Energy Dynamics of the Eutrophic Chironomid Chironomus plumosus f. semireductus from the Bay of Quinte, Lake Ontario

Abstract

Relationships between feeding rate, temperature, body size, and time of day were investigated and collated with seasonal assimilation efficiencies of in situ chironomids to construct a picture of chironomid energetics over the year. Temperature controlled feeding rate, and larval size and time of day exerted no effect. The temperature optimum plateaued between 22.0 and 24.5 °C, decreasing logarithmically outside this range. Both assimilation efficiency (AE) and organic content of the food varied seasonally, but were not correlated. Periods of high AE corresponded with the latter part of Melosira or Melosira–Stephanodiscus blooms, while periods of low AE occurred between diatom blooms and during the late summer blue-green bloom. Consequently, growth fluctuated throughout the year, being a result of the interaction of temperature and AE. Anabolic processes dominated at AE greater than 3.5%. Maximum net growth efficiency (NGE) was attained when AE ≥ 6% and temperature ≥ 15 °C. NGE was more sensitive to changes in AE than temperature. Instantaneous growth rate, however, was more sensitive to changes in temperature. Daily ingestion (mg) exceeded body weight by as much as 460–480%, which equals the sediment-processing capacity of freshwater detritivores.Key words: chironomid, feeding rate, assimilation efficiency, instantaneous growth rate, net growth efficiency, algal community, Bay of Quinte