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The Purple Marsh Crab

June 26, 2017

The Purple Marsh Crab

- as seen by -

Jason M. Aloisio Jason M. Aloisio

Once accounting for about 10% of the total area of Manhattan Island, wetlands now make up less than 1% of Manhattan today. This loss of wetland habitat, pervasive across the United States, was primarily a result of draining and in-filling of wetlands for development because they were historically considered unproductive and reservoirs of disease.

During the last 50 years, however, scientists have realized that wetlands are among the most biologically diverse ecosystems in the world and provide important ecosystem services for humans, including water filtration and storm-surge mitigation.

During 2016, students from Project TRUE (Teens Researching Urban Ecology) conducted wildlife surveys in wetlands across New York City and found dozens of species, including the purple marsh crab (Sesarma reticulatum). While the beautiful purple marsh crab is a native species in NYC, it may be a wolf in sheep’s clothing.

The purple marsh crab (above) eats wetland plants, but is eaten by other predators like blue crabs. Overfishing of blue crabs could cause an increase in the population of purple marsh crabs because of decreased predation. As the population of purple crabs grows, the consumption of wetland plants increases as well. This could, unfortunately, lead to wetland erosion and loss of even more of the little wetland habitat that still remains.

Currently, there are no studies that describe the distribution and abundance of the purple marsh crab in NYC. As a result, in summer 2017, Project TRUE participants will conduct the first-ever survey of the purple marsh crab in NYC to begin to understand its population dynamics.

Project TRUE is a collaborative program between the Wildlife Conservation Society and Fordham University. Each summer, Project TRUE supports a team of 75 student researchers (high school, undergraduate, graduate) in their exploration of the wildlife and wild places of NYC.

Panasonic Lumix DMC-TS5

Manhattan, USA Map It


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