Observations in guanotrophic environments

Summary

Examples are given of initial guanotrophy in acid oligotrophic environment and of stabilized guanotrophy of long standing, both in acid oligotrophic and eutrophic environment.

Characteristic of a guanotrophic environment is the accumulation of phosphate. In hard waters phosphate is accompanied by large amounts of saline nitrogen compounds. In soft waters the saline nitrogen production seems to be inhibited through low bacteriological activity. In eutrophic guanotrophic environments oxygen production and biochemical oxygen demand are both high. In oligotrophic guanotrophic environments the oxygen content as a rule does not reach saturation and biochemical oxygen demand is fairly low. The amounts of chloride and calcium do not change significantly by the addition of excrements of birds.

Diatoms, blue green algae and desmids are very scarce in guanotrophic environments. In hard waters mesosaprobic forms are present in the plankton community. In soft waters no strong saprobic tendencies could be found.

During the initial stage of guanotrophy in an acid oligotrophic environment, the desmids disappear together with other sensitive species as Dinobryon pediforme and Bosmina obtusirostris. Unicellular flagellates as Chlamydomonas appear in increasing numbers. Several factors in the environment respond to the changes by increasing fluctuations of the values recorded.

There was evidence of transport and introduction of microorganisms by waterfowl.