266 



R. G. Stross et al. 



TABLE 6-7 A nnual Production of Crustacea in Pond C ' '^ 



1971 



1972 



1973 



Cyclops vernalis 

 Diaptomus bacillifer 

 D. glacialis 

 Heterocope 

 Fairyshrimps 

 Daphnia 



Total 



1398.1 



1187.1 



820.6 



^ llg C liter ' . 



Except for Daphnia all annual rates are exclusive of the production of diapausing 

 embryos. Since the initial stock each year is not subtracted, each estimate in effect 

 assumes 100% survival of the overwintering individuals. 

 95% or more Polyartemiella. 



However, in Pond C the distribution of this production did vary 

 between the groups; the fairyshrimps had the highest production in 1971 

 while Daphnia were the highest in 1972 and 1973. The very high value for 

 Daphnia in 1972 is real but somewhat misleading as the young and adults 

 were concentrated by the low water levels of late July. There may also 

 have been an unusual second brood of young in 1972 as a result of 

 minimum July water temperatures of 10°C or higher during a critical 

 interval. On the other hand, the Cyclops and fairyshrimp that have most of 

 their production early in the year, when water levels were high, had their 

 apparent production (on a per liter basis) lowered as a result of the greater 

 pond volume at that time. 



Daphnia Feeding, Growth, and Reproduction 



Filtering rates were determined with the short-term feeding method 

 (Nauwerck 1959) using ^^C-labeled Chlamydomonas reinhardtii (see 



o 



E 



2.0 



I .5 



.9 10 



u 

 o 



q: 05 



C 



< 



D 



BCFEDX BCFEDX BCFE 



1971 1972 1973 



FIGURE 6-8. Annual production of the planktonic 

 Crustacea in ponds for the years 1971, 1972 and 1973. 



