Green Crabs Observation Report

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We set out to determine what impact green crabs would have when introduced to intertidal communities in Washington. Specifically, we examined how the alien green crabs interacted with the native intertidal species and how the entire intertidal community was impacted. To research the interactions, we first collected population size data of an intertidal community where we could keep additional creatures from invading. We then added eight green crabs to the community and recorded the population size of the species at the end of 200 weeks. At the end of the 200 week period, the green crabs had greatly disrupted the intertidal community. The community supported about ten different species before the green crab was introduced, all which appeared to be at relatively stable population sizes. At the end of the 200 weeks, only four of the original species remained. Apart from the acorn barnacle that had a population size of four at the end of the observation, the other three …show more content…

Since the green crabs were eating the gooseneck and acorn barnacles, the crabs competed with the food sources for the starfish and whelk populations. This caused the starfish to rely more heavily on the chilton and muscles as food sources and the whelk were outcompeted by the green crabs which led to their depletion. After a period of time, both the chiton and muscles had been depleted and the starfish were then outcompeted for the barnacles; this lead to the depletion of starfish. By having the chiton depleted, the nori seaweed, coral weed, and black pine were able to thrive since their only predator had been wiped from the community. Our findings prove that the introduction of the green crab to the intertidal communities of Washington will have a massive impact on the diversity of the communities and could lead to a complete depletion of many of the

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