Benthic secondary production in eight oligotrophic arctic Alaskan lakes

Across aquatic ecosystems, benthic secondary production generally is thought to be limited by autochthonous primary production. We estimated secondary production in 8 oligotrophic arctic lakes of varying morphometric characteristics for which we also had estimates of pelagic and benthic primary production during the summer of 2001. Four of the lakes supported similar communities of fish, and 4 were fishless. The size–frequency method was used to calculate cohort production interval (CPI)-corrected lake benthic secondary production and production to biomass (P:B) ratios for all taxa in all lakes. Taxa examined from sediment samples included Baetis spp., Grensia praeterita, and larval chironomids. Larval chironomids had the greatest secondary production overall. Whole-lake benthic secondary production ranged from 1.02 to 20.52 g dry mass m−2 y−1. No significant relationship or trend was found between benthic secondary production and primary production (whole-lake, benthic, or pelagic). A stronger trend (p = 0.2) suggested higher benthic secondary production in fishless lakes than in lakes with fish, but within fishless lakes, no pattern was found that suggested autochthonous control of benthic secondary production. Our study is unique in that we examined multiple oligotrophic lakes and demonstrated that the secondary production of benthic fauna was, at most, weakly related to autochthonous primary production. This result is in contrast to the commonly accepted paradigm that autochthonous production limits secondary production. We suggest that allochthonous organic matter sources were very important for supporting secondary production in these oligotrophic arctic lakes.