Studying bacterial community composition gives gives important information on disturbances in the marine environment. Researchers have investigated how bacterial communities change when exposed to combinations of increased organic matter and environmental toxins.
Text: Kristina Viklund
As a result of climate change, the amount of organic material flowing into the seas will increase, especially in the northern regions of the Baltic Sea. This leads to major changes in the basic levels of the food web, which then affects the entire food web. The clearest effect is that bacteria will benefit from the influx, while phytoplankton will be disadvantaged.
These changes can have effects not only on the food web itself, but also on how environmental toxins are absorbed and disseminated in the food web. EcoChange researchers investigated how bacterial communities change and how this may affect the uptake of environmental toxins.
To study the changes under carefully controlled conditions, so-called mesocosms were used. To mimic the inflow of organic matter, soil was added. A mixture of organic pollutants occurring in the Baltic Sea was added, and bacterial production and the composition of the bacterial community could be studied by the addition of different combinations of soil and environmental toxins.
Soil and pollutants led to changes
It is already known that bacteria can react differently to organic pollutants. Some are inhibited in their growth, many are not affected at all, and some can even benefit from the toxins. Bacteria that benefit likely can use the organic environmental toxins as food.
Outdoor mesocosms where used to perform the experiments. Soil was added to mimic the inflow of organic matter.
The results of the experiments clearly showed that the combination of increased amounts of organic material and environmental pollutants can change the composition and function of bacterial communities. In general, the bacteria were favoured by the organic material and disadvantaged by the environmental pollutants. When the environmental pollutants were combined with organic material, the inhibitory effect of the environmental pollutants became even greater.
Uncommon types were eliminated
The diversity of the bacterial community increased with increasing amount of organic matter, and decreased with the amount of environmental pollutants. It was primarily the less common types of bacteria that were eliminated by the environmental pollutants, while the more common types were less affected, possibly because more common bacteria have the ability to adapt to changes in the environment.
The study shows that bacterial communities are affected, both in terms of composition and function, when they are exposed to environmental disturbances in the form of environmental pollutants. The researchers therefore suggest that analyses of bacterial communities should be included in the environmental monitoring as an indicator of disturbances in the marine environment. It could work quickly and efficiently, and to a low cost.
The article has earlier been published in the EcoChange annual report. The text is based on: