Meeting Abstract

34.4  Thursday, Jan. 5  Environmental Effects on Native and Non-Native Copepod Populations in San Francisco Bay GONG, S.Y.*; TSUKIMURA, B.; California State University Fresno; California State University Fresno stevengong0083@yahoo.com

Plankton distribution patterns are important to study due to their potential influences on food web dynamics as predator and prey contributors. Copepods are among the most numerous aquatic microorganisms and are critical to energy flow between trophic levels. Introduced species can potentially create additional competitive pressure to native species over resources and predation, which could translate into altered community assemblages. San Francisco Bay is among the most invaded habitats, making it ideal for studying invasive species impacts. Plankton samples from fixed sites around San Francisco Bay from 1998 to 2009, taken at monthly intervals, were collected and sorted for three copepod species: an established species (Eurytemora affinis) and invasive species (Pseudodiaptomus forbesi and Tortanus dextrilobatus). These copepods were identified to species and their relative abundances determined by catch-per-unit-effort. Results over the 12 year period showed a positive correlation between water temperature and P. forbesi (r=0.902) and T. dextrilobatus abundances (r=0.948). E. affinis abundances had a positive correlation (r=0.798) with dissolved oxygen levels, which indicate a preference towards regions with high mixing that resulted in decreased secchi depth (r=-0.776) and less primary productivity (r=-0.867). The invasive T. dextrilobatus and P. forbesi populations were directly related to each other over time (r=0.946) but were inversely related per site (r=-0.749) which might indicate a predator-prey relationship. The overall population differences were indicative of environmental selection on community assemblages by abiotic and biotic factors which can be used towards developing an assessment model.