Workshop Organizer: Rudolf
Jaffe
Key Participants:
Rudolf Jaffé,
Keywords:
dissolved organic matter, DOC, DON, analytical methods
Abstract: The
importance of dissolved organic matter in biogeochemical and ecological
processes in aquatic environments has clearly been established. However,
understanding the role of DOM is difficult if DOM is treated as a single
biogeochemical parameter, and not characterized with enough resolution to
detect the influence of different sources and processes. DOM (DOC and DON)
consists of a quite complex mixture of organic compounds derived from
terrestrial and aquatic sources. The assessment of these sources, its
transformations, transport and ultimately its environmental fate is strongly
dependent on the chemical characteristics. While identification of individual
components can be accomplished for only a small percentage of the DOM, a range
of chemical characterization approaches, such as spectroscopic characterization
and molecular weight distribution, can be applied to whole DOM or major DOM
fractions. Unfortunately, such chemical characteristics often remain unknown
due to the fact that analytical methods used can be complex, time consuming and
expensive. However, the molecular level data that can be generated may be
invaluable in explaining DOM dynamics, its function in the microbial loop, and
its overall biogeochemical role in a particular ecosystem. This workshop is
intended as a venue to present participants with presently on-going DOM characterization
studies at different LTER sites, exchange methods and expertise in DOM
analyses, and identify present and future needs for such characterizations as a
tool for the better assessment of biogeochemical and ecological processes in
the LTER program.
Workshop Report: The
above described workshop was primarily of technical nature, in the sense that
is was designed as an information based venue to make LTER scientists aware of
analytical methods for the analysis of DOM, and to present such information from
different LTER sites (primarily FCE and Arctic) to demonstrate the added value
of this information in long term ecological studies. The workshop was set up
such that the complexity of the DOM analyses increased sequentially. As such,
DOM bulk measurements, sorption-based fractionation, isolation/concentration
methods, and optical property determinations, including a variety of different
UV-Vis and fluorescence techniques, were presented
and discussed. These were followed by specific ‘wet chemistry’ methods for the
analysis of proteins and carbohydrates among others and by more sophisticated
methods including 13C and 15N CP/MAS NMR, neutral sugar
analysis, amino acid analyses, protein fingerprinting, pyrolysis-GC/MS,
TMAH thermochemolysis, mass spectrometry and others.
Finally, relatively simple and more advanced methods for the assessment of
molecular weight distributions were presented and data from the FCE-LTER site
discussed as examples.
Overall, the participation of the audience was active and
the general interest in the implementation of such methods and techniques at
other LTER sites was made clear. It was quite apparent that chemical and/or
molecular characterizations of DOM, a key biogeochemical parameter, were not
being performed at the majority of existing LTER sites. The needs and
advantages of such analyses to on going biogeochemical research were made quite
clear during the workshop, and several workshop participants were interested in
getting involved in such activities. The possibility of inter-site
collaborations were discussed and it was suggested that such an activity could
start with the determination of bulk and optical DOM parameters at a limited
number of representative locations/environments at different LTER sites. Such a
study would not only contribute to the on-going LTER activities, but also
provide new information on the characteristics of the ever increasing DOM load
in a variety of geomorphologically different aquatic
systems and watersheds.
Workshop participants:
J. Campbell Hubbard
Brook jlcampbell@fs.fed.us
T. Heartsill
E. Marin-Spiotta
M. A. Evans Arctic mevans@umich.edu
G. Gettel Arctic gmg7@cornell.edu
N. Werdin Bonanza Creek ftnrw@uaf.edu
S. Y. Newell GCE newell@uga.edu
J. Melack SBC melack@lifesci.ucsb.edu
N. Maie FCE nagamits@fiu.edu
R. Neto FCE netor@fiu.edu
J. Cloutier FCE Joshua.cloutier@fiu.edu
M. Gao FCE min.gao@fiu.edu
Y. Xu FCE yxu@fiu.edu
K. Parish FCE kpari001@fiu.edu