Doliolid abundance, carbon and nitrogen content, chlorophyll-a, temperature, salinity, and depth from CTD casts from 25 RV Savannah cruises at the South Atlantic Bight, 2015-2017 (NCEI Accession 0278094)

Acquisition Description:
Depth, Temperature, salinity and in situ chlorophyll a salinity were recorded during the cruise from the real-time CTD data feed, recorded in log books. Complete CTD cast records are included as an independent dataset associated with this deployment. Surface values were recorded during the period when the CTD rosette entered the water and were logged once values had stabilized. Near bottom values were logged when CTD had reached its maximum deployment depth and values stabilized.

Extracted chlorophyll a and phaeophytin values were determined following overnight extraction in 90% acetone essentially as described by Parsons et al. (1984) after filtering 100 – 250 ml of water sample through either 0.2 microns (total) or 8 microns (> 8 microns) polycarbonate membrane filters. Filtrations were conducted in a darkened room. Filtration times were kept to less than 20 minutes per sample and less than 10 mm Hg vacuum. Following filtration, filters were placed directly into clean extraction tubes and stored frozen at -20ºC. Filters were extracted and analyzed within one week of collection. Fluorescence was measured using a 10AU Turner Designs fluorometer that was calibrated regularly using a chlorophyll standard solution (Sigma Chl std cat #C6144 – 1 mg). Standard curves were prepared as a 12-point dilution series from 0.05 – 500 micrograms L-1.

Water particulate organic matter (POC and PON) concentrations and isotopic composition were estimated from water samples (200 – 500 ml) filtered through pre-combusted Whatman GF/F filters. Filters were dried and stored at 60 deg.C until analysis.

Organic matter (C and N) isotopic composition of animals was also estimated. Individual animals were placed in 8x10 mm tin cups (Elemental Microanalysis) with a minimum of fluid, and dried at 60ºC for at least 48 hours prior to analysis. Samples were stored in 48-well plates at 60ºC prior to final preparation.

Sample analysis for %C, % N, d13C and d15N were performed on a ThermoFisher Delta V plus isotope ratio mass spectrometer interfaced to a Thermo Flash Elemental analyzer (Fry 1992). Isotopic and elemental composition calibrations were performed using commercially available powdered chitin (Sigma Chemical), which in turn had been calibrated against a variety of international (USGS 40 Glutamic Acid) and commercial (Elemental Microanalysis B2151 and B2155) isotopic and compositional standards. Chitin standards were run at the start of each analysis across the range of C amounts anticipated to be present in the samples, and every 10 samples as a drift check.