4 J. E. Hobbie 



FIGURE 1-3. To avoid disturbing the water and sediments of Pond B, an 

 investigator takes samples from a cable car. 



The pond waters contain small amounts of salts and have a pH 

 around 7.3. The light, flocculant sediments are made up of 80% organic 

 matter. 



The dominant primary producers of the ponds (Table 1-1) area sedge 

 {Carex aquatilis) and a grass {Arctophila fulva) which live in the shallow 

 margins of the pond and cover 30% of the surface (Figure 1-4). Benthic 

 microalgae, mostly diatoms and blue-greens, are also important producers 

 but their numbers are kept low by the continual mixing of the upper few 

 centimeters by animals, which keeps most of the algae away from light. 

 Algae in the water above are all small flagellated nannoplankton, 

 especially greens and chrysophytes. Their total productivity is low and 

 they are heavily grazed by zooplankton such as Daphnia and fairyshrimp. 

 In turn, these herbivores are preyed upon by predaceous zooplankton 

 {Cyclops, Heterocope) but there are no important vertebrate predators 

 (although shorebirds do feed on zooplankton). The leaves, rhizomes, and 



