Table of Contents

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

S-CAN and geochemical data for Groves Creek

In situ instruments deployed at 1 m depth below the surface and as per: Tait, Z. S., M. Thompson, and A. Stubbins (2015) Chemical fouling reduction of a submersible steel spectrophotometer in estuarine environments using a sacrificial zinc anode. Journal of Environmental Quality. doi: 10.2134/jeq2014.11.0484

Samples for laboratory analyses were collected using a refrigerated autosampler (ISCO) which pumped samples from a depth of 1 m below the water surface. Samples were returned to the laboratory and filtered through 0.2 micron Polycap filters within 24 hours of collection. 

DOC and TDN using a Shimadzu TOC/TDN analyzer as per automated setup in Stubbins, A., and Dittmar, T. (2012) Low volume quantification of dissolved organic carbon and dissolved nitrogen. Limnology and Oceanography: Methods. doi: 10.4319/lom.2012.10.347.

Lignin via cupric oxide oxidation and GC-MS as per: Spencer, R.G.M., Hernes, P.J., Ruf, R., Baker, A., Dyda, R.Y., Stubbins, A., and Six, J. (2010) Temporal controls on dissolved organic matter and lignin biogeochemistry in a pristine tropical river. Journal of Geophysical Research – Biogeosciences. doi:10.1029/2009JG001180.

Dissolved black carbon by nitric acid oxidation to BPCAs followed by HPLC with spectrophotometric detection as per the non-isotopic method in Wagner, S., Brandes, J., Goranov, A.I., Drake, T. W., Spencer, R. G. W., Stubbins, A. (2017) Online quantification and compound-specific stable isotopic analysis of black carbon in environmental matrices via liquid chromatography-isotope ratio mass spectrometry. Limnology and Oceanography: Methods. doi: 10.1002/lom3.10219.
Nutrients were analyzed using a nutrient analyzer as per: Bittar, T. B., S. A. Berger, L. M. Birsa, T. L. Walters, M. E. Thompson, R. G. M. Spencer, E. L. Mann, A. Stubbins, M. E. Frischer, and J. A. Brandes (2016) Seasonal dynamics of dissolved, particulate and microbial components of a tidal saltmarsh-dominated estuary under contrasting levels of freshwater discharge. Estuarine, Coastal and Shelf Science. doi: 10.1016/j.ecss.2016.08.046.

BCO-DMO Processing Notes:

- combined two data tables into one data table with the same field identifiers.
- added conventional header with dataset name, PI name, version date
- modified parameter names to conform with BCO-DMO naming conventions
- added lat and lon columns
- added date_time column
- added depth column
- removed columns SCAN1,2,3 as the column SCAN_no contains the same information

Description from NSF award abstract:
Large fluxes of apparently refractory terrigenous dissolved organic matter (t-DOM) are transported through rivers to the coast each year, yet there are vanishingly low traces of t-DOM in the oceans. The removal of t-DOM is central to the global carbon cycle, yet the mechanisms that drive removal remain poorly understood. In soils, the presence of labile organic compounds is known to enhance the remineralization of recalcitrant compounds, a phenomenon known as the priming effect (PE). The PE is quantitatively important in soil systems, but has received little attention in aquatic systems despite its potential to explain C mineralization patterns at the land-sea interface. This project investigates the magnitude of PE in the coastal ocean and the metabolic and ecological mechanisms that give rise to it. It focuses on the microbial communities of US Atlantic Ocean coastal marshes. In these systems, river-borne t-DOM provides a particularly valuable and tractable model for evaluating the magnitude of the PE. The study utilizes a well-characterized DOM standard collected from a Georgia river as the model t-DOM material in a series of laboratory experiments with natural coastal microbial communities and cultures of heterotrophic marine bacteria of the Roseobacter lineage. Roseobacters are particularly appropriate biological models for this work as they are abundant in southeastern US coastal zones and are known to catabolize lignin and other plant-derived aromatic compounds. Long-term (60 day) incubation experiments will track the PE resulting from addition of labile DOM of differing chemical complexity. Changes in lignin phenols will be the primary measure of the influence of PE on t-DOM degradation, but the research also monitors a broader suite of aromatic compounds represented by optical properties and identified by high-resolution mass spectrometry. Measurements of the microbial response to added labile organic matter, via extracellular enzyme activities, bacterial production, community composition and gene transcript analysis, will reveal the biological mechanisms responsible for the PE. Experiments using Roseobacter strains will allow detailed investigation of the relationship between metabolic pathways, specific bacteria, and organic carbon mineralization in a well-defined experimental system. Data on gene expression, microbial activity, and DOM transformations from the lab experiments will be integrated to elucidate the specific metabolic pathways invoked as part of the PE and guide development of molecular tools to track genetic signatures along a river to coastal ocean transect in the final year of the project.

The role of heterotrophic microorganisms in remineralizing t-DOM at the land-sea interface is a central question in biological oceanography. Components of t-DOM, principally lignin, are refractory in the sense that degradation rates are typically slow relative to other biomolecules, and yet lignin is effectively removed somewhere between land and the open ocean. The project will determine whether priming plays a role in the rapid removal of t-DOM in the coastal ocean, provide evidence for the types of labile organic matter most effective as priming agents, and attemp to discover the metabolic pathways by which the PE is mediated. These studies have the potential to reveal conserved and predictable metabolic responses that may contribute to regulation of the transformation and turnover of naturally occurring semi-labile/refractory DOM in marine environments. As climate change is likely to affect fluxes of both terrigenous carbon and nutrients to the coastal ocean, understanding the magnitude and mechanisms of PE will be necessary to predict the geochemical consequences of these changing fluxes.

This project is related to the project "Tempo and mode of salt marsh exchange" found at https://www.bco-dmo.org/project/564747.