Unleashing the Green Menace: A Closed Mesocosm Study Assessing the Effects of an Invasive Green Crab (Carcinus maenas) on Eelgrass and Benthic Infauna

Eelgrass estuaries are diverse coastal ecosystems severely threatened by the synergistic effects of climate change and invasive species. The invasive European green crab (EGC; C. maenas), a known ecosystem engineer and voracious omnivore, can devastate eelgrass beds and displace native species, with rising temperatures facilitating their northward spread along the North American coast. Despite this threat, the overall ecological impact of EGC on eelgrass and benthic infauna—key components of estuarine food webs—remains poorly understood in the Salish Sea. One of the largest eelgrass beds in North America, the Padilla Bay National Estuarine Research Reserve, is facing an early-stage C. maenas invasion, prompting concerns over continued sustainability and conservation. We conducted a short-term study to understand how EGC might alter eelgrass survival (Zostera marina and Z. japonica) and benthic communities in the bay. In an approved quarantine facility, replicate mesocosm tanks containing sediment and eelgrass transplanted from Padilla Bay were divided into two treatments: EGC and no EGC. After nine days, we assessed eelgrass loss and infaunal species diversity. Preliminary results indicate visible eelgrass loss with EGC exposure and higher average macroinvertebrate abundances in the control tanks. These results suggest trophic cascades may occur in response to EGC habitat disturbances and foraging. Understanding how EGC influences Padilla Bay is crucial for enhancing conservation and sustainability efforts within this vital estuary.

Presentation Preference: Oral

Primary Presenter: Kaitlin Macaranas, Western Washington University (macarak@wwu.edu)

Authors:

Kaitlin Macaranas, Western Washington University  (macarak@wwu.edu)

Brian Bingham, Shannon Point Marine Center  (bingham@wwu.edu)