Charles M. Weiss

Physiological Effect of Organic Phosphorus Insecticides on Several Species of Fish

Abstract Fish brain acetylcholinesterase is inhibited in vivo by organic phosphorus insecticides at concentrations of 0.1 mg/1 and lower. The degree of inhibition is a function of the concentration of the insecticide, the extent of exposure, specific chemical nature of the inhibiting substance, and fish species. Species used were largemouth bass (Micropterus salmoides), bluegill (Lepomis macrochirus), golden shiner (Notemigonus crysoleucas), goldfish (Carassius auratus), and fathead minnow (Pimephales promelas). Fish removed from exposure to acetylcholinesterase-inhibiting insecticides, prior to reaching lethal limits, demonstrate the capacity for regeneration of this enzyme. The time required to regenerate the brain acetylcholinesterase to normal levels depends on the extent of the initial inhibition, the specific nature of the compound producing the inhibition, and the particular species. The curve of brain enzyme inactivation and recovery, as defined by percentage changes in normal activity, describes ...

The Elimination of DDT-C14, Dieldrin-C14, and Lindane-C14 from Fish following a Single Sublethal Exposure in Aquaria

Abstract Groups of 60 to 70 small bluegills, Lepomis macrochirus, and goldfish, Carassius auratus, were exposed in polyethylene tanks to 0.03 ppm of DDT-C14, dieldrin-C14, or lindane-C14 for periods ranging from 5 to 19 hours. Following the exposure, these fish were rinsed with uncontaminated water and placed in 145-liter recovery aquaria. The water in these aquaria was continuously renewed at the rate of 2.5 complete changes daily. An equivalent number of unexposed fish were also placed in the recovery aquaria to serve as controls. During a recovery period of 32 days, 10 samples, each consisting of five exposed and five control fish, were removed from each aquarium for determinations of whole-body insecticide content. The results indicated that the initial lindane-C14 was eliminated by both species of exposed fish within two days. More than 90% of the initial dieldrin-C14 was eliminated in the first two weeks of recovery, however, less than 50% of the DDT-C14 was eliminated after 32 days of recovery. The...

The Accumulation of DDT by the Dragonfly Nymph, Tetragoneuria

Abstract Final instar Tetragoneuria spp. dragonfly nymphs were exposed to sublethal concentrations of DDT dispersed in water. Uniformly labeled DDT-C14 was employed. The activity of the DDT-C14 accumulated by the nymphs and of the DDT-C14 in the exposure water was measured by the liquid scintillation counting technique. The accumulation of DDT from aqueous solution by both live and dead nymphs as a function of DDT concentration and exposure time was determined. The DDT accumulation of the live nymphs increased exponentially with increased concentration at a given exposure time. At a given concentration, accumulation increased with increased exposure time. The DDT accumulation of the live nymphs greatly exceeded that of the dead nymphs at the higher DDT concentrations studied. The results of this investigation indicate that both biological and physical mechanisms contribute to DDT uptake by this organism and that rates of uptake by these mechanisms are concentration dependent.

Light intensity and the vertical distribution of algae in tertiary oxidation ponds

Abstract Studies on the use of oxidation ponds for the tertiary treatment of municipal waste waters had shown that solar heating results in thermal stratification. Under these conditions there is probable short circuiting of flow. Installation of weirs to minimize stratification by forcing an under-over flow pattern was followed by the development of two distinct algal associations as a result of the skimming action of the surface weir. Upstream of the surface weir a thick algal mat developed which consisted of an interlocking complex of cysts of Euglena rostifera Johnson and filaments of Oscillatoria tenuis. Downstream of the skimming weir, the surface of the pond was free of the mat but deep green in appearance. This color was due to a population of a single species, Euglena rostifera. The green color of the clear pond areas was observed to change considerably in intensity in the course of the diurnal cycle. Detailed investigation of this phenomena revealed a vertical migration rhythm of the Euglena associated with the diurnal cycle. Examination of the diurnal migration and associated factors showed the following: 1. (1) The Euglena moved from the bottom sludge, where it settles at night to levels in the pond where light intensity measurements did not exceed 75 c ft−2. 2. (2) Diurnal temperature changes did not affect the vertical migration of the Euglena. 3. (3) Under the algal mat, consisting of Oscillatoria tenuis and encysted Euglena rostifera, there was no vertical migration. Isolation and growth of single cell isolates of E. rostifera showed that optimum growth was at the same light intensity range found in the ponds where the maximum populations were located. At higher light intensities the proportions of chlorophylls a, b, and c decreased and carotenoid pigments increased. Growth in total darkness produced complete loss of chlorophylls but also a sharp increase in carotenoid pigments.