70 Union Bay 



the channel which had the most trees along its margin. The 

 dragonflies hunted for insects back and forth over similar 

 territory. Each live thing followed a certain pattern, occupied 

 a certain territory, and preferred a certain diet. I could as- 

 sume, as many ecologists had pointed out in other localities, 

 that this marsh was quite well stabilized in its plant and ani- 

 mal population, and that the life within its confines was little 

 changed from year to year. 



Of course there were some shifts. I thought the marsh 

 especially susceptible to modification through the action of 

 man. The delicate mechanism of such a community could be 

 affected by apparently remote things. I recalled the state- 

 ment of a game management expert who said that man's 

 introduction of the European carp had seriously affected the 

 supply of duck food. He said no arrowhead could be raised 

 in an area if numbers of carp made a practice of rooting 

 about in it. I noticed the gradual recession of the dense cat- 

 tail stand in the place where the water from the boiler of the 

 University power plant is discharged. Something proved in- 

 jurious enough to make the plants retreat until now an area 

 of perhaps two acres is bare. If man filled a place by dumping 

 soil, water-loving plants immediately disappeared and soon 

 Willows and cottonwoods began to sprout. If his dredges 

 made a new channel, then the change of plants was almost 

 complete. 



There were other changes not due to man. When the tiny 

 duckweed found the season entirely to its liking, i't floated 

 about in sheets so dense that a wind would blow it up on a 

 low spot in windrows. The shutting off of light by such float- 

 ing blankets seriously retarded the bottom growth and thus 

 indirectly affected the frogs, minnows, and other aquatic 

 animals which depended on the plants for sustenance and 

 shelter. I did not find it difficult to watch the struggle year 

 after year as each plant maintained itself successfully in the 

 areas for which it was best fitted, continually reached out to 



