NUMERICAL METHODS FOR THE INFERENCE OF pH VARIATIONS IN MESOTROPHIC AND EUTROPHIC LAKES IN SOUTHERN SWEDEN—A PROGRESS REPORT

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Abstract
A new numerical method for determination of pH variation through time in Holocene lake sediment has been developed. Normal probability curves and a parabolic curve were adjusted to the plotted values of percentages for the five pH preference groups of diatoms (alkalibiontic, alkaliphilous, indifferent, acidophilous and acidobiontic) in surface sediment samples from 24 lakes with known mean pH. Based on these curves a transfer function for pH inference was derived. A multiple regression formula based on the same data base was also developed. An attempt to create a single Index formula for the whole pH interval, based on the same idea as the known Index B, failed, and three different indices had to be derived. The results of regression line statistics on the calculated pH values for the 24 lakes, compared to the observed pH values, are presented in diagram form together with values for the standard error of estimate (Sy), the squared coefficient of correlation (r2), and regression line equations. In order to show the applicability of the different methods, they have been used on a sediment core from Lake Trummen, southern Sweden.