COMET Composition of dissolved organic matter and its interaction with metals and ultraviolet radiation in river-ocean systems: impact on the microbial food web

Country: EU Projects
Start Date:           Duration: 36 months         Project Type: RTD
Contract Number: EVK1-CT-1999-00034
Organisation Type:  EC Project
Diffuse pollution-->Diffuse pollution overview
Water resources and their management -->Stresses, quality and ecological status
Project objectives:
The field work will concentrate on 4 characteristic study sites (Rhine River, Rhine estuary, coastal North Sea and Skagerrak). Additionally, a high latitude 
coastal Arctic station will be sampled. We will characterize the DOM pool and its molecular weight fractions and determine the trace metal concentration (Fe,
Cu, Cd, Mn) and speciation in the different DOM molecular weight fractions. In situ and lab experiments will be performed to determine the alterations in the
DOM-metal complex upon exposure to UV radiation. In these experiments, the formation of photoproducts from the DOM will be followed as well as the changes in
metal speciation. In bio-assay experiments, the UV-induced changes in the bioavailability of selected metal species will be investigated. Biological weighting
functions for the response of microbial community to the exposure to UV radiation and its subsequent recovery are determined. Micro- and mesocosm experiments
at selected sites will be performed to investigate the complex interaction between the DOM-metal complex and the microplankton component of the food web in
the presence of UV radiation. All the data acquired are directly entered in an existing model, which will be expanded significantly to allow predictions on
the future development of the physico-chemical interactions in the DOM-metal complex model and its interaction with the planktonic component of the food
web in European waters.
Project Summary:
The COMET project addresses the basic scientific problem of how UV radiation interfaces with the trace metal load (Fe, Cu, Cd, Mn) and dissolved organic matter 
(DOM) at the land/ocean interface, and how those loads are influencing the microbial foodwebs in surface fresh waters and in the coastal environment. The improved
knowledge base on the above mentioned complex interactions will be integrated into a predictive model for the coastal zone.
Achieved Objectives:
Water column profiles of the underwater radiation regimens including the ultraviolet radiation (UVR) were made in October/November 2000 in the coastal North 
Sea, the estuary of the River Rhine and the River Rhine. Attenuation coefficients have been calculated from these data and formed the input required for WPs
3 to 5. These data are now used for the modelling component as well (WP6). Following the intensive sampling campaign outlined in the 3rd Management Report in
the Rhine river estuary (Lek, Waal, Schelde) and the coastal North Sea analysis were performed on the collected samples. Water samples were taken for dissolved
organic carbon (DOC), absorbance, and fluorescence measurements as well as for ultrafiltration. According to WP 2 the following detailed analysis were conducted
on the high molecular weight fractions of Rhine river, estuarine, and North Sea samples during summer and fall 2001. We have completed measurements of BWFs,
on three phytoplankton species in culture, using three different parameters (14Carbon fixation, photosynthetic electron transport [PAM] and growth).
Each measurement is performed on a spectral radiation resolution of 1 nm. We are now doing the modelling part using the technique developed by Cullen et al using
PCA. We will however compare this technique with the more traditional technique described by Rundel. To elucidate the influence of UVB on the bioavailability of metal and DOC mesocosm/microcosm experiments were made with 3 different water types: arctic
water (Ny-Ålesund/Svalbard), temperate waters strongly influenced by terrestrial matter (Isefjord/Denmark) and surface water from Øresund/Denmark
only weakly influence by terrestical matter. The bioavailability of metals was measured by means of Diffusive Thinlayer Gradients (DGT), a new sensitive
methods for time-integrated monitoring and very easy to handle. UVB effect on DOM was only seen in the Isefjord water. In the two others water types no effects
of UVB were seen on the DOC, neither in concentration nor in absorbance at 250 and 365 nm. UVB has no effect on the bioavailability of the metals in any of the water
types, however the DOM concentration and quality in the water tested was very different. Comparison between the arctic water and Isefjord water indicates
3-4 times lower concentration of the bioavailable Fe, Mn and As in the arctic water. Opposite, the concentration of bioavailable Cd, Cu, Cr and Zn was 3-10 times
higher in the arctic water. Bioavailable concentrations of Al, Co, Ni and Pb were almost similar in the two water types. The result is important since the impact
of metals on biota does not depend primarily on their total concentrations but on the concentration of the bioavailable form(s). Moreover, single species
experiments were performed at the Univ. Göteborg using phytoplankton cultures in the laboratory. One aim was to measure combination effects of copper and
UVBR for inhibiting photosynthesis and growth of a diatom (Phaeodactylum tricornutum). The ERSEM (European Regional Sea Ecosystem Model) has been used to
incorporate a module for the UVR-DOM-metal interactions and their role in pelagic food webs. To the ERSEM the Princeton Ocean model has been added and parameters
which should enter the model have been determined
Product Descriptions:
not public available 
Additional Information:

Project Resources:
Funding Programme(s): 
EC Framework Programme 5
Link to Organisations:
Submitted by: EUGRIS Team Dr Stefan Gödeke  Who does what?  06/12/2004 11:24:00
Updated by: EUGRIS Team Professor Paul Bardos  Who does what?  29/09/2006 16:14:00