Temperature is another common pollutant that is often difficult to 

 detect unless continual monitoring is carried out, and then it is sometimes 

 difficult to predict the temperature regime in the river. However, shifts 

 in algal species will clearly denote these kinds of changes. For example, 

 we have found that if the temperature of the water consistently remains 

 below 30 C and no other pollutant is prevalent, diatoms will be dominant 

 throughout the year in most streams, particularly in eastern United 

 States. If the temperature during the summer increases to between 30 C and 

 33 C green algae will predominate, and some blue-green algae will become 

 very common. Thus one can estimate the temperature regimes in various 

 parts of a body of water. 



Another type of determining change, particularly in lakes, has been to 



examine the fossil record. In such studies sediment cores are taken and 



dated. The shift in diatoms and invertebrates species enables one to deter- 

 mine trends toward eutrophi cation. 



From this discussion it is evident that the monitoring of biological 

 organisms can be ^ery valuable in determining the effects of wastes. As 

 contrasted with chemical and physical determinations of water quality, the 

 organisms integrate over time all deleterious effects, whereas a chemical 

 examination only determines the presence of the chemical for which analysis 

 is made at the particular time. Actually it is important that both types 

 of studies be made. The biological studies often give an indication of a 

 certain type of chemical or deleterious conditions being present. It is 

 then necessary to determine exactly what chemical is causing the effect. 

 Therefore, both types of studies become important, but the biological 

 studies are the better continual monitoring studies if only one type of 

 monitoring is to be made, because it integrates all changes which may occur, 



In the United States we are also realizing the importance of preserving 

 specimens from monitoring studies. Recently there was a considerable scare 

 about the accumulation of mercury in fish. However, an examination of fish 

 in our museum collections showed that these older specimens had similar 

 amounts of mercury and the sudden awareness of the presence of mercury was 

 due to better analytical techniques. Without these specimens in our 

 museums such comparisons would not have been possible. 



From these various examples it is evident that biological monitoring 

 can be useful to determine the extent and degree of harm in an area of a 

 specific waste. Diatometers and similar samplers can be very useful in 

 determining trends over long reaches in a river system of increases in 

 pollution. Organisms such as diatoms and some invertebrates can pick up 

 and concentrate over time amounts of chemicals infrequently discharged that 

 would probably not be picked up by ordinary chemical monitoring. 

 Continuous monitoring as well as intermittent monitoring is extremely 

 useful in comparing changes over long periods of time in various bodies of 

 water. 



The program of monitoring depends on the questions one wishes to ask, 

 particularly whether one wants to determine general changes or whether one 

 wants to determine trends or more precise causes of change. 



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