Reversibility of Man‐Induced Eutrophication. Experiences of a Lake Recovery Study in Sweden

Abstract

Recovery of polluted lakes is a complicated process involving many factors. Different lake rehabilitation techniques and former experiences with advanced wastewater treatment and sewage diversion are reviewed. The response in water quality after a nutrient reduction may vary significantly, despite a lowering of the phosphorus concentration in the lake. The different factors influencing the process, such as climatic fluctuations, the growth‐limiting effect of nutrients and phosphorus release from the sediments, are discussed, based on examples from a lake recovery study in Sweden carried out in 30 lakes. Due to various interrelationships between physical characteristics and biological mechanisms involved, and to significant fluctuations in these factors from one year to the next, it is difficult to generalize and to forecast the actual response of a certain water body to a reduced nutrient input. Unfortunately, too many monitoring programmes aimed at elucidating the effects of remedial efforts are not designed in such a manner that relevant information can be obtained about the nutrient load — lake response relationships. Ways for optimizing and increasing the predictive power of inventory studies and monitoring programmes are discussed.

Dynamics of key plant nutrients (N & P) in hokersar, a typical wetland of Kashmir Himalaya, India

“…A strong and similar seasonality have been attributed to high retention capacity of shallow lakes throughout world [65,66]. This capacity of retainability of P has been attributed to many factors, primary being the temperature simultaneously coupled with biological processes [64,[67][68][69][70].…”

Different patterns of phosphorus release from lake sediments in laboratory experiments

“…The phosphorus release from sediment surfaces in contact with or close to well-aerated water can be substantial and much evidence exists from mass balance studies, mainly performed on shallow sewage-loaded lakes (Stevens & Gibson 1977;Ryding & Forsberg 1977;Ryding 1981). Laboratory studies have also confirmed the occurrence of significant aerobic phosphorus release from sediments (Lee et al 1977;Bates & Neafus 1980;Holdren & Armstrong 1980).…”

Phosphate Equilibrium Between Stream Sediments and Water: Potential Effect of Chemical Amendments

“…Sediments are often long−term sources of P to aquatic systems (especially lakes and reservoirs) after external P inputs from the watershed have been reduced or removed (Larson et al, 1979;Ryding, 1981). The flux of P from bottom sediments is often much greater under anaerobic conditions in the hypolimnion of lakes and reservoirs than under aerobic conditions (James et al, 1995).…”