Hardwater lakes

Burkholder, J. M., and R. G. Wetzel. 1989. Epiphytic microalgae on a natural substratum in a hardwater lake Seasonal dynamics of community structure, biomass and ATP content. Archiv fur Hydrobiologie/Suppl. 83 1-56. 

Lake Plussee (Muenster, in preparation) is a eutrophic hardwater lake of the Plon lake district. During the summer, concentrations of dissolved combined phenolic compounds oscillate drastically over short periods of time (as shown in Fig. 17 for epilimnetic waters), although DOC concentrations (measured as COD in glucose-carbon equivalents) were much more stable. Fluctuations in combined phenolic compounds correlate poorly with phytoplankton standing crop (Fig. 17, lowermost panel). Thus, distribution patterns of free phenols and phenolic compounds may result primarily from abiotic factors (e.g., photolysis, allochthonous inputs by rainstorms, or adsorption onto autochthonous calcite) or biotic ones other than release by phytoplankton (e.g., biodegradation after photolysis). These processes, which have not yet been quantified, obviously influence the upper water layers most, since absolute concentrations of phenolic compounds (as well as oscillations within the concentrations) are significantly lower in the deeper-water layers. Perhaps many of the phenols in the deeper strata occur in a particulate state, adsorbed onto sedimentary matter. Alternatively, total phenolic concentrations are really lower in the deeper strata if true, the reasons remain obscure. 

Prepas E. E., Pinel-Alloul B., Chambers P. A., Murphy T. P., Reedyk S., Sandland G., and Serediak M. (2001a) Lime treatment and its effects on the chemistry and biota of hardwater eutrophic lakes. Frcifiwnter Bio/. 46, 1049-1060. 

As mentioned above, weak UV irradiation (325-427 nm) is frequently used for excitation. When far-UV radiation is used, however, increased fluorometric response and more information on structural properties of dissolved organic compounds can be obtained, since organic molecules found in natural waters have a greater absorbance at shorter wavelengths. Stabel (personal communication) attempted to differentiate between probable sources of DOM in lakes using fluorescence spectra of DOM from various inland waters, such as softwater, hardwater, and saline systems. With exci-... 

M. A. Soukup, The Limnology of a Eutrophic Hardwater New England Lake with Ma/or Emphasis on the Biogeochemisty of Dissolved Silica, No. 75-27-527, University Microfilms, Ann Arbor, Mich., 1975. 

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