Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Related Publications
• Parameters
• Instruments
• Deployments
• Project Information
• Funding

This dataset includes Doliolid abundance, carbon and nitrogen content, depth, temperature, salinity and in situ chlorophyll a from 25 cruises on the RV/Savannah at the South Atlantic Bight, Mid-Continental Shelf, (31 N 80 W) during 2015-2017. From the bottle samples, the following parameters were also measured:
- Average chemical extracted size fractionated total and > 8 um chlorophyll a and phaeophytin (mg m-3)
- Total and size fractionated (<10 um) POC (mg m-3 and mole L-1)
- Total and size fractionated (<10 um) PON (mg m-3 and mole L-1)
- Total and size fractionated (<10 um) delta13C (per mil vs PDB standard)
- Total and size fractionated (<10 um) delta15N (per mil vs air N2)
- Average delta13C (per mil vs PDB standard) and delta15N (per mil vs air N2) of starved D. gegenbauri zooids.
- D. gegenbauri abundance (individuals m-3)

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.

All data collected is thoroughly reviewed and quality controlled prior to finalization and reporting. Data that exceeded two standard deviations from mean data (of 3 or more samples) were flagged and removed. With respect to data for isotopic composition analysis, samples that did not contain sufficient biomass for instrument detection were not included and reported as NA (not available). In cases where observations were not logged, data is reported as NR (not reported). In cases where sample was not analyzed, data are reported as nd (not done). Blank data cells indicate data that are currently being analyzed.

BCO-DMO Processing Notes:
- added conventional header with dataset name, PI name, version date
- modified parameter names to conform with BCO-DMO naming conventions
- changed ND to nd to allow BCO-DMO statisticker to work
- replaced blanks with nd
- replaced space between lat/lon minutes and seconds with a decimal point and calculated decimal degrees
- converted date format from m/d/yyyy to yyyy-mm-dd

Project description from NSF award abstract:
Gelatinous (soft-bodied) zooplankton can play a crucial role in food webs and in cycling of materials in the world's oceans, and it has been suggested that they may become even more important in the future. However, because they are so difficult to study, gelatinous species remain poorly understood. This is especially true for smaller filter feeding gelatinous animals such as pelagic tunicates (salps, larvaceans, and doliolids). For example, it remains unclear what and how much these abundant filter feeders eat in nature and who eats them. This project will address this large and significant knowledge gap by using a combination of new and traditional methods to investigate the diet of the gelatinous pelagic tunicate Dolioletti gegenbauri, a species common on productive continental shelves such as the South Atlantic Bight. This project will also help train the next generation of ocean scientists to be competent in classical biology, modern molecular biology, and ecosystem modeling. Training will also focus on increasing representation of African Americans in the future science, technology, engineering, and math (STEM) workforce.

This study will provide the first quantitative estimates of the in situ diet of a key continental shelf gelatinous zooplankton species, the doliolid Dolioletta gegenbauri. Large blooms of doliolids have the potential to control the trophic structure of shelf pelagic ecosystems by shunting primary production to the microbial food web and by limiting copepod production via the consumption of their eggs. The long-term objective is to understand the ecological role and significance of doliolids in continental shelf pelagic ecosystems, specifically the underlying processes that lead to their high level of spatial and temporal patchiness. The basic questions to be addressed here include: What do doliolids eat, in situ, at different life stages? Are early life stages of larger metazoans important components of their diets? Do doliolids act as trophic cascade agents promoting primary production and phytoplankton diversity? Because of methodological challenges, there have not yet been definitive studies addressing these fundamental questions. In this project, the investigators will conduct field-based studies that will combine state-of-the art molecular techniques with more traditional methods in zooplankton ecology to answer questions about trophic interactions. Monthly oceanographic expeditions in the South Atlantic Bight will allow the research team to study wild doliolids at different time points in their life cycle and under different plankton bloom conditions. Application of recently developed molecular diagnostic assays will enable the quantitative description of the diversity and quantity of prey consumed, unbiased by experimental manipulation. Additional experimental and theoretical modeling will allow the investigators to link these data with larger ecological significance and scale.