I am really surprised that practically every week new papers on meromictic lakes are published. Meromictic lakes (lakes in which the water column is not completely mixed for the period longer than one year) are not so rare. Moreover it is speculated that many inland lakes might become meromictic due to climate change or human interventions to water balance. I am not sure that both mentioned factors will inevitably switch a lake to meromixis. Most probably we should emphasis that any relatively deep salt lake under certain conditions might become meromictic and we need general understanding of these conditions.
I should say that previous year we applied with our German colleagues with project proposal to study on several different lakes factors which promote switching to or stability of the meromixis. The project was not supported but the idea is still valid. Paper I selected perfectly demonstrates that it is not easy task to understand what factors support meromixis in a given lake.
Celine Bonhomme from University Paris-Est with her colleagues studied deep meromictic Lake Pavin. They used high precision and high frequency temperature and conductivity profiles and continuous temperature measurements to detect the presence of a cold spring at the bottom of the mixolimnion of the lake at a depth between 50 and 55 m. They performed quite detailed measurements and used mathematical model to understand the role of the spring within the water column in maintaining the meromictic conditions in the lake. What they compared is two subsequent years different in terms of water column stability. The difference between the 2006 and 2007 profiles of water temperature finally is explained by the varying hydrological processes, favoring either the occurrence of water inflow from the spring or an absence of such inflows.
This research might surprise person unfamiliar with studies on water column stability that our knowledge on this subject is rather vague. Even though the sudden instability of a meromictic lake can lead to limnological disaster by massive discharge of toxic gases into the atmosphere (a lethal eruption of Lake Nyos happened in 1986 is sad example) we cannot easily predict the stability of a given lake without extended and expensive studies.