A STUDY OF THE ENVIRONMENTAL CONDITIONS IN A BOG POND WITH SPECIAL REFERENCE TO THE DIURNAL VERTICAL DISTRIBUTION OF GONYOSTOMUM SEMEN

¹ From the Marine Biological Laboratory, Woods Hole, Mass., and the Johns Hopkins University, Baltimore, Md.

1. The vertical distribution of the green, euglenoid-like organism, Gonyostomum semen, in a bog pond, has been studied at intervals of four hours, throughout twenty-four hours, with reference to air temperature, water temperature, illumination at the surface of the pond, total-, free- and bicarbonate CO₂ in the water, O₂ in the water and the pH value of the water.

2. The practically undisturbed condition of the water in the pond made it possible to demonstrate an oxygen and a carbon dioxide "pulse." These are mainly the result of the photosynthetic activities of Gonyostoum.

3. The acidity of this bog pond is partly due to the acid water which enters from the sphagnum bog.

4. A striking chemical characteristic of the pond is the sudden increase in the free CO₂ content of the water. between 0.5 and 1.0 meter.

5. Many individuals of the Gonyostomum population of this pond move upward during the early morning hours and congregate in maximum numbers somewhere between one meter and the surface. The level at which this occurs seems to be dependent on the proper combination of light, water temperature, and CO₂ content of the water. During the late afternoon and night many individuals move downward so that the maximum counts are found in the lower layers. The upward movement of individuals of Gonyostomum from the lower levels is probably due to an increase in the light at the source combined with an increasing gradient of light, temperature, and CO₂ from the bottom to the surface, acting on Gonyostomum individuals which have been living in darkness.

The downward movement is probably due to some physiological condition resulting from a sufficient amount of photosynthetic activity or a reproductive tendency or both which is followed by a quiescent sinking.