b'Quantifying components of the aquatic organic carbon cycleof a humic lake: a case study from the Burrishoole catchment,Co. Mayo.Poole R1, de Eyto E1, Doyle B1,2, Dillane M1, Ryder E1,3 and Jennings E21Fisheries and Ecosystems Advisory Services (FEAS), Marine Institute, Furnace, Co. Mayo, Ireland2Centre for Freshwater and Environmental Studies (CFES), Dundalk Institute of Technology, Dundalk, Co. Louth, Ireland3School of Biological, Earth and Environmental Sciences (BEES), University College Cork, College Road, Cork, Co. Cork, IrelandDirectional climate change is proceeding rapidly. Assessing the impacts of the resulting changes in local climate on ecosystem function and formulating appropriate adaptation and mitigation strategies are the greatest scientific challenges that we now face. Warmer temperatures and shifts in seasonal precipitation patterns, as have been predicted for Ireland, will drive changes in the quantity and composition of nutrients, including organic carbon (OC), entering aquaticecosystems. This has particular relevance for Ireland, where peatlands store between 53 and 62% of the national soil OC. Peatlands are acknowledged to be particularly important for current and future carbon cycling, due to their sensitivity to climate change, and the fact that they are hotspots for carbon storage. Interest in the carbon cycling of aquatic systems has increased internationally as evidence mounts that freshwater waterbodies can play significant roles as carbon sinks or sources. Peatland degradation represents a major transfer of OC fromlong-term stable terrestrial stores to more active and biological available forms and ultimately to the atmosphere. The role of aquatic transport from streams, ponds, rivers and lakes is central to this transfer. Over the last 20 years, considerable progress has been made on resolving thecarbon budget of Lough Feeagh, Co. Mayo, primarily through the use of the long-termenvironmental monitoring data that are collected by the Marine Institute in the Burrishoole catchment. Burrishoole is a typical western peatland catchment and is an important index site for diadromous fish monitoring and catchment change. Here, we describe some of the outputs from several decades of data collection and research, including the historical context, seasonal patterns and drivers in dissolved OC export, CO 2emissions from Lough Feeagh, and the role of allochthonous and autochthonous carbon in the foodwebs of Burrishoole.19'