Hopkins Marine Station Student Paper

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Title: Hard substrate communities in the reefs of the invasive tubeworm Ficopomatus enigmaticus and the native oyster Ostrea lurida in Elkhorn Slough, CA
Student Author(s): Vidargas, Nicholas
Faculty Advisor(s): Watanabe, Jim
Pages: 28
Location: Final Papers Biology 175H
Date: June 2003
Abstract: The spread and impact of invasive species is a major threat to ecosystem integrity and biodiversity. Understanding the dynamics of invasions is vital for successful management of estuaries and wilderness areas worldwide. The reef building tubeworm, Ficopomatus enigmaticus adds hard, complex structure to Elkhorn Slough, an environment without much native hard substrate; Ostrea lurida, a native oyster, creates the only analogous microhabitat. To determine if changes in community structure are associated with the introduction of F. enigmaticus reefs, 10 cm diameter cores from both types of biogenic microhabitats were collected from intertidal sites in Elkhorn Slough. Three sites were sampled, one with both F. enigmaticus and O. lurida, one with only O. lurida, and one with only F. enigmaticus; each site comprised 3 cores. Cores were sieved to >500 µm in the field, preserved, and all organisms were sorted to species and counted. Of the 24 species found in the cores, 7 are not native to Elkhorn Slough. Average number of individuals per core was much larger in F. enigmaticus (177.67) than O. lurida (69) and F. engimaticus harbored, on average, 18.78 times more invasive individuals than O. lurida. The ratio of invasive to native individuals, however, is similar in both (4.73 and 3.75, respectively). Multidimensional Scaling (MDS) and analysis of similarity showed clear segregation between habitat types and amnong sites. However, analysis of similarity using data for invasive species only showed significant dissimilarity between habitat types (P = .006), dissimilarity between sites was not significant (P = .084). Dissimilarity between habitat types was driven primarily by the abundances of four invasive species, Monocorophium insidiosum, Melita nitida, Tubificoides brownae and Streblospio benedicti.