Ecology and Population Dynamics of Chironomus plumosus (Diptera: Chironomidae) in Lake Winnebago, Wisconsin1

Abstract

The ecology and population dynamics of Chironomus plumosus (L.) were studied in 4 areas of Lake Winnebago for 3½ years to gain insight into the factors that cause fluctuations in populations of this insect. Numbers of C. plumosus and other benthos in each area were determined, as was the ammonium, nitrate, phosphorus, pH, suspended solids, oxygen, and temperature of the water, and the ammonium, phosphorus, pH, redox potential, percentage of water, and temperature of the mud. Populations of C. plumosus fluctuated drastically, both from year to year and from one part of the lake to another. None of the physical or chemical characteristics in the water appeared to affect C. plumosus populations, but several characteristics of the mud apparently were related to these populations. Other benthic organisms seemed to exert only a minor influence on populations of C. plumosus. Climatic factors, especially wind direction and velocity at the time of emergence and oviposition, appeared to be very important in determining the distribution and abundance of C. plumosus in Lake Winnebago. Fish predation probably also influenced C. plumosus numbers, but microsporidia and unknown viruses, fungi, and bacteria were probably the most important regulators of the populations.