Carbon cycle in lakes
Lakes, and inland waters in general, play a remarkable role in the global carbon cycle. In those ecosystems production, storage, transformation and consumption of carbon are activities mainly mediated by microorganisms. We studied the organic carbon cycle in prealpine and alpine lakes and quantified the total organic carbon standing stock (TOC) both as dissolved (DOC) and particulated (POC) forms (Bertoni and Callieri 1989; Callieri and Bertoni 1999; Callieri et al. 1999; Bertoni et al. 2010). The in-lake processes causing the organic carbon variation in time and space have been studied in detail. Primary production (Callieri and Piscia 2002), dark uptake (Callieri et al. 2014), grazing (Callieri et al 2002; Callieri et al 2006) and sedimentation (Callieri 1997) have been measured to get a dynamic picture of the functioning of lakes.
Our recent attention has been focussed on the Transparent Exopolymer Particle (TEP). This fraction in Lake Maggiore can reach 56% of TOC in the photic layer, while it never exceed 2% in the hypolimnion, below 200 m depth. TEP are driven by chlorophyll a and can increase in lakes due to climate change (Callieri et al. submitted).