Dissolved organic material (DOM) is a major pool of organic carbon in all aquatic ecosystems and has high concentrations in soil interstitial water. DOM represents both a substrate for microbial growth and an important characteristic of aquatic and soil environments, regulating light penetration in lakes and streams and the bioavailability of trace metals and organic contaminants, for example.
Diverse studies have shown that the concentration and chemical properties of DOM reflect the predominant DOM sources. In lakes and streams, DOM can originate from the surrounding watershed (allochthonous sources) and from production and decomposition of DOM within the aquatic ecosystem (authochthonous sources). The understanding within the LTER network of the dynamic processes controlling DOM fluxes and reactivity within and among ecosystems can be advanced by increasing the application of modern spectroscopic methods and calculation of indices associated with DOM source, molecular weight, humification, and biological processing. The interpretation of various fluorescence indices has advanced recently and provides more support for using these indices in long-term studies. Additional biogeochemical information can also be determined from statistical processing of DOM spectra, e.g. parallel factor analysis (PARAFAC) and principle component analysis (PCA). Recently, the fluorescence PARAFAC model developed from FCE LTER samples was successfully used to model DOM transformation along a transect of the Okavango Delta, another subtropical wetland (Cawley K, Wolski P, Mladenov N, Jaffe R, 2012 Dissolved organic matter biogeochemistry along a transect of the Okavango Delta, Botswana, Wetlands vol. 32, p. 475).
The working group session will begin with an overview presentation on DOM quality variations in the LTER network and continue with presentations and discussion of analytical approaches for characterization of DOM using spectroscopic indices and statistical analyses to better understand changes in carbon cycling and biogeochemistry. The participants will develop and refine overarching hypotheses and recommendations for DOM research in the LTER network.
In addition to a working group session during the ASM, the DOM Characterization Working Group led by Kaelin Cawley and Rudolf Jaffe (FCE-LTER) and Diane McKnight and Rachel Gabor (MCMLTER & NWTLTER) will hold a 2-day pre-conference training workshop on fluorescence methods for characterization of dissolved organic material in surface waters and soil interstitial waters. The workshop will be held at INSTAAR at the University of Colorado in Boulder on Friday and Saturday, Sept 7 and 8, 2012 and will include training in spectroscopic methods and data analysis using PARAFAC (parallel factor analysis). Participants (up to 15) should bring a laptop with MATLAB installed. Participants may bring a small number of samples (3-4) for analysis during the workshop. Please contact Christopher Jaros (email@example.com) for more information about logistics for the pre-conference training workshop and to confirm attendance. Some housing will be available in Boulder, and a block of rooms will be reserved at a nearby hotel.