PLANKTON AND NUISANCE CONDITIONS IN SURFACE WATEE 



61 



TABLE IV 

 Inorganic Nitrogen and Phosphorus in Wisconsin Lakes 



On the basis of this and other data Sawyer reasons: "In general, it may 

 be concluded that lakes showing average annual concentrations of inor- 

 ganic nitrogen and phosphorus in excess of 0.30 and .015 ppm, respectively, 

 will produce frequent 'nuisance blooms.' " Table IV generally bears this 

 out, but of course there are exceptions. Mendota produced one nuisance 

 bloom in the two years' study, unless the masses of filamentous algae be 

 so called despite its low nitrogen average. Wingra and Geneva, despite low 

 phosphorus averages, produced many blooms. But virtually all of these 

 were very small organisms, and the term bloom applied only when there 

 were more than 500 of some species per ml of raw water. No discolora- 

 tion or nuisance would have been evident. 



Positive results are equally evident in Monona, Waubesa and Kegonsa. 

 Here a large amount of contributed fertilizing minerals came from properly 

 functioning sewage plant effluents, although agricultural drainage and indus- 

 trial drainage were also contributors. Blooms in these lakes were so 

 abundant and so frequent as to evoke legislative action on the part of the 

 shore residents. Most of the nuisance conditions here were due to blue- 

 green algae. Microcystis and Anabaena being the chief offenders. 



But there is far too little evidence as to the causes of specific swarm- 

 ing growths of organisms. In shallow, warm lakes, accumulating nitrates 

 and phosphates seem to produce blue-green algae; but agricultural drain- 

 age into streams of moderate hardness seems to produce swarms of euglenoid 

 flagellates, small non-motile green algae and green flagellates belonging to 

 the Volvocales. Sulfuric acid drainage from exposed coal seams produces, 

 particularly, Euglena mutabilis (Lackey 1939). Distillery wastes have 

 shown most abundantly, Volvocales: the first United States record of 



