No abstract

No abstract

United Chrome Products, Inc. (Corvallis, OR), discharged liquid chrome-plating wastes into an on-site dry well from 1957 to 1977. Samples were collected from ground and surface waters during February and December 1984 and evaluated for toxicity potential using 96-h Selenastrum capricornutum bioassays. Bioassays of the February samples were used to calculate predicted EC50 values for different chromium concentrations, which %ere then compared with the chromium concentrations measured in the December samples and with the results of S. capricornutum bioassays on these samples. An excellent correlation was obtained between the predicted EC50 values and the actual bioassay response values for ground water and drainage ditch samples. However, no correlation was obtained with the off-site surface water samples. These results could not be explained by changes in chromium valence, and they demonstrate that, even in simple systems, toxicity cannot readily be predicted based solely on chemical analysis.

I. A taxonomic analysis of 171 phytoplankton samples obtained from Crater Lake. Oregon, between 1985 and 1987 revealed \M taxa in the upper 250 m of the water column. Ihe greatest temporal variation in taxonomic structure tKX'urred between 40 and 80 m below the water surface, a depth range which corresponded to the zone of maximum primar)' production.2. Phytoplankton cell biovolume in the upper 20 m of the water column was relatively high during the summer months, a period when Niiz.Mluu gracilLs was dominant in the epilimnlon. However. 72% or more of the cell biovolume between 0 and 200 m was distributed below 20 m and, during the winter and spring months. 61% was found below 80 ni.?>. Cluster analysis identified a sparse, temporally ubiquitous llora which was modified to various degrees when environmental conditions became favourable for the growth of a few dominant taxa. These surges of dominance by individual laxa accounted for 2 to 5-fold increases in cell biovolume and generated a pronounced taxonomic discontinuity between the floras in the epilimnion and hypolininion.4. While the taxtmomic structure of the phytoplankton in the epilimnion corresponded closely with the structure found in a 1978-80 study, the flora below the metalimnion was more diverse and less predictable in species composition than the pattern reported in the earlier study.

United Chrome Products, Inc. (Corvallis, OR), discharged liquid chrome‐plating wastes into an on‐site dry well from 1957 to 1977. Samples were collected from ground and surface waters during February and December 1984 and evaluated for toxicity potential using 96‐h Selenastrum capricornutum bioassays. Bioassays of the February samples were used to calculate predicted EC50 values for different chromium concentrations, which were then compared with the chromium concentrations measured in the December samples and with the results of S. capricornutum bioassays on these samples. An excellent correlation was obtained between the predicted EC50 values and the actual bioassay response values for ground water and drainage ditch samples. However, no correlation was obtained with the off‐site surface water samples. These results could not be explained by changes in chromium valence, and they demonstrate that, even in simple systems, toxicity cannot readily be predicted based solely on chemical analysis.