NEWS
What will happen to the organic contaminants in the climate changed future? Higher temperature and larger runoff is expected, and with the larger runoff a higher load of dissolved organic carbon. To study how this will affect the distribution of organic contaminants in the ecosystem, Matyas Ripszam has in his thesis developed an analytical method, and performed field large scale mesocosm studies.
Matyas presenting results at an EcoChange conference. Photo: Kristina Viklund.
Climate change models project not only higher temperatures, but also an increased freshwater runoff into the Baltic Sea. This will result in increased inflow to the Baltic Sea of terrestrial dissolved organic carbon, DOC. DOC is the dissolved fraction of organic compounds from degradation of biological material.
The association of organic contaminants to DOC has earlier been shown to have an immense impact on their bioavailability. At a microbial level the organic contaminants enter the food web either by direct uptake in phytoplankton, or through sorption to DOC. DOC serves as a food source for bacteria, and therefore the sorption of contaminants to DOC is expected to have a high relevance in bacteria-based food webs.
Matyas with colleagues analyzing samples at Umeå Marine Sciences Centre. Photo: Kristina Viklund.
The sorption of organic contaminants to DOC is known to decrease the concentration of free contaminants in natural waters, which still doesn’t mean that the contaminants are less harmful for the ecosystem. The climate change induced higher organic carbon load is expected to lead to a higher degree of bacteriabased ecosystems, especially in the northern parts of the Baltic Sea. Thereby the pollutants may enter the food-web and cause problems on higher levels, as fish. The results of this thesis indicate that a higher fraction of organic contaminants are associated to DOC in the northern parts of the Baltic Sea compared to the southern parts, due to specific, chemical properties of the terrestrial DOC in the north.
Matyas presents a newly developed method to measure the extent to which contaminants partition to dissolved organic carbon. This method was applied to samples taken along the Baltic Sea coast. Most of the studied pollutants showed decreasing affinities from north to south.
The mesocosm facility used in the experiments. Photo: Kristina Viklund.
He also used a large scale mesocosm to examined the effects of higher temperature and organic carbon content on the distribution of pollutants. Higher temperature alone led to increased losses of pollutants, whereas higher organic carbon content retained more pollutants in the model ecosystems. The combined effect of higher temperature and higher DOC load showed no real patterns. Some pollutants were more sensitive to changes in temperature, while others were sensitive to increased organic carbon content.
