PARENT SESSION
Oral Session # 25: Invasive Species II: Aquatic Systems.
Presiding: G Rilov
Tuesday, August 5. 8:00 AM to 11:30 AM, SITCC Meeting Room 205.

The impacts of the habitat-forming invasive tubeworm, Ficopomatus enigmaticus, in a heavily-invaded central California estuary.

Heiman, Kimberly ^*,1, Micheli, Fiorenza ¹, ¹ Hopkins Marine Station of, Pacific Grove, CA, USA

ABSTRACT- The number of invasive species in coastal marine environments is on the rise. Many of these invasives can threaten biodiversity and alter ecosystem function through competition, predation, habitat modification, or by changing the availability of limited resources. Elkhorn Slough is a central California estuary with very little natural hard substrate, its native intertidal habitat being mudflats. In 1994 the reef-building tubeworm, Ficopomatus enigmaticus, was discovered in the system. Over the past 8 years, F. enigmaticus has spread to several sites within Elkhorn Slough. At one site it occupies nearly 100% of the available substrate forming reefs that grow out from dock pilings and spread over the surrounding mudflats. The reefs greatly increase the amount of complex hard substrate and create a new unique habitat type. We explored the role of the new complex structure, F. enigmaticus reefs, on the invertebrate community composition in surrounding mudflats. Replicate reefs were removed in an experiment designed to identify their impacts on infaunal communities under the reefs, as well as those 5cm and 100cm away from the edge of the reefs. Initial multivariate and univariate analyses showed that there is a significant effect of reef removal on infaunal mudflat communities 6 months after the removal. Differences in the abundances of several invasive species including the amphipods Monocorophium insidiosum, Grandidierella japonica, and the cryptogenic polychaete Capitella capitata drive the observed community effects of reef removal.

Key words: invasive species, Elkhorn Slough, Ficopomatus enigmaticus, habitat modification