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= Narragansett Bay Plankton Time Series =

The Narragansett Bay Plankton Time Series is a long-term monitoring study located in the highly productive estuary of Narragansett Bay, Rhode Island and is regarded as one of the world’s longest running plankton time series. It was launched in 1959 by Professor T. Smayda and his lab at the University of Rhode Island (URI) who began taking weekly plankton samples at Station II (41 34.2N; 71 23.4W) in Narragansett Bay (though some measurements have been taken at URI’s Graduate School of Oceanography’s dock) and sampling has continued to the present day. The accumulated data from the study has allowed for the rare opportunity to examine decadal changes in nutrient cycling, phytoplankton, zooplankton and fishing dynamics. The biological and physical data from the time series has since been made available to the public.

Overview of Sampling Data
Sampling is taken at one week intervals, regardless of the tidal stage at the time of sampling, and include measurements of temperature, salinity, turbidity, size-fractionated chlorophyll a and other nutrients. The microplankton community composition greater than 10 μm is characterized and quantified from the field sample aliquot in the laboratory using a light microscope. The species list for the specified size fraction includes over 240 different species or species complexes of protists. The concentrations of copepod and ctenophore populations are also quantified. All available data can be accessed through the University of Rhode Island’s Graduate School of Oceanography website.

Phytoplankton
Identification and quantification of the station’s phytoplankton community is measured from a weekly surface, bottom and net tow sample. Historically, phytoplankton counts were taken from a combined sample volume of surface and bottom waters, but beginning in May 2000, separate phytoplankton counts of surface and bottom waters were taken from their respective sample volumes. Collected samples are preserved in 1% Lugol’s preservative and are then phytoplankton cells are counted under a compound microscope using a Sedgewick-Rafter counting chamber. The sample from the 20 μm mesh net tow samples are also observed in the same manner as above, but species are only identified and not enumerated. Species are identified visually in the Sedgewick-Rafter chamber and are supplemented with permanent mounts examined with phase contrast and interference contrast optics. Even with the supplements, accurate identifications of very small and problematic species are not guaranteed. Samples counts in the database taken between 1999 and 2008 have been subjected to quality control and includes an analysis of changes in community composition.

Cell count (cells/L) data are available as Microsoft Excel spreadsheets and was released for public access beginning in January 1999.

Chlorophyll A
Beginning in September 1972, weekly Chlorophyll A concentrations were recorded as a part of the weekly plankton tow. Chlorophyll A is first extracted from filtered samples using 90% acetone and then sample fluorescence is measured with a Turner fluorometer, which is then used to calculate the concentration of Chlorophyll A. Between 1999 and June 2008, collected samples were filtered and then stored at -20 °C on location prior to extraction and analysis, but starting in May 2007, additional samples weren’t initially frozen and were analyzed using immediate extraction methods. It was found that upon comparison of the two protocols there was a significant loss of Chlorophyll A in samples that had been previously frozen and stored. A linear regression analyses between the two methods produced correction factors that are needed to more accurately reflect that standing stock of Chlorophyll A at Station II. Data sets of the adjusted and non-adjusted values are provided in the datasheets. Since July 2007, the immediate extraction protocol described by Graff & Rynearson is the current methodology used in the Narragansett Bay Plankton Time Series.

Chlorophyll A concentrations (μg/L) have been made available as Microsoft Excel spreadsheets with reported data starting in January 1999.

Zooplankton
Weekly vertical net tows of zooplankton are taken from the same location as the phytoplankton vertical net tow. The top five meters of the water column is sampled using a 0.25 m diameter, 64 μm mesh net for a total volume of 0.25 m3. The sample is then preserved immediately in a final concentration of 4% buffered formalin-seawater solution. Under a dissecting microscope, subsamples are added to a counting slide with a wide bore pipette calibrated in milliliters and the zooplankton community is identified and quantified. The total subsample volume is chosen to ensure the enumeration of at least 200 organisms. Species identification is made for all copepodite stages of copepod and copepod nauplii are lumped. Other taxa are identified to species when known and to order, when species identification is not certain (as in the case of benthic larvae). Gelatinous zooplankton species are collected on location with a separate vertical net tow using a 0.5 m diameter, 1 mm mesh net. This net is fitted with a flowmeter which allows for the total sample volume to be measured, which is 1.1 m3. This sample is immediately counted upon arrival to the laboratory because the live ctenophores are unable to withstand preservation and allowing the sample to sit for long periods of time could lead to inaccurate counts. The diameter of medusae and ctenophores are measured and then identified to the level of species. Sampling began in 1999 but samples were stored and only those from October 2001 to the present have been counted with funding from the National Science Foundation and the Vetleson Foundation Grants to Barbara K. Sullivan.

Zooplankton and gelatinous zooplankton data, starting from October 2001, have been made available as Microsoft Excel spreadsheets.

Physical Data
The physical parameters of temperature, salinity, turbidity and dissolved oxygen, along with the above mentioned chlorophyll fluorescence, are measured weekly at Station II in Narragansett Bay. The water column profile of the observed physical parameters are available for download (Microsoft Excel) with the available data beginning in 1999. Nutrient concentrations are measured from surface and bottom samples. Samples are collected, kept on ice and filtered within a few hours of collection. Filtering is done by using an acid washed filtration manifold (60 ml syringe and Millipore filtering tips) with 0.45 mm cellulose filtering membranes. The filtrate is then placed in 60 ml polyethelene bottles and held at -20 °C until analysis. This analysis was conducted with support from the RI Sea Grant from 2003-2009.

Nutrient data spreadsheets are available for download (Microsoft Excel) with the available data beginning in 2003.

Additional Resources
Costello, J.H., Sullivan, B.K., Gifford, D.J., 2006. A physical-biological interaction underlying variable phenological responses to climate change by coastal zooplankton. J. Plankton Res. 28 (11), 1099-1105. Hargraves, P.E. 1988. Phytoplankton of Narragansett Bay. pp. 136-143, In: Freshwater and Marine Plants of Rhode Island. R.G. Sheath & M.M. Harlin (eds.). Kendall-Hunt Publ. Co., Dubuque, Iowa. 149 pp. Li, Y., Smayda, T.J., 1998. Temporal variability of chlorophyll in Narragansett Bay, 1973‚Äì1990. ICES Journal of Marine Science: Journal du Conseil 55 (4), 661-667. Li, Y., Smayda, T.J., 2001. A Chlorophyll Time Series for Narragansett Bay: Assessment of the Potential Effect of Tidal Phase on Measurement. Estuaries 24 (3), 328-336.

Smayda, T.J. 1998. Patterns of variability characterizing marine phytoplankton with examples from Narragansett Bay. ICES Journal of Marine Science 55: 562-573. Smayda, T.J. & Borkman, D.G. 2008. Nutrient and Plankton Dynamics in Narragansett Bay. In: Desbonnet, A., B.A. Costa-Pierce [Ed.] Science for Ecosystem-based Management. Springer, New York, pp. 431-484.