Document Type

Master's Thesis

Degree Name

Master of Science (M.S.)


Moss Landing Marine Laboratories


I studied the variability in Ulva spp. in Elkhorn Slough, CA temporally and spatially. I measured changes in cover and biomass and combined them to determined changes in total abundance seasonally (every three months) from July 2003 to July 2004. Over this time period I found a significant seasonal difference in Ulva cover and a significant seasonal difference in Ulva biomass. There was also a significant interaction between season and section. Total abundance followed the same pattern of change as cover, suggesting Ulva mat cover was a better indicator of total abundance in Elkhorn Slough. To determine if seasonal changes were occurring at sub-seasonal time scales, the seasonal experiment was repeated at a smaller spatial scale from June 2004 to August 2004 with bi-weekly samples of cover and biomass. I found that seasonal variation in cover was significantly greater than sub-seasonal variation; however, seasonal and sub-seasonal biomass measurements were not significantly different. These results indicated that changes in cover were more gradual over time and biomass was highly variable at both time scales. I also investigated tides as a possible factor regulating Ulva mats in Elkhorn Slough. I found a localized phenomenon where increased Ulva mat movement was related to increased tidal range. Although the second sampling location did not show this same relationship, I hypothesize that tidal range plays an important role in the regulation of Ulva mats in Elkhorn Slough.


Thesis (M.S.) Division of Science and Environmental Policy. Moss Landing Marine Laboratories