Production of Chironomus, Procladius, and Chaoborus at Different Levels of Phytoplankton Biomass in Lake Memphremagog, Quebec–Vermont

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Abstract
In Lake Memphremagog a north–south gradient in algal production and biomass exists during the ice-free period, with highest production in the southern areas. In response, the mean annual benthic standing stock (dry weight) in the south basin was 2.8 times greater than in the north basin at comparable depth. Mean annual standing stock of Procladius denticulatus and Chironomus anthracinus were significantly (5.8 and 3.1 times, respectively) higher in the south, while that of Chaoborus punctipennus did not differ significantly between areas. Annual production of P. denticulatus was greater in the south (0.861 g/m2) than in the north (0.143 g/m2). Similarly for Chironomus anthracinus annual production was greater in the south (3.393 g/m2) than in the north (1.264 g/m2). Production of Chaoborus punctipennis was greater in the north (0.066 g/m2) than in the south (0.348 g/m2). P:B ratios were less variable. Key words: Lake Memphremagog, benthos, production, nutrient gradient, mortality