Benthic macroinvertebrate community response to environmental changes over seven decades in an urbanized estuary in the northeastern United States.

Narragansett Bay is representative of New England, USA urbanized estuaries, with colonization in the early 17th century, and development into industrial and transportation centers in the late 18th and early 20th century. Increasing nationwide population and lack of infrastructure maintenance led to environmental degradation, and then eventual improvement after implementation of contaminant control and sewage treatment starting in the 1970s. Benthic macroinvertebrate community structure was expected to respond to these environmental changes. This study assembled data sets from the 1950s through 2010s to examine whether quantitative aggregate patterns in the benthic community corresponded qualitatively to stressors and management actions in the watershed. In Greenwich Bay and Providence River, patterns of benthic response corresponded to the decline and then improvement in sewage treatment at the Fields Point wastewater treatment plant. In Mount Hope Bay, the benthos corresponded to changes in bay fish populations due to thermal discharge from the Brayton Point power plant. The benthos of the Upper West Passage corresponded to climatic changes that caused regime shifts in the plankton and fish communities. Future work will examine the effects of further environmental improvements in the face of continued climatic changes and population growth.

Six decades of change in pollution and benthic invertebrate biodiversity in a southern New England estuary.

Pollution has led to a decline of benthic invertebrate biodiversity of Narragansett Bay, raising questions about effects on ecosystem functions and services including shellfish production, energy flow to fishes, and biogeochemical cycles. Changes in community composition and taxonomic distinctness (biodiversity) were calculated from the 1950s-when quantitative benthic invertebrate data first became available-to 2015. Change in community composition of the bay was correlated with changes in dissolved inorganic nitrogen, dissolved oxygen, and sediment contaminants. A mid-bay reference site showed moderate changes in community composition but no change in biodiversity. In contrast, a more impacted site in the upper bay showed substantial differences in community composition over time and a decline in taxonomic distinctness. Bay-wide, as inputs of some stressors such as nutrients and sediment contaminants have declined, there are signs of recovery of benthic biodiversity but other stressors such as temperature and watershed development are increasing.

Subtidal Benthic Invertebrates Shifting Northward Along the US Atlantic Coast.

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.