The rate of C1402 uptake in a bacterized isolate of Oscillatoria rubescens indicates that within the ranges studied temperature caused the greatest variation followed by light intensity and nutrient concentration . The variation within interaction effects of light, temperature, and nutrients was higher than that within any other combination of interactions . High temperatures (25°C) shifted the light optimum of 0. rubescens growing in low to moderate nutrient levels from 1950 lux to 8oo lux .

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Relationships among the phytoplankton standing crop, rate of photosynthesis, and the distribution of C—14 in primary products of photosynthesis were investigated in western Lake Erie from July to August 1965. Sixty species of phytoplankton were noted during the study, but only four species, Coscinodiscus sp, Ceratium hirundinella (O.F.M.) Schrank, Aphanizomenon flos—aquae (L) Ralfs, and Microcystis aeruginosa Kutz accounted for over 98% of the total cell volume. Cell volumes ranged from 10 to 282 mm3 liter—1. Total photosynthesis (mgC m—3 day—1) in the upper photic zone averaged 566, ranging from 55 to 1690. Relative photosynthesis (mgC day—1 mm—3) ranged from 1.6 to 332. Ethanol—soluble C—14 fractions (mostly carbohydrate and lipids) of the phytoplankton accounted for 25—60% of the total C—14 assimilated. Insoluble C—14 fractions (mostly proteins) accounted for 20—48% of the total C—14 uptake. Large carbohydrate and small protein fractions occurred in Coscinodiscus standing crops under moderate illumination and in steady—state Alphanizomenon—Microcystis standing crops under high illumination. C—14 labeled protein fractions exceeded carbohydrate fractions in rapidly growing Aphanizomenon—Microcystis standing crops under moderate illumination and at the peak of a blue—green algae bloom under low illumination.

The Cuyahoga River is a heavily polluted tributary of Lake Erie located in N. E . Ohio (USA).One hundred seventy taxa of diatoms were identified from seven locations along the Cuyahoga River . The most frequently collected diatoms from each station were Cyclotella meneghiniana, Gomphonema parvulum, Navicula cryptocephala, N. cryptocephala var . veneta, N. lanceolata, N. menisculus, N. minima, N. minuscula, N. pelliculosa, Nitzschia amphibia, N. ovalis, N. palea, and Rhoicosphenia curvata .In the most heavily damaged region of the river these widelydistributed taxa were the only frequently collected diatoms .The relatively undamaged section of the river contained 94% more taxa than the most heavily damaged section . Chief among these additional taxa were Achnanthes lanceolata, A . lanceolata var . dubia, Cocconeisplacentula, Fragilaria vaucheriae, Melosira varians, Meridion circulare, Navicula mutica var . tropics. N. symetrica, Nitzschia dissipata, Stephanodiscus astraea, and Synedra rumpens.The degree of similarity between diatom assemblages along the Cuyahoga River as measured by a modification of Sorensen's index of similarity in species-frequency of occurrence composition was related to the degree of chemical-physical water quality similarities and to the extent of similarity between areas of geologic and biologic substrates . The most dissimilar diatom assemblages usually occurred between locations that were the most dissimilar with respect to chemical-physical water quality conditions rather than to dissimilarities with respect to sedimentsubstrate composition.