Temperature, discharge and light data for Ivishak Hot Spring, Alaska

The productivity of a perennial, Arctic spring-stream was investigated. Ivishak Spring has the stable discharge (~131 L/s) and temperature (~4-8 deg C) typical for springs. It is unusual, however, in having an annual cycle of daylight from 24 hrs/d (summer) to 0 hrs/d (winter). It was tested from the hypothesis that stored detritus would buffer carbon limitation during winter when gross primary production (GPP) is minimized, resulting in constant rates of community respiration (CR) year-round due to constant temperatures. Open-channel methods were used to measure GPP and CR monthly from March 2007 to August 2009. Mean annual GPP was 458 gC/m2. Such a level is typical for temperate desert streams but was surprising for an Arctic stream. Annual CR (887 gC/m2) was also remarkable. The high metabolism of this stream is explained by an open canopy, moderate year-round temperatures, stable bed, and high bryophyte biomass (48 gAFDM/m2). Strong seasonal cycles of GPP were mirrored by CR (r=0.65) indicating the possibility of carbon limitation during winter. This result falsified the hypothesis that CR would be relatively stable year-round due to a detritus buffer and constant temperature.