Invasive Species
Monterey Bay

photo of ia nudibranch crawling over red bryozoan
The opalescent nudibranch Hermissenda crassicornis crawls over the red invasive bryozoan Watersipora subtorquata on a pier piling in Monterey Harbor. Invasive species can exacerbate biotic homogenization, the process of communities becoming more similar due to a growing proportion of shared non-native species. Credit: Steve Lonhart, MBNMS, NOAA

Why is it a concern?

Invasive species (aka introduced species, exotic species, aquatic invasive species [AIS], nonindigenous species [NIS]) in the marine and estuarine environments of MBNMS can alter species composition and native biodiversity, impact ecosystem structure and function, and disrupt commercial and recreational activities. Invasive species prey on native species and/or compete with natives for food, space and other resources. Once established, invasive species can be difficult to eradicate. They also exacerbate biotic homogenization, the process of communities becoming more similar due to growing proportion of shared non-native species.

Compared to the open coast of the sanctuary, a high number of introduced species occur in Elkhorn Slough, a large estuary. Wasson et al. (2005) documented 527 invertebrate species inhabiting Elkhorn Slough. Of these, 58 were introduced, 25 cryptogenic (i.e., possibly introduced or possibly native), and 444 were native species.  In contrast, surveys of adjacent rocky intertidal areas on the open coast documented 588 species, but only 8 were introduced, 13 were cryptogenic, and 567 were native species (Wasson et al. 2005).   

In addition to known vectors for species introduction (e.g., vessels, mobile equipment, drifting debris, and intentional transport of animals and plants), there is concern that climate change will promote the spread of introduced species into areas where they may have previously been restricted. In the case of MBNMS, this could put increasing pressure on outer coast and offshore resources. Although there are several agencies and organizations that document and eradicate introduced species in the area, a coordinated effort is need to compile existing information and data, identify data gaps, and update maps of abundance and distribution. It is also necessary to identify the pathways by which new species are introduced into the sanctuary, and prioritize which pathways pose the greatest threat to sanctuary resources.

Overview of Research

Project Name PI and contacts Links

Invertebrate Monitoring in Elkhorn Slough

Kerstin Wasson

Detecting non-native species in kelp forests and on rocky shores

 Greg RuizJonathan Geller, Andy Chang, Chela Zabin

Science Needs and Questions

There is a need to further assess the known pathways of introduction: aquaculture, aquarium trade, ballast water, biological control, fisheries enhancement, hull fouling and other non-ballast vessel introductions, live bait, commercial businesses, scientific research institutions, and dispersal of adults, eggs and larvae.  We also need to establish baseline data collection and monitoring programs, including an expansion from the Elkhorn Slough region to investigate areas of Santa Cruz and Pillar Point harbors, and the outer coast.  

  • What are the ecological and economic impacts of introduced species within the sanctuary?
  • What are the pathways by which species are introduced into the sanctuary?
  • What process can be used to evaluate the pathways posing the greatest threat to sanctuary resources?
  • Which agencies, organizations, regulations, or policies already address introduction pathways?
  • Can we detect new invasions (including Elkhorn Slough and tsunami debris from Japan)?
  • What are the most feasible and efficient methods of eradication, containment or management for existing and future introduced species in the sanctuary?
  • Where, how, and for how long should monitoring be conducted in the sanctuary to further our understanding of species already introduced to the sanctuary?

Education and Outreach Material

There are no materials available at this time.

photo of invasive kelp
Asian kelp, or "wakame" (Undaria pinnatifida) is an invasive species of kelp from Japan that has colonized many harbors along the California coastline, including Monterey and San Francisco. Credit: Chad King, MBNMS, NOAA


Bullard, S.G., G. Lambert, M.R. Carman, J. Byrnes, R.B. Whitlatch, G. Ruiz, R.J. Miller, L. Harris, P.C. Valentine, J.S. Collie, J. Pederson, D.C. McNaught, A.N. Cohen, R.G. Asch, J. Dijkstra and K. Heinonen. 2007. The colonial ascidian Didemnum sp. A: current distribution, basic biology and potential threat to marine communities of the Northeast and West coasts of North America. Journal of Experimental Biology and Ecology 342:99-108.

Byrnes, J. E., P.L. Reynolds and J.L. Stachowicz. 2007. Invasions and extinctions reshape coastal marine food webs. PLoS ONE 2(3): e295. doi:10.1371/journal.pone.0000295.

Cohen A. and J. Carlton. 1998. Accelerating invasion rate in a highly invaded estuary. Science. 279:555-558.

deRivera, C.E., G.M. Ruiz, J. Crooks, K. Wasson, S. Lonhart, P. Fofonoff, B. Steves, S. Rumrill, M.S. Brancato, S. Pegau, D. Bulthuis, R.K. Preisler, C.G. Schoch, C.E. Bowlby, A. DeVogelaere, M. Crawford, S.R. Gittings, A.H. Hines, L. Takata, K. Larson, T. Huber, A.M. Leyman, E. Collinetti, T. Pascot, S. Shull, M. Anderson and S. Powell. 2005. Broad-scale non-indigenous species monitoring along the west coast in national marine sanctuaries and national estuarine research reserves. Report to National Fish & Wildlife Foundation. Smithsonian Institute, National Estuarine Research Reserve System, National Marine Sanctuary Program, Washington, D.C. 125 pp.

Lockwood, J.L., M.F. Hoopes, M.P. Marchetti. 2007. Invasion Ecology. Blackwell Publishing, Malden, MA.

Maloney E., R. Fairey, A. Lyman, K. Reynolds, M. Sigala. 2006. Introduced aquatic species in California open coastal waters. Final Report. California Department of Fish and Game. Office of Spill Prevention and Response. Sacramento, CA., 93 pp. 

Sax, D.F., J.J. Stachowicz, S.D. Gaines. 2005. Species invasions: Insight into ecology, evolution, and biogeography. Sinauer Associates, Inc. Sunderland, MA.

Wasson, K., K. Fenn, J.S. Pearse. 2005. Habitat differences in marine invasions of central California. Biological Invasions 7:935-948.