The role of catchment and in-lake processes in shaping trophic conditions of the shallow lake Syczyńskie (Eastern Poland)

Lake Syczyńskie is located in an important border zone between highland and lowland belts. This small and shallow reservoir is exceptional (among Łęczna–Włodawa Lakes) whith respect to an extraordinary intensity and seasonal changeability of eutrophication processes. Seasonal changes of ion total loads proved that despite high biogenic compounds supply, there are periods of shortages of phosphorous and nitrogen forms in lake waters. The main territorial factor, which determined ion shortages, was the type of supply and temporally increased water mixing. Eutrophication processes were slowed after many winter thaws, as a result of high ion load outflow, not compensated by loads inflow.