Spatial and Temporal Variation in the Composition and Biomass of Algae Present in Selected California Rice Fields

ABSTRACT

We sampled eight California rice fields every two days from May 1 to June 1, 2004 for algal biomass, 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 genera of green algae (Sphaeroplea, Tribonema, Ankistrodesmus, Tetraspora) and diatoms (Navicula) early in May to dominance by blue-green algae genera (almost totally Nostoc, with Anabaena and Phormidium also present) in late May-early June The same taxa 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 spongiaeforme. 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.