Kayfetz, K.R. (2014). Biotic vs. abiotic effects on distribution of the estuarine copepod Pseudodiaptomus forbesi. M.Sc. Thesis, San Francisco State University, San Francisco, California, USA.

480821

Kayfetz, K.R.

2014

Publication

http://hdl.handle.net/10211.3/131290

Distribution of species in estuaries is classically described in relation to salinity, however it has been increasingly shown that estuarine species are not necessarily found in salinities most physiologically beneficial to them. Species invasions provide insight into interspecific mechanisms that affect species distributions and may be useful for studying biotic effects on natural populations. Here I investigate controls on the distribution of Pseudodiaptomus forbesi in the upper San Francisco Estuary (SFE) including salinity tolerance and the potential effects of introduced species. I found that P. forbesi was tolerant of a broader range of salinities than it inhabits in the SFE and that its reproduction is highest in brackish water, despite the fact that the population is mostly restricted to freshwater. I compared feeding by P. forbesi and the introduced copepod L. tetraspina and found that they overlap somewhat in diet, though P. forbesi takes advantage of a broader range of prey taxa than L. tetraspina. I tested for but found no evidence of direct predation of L. tetraspina on P. forbesi. I conclude that other interspecific interactions, especially with the invasive clam Potamocorbula amurensis and the invasive predatory copepod Acartiella sinensis, are important determinants of habitat suitability for P. forbesi in the SFE. Invasive species have ecosystem disrupting effects that take many years to sort out. The difficulty of studying interspecific interactions in this system is compounded by the number and frequency of invasions.

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