Invasive clams in Lake Tahoe: Reproductive strategies and impacts to native benthic community structure

Invasive species are of concern to ecologists and resource managers due to the growing ecological and economic impacts associated with their introduction. In North America, invasive species cause significant environmental impacts with costs estimates of ;Recently there has been an invasion of C. fluminea in Lake Tahoe, a large, deep subalpine lake located in the central Sierra Nevada of California and Nevada. Very little is known about the life history or impacts of clams on the ecology of the lake; however, preliminary research suggests they may linked to increased nearshore algal blooms. The chapters included here examine the reproductive strategies (Chapter 1) and impacts to native benthic community structure (Chapter 2) by C. fluminea in Lake Tahoe. In Chapter 1, it was determined that C. fluminea in Lake Tahoe had a low reproductive effort with a single spawn that occurred in late summer that is likely linked to the temperature and low food availability. Moreover, deeper water populations of clams are likely populations sinks dues due to the cold temperatures. Chapter 2 shows how C. fluminea changes benthic community structure depending on the level of infestation. It was determined that three taxa had greater abundances where abundances of C. fluminea are low. In areas with greater abundance, C. fluminea facilitate two taxa, Chironomidae and Trichoptera. While the mechanisms were not studied, the shells of clams may provide structure and thus habitat for certain invertebrates. Other mechanisms of facilitation such as competition or providing increased food supply through the release of pseudofeces may also impact community structure. Other behavioral experiments and raw data not formally presented in chapter form are presented in the Appendix. As the establishment of C. fluminea is still in an early stage of invasion, future studies and monitoring will be essential to further determine how the clam impacts Lake Tahoe's ecosystem.