7. The model could be used to generate a surface of net production as a function of solar 

 radiation and air temperature, which could be used to fit a less elegant and less expensive 

 model of production. 



Aquatic production and photosynthesis 



Bob Barsdate* University of Alaska 



Vera Alexander* University of Alaska 



Alex Fu University of Alaska 



Tom Tribble University of Alaska 



Richard Prentki University of Alaska 



Don Schell University of Alaska 



Mary Nebert University of Alaska 



Production in arctic lakes and ponds is extremely low, even compared to oligotrophic lakes 

 in temperate latitudes. Although the phosphorus levels in tundra ponds are not extremely low 

 according to standards of temperate latitudes, nutrient limitations (particularly of phosphorus) 

 in combination with the effects of light and temperature have been held responsible for the low 

 rates of primary productivity in this environment. Thus it seems likely that changes in the rate 

 of phosphorus input into the pond environment will have a marked influence on plankton produc- 

 tivity. In addition, perturbations of the aquatic phosphate levels may affect microfloral regenera- 

 tion rates and the flux of phosphorus and other nutrients back to the terrestrial environment through 

 the emergence of the adult forms of the abundant invertebrate fauna and other pathways. 



The main objectives of these studies were to determine the importance of phosphorus in 

 small pond ecology and to assess the sensitivity of the system to variations of the incoming 

 flux of phosphorus. The primary concern is to determine: 



1. the relationships between the rate of supply of dissolved inorganic phosphorus and the 

 standing stock and rates of plankton primary productivity, and 



2. the rate of uptake and regeneration of phosphorus from detritus and suspended particulates 

 as a function of phosphorus concentration. 



These studies will provide flux rates and residence times for phosphorus and will provide 

 some indication of changes in the nature of the phosphorus cycle resulting from various levels 

 of incoming phosphorus flux. In addition they should indicate to what extent the rate of primary 

 productivity in these ponds is controlled by the supply of phosphorus. These investigations will 

 hopefully result in a sufficient understanding of this aquatic environment so that predictions 

 concerning perturbations resulting from land surface disturbances or fertilization can be made 

 more usefully than is now possible. For these reasons, the scope was expanded to include several 

 perturbations and observations of previously stressed aquatic ecosystems. 



A series of small ponds (site 7) adjacent to site 2 were selected and subjected to detailed 



observation and experimental manipulation during the summer. A group of these small ponds, 



designated B, C, D, and E, are similar in size and general appearance (Fig. 3). These basins 



are shallow, permanent ponds located in an area of poorly drained low-centered polygons. Samples 



were taken throughout the summer for baseline primary productivity determinations, estimates of 



biomass. nutrient chemistry, and kinetics, and certain routine physical and chemical determinations. 



Ponds B and C were used as control ponds, and manipulations carried out on these were confined 



within polyethylene containers. Pond D was the site of two manipulative studies of the effects 



of phosphorus addition. Pond E was also used for baseline studies until mid-July, when an oil 



spill was introduced. Ponds F, G, H, and I are different from each other, and from the ponds 



mentioned above. They were included to broaden the scope of the pond types represented. Pond 



F is small and shallow, and is probably epliemeral in dry years. Ponds G, H, and I are located 



in a drier teixain on an area of h igh-centered polygons about 500 m west of tlie control ponds. 



* Principal auihors 



o7 



