Water & Wastewater Treatment Magazine
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Mesocosm research: testing the waters An innovative facility consisting of 32 tanks is helping researchers in Lancaster understand how large bodies of water such as reservoirs behave in response to the elements www.wwtonline.co.uk | WWT | APRIL 2019 | 23 DR HEIDRUN FEUCHTMAYR, CENTRE FOR ECOLOGY & HYDROLOGY (CEH) The Knowledge Water quality and tanks and, by the addition of lake sediment, water and lake organisms, we can simulate a range of highly realistic lake environments under controlled conditions. The advantage this facility has over natural lakes or reservoirs is that it provides us with replication and con- tinuous monitoring. Whatever treatment or manipulation we choose, we can replicate it in various mesocosms as we have so many of them. This gives us statistically robust evidence of how freshwaters react to whichever factors and manipulations we want to investigate. The facility at CEH's site in Lancaster is especially well equipped, including sensors within each mesocosm that allow us to monitor physi- cal and chemical conditions 24/7. For example, we perform climate warming experiments by having all mesocosms fitted with heating elements mounted above the sediment. Computer-control allows us to warm the water temperature of half the mesocosms by up to 5 degrees Celsius higher than the non-heated mesocosm wa- ter temperature. Temperatures in the warmed mesocosms are adjusted every minute, ensur- ing a constant temperature A cquiring detailed pro- cess understanding in a 'real-world' reservoir is very challenging due to a lack of environmental controls and the lack of replication. In order to bridge the gap between the real-world environment of a natural reservoir and experiments in a small beaker inside a laboratory, mesocosm difference between the heated and non-heated mesocosms. Data feeds from sensors to our analytical soĊ ware allows us to view a near-real-time picture of the processes taking place in each mesocosm. How has the facility been used so far? So far, the mesocosm facility has been used extensively to run climate change experi- ments. Specifically, we have investigated the combined effects of climate warming, or- ganic matter increase, nutrient addition and extreme rainfall events. Brownification - the increase in organic matter con- centrations in lakes and reser- voirs across the temperature region - is of growing concern and the impact upon freshwa- ter communities is largely un- known. By manipulating water temperature and organic mat- ter input in nutrient-rich sys- tems, we aimed to test if algal growth would be stimulated by warming and the additional nutrients within this organic matter, or whether organic matter actually decreases algal growth due to reductions in underwater light. We found high dissolved organic matter increase, as experiments are conducted at the Centre for Ecology & Hydrology (CEH) in Lancaster. The modern mesocosm facility consists of a large number of 3,000-litre tanks; in essence each of the 32 tanks simulates a small lake where all vari- ables can be controlled. Each mesocosm is open to the elements like a real lake