Showing papers on "Chlorococcum published in 1977"

Influence of four herbicides on the algal flora of a prairie soil

Abstract: Four herbicides (2,4-D, trifluralin, MCPA and TCA) were applied at two concentration levels to isolated cores of a grassland loam soil. After herbicide contact times of 1, 5, and 20 days, samples were taken and the algal population estimated both quantitatively and qualitatively using two selective mineral salts media. Thirty one genera of algae were identified as occurring in the soil. Of these, Chlamydomonas, Chlorococcum, Hormidium, Palmella, and Ulothrix proved to be so sensitive to the four herbicides that they were rarely isolated from the cores after treatment. Other algal genera were found to be less sensitive, and the theoretical percentile sensitivity of fifteen genera was calculated. Chlorella, Lyngbya, Nostoc, and Hantzschia were found to be the most resistant algae, having percentile sensitivity to all four herbicides of less than 50%. Some algal genera varied in their sensitivity to each of the herbicides. Scytonema was sensitive to all of the herbicides except 2,4-D, while Tolypothrix showed a greater tolerance to MCPA. In the top cm of the soil, the reduction in cell numbers experienced by many algal genera after herbicide treatment was offset by an increase in the population of Chlorella. Stichococcus, Oscillatoria, and Spongiochloris all exhibited the ability to recover rapidly after a reduction in cell numbers resulting from the application of one of the herbicides. An overall reduction in cell numbers was noted for the algae growing preferentially on a nitrogen-free medium (i.e. potential nitrogen-fixers). re]19760511

Toxicity and uptake of Kepone in marine unicellular algae

Abstract: Four species of marine unicellular algae were exposed to Kepone in laboratory bioassays. EC50 values after seven days’ growth, in mg/liter (ppm), were:Chlorococcum sp., 0.35;Dunaliella tertiolecta, 0.58;Nitzschia sp., 0.60;Thalassiosira pseudonana, 0.60. When exposed to 100 μg/liter (ppb) Kepone for 24 hr, residues associated with the algae, in mg/kg (ppm) wet weight, were:Chlorococcum sp., 80;D. tertiolecta, 23;Nitzschia sp., 41;T. pseudonana, 52.

Antibiotic properties in Chlorococcum humicolum (Naeg) Rabenh. (Chlorophyceae)

Abstract: The antibiotic properties of Chlorococcum humicolum (Naeg) Rabenh. (Chlorophyceae) have been investigated. The alga contains a wide spectrum antibiotic substance, which forms zones of inhibition up to 30·5 mm wide. Of the seven test organisms studied, it is effective against Cryptococcus neoformans, Bacillus pumillus, Escherichia coli, Sarcina lutea, Bacillus subtilis and Staphylococcus aureus.