The Plankton Alyae of the Palisades Interstate Park loi 



drawn through the water of a lake for a while, one always finds at 

 the bottom, of the net a brownish to greenish sludge which a micro- 

 acopical examination shows is composed of algae and simple animals. 

 The algae that live free-floating in the middle of the large lakes are, 

 as a rule, quite distinct from those dwelling on the shallow bottom 

 or along the shore, and they form a flora that, for the biologist, 

 differs as much from the shore and bottom algal growths as a tropical 

 flora differs from that of New York. This special free-floating 

 minute life found in mid-lake is known as the plankton, and the 

 algal or plant portion of it is called the phytoplankton. Even the 

 clearest lake, and one which never develops a bloom, has its plankton 

 flora, and though the total number of individuals in a gallon of 

 water may be small there may be surprisingly different types present. 

 In fact, the students of these minute organisms have made some of 

 their richest collections of species in clear-water lakes. It matters 

 not at what season of the year the collections are made, plankton 

 algae will always be present in the lakes ; although they are much 

 more common at certain seasons, especially midsummer, than at 

 others. The kinds of algae found also vary from month to month, 

 some being most abvmdant in early spring, others in midsummer, and 

 still others in greatest quantity in the fall. 



Injurious Effects of Blooms. The question is often asked 

 whether an algal bloom is really inimical to the health of man or 

 animals drinking the water. Although there have been reports of 

 mysterious deaths of farm animals that have been ascribed to the 

 drinking of water containing large numbers of algae (Nelson, '03; 

 Francis, '78; and Arthur, '84) there seems to be but little direct 

 evidence that bloom organisms contain poisonous substances. The 

 widespread occurrence of blooms in lakes every year, and the wide 

 use of these lake waters by domestic animals, furnishes justification 

 for the statement that these organisms are not directly poisonous. 



Cases have been reported, likewise, where the sudden dying of 

 fish has been considered due to the presence of heavy algal growths. 

 Among these may be mentioned the observations of Haine ('18), 

 Hyams and Richards ('01), and Baldwin and Whipple ('06). Those 

 of Baldwin and Whipple have been the most complete, and their 

 results show that while the algae killed the fish they did not poison 

 them directly, but that the death of the algae following their period 

 of blooming caused an exhaustion of the oxygen supply, and that, 

 in turn, caused the death of the fish. That this death of fish in 

 connection with blooming is due to the exhaustion of oxygen is 

 borne out by the observations of Haine, who shows that when algae 

 have been killed by copper sulphate there is a sharp decrease in the 

 oxygen content of the water following such treatment, due to the 

 bacterial oxidation of the dead algae, and that this oxygen reduction 

 may affect the fish. 



Although the direct effects of blooms upon the life in the water 

 or upon the animals using the water for drinking purposes are small, 

 blooms are of great importance from the aesthetic point of view. 

 When a lake contains heavy algal growths the odors arising from 



