Limnological studies on diurnal fluctuations in shallow ponds in Indonesia

Summary

In a Javanese fishpond, thermal stratification is built up during the day, followed by homothermy at dusk and inverse stratification — owing to cooling of the surface — at night, again followed by homothermy after sunrise.

In a 2-meter-deep pit with a diameter of 2 meters, the surface temperature follows the same course, but the bottom temperature shows a rise of 1.3° only. During maximal insolation a difference of 4½° was found between surface and bottom. At night inverse stratification occures with a temperature gradient of ½°. Diurnal changes in pH, CO₂ and O² were measured and explained by the interaction of stratification, mixing, photosynthesis, respiration and mineralisation of organic substances on the bottom.

A striking difference was found between the scanty vegetation of the open water of the newly excavated pit, the outburst of Desmids between the Nitella along its edges, and the Diatoms, Rotifera etc. of the eutrophiated pond.