Aerial photograph of the meres at NWT East Wretham Heath by Mike Page
What is a mere?
Mere in English refers to a lake that is broad in relation to its depth. A significant effect of its shallow depth is that for all, or most of the time, it has no thermocline- the middle layer of the water body that may change depth throughout the day.
The meres of the Brecks
This is naturally a very rare habitat, both in the UK and internationally. The meres of the Brecks are Ice Age in origin. These are twelve semi-permanent water bodies in the Norfolk Brecks. They lie in depressions in the Ice Age topsoil and are fed by water from the underlying chalk aquifer. Their water levels fluctuate, in ways which are not understood, and because of this the meres are unique among water bodies in not being subject to succession to drier, more vegetated habitats. Instead they are home to many specialised species of plants and animal, including rare pondweeds and stoneworts, which are adapted to the short-term availability of water and the unpredictable cycle of flood and drought.