Toxicity of 2,4-D acid to phytoplankton

The toxic effects of 2,4-D on Phaedoactylum tricornutum (Bohlin) and Dunaliella tertiolecta (Butcher), two species of phytoplankton well suited to bioassay studies and responsive to pollutants, were studied by monitoring changes in growth in terms of cell populations, chlorophyll fluorescence and the rate of (CO2)-C-14 assimilation. Short term bioassays, batch and continuous cultures were studied. Pure 2,4-D acid appeared more toxic than the commercial amine form of the herbicide but this may have been due to small quantities of acetone present in the solvent. Concentrations of amine herbicide in excess of 100 mg l(-1) extended the duration of the lag phase and inhibited growth but smaller concentrations stimulated growth, the amine being consumed by phytoplankton in preference to nitrate. Continuous culture confirmed the ability of phytoplankton to adapt slowly to herbicide concentrations even as high as 500 mg l(-1). It is suggested that green algae adapt more rapidly to environmental change than do diatoms

EFFECTS OF 2 HERBICIDAL WASTEWATERS ON CHLORELLA SP AND PHAEODACTYLUM-TRICORNUTUM

The effects on Chlorella sp. and Phaeodactylum tricornutum of two industrial wastewaters known to contain the herbicide residues of Trifluralin and Propanil have been determined by monitoring the number of cells, the chlorophyll fluorescence and the carbon dioxide assimilation simultaneously for a period of 14 days. The growth of the diatom, Phaeodactylum tricornutum, was inhibited by concentrations of herbicidal waste of the order of 0.1-0.5%, apparently because the rate of reproduction was reduced. Chlorella sp. cells, on the other hand, whilst dramatically inhibited by 1% concentrations of herbicidal waste, were able to recover over a period of 14 days. If discharged at concentrations below 0.01%, the industrial wastes appeared not to affect phytoplankton

Trophic characteristics of the Sapanca lake (Turkey)

Systematic measurements of optical properties, concentrations of major and minor chemicals and primary production throughout 1989-1992 enabled us to identify the oligotrophic state of Sapanca lake, Marmara region, Turkey. Lake waters which have low concentrations of major anions and cations (total = 49 mu M) overturn every February-March, ventilating the bottom waters and enriching the surface waters with nutrients. Surface waters cool down to 6.5 degrees C by late winter and then warm steadily to 26 degrees C by late summer, while temperatures in deep waters range between 6.5 and 10.0 degrees C throughout the year. When the seasonal thermocline develops, the dissolved oxygen profiles exhibit a subsurface maximum in the thermocline, while in the hypolimnion water, the content varies seasonally from 11.5-12.0 ppm (350-375 CIM) in March to 0.5-1.7 ppm (16-56 mu M) in late autumn. Surface nitrate concentrations vary markedly with season, from < 0.15 mu M in summer to 5.7 mu M in early March, whilst the bottom water concentrations range from 13.5-14.0 mu M in late autumn to 5.7 mu M after the winter overturn. Phosphate concentrations are always less than 0.1 mu M throughout the entire water column. Subsurface chlorophyll-a maximum descends in late summer to 20-25 m depths, where the Light intensity is less than 1% of the surface value. Below 10-15 m depths, corresponding to the upper thermocline, primary productivity is very low. The range was from 35 to 93 mg C/m(2) day(-1) during 1989-1991, consistent with the values in other oligotrophic lakes