Changes in fossil midge (Chironomidae) assemblages in response to culturalactivities in a shallow, polymictic lake

Chironomid (Diptera: Chironomidae) head capsules were studied from a core o f recent sediments from shallow, macrophyte-dominated Lake Opinicon, Ontari o, Canada, to determine if assemblages have changed in response to lake-lev el changes and other watershed disturbances, including deforestation and ag riculture. Our results indicate that the construction of the Rideau Canal i n the early 1830s and subsequent flooding of Lake Opinicon has had the grea test impact on this system, but that even this disturbance did not greatly affect chironomid assemblages. Despite other significant cultural disturban ces in the watershed, the lake sediments have recorded only minor changes i n its recent history, providing support for the hypothesis of alternative l ake equilibria. These results correspond well with diatom inferences of onl y minor changes in past lake trophic status.