| Increased rainfall and warmer temperatures due to climate change in the boreal zone is predicted to increase the inflow of terrestrial dissolved organic carbon (T-DOC) to aquatic ecosystems. This will have important consequences for basal energy production (phytoplankton and bacteria) in aquatic ecosystems and also affect the production of higher trophic levels such as fish. As T-DOC is a coloured substance, increased T-DOC concentrations can lead to ‘brownification’ of lakes and a reduction in benthic production due to reduced light penetration. This may reduce the total amount of basal energy available for zooplankton and their predators such as young-of-the-year fish. Still, T-DOC also contains nutrients and organic carbon, which can stimulate phytoplankton production in the pelagic zone and therefore may compensate for reduced benthic production. However, the exact outcome of increased T-DOC inflows for young-of-the-year fish production is unclear. Previous research has predicted that T-DOC inflows may both stimulate and depress fish production in lakes; however this has not been explicitly tested. In this study I aim to examine how the importance of benthic and pelagic resources changes and how young-of-the-year fish growth is affected by increasing T-DOC concentrations. This is highly relevant for fish recruitment in northern Sweden, as many young-of-the-year fish are planktivorous (e.g. perch), and increased inflows of T-DOC could lead to a decreased importance of benthic production and decreased fish recruitment in both the Baltic Sea and freshwater lakes. |