Improving Conditions for Fish in Brown-Water Bog Lakes by Alkalization

The object of this study was to discover methods for increasing the productivity of small kettle lakes which have characteristically brown-colored water. Owing to the light-absorbing action of the pigmented solutes and suspensoids of the water, the sun's energy cannot express its optimum effect on the basic fish food supply-plants. Hence, any treatment which would free the water of its brown color and still not be toxic to fish would enhance productivity, since such a treatment would increase the depth of light penetration and therefore the volume of the food-producing (trophogenic) zone. Increased fish production should follow. James and Birge (1938) and Sauberer and Ruttner (1941) demonstrated that the colored materials of lake water reduced the depth to which the light penetrated. Their results showed also that it was absorbed selectively, especially those wave lengths which were most effective in photosynthesis. It has been generally observed that seepage water from limed and undrained peat marshes now in use for agriculture is clear, while that from unlimed ones is tea-colored. This observation suggested to us (Hasler and Einsele, 1948) that lime treatment of acid, brown-water, lakes might likewise clear up the water and therefore increase the epth of the trophogenic zone. Theoreti ally, if lime were added to lakes the calcium would combine with the humic colloids forming a humate which would flocculate and fall to the bottom. Moreover, alkalization of the water would produce a better medium for bacteria so that suspended organic colloids would be, in part, degraded. It is well known that acid conditions are unfavorable to decomposition by micro-organisms. We therefore postulated that alkalization through lime treatment might also augment the activities of organic decomposition at the bottom as has been observed in European fish ponds and reviewed by Neess (1948). This action would, theoretically, reduce the rate of accumulation of debris and therefore retard the aging process of the lake and give it additional years of life.