The Hydrogen‐Ion Concentration of a Creek, Its Waterfall, Swamp and Ponds

Abstract

This investigation was undertaken with the view of studying certain rather striking ecological features which occur in a creek situated in part on the campus of Johns Hopkins University at Homewood, Baltimore, Maryland. The creek originates as seepage in a shallow gulley which gradually becomes wider and deeper. At the base of this gulley the water collects in a slight depression, hereafter to be designated as the Small Pool (see Map of Creek, fig. 1). From this pool a stream arises which, by the addition of further seepage, becomes larger and widens out into several ponds, one of which is 100 feet in width and 105 feet in length (see Map, Small Pond, Bay, Euglena Pond ). The stream, continuing as rapids through the deepening gulley, which here assumes the proportions of a ravine, reaches a precipice marking the entrance of the ravine into a rather spacious, old quarry which is no longer in use. A small Waterfall forms as the stream flows over the precipice. In the quarry is a Swamp and a pond called the Quarry Pond on the map. The main interest in this stream centers in the fact that one of the ponds, the large one or the Euglena Pond mentioned above, has been covered for a number of years during most of the summer with a layer of Euglenae, while the other ponds, including the swamp, seemed to be free from that interesting plant-like animal. Accordingly, the authors made an effort during the summer of 1921 to study the factors which limit the distribution of Euglena and which localize it in the large pond. It was thought that the determination of the degree of acidity (hydrogenion concentration), the amount of free and combined carbon dioxide, and the temperature of the water at selected stations along the whole watercourse at definite intervals throughout a 24-hour period, would be a good introduction to the chemical side of the problem. Thirteen stations were chosen for their presumed critical importance with reference to the subject-matter of the investigation (compare with map). Station I. Small Pool. Bubbling, running water, in a pool about 18 inches in diameter. Near head of creek, with no aquatic vegetation. Shaded.