Urbanization Affects Freshwater and Coastal Marine Biodiversity Differently

Researchers studied how urbanization affects marine and freshwater ecosystems by comparing biodiversity and ecosystem functions across six pairs of urban and less-urban watersheds in Puget Sound, Washington. Surprisingly, they found that while freshwater biodiversity declined with urbanization, coastal marine biodiversity increased. Researchers compared six pairs of more and less urbanized coastal watersheds in Puget Sound, measuring biodiversity of bottom-dwelling invertebrates and ecosystem functions like primary productivity and decomposition in both freshwater and marine sites using statistical analyses including principal components analysis and analysis of covariance. Greater upland urbanization was associated with reduced freshwater biodiversity, measured as density and evenness of epibenthic invertebrate families. Coastal marine biodiversity tended to be higher at more urbanized sites, suggesting low to moderate urbanization-related disturbance may increase marine diversity. No statistical association was found between urbanization and ecosystem functions in either freshwater or coastal marine habitats. There was no evidence that urbanization effects were more severe in freshwater than coastal marine habitats, contrary to expectations. The research challenges assumptions about how urbanization affects connected ecosystems and has consequences for Pacific salmon conservation, as these endangered species depend on both freshwater and marine habitats during their life cycles. The findings suggest that ecosystem-based management must consider terrestrial, freshwater, and coastal marine systems together.

Citation

Samhouri, Jameal F.; Shelton, Andrew Olaf; Williams, Gregory D.; Feist, Blake E.; Hennessey, Shannon M.; Bartz, Krista; Kelly, Ryan P.; O’Donnell, James L.; Sheer, Mindi; Stier, Adrian C.; Levin, Phillip S. (2022). How much city is too much city? Biodiversity and ecosystem functioning along an urban gradient at the interface of land and sea. Frontiers in Marine Science.

"Surprisingly, they found that while freshwater biodiversity declined with urbanization, coastal marine biodiversity increased."

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