Accession Number : ADP007791

Title :   Sedimentary Oxygen Demand and Its Effect on Winterkill in Lakes,

Corporate Author : MINNESOTA UNIV MINNEAPOLIS

Personal Author(s) : Stefan, Heinz G.

Report Date : JUN 1992

Pagination or Media Count : 6

Abstract : 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 mg/l depending on fish species. Aeration or unlimited fishing are usually implemented when that happens.

Descriptors :   *LAKES, AERATION, BUDGETS, EQUATIONS, EXCHANGE, FISHES, ICE, LAYERS, LIGHT, OXYGEN, PHOTOSYNTHESIS, SNOW, WATER, SYMPOSIA.

Subject Categories : Geology, Geochemistry and Mineralogy
      Physical and Dynamic Oceanography
      Snow, Ice and Permafrost

Distribution Statement : APPROVED FOR PUBLIC RELEASE