Evo Forest Lakes

In Finland, thousands of lakes are characterized by high water colour (high DOC concentration), originating from the forested catchment areas. We are currently performing studies to clarify the effects of the high water colour on the functioning of the food webs. The study area is situated in the Evo district (61 º13´N, 25 º 12´E) in southern Finland. The area includes dozens of forest lakes differing in morphometry and water quality.

So far the studies (started in 2005) have demonstrated, for instance, that in humic lakes the importance of the littoral zone as a refuge for zooplankton decreases with decreasing transparency of the water and that low water transparency protects cladocerans from fish predation. It also seems that invertebrate predators have an important role in these food webs. The results also indicate that the water quality substantially affects the size-selectivity of fish predation and competitive interactions between different fish species.

Studies during the following years will focus, for instance, on the spectral quality of light and its effect on predation efficiency by fish and invertebrates,  inter- and intraspecific competition between different fish species in relation to water colour, and on the role of macrophytes in the food webs of high-colour lakes.