Introduction and Site Description 21 



1. We must first understand as completely as possible the system to 

 be modeled. 



2. Only the important parts of a system, and their controls, can be 

 modeled. 



3. Wherever possible, constants, rates, and relationships included in 

 the model must be measured and not taken from the literature. 



4. The modeling exercise and the resultant simulations are regarded 

 as tools to be used to further our understanding of how the 

 ecosystem operates. 



5. The modeling must be done by ecologists with the aid, if necessary, 

 of a professional modeler rather than vice versa. 



LIMNOLOGY OF THE ARCTIC 



Circumpolar 



For this report, the Arctic is defined as the region north of the tree- 

 limit which has a mean air temperature of less than 10°C during the 

 warmest month. Until very recently, arctic limnology was entirely 

 organism-oriented. This was in part due to the great difficulties of carrying 

 out anything more than expedition-type collecting activities and in part 

 due to the particular interests of the people involved. Modern studies of 

 the physical, chemical, and limnological processes in lakes and ponds 

 began after 1950 or so when research stations became established (e.g., at 

 Disko Bay, Greenland, and Barrow, Alaska). As a result, the first review 

 of arctic limnology (Rawson 1953) mentioned only seven papers that dealt 

 with arctic lakes. 



The availability of these research stations, plus the realization that 

 long-term studies were needed, led to a number of detailed investigations. 

 In Scandinavia, the biology of Lapland lakes has been investigated by 

 Ekman (1957), Holmgren (1968), and Nauwerck (1968). In Spitzbergen, 

 water chemistry and zooplankton biology have been studied (Amren 

 1964a) and there are a number of reports of investigations of Greenland 

 lakes (e.g., Hansen 1967, Holmquist 1959). Several investigators, such as 

 McLaren (1964), Kennedy (1953), and Oliver (1964), worked in northern 

 Canada. By far the greatest number of studies were made in northern 

 Alaska (e.g., Livingstone et al. 1958, Hobbie 1964, Kalff 1967a, Stross 

 and Kangas 1969, Carson and Hussey 1960) of the chemistry, biology, and 

 physics of a wide range of lakes and ponds. 



The results from all these and other arctic studies are summarized in 

 reviews by Livingstone (1963a), Kalff (1970), and Hobbie (1973). In brief, 

 arctic lakes and ponds have the following characteristics: 



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