The effect of aquatic macrophytes on selected limnological characteristics of an east-central Indiana barrow pit lake

Abstract

Selected linmological characteristics were evaluated during the summer of 1977 on an east-central Indiana borrow pit lake to determine the effect of aquatic macrophytes on major chemical parameters, e.g., alkalinity, pH and dissolved oxygen. The lake was sampled at approximately weekly intervals in the evening and again the next morning in the shallow littoral area and the open water deeper pelagic area. A variety of physical and chemical tests were conducted to measure macrophyte metabolism.Macrophytes visible from the surface of the lake were found to cover over 50% of the lake area by the middle of August after which they. began to die off quickly. Potamogeton pusillus and P. pectinatus were the dominant species present.Due to lack of precipitation and extremely hot weather, the water level was found to be very low over the summer which might have lead to more extensive areas of the lake being inhabited by the macrophytes than when the lake is full. Visibility indicated that macrophytes could probably inhabit the entire lake bottom.Little difference between evening temperatures at the shallow station and deep station was noted but daily temperature fluctuations at the deep station were of less magnitude due to increased depth.Dissolved oxygen values were found to be higher in the evening and correspondingly lower in the morning at the shallow site as compared to the pelagic region of the lake due to photosynthetic and respiratory activities of the dense population of aquatic macrophytes in the littoral zone.Macrophytes at the littoral site were responsible for more intense seasonal and daily fluctuations in alkalinity concentrations than those recorded at the pelagic site. They were implicated in decreased total and bicarbonate alkalinity and in increased carbonate alkalinity during the daytime.Seasonal and daily fluctuations in the hydrogen ion concentration were much more pronounced in the littoral zone, with evening pH values being higher and morning values lower than those recorded at the pelagic site, which was also a direct result of macrophyte metabolism.