The Lives and Times of the Narragansett Bay Benthos: Biodiversity Trends over 182 Years
Citation:
Hale, S., M. Hughes, AND H. Buffum. The Lives and Times of the Narragansett Bay Benthos: Biodiversity Trends over 182 Years. Coastal & Estuaring Research Federation (CERF) 24th Biennial Conference, Providence, RI, November 05 - 09, 2017.
Impact/Purpose:
Narragansett Bay has high benthic invertebrate biodiversity that supports many ecosystem functions and services important to people living on the surrounding shores. Over time, natural and human-driven forces have caused changes in biodiversity, resulting in changes to ecosystem services generated for people. Because of sporadic sampling and lack of consistent methods, it has been difficult to quantitatively assess changes in the benthic community over three centuries. Use of a relatively new statistical technique for measuring biodiversity called Average Taxonomic Distinctness (a measure of complexity of the community’s taxonomic tree), along with a measure that determines the similarity of two different communities, allowed such analyses. We found that biodiversity had undergone many changes since the late 1800s. More recently, since the 1970s, varying natural and anthropogenic factors at a site in Mount Hope Bay have forced changes in community composition and taxonomic distinctness of the benthic community. In contrast, a site at North Jamestown, a place with fewer human impacts, showed fewer significant changes from the 1950s to the 1990s, although it appears that this has shifted in the most recent decade. Biodiversity is an important ecological indicator of what is happening in our environment and is being used by the Office of Water as a key indicator in the National Conditional Coastal Assessment. Also, an inventory of what species are in an area and how they are likely to be affected by a proposed activity is needed with permitting decisions. Biodiversity is a useful measure in assessing whether particular EPA and state programs are effective in what they are trying to achieve for water quality and ecosystem health in our bays and coastal areas. Community similarity and taxonomic distinctness make it possible, for example, to compare the benthic community before and after passage of the Clean Water Act, or before and after recent improvements to sewage treatment plants at the head of Narragansett Bay.
Description:
Narragansett Bay has high benthic invertebrate biodiversity that supports many ecosystem functions and services. A master list was compiled of all benthic species collected from the Bay beginning in 1862, including a U.S. Bureau of Commercial Fisheries survey in 1871 and studies at Alexander Agassiz’s Marine Zoological Laboratory in Newport, 1877–1910. The list, spanning 154 years, was compiled from 77 studies and includes invertebrate macrofauna (>0.5 mm) and more limited studies of meiofauna. It currently holds 1,150+ unique taxa from 22 phyla, 62% of all animal phyla on Earth. A species accumulation curve suggests more species are yet to be discovered. Often, the only data collected by early studies were lists of species. Also, when abundance data were available, widely-varying sampling gear and sieve mesh sizes in the early studies precluded a quantitative comparison of abundances. Instead, non-metric multidimensional scaling and Average Taxonomic Distinctness were used with presence-absence data (species lists) to examine trends over time. Trends using quantitative abundance data from later studies were examined at a reference site (North Jamestown in mid-Bay) and at a more impacted site at Spar Island in Mount Hope Bay. The North Jamestown site is characterized by the typical Narragansett Bay Nephtys-Nucula community and has been sampled by 17 different studies, 1957–2010. Community composition and biodiversity were relatively constant, making it a good control site. At Spar Island in Mount Hope Bay (five studies, 1975–2015), changes in natural and anthropogenic factors—including an end to the discharge of heated water into the Bay by a power plant at Brayton Point—forced changes in the benthic community, as shown by significant decade-to-decade differences (<0.01) in an Analysis of Similarity on a Bray-Curtis similarity matrix and an ANOVA on Average Taxonomic Distinctness. Biodiversity is a useful ecological indicator of historic trends.