. The ecology and life history of the common frog (Rana temporaria temporaria) . -45-39-33-27-2 1 -15-9 -3 0+3 +9 +15+21+27+33+39+45+51+57 DEPARTURE FROM MEAN SPAWN DATE IN DAYS Fig. 41. Histogram Showing the Distribution of Spawn Records They are plotted as departures from the mean date in each year, for 24 years in a fairly uniform area, SE England. This curve is not of the normal form being sharply peaked and negatively skewed. Phosphates tend to be the limiting factor, and in fact water undertakers use the level of phosphate as an indication that the peak of algal production has been reach
. The ecology and life history of the common frog (Rana temporaria temporaria) . -45-39-33-27-2 1 -15-9 -3 0+3 +9 +15+21+27+33+39+45+51+57 DEPARTURE FROM MEAN SPAWN DATE IN DAYS Fig. 41. Histogram Showing the Distribution of Spawn Records They are plotted as departures from the mean date in each year, for 24 years in a fairly uniform area, SE England. This curve is not of the normal form being sharply peaked and negatively skewed. Phosphates tend to be the limiting factor, and in fact water undertakers use the level of phosphate as an indication that the peak of algal production has been reached, so that their troubles with consumers over tastes and smells are nearly over. Light is obviously an important factor, and, indeed, with certain underground waters, every effort must be made to avoid exposing the water to light before passing it into the mains, for, otherwise, algal growth is certain to be troublesome. In spite of modern methods of control, it is still necessary sometimes to take a reservoir temporarily out of service until the algal peak has passed. There have been cases of reservoirs proving so troublesome that, in spite of the cost, they have been abandoned. If indeed it is
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Keywords: ., bookcentury1900, bookcollectionbiodiv, booksubjectranatemporaria
