| MadSci Network: Environment & Ecology |
Hi Sarah,
A flowing freshwater ecosystem (lotic) consists of rivers or streams. Animals and plants in flowing freshwater have to be able to deal with the physical effects of the current, which may be very strong at certain periods of the year.
Standing freshwater ecosystems (lentic) consists of ponds or lakes. Organisms in standing freshwater may have to tolerate low levels of oxygen because oxygen diffusion slows down considerably when water is not flowing. This is particularly true in summer when oxygen consumption is higher but the solubility is greatly reduced by higher temperatures. In addition, water at higher temperatures has a lower density than cooler water which results in cool water remaining at the bottom of a lake. This cool water remains unmixed with the water above preventing oxygen from being replenished in this part of the lake until the autumn when the temperature change causes mixing.
Richard Kingsley
Try the links in the MadSci Library for more information on Environment & Ecology.