Abiotic factors related to accrual of common filamentous macroalgae in California's central coast streams
Thesis (M.S.) Division of Science and Environmental Policy
In an effort to develop regional autecological information on nuisance-prone filamentous macroaglae in the Mediterranean climate of California's Central Coast, I explored relationships between stream conditions and presence and abundance of 4 common macroalgal taxa. Algae samples and stream data were taken from a regional bioassessment study conducted during the dry seasons of 2006 and 2007 at 199 low-gradient streams. I developed a priori hypotheses based on a review of algal ecology literature. Within a two-part conditional model framework, I used an information theoretic approach to compare algal presence and abundance (biovolume per area of substrate) response to cover of riparian canopy, total nitrogen (TN) and total phosphorus (TP) concentrations, flow velocity, substrate size, pH, conductivity, and season. Model comparison and multi-model inference results supported two main findings for each of three target taxa: Cladophora spp. presence and abundance increased with a higher percentage of stable substrata in the stream reach and a lower percentage of riparian canopy cover; Spirogyra spp. presence increased with a lower canopy cover and lower TP concentrations; and Ulva spp. presence increased with lower canopy cover of and higher conductivity. Post hoc analyses showed dissolved oxygen saturation to be higher in the presence of Cladophora spp. and Ulva spp. These results highlight the role of riparian canopy in regulating filamentous macroalgal accrual and maintaining stream health in the region.