When an animal’s pigmentation matches the background across various types of environments, it is potentially an example of cryptic pigmentation, most likely as a response to natural selection by visually oriented predators. One example of cryptic pigmentation is phenotypic plasticity, meaning that an organism can exhibit different phenotypes in different environments. The freshwater isopod Asellus aquaticusliving in stands of reeds tends to have darker pigmentation than individuals living amongst lighter-coloured stoneworts, which has been suggested to result from visual predation. A recent study showed, however, that pigmentation in A. aquaticus is partly plastic, influenced by the nutritional composition in their diet. Here, I performed a laboratory experiment on A. aquaticusto see if the nutritional composition in stoneworts decreases pigmentation. Isopods were provided with a diet of either decaying leaves or stoneworts. The experiment took place over four weeks and pigmentation and growth were analysed at 0, 15 and 31 days. I found that pigmentation in A. aquaticusincreased significantly on both diets. And, there was no difference between both diets in amount of change in pigmentation. The fact that isopods that were feeding on stoneworts did not become lighter to match their background colour preferably depend on a high nutritional composition in the provided food, considering they also more than doubled their weight. In other words, phenotypic plasticity due to different diets between habitats is not the explanation to lighter coloured isopods living amongst stoneworts. However, these results do not exclude that differences can arise over a longer time or differs between different species of stoneworts.

The aim of this study was to investigate whether the water chemistry in lake Lillsjön have changed significantly due to human impact of surrounding areas. Lake Lillsjön is located outside the central parts of Östersund. It is an important recrational area, and has great natural values, among other things it is habitat for several species of Chara stoneworts. Chara requires clear calcareous water, high pH, relatively low levels of nitrate-nitrogen and low phosphorus concentrations. Lake Lillsjöns is recepient for surface water from a nearby commercial and industrial area, as well as melt water from an adjecent snow dump. Compared to ten other Chara-lakes in the region, lake Lillsjön shows higher concentration of total phosphorus and higher water colour. The study concludes that the surface water from surrounding areas, as well as melting water from the snow dump, are the main sources of the higher concentration of total phosphorus in lake Lillsjön. While the colour of the incoming water only shows a weak difference compared to the water colour of the reference lakes, the source of the higher water colour cannot be established. The water of lake Lillsjön can not be consider a suitable habitat for Chara.