundant growth. We found that it was Nostoc spongiaforme. The most abundant algal biomass was associated with fields with high concentrations of ammonium, phosphate, sodium, and calcium and with high nitrogen to phosphorus ratios in the water. This information will be used to design alternative control strategies.
Technical Abstract: We sampled eight California rice fields every two days from May 1 to June 1, 2004 for algal biomass and species composition and water quality parameters. Soil samples were collected prior to filling the fields with water and analyzed for selected nutrients. Algal abundance shifted from dominance by green algae (Sphaeroplea, Tribonema, Ankistrodesmus, Tetraspora) and diatoms (Navicula) early in May to dominance by blue-green algae (almost totally Nostoc, with Anabaena and Phormidium also present) in late May-early June The same species occurred in all the fields at around the same time. The most abundant species consistent with the description “black algae” collected from these fields was Nostoc. Results from multiple regression analysis showed that algal biomass was negatively related to total alkalinity and sulfate concentration, and positively related to the N:P ratio and the concentrations of ammonium, phosphate, sodium, and calcium. These variables explained 51% of the variance associated with total algal biomass. When soil characteristics were used in a similar multiple regression analysis, none of them was significantly (P > 0.1) related to total algal biomass.