Project leaders:
Dr. Pamela Rossel Cartes
Dr. Thorsten Dittmar
The release of refractory dissolved organic matter to the deep ocean from fossil sources.
Dissolved organic matter (DOM) is one of the largest and more complex organic pools on Earth. The major fraction of this pool is characterized by a refractory mixture of molecules that remain in the system for thousand of years. Because of this “inert” behavior, we hypothesize that an important part of the DOM pool is from a thermogenic origin. Thermogenic products formed during the transformation of organic matter by geothermal heat and elevated pressure in deep sediments may be later solubilized into the deep ocean. Under these conditions, condensation reactions take place producing polycyclic aromatic structures (Fig. 1), which are particularly resistant to biodegradation. Similar molecular structures are also produced during fossil fuel and biomass burning (“black carbon”). Based on first results using quantitative methods to trace thermogenic DOM its has been showed that this pool has a homogenous distribution in the deep ocean (Fig. 2, Dittmar and Paeng, 2009), which is in agreement with its refractory character. Pre-industrial signal of thermogenic DOM in the deep ocean suggest the contribution of a natural source of refractory DOM that link the fossil sedimentary organic carbon with the more active cycles in the surface ocean. The combination of quantitative methods and high resolution mass spectrometry (Fourier Transform Ion Cyclotron Mass Spectrometry, FT-ICR-MS) will allow us to evaluate the thermogenic component of DOM in the ocean.
In collaboration with colleagues at the MPI (Nicole Dubilier), Schlumberger Oilfield Service (Oliver Mullins) and at the University of Bremen (Kai-Uwe Hinrichs and Verena Heuer), this work will address several aspects of fossil dissolved organic matter (DOM) in the ocean: quantification, molecular characterization of fossil DOM, its formation in deep sediments, origin (sedimentary fossil or biomass burning), and its cycling and turnover in the ocean by several processes.

Fig. 1. Two possible structures of thermogenic DOM (based on Dittmar and Koch, 2006).

Fig. 2. The distribution of thermogenic DOM in the Southern Ocean (Dittmar and Paeng, 2009), expressed as the concentration of total polycyclic aromatic hydrocarbons (PAHs, nmol carbon per liter)

Second Project

Project of bilateral research cooperation between Germany and Chile, funded by Deutsche Forschungsgesellschaft (DFG)

Project leaders:
Dr. Pamela Rossel Cartes
Prof. Dr. Silvio Pantoja

The Chilean Patagonia: A natural laboratory for studying the role of dissolved organic matter in sub-polar ecosystems in a changing climate.

The role that dissolved organic matter (DOM) has in systems highly sensitive to environmental variations, such as fjords areas in the sub-polar ecosystems, has been poorly constrained. Fjords formed by glacier abrasion in sub-polar regions are environments in which a close link between terrestrial, marine and freshwater systems occurs. Additionally, due to their location, these environments are affected by strong seasonal climatic changes caused by the variability of solar radiation, precipitation and wind, which in turn may affect the DOM supplied by terrestrial, marine and freshwater systems. Furthermore, there is evidence that glaciers in areas such as the Chilean Patagonian fjords (Fig. 1) exhibit a general retreat in response to climatic changes, which may also influence the type and amount of organic matter that is flushed from the continent and reaches the fjords. The influence of the environment in combination with other local effects (e.g., anthropogenic activities and glacier influence) on the carbon cycle and the functioning of sub-polar ecosystems are understudied. One aspect that has been neglected is the detailed evaluation of the structure, size and dynamic of DOM caused by seasonal and spatial fluctuations in response to global and local effects in the diverse high latitude fjord ecosystem. Therefore, the fluctuations in DOM composition and dynamic in relation to the fjord characteristics, terrestrial organic matter supplied, occurrence of aquaculture activities and influence of glaciers, as well as the effects that these DOM variations may have on the microbial community living in the water column will be addressed during this study.

Fig.1. Location of stations included in the oceanographic platform of continuous observation from the COPAS Sur-Austral in 2008, which will be part of our study area.