Acetylene reduction assay for determination of phosphorus availability in wisconsin lakes.

Phosphorus-starved cells of Anabaena flos-aquae rapidly increase their capacity to reduce acetylene to ethylene when they receive phosphorus. This response may be used as a bioassay for detecting available phosphorus in aquatic ecosystems. The sensitivity of the method compares favorably with conventional methods for measuring dissolved orthophosphate, and has the additional advantage that it measures available phosphorus. Studies on Wisconsin lakes show that available phosphorus generally is present, that the concentrations are higher at the lower depths than at the surface, and that there may be diurnal variations in the available phosphorus content of surface waters. Important sources of available phosphorus in Lake Mendota are the waters below the thermocline and the input from storm sewers.

Pseudomonas aeruginosa for the evaluation of swimming pool chlorination and algicides.

Concentrations of ammonia and the chlorine stabilizer, cyanuric acid, which could be expected in swimming pools decreased the rate of kill by chlorine of the potential pathogen, Pseudomonas aeruginosa. The effect of cyanuric acid increased as the concentration of chlorine decreased, a fact of significance from a public health view. Quaternary ammonium algcides had little effect on the kill rate of chlorine, but an organic mercury algicide had a synergistic effect with chlorine when the chlorine activity was stressed by the addition of ammonia or the use of 100 times the normal concentration of bacteria. The effect of natural waters, rain, beaches, and swimming pools on the kill rate by 0.5 mg of chlorine per liter indicated that a treatment time of 1 hr or more was required to kill 99.9% of 10(6)Pseudomonas cells per ml. The synergism of chlorine and the organic mercury algicide was also demonstrated with these waters and with sewage treatment plant effluents. The necessity of developing and using laboratory tests which simulate conditions in swimming pools with heavy loads of swimmers, as opposed to tests in chlorine demand-free conditions, is discussed. Samples taken from well-supervised swimming pools when the swimmer load had been especially high required treatment times of 1 to 3 hr to obtain 99.9% kills of the potential pathogen, P. aeruginosa, with 0.5 mg of chlorine per liter.

DETECTION OF LIMITING OR SURPLUS NITROGEN IN ALGAE AND AQUATIC WEEDS(1).

The rate of NH4 +-N absorption by algae and aquatic weeds in the dark has been shown to be 4-5 times greater for plants which are N-limited as compared to plants with sufficient available N. Eight species of green algae, 2 blue-green algae, 2 diatoms, and 3 aquatic weeds were used to demonstrate the usefulness of the test in determining if available N was in surplus or limited supply in a particular environment. The test was shown not to differentiate between blue-green algae capable of fixing N (4 species) from media with NO3 -N or without combined nitrogen. The factors influencing the results of NH4(+) -N absorption tests have been investigated. In order to differentiate between plants with sufficient available N and those which are N limited, the rate of NH4 (+) -N absorption (0.1 mg N) over 1-hr incubation in the dark by 10-20 mg of algae or aquatic weed tissues is measured. The relatively simple analysis for NH4 (+) -N in the samples makes it very easy to follow the changing N nutrition of plants in cultures with a limited N supply or in the presence of possible N sources.

Factors influencing the effectiveness of swimming pool bactericides.

Techniques for culturing, harvesting, and testing bacteria to evaluate bactericidal chemicals for swimming pools are described. Concentrations of 25, 50, and 100 mg of the chlorine stabilizer cyanuric acid per liter increased the time required for a 99% kill of Streptococcus faecalis by 0.5 mg of chlorine per liter at pH 7.4 and 20 C from less than 0.25 min without cyanuric acid to 4, 6, and 12 min, respectively. The effect of concentrations of ammonia nitrogen in the range found in swimming pools on the rate of kill of 0.5 mg of chlorine per liter and of chlorine plus cyanuric acid was tested. At concentrations of ammonia nitrogen greater than 0.05 mg per liter, faster rates of kill of S. faecalis were obtained with 100 mg of cyanuric acid per liter plus 0.5 mg of chlorine per liter than with 0.5 mg of chlorine per liter alone. When water samples from four swimming pools with low ammonia levels were used as test media, 0.5 mg of added chlorine per liter killed 99.9% of the added S. faecalis in less than 2 min, but water from a pool with a large number of children required 60 to 180 min of treatment.

EXTRACTIVE AND ENZYMATIC ANALYSES FOR LIMITING OR SURPLUS PHOSPHORUS IN ALGAE.

An extractive procedure for detection of surplus-stored phosphorus (luxury consumption) in algae and an enzymatic analysis for conditions of P-limited growth in algae have been evaluated. A simple 60-min boiling water extraction of algae known to contain surplus P separates essential P compounds and surplus-stored P compounds. Surplus P compounds can be measured in the extract as orthophosphate. Extracts of algae limited in their growth by the amount of available P contain little or no orthophosphate. Limitation of algal growth by P supply induces the enzyme alkaline phosphatase. The activity of this enzyme can be measured at pH 9 using p-nitro-phenylphosphate as substrate. Algae which were P-limited and contained no extractable orthophosphate have as much as 25 times more alkaline phosphatase activity than algae with surplus available P.