. L'écologie des algues : un colloque organisé au laboratoire de biologie Pymatuning Domaine les 18 et 19 juin 1959 . 68 10 12 |i| 16 MILES DE LA RIVIÈRE DU LAC 20 22 EFFET DES ALGUES DU LAC KEGONSA SUR LA RIVIÈRE YAHARA Figure 9 Ressources d'oxygène et de stabilisation des déchets est facilement perdu à l'at- mosphere . Ce type de perte s'applique en principe aux rivières aussi mais il y a généralement lieu à bien moindre degré d'intensité. Pour la stabilisation des déchets il serait beaucoup mieux d'oxygène con- tinuously mais inférieur à un niveau constant de la "fête" de la famine et de situation qui se produit naturellement. Deat

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. The ecology of algae : a symposium held at the Pymatuning Laboratory of Field Biology on June 18 and 19, 1959 . 6 8 10 12 |i| 16 RIVER MILES FROM LAKE 20 22 EFFECT OF LAKE KEGONSA ALGAE ON YAHARA RIVER OXYGEN RESOURCES Figure 9 waste stabilization and is readily lost to the at- mosphere . This type of loss applies in principle to rivers also but usually occurs there at a much lower degree of intensity. For waste stabilization it would be far better that oxygen be available con- tinuously at a lower but constant level than the "feast and famine" situation that occurs naturally. Death of fish has been reported in natural waters where high concentrations of dissolved oxy- gen were produced by a bloom of Chlamydomonas (Woodbury, 1941). At oxygen concentrations of 30-32 ppm., characteristic lesions of the fish con- sisted primarily of gas emboli in the gill capillaries and gas bubbles in the subcutaneous tissues. Al- though not tested, the gas was believed to be oxy- gen. Occurrences such as this are not common. The Lower Fox River mentioned above is an example of a stream that receives its principal flow from a lake (L. Winnebago). During late summer and early fall, tons of algae produced in the lake enter the river and move downstream. Prominent in the phytoplankton are large quantities of Anabaena, Aphanizomenon, and Microcystis, which are more characteristic of standing than flowing water. These algae are reduced in numbers progressively downstream, apparently by dying off. Field and laboratory study showed that seasonal decomposi- tion of such algae is a serious factor in decreasing the assimilation capacity of the river, which re- ceives residual wastes from several cities and from pulp and paper mills. Another more explosive example of excessive use of oxygen resources by algae occurred in the Yahara River in Wisconsin (Mackenthun, Herman and Bartsch, 1945, Published in 1948) where, in October of 1946, tremendous quantities of blue- green algae, almost

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