Citation:

Hale, S., H. Buffum, J. Kiddon, AND M. Hughes. Subtidal Benthic Invertebrates Shifting Northward Along the U.S. Atlantic Coast. Estuaries and Coasts. Estuarine Research Federation, Port Republic, MD, 40(6):1744-1756, (2017).

Impact/Purpose:

This study made novel use of data from a USEPA national estuarine and coastal monitoring program to look at shifts in the spatial distributions of bottom-dwelling invertebrate species during a time (1990–2010) of warming U.S. Atlantic coastal waters. The objective was to document species distributional shifts in the area from mid-Florida to Cape Cod so that environmental managers could be prepared for changes in the mix of species living in their local estuaries and bays. All animals have a preferred zone of temperature. If that zone shifts northward, the animals may also try to shift northward in an effort to maintain the temperature range to which they are accustomed. Animals vary both in how broad a band of temperatures they can tolerate and in their ability to adapt to or to migrate away from a change in their thermal environment. This means that the mix of species in any particular bay along the Atlantic coast will change over time as certain current animals that prefer a colder temperature will tend to leave the bay and as some animals from further south move into the bay. This change in the mix of species can have large consequences for the local ecosystem. For example, populations of American lobsters in southern New England have declined in the last few years as the center of population has shifted northward. Meanwhile, black sea bass and other more southern species have increased their abundance in the area. We found that range shifts are also happening with some of the clams, crustaceans, and worms that are food for many fishes of commercial and recreational importance.

Description:

Numerous marine and terrestrial species have shifted their ranges poleward in response to warming from global climate change. However, few studies have examined range shifts of subtidal benthic communities in estuarine and nearshore waters. This study examined 20 years (1990–2010) of occurrence and abundance data of soft-bottom, benthic invertebrates along the Atlantic coast of the USA. Data from two biogeographic provinces (Carolinian and Virginian), which spanned 15° of latitude from mid-Florida to Cape Cod, were extracted from a national coastal assessment program. Mean water temperatures increased significantly during the study period, bottom water by 1.6 °C and surface water by 1.7 °C. Of 25 species with significant changes in centers of abundance (out of the 30 most prevalent), 18 (60%) shifted northward and 7 (23%) shifted southward. Species that shifted north moved an average distance of 181 km, in contrast with 65 km for species that shifted south. The southern limits of 22 species showed significant northward shifts; because there was little change in northern limits, this resulted in an average 25% range contraction. Community composition changed during the study period, most notably in southern latitudes. Five Carolinian species surmounted their northerly biogeographic boundary. Consequences of these range shifts include changes in benthic community structure and function, which have strong implications for ecosystem functioning and services including changes in fisheries dependent upon benthic prey.

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