Lake dissolved oxygen DO budgets are composed of the following major components Sources Reaeration at the surface Ra Photosynthesis by aquatic plants P Inflow I Sinks Sedimentary oxygen demand SOD Water column oxygen demand WOD Outflow O Lakes are often stratified and a DO budget equation must then be applied to each layer separately. In stratified lakes exchange between layers must be included in the equation, e.g. as a diffusive flux. In ice-covered lakes, the sources are drastically reduced ice-covers prevent reaeration and snow on ice screens most of the light necessary for photosynthesis inflows are often only from groundwater with low DO. As a result it is not uncommon for the DO to decline steadily after an ice-cover has formed. Particularly in very shallow lakes DO may be depleted by February or March. Fish begin to be stressed at different levels of Do depending on species. Winterkill begins to occur when DO falls below 0.2 to 2.5 mgl depending on fish species. Aeration or unlimited fishing are usually implemented when that happens.
This article is from 'Proceedings of the US Army Corps of Engineers Workshop on Sediment Oxygen Demand Held in Providence, Rhode Island on 21-22 August 1990,' AD-A253 650, p137-142.