Ecosystem lentic

At whole lake scales, littoral zones are a major component of autochthonous DOM production and important sources of labile organic matter for aquatic bacteria. Of the approximately one billion lakes in the world, the littoral zone accounts for more than 95% of lake surface area in nearly 99.8% of all lakes (Wetzel, 1983 Fig. 3a). The importance of shallow waters is even more marked when the bounds of lakes are expanded to include wetlands. With such an expanded view, the littoral zone and wetlands comprise more than 95% of the area in 99.999% of all lakes (Fig. 3a). Clearly, shallow waters are a dominant feature of lentic ecosystems. 

Munawar, M., Dermott, R., McCarthy, L.H., Munawar, S.F. and van Stam, H.A. (1999) A comparative bioassessment of sediment toxicity in lentic and lotic ecosystems of the North American Great Lakes, Aquatic Ecosystem Health and Management 2 (4), 367-378. 

Hamelink, J.L., Waybrant, R.C. (1976) DDE and lindane in a large-scale model lentic ecosystem. Trans. Am. Fish Soc. 105, 124. Hamilton, D.J. (1980) Gas chromatographic measurement of volatility of herbicide esters. J. Chromatogr. 195, 75-83. 

Predicted no-effect concentrations (PNECs) are traditionally used in risk assessments and form the basis of most EQS values. There are 3 basic approaches to the derivation of PNECs and resultant EQS values. The traditional method uses standard toxicity data and applies an AF to the most sensitive endpoint to derive a protective concentration. The SSD approach utilizes all available toxicity data to derive a value that is protective of a given percentage (e.g., 95%) of the species and is increasingly being used by many countries, often with a small AF placed on, for example, a predicted HC5 (hazardous concentration to 5% of species, i.e., the 5th percentile of the SSD) based on chronic data. Finally, model ecosystems such as lentic mesocosms can be used to derive safe values, again usually with a small AF. 

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