Optical signatures of the aquatic carbon cycle – relating DOM color to chemistry and source.
Coordinador: Dr. Aron Stubbins, Skidaway Institute of Oceanography, University of Georgia, Savannah, USA y Dr. Jorge Nimptsch, Universidad Austral de Chile.
Fecha: 3 de Noviembre
The optical signatures of DOM can be rapidly and inexpensively measured in the field and laboratory, providing valuable information about carbon cycling in aquatic ecosystems. Examples of how both absorbance and fluorescence can be linked to DOM chemistry, source, and reactivity will be presented and discussed. A section of the workshop will discuss how the optical properties of DOM can be utilized to track inputs of DOM to natural waters, with example data from salmon aquaculture studies in the Valdivia region.
INVITADO ESPECIAL (Keynote Lecture) Norbert Kamjunke (Helmholtz Centre for Environmental Research)
Title: Release and degradation of dissolved organic matter in freshwaters: Lessons learned from Europe and South America.
Elevated concentrations of dissolved organic matter (DOM) in freshwaters are an increasing problem in Europe and North America. Data from 110 catchments in Germany indicate that high DOM concentrations were found only in catchments with low hillslope, low nitrate concentration, and high proportion of forest. The long-term and seasonal dynamics of DOM was parallel to those of iron but inverse to those of nitrate suggesting a joint release of DOM and iron under low nitrate availability. Bacterial DOM degradation in streams was related to water temperature and DOM properties, it was negatively correlated to discharge and was negligible during flood events. In Chile, salmon aquacultures are an important point source of DOM. Fluorescence measurements, ultrahigh-resolution mass spectrometry, and nuclear magnetic resonance spectroscopy of DOM revealed specific and extensive molecular alterations caused by aquacultures. Aquacultures released large quantities of readily bioavailable metabolites (primarily carbohydrates and peptides/proteins, and lipids) causing the organic matter downstream of all investigated aquacultures to deviate strongly from the highly processed, polydisperse and molecular heterogeneous DOM found in pristine rivers. Bacterial DOM degradation rates explain the attenuation of aquaculture DOM within the subsequent stream reaches. The DOM pollution shifted stream ecosystems to a more heterotrophic state. Further investigations should relate molecular DOM characterization with bacterial activity.