The Role of hydraulic loading and nutrients in the ecology of mediterranean shallow lakes

Coppens, Jan Emma Pieter
In this Ph.D.-research three approaches were used to study the relationship between external nutrient loading, hydraulic loading and in-lake nutrient processes in shallow lakes under different climate conditions: a space-for-time mesocosm experiment on a climate gradient across Europe; time series analysis of long-term water and nutrient budgets of Lakes Eymir and Mogan; a combination of catchment and lake modelling of Lake Mogan under the projected climate conditions for 2020-2090. The mesocosm experiments showed that nutrient retention in lakes depended on external nutrient loading but plant and phytoplankton biomass production played an important role and were influenced by climate. Phytoplankton production increased with temperature, but warmer temperatures also led to lower water levels which favoured macrophyte development in shallow mesocosms leading to higher nutrient retention. Both the time series analysis and the modelling projections showed the sensitivity of shallow lakes to changes in precipitation and evaporation, leading to periods with low water levels and a risk of drying out. During wet years with high water levels nutrient concentrations were low and determined by external nutrient loading in winter and spring. During dry years, external loading in winter and spring was lower, due to reduced runoff, but evaporative water loss and internal loading from the sediment during summer caused peaks in lake nutrient concentrations. The modelling approach showed that under a future drier and warmer climate, nutrient concentrations can increase, even when external loading decreased.


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Citation Formats
J. E. P. Coppens, “The Role of hydraulic loading and nutrients in the ecology of mediterranean shallow lakes,” Ph.D. - Doctoral Program, Middle East Technical University, 2016.