The present study sought to falsify three distinct hypotheses about how the interactions of freshet clay turbidity with Flathead Lake may be affecting its trophic state: 1) that freshet-derived turbidity causes precipitation of organic detritus from the water column by flocculation and/or coagulation of dissolved and colloidal organic carbon and seston; 2) that flocculated clay-organic detritus complexes become increasingly infested with microbial biomass as they sink through the water column; and 3) that primary productivity is reduced and subsequently maintained at low levels throughout the summer and fall because of the phosphorus stripping action of sedimenting clay particles. In addition, this study attempted to firmly document mass balances for some ecologically important elements, nutrient loading rates, steady state nutrient concentrations and annual lake primary productivity. It was also necessary to assess the trophic status of the lake in light of any new findings from this research, especially related to the ecological role of freshet turbidity.

The feeding ecologies of leaf pack-associated systellognathan stoneflies were examined from 6 June 1980 21 May 1981. Species composition, seasonal abundance, nymphal growth, feeding habits and mouthpart morphology were determined for the eight dominant stonefly species. Prey preferences and predator-prey size relationships were also examined for omnivorous and carnivorous species. Foregut analysis from 2860 individuals indicated opportunistic feeding on the most abundant prey insects, usually in proportion to prey frequency. Feeding preference studies generally indicated random feeding on major prey groups. Prey and predator sizes were usually highly correlated (p<0.01), with predators expanding their prey size thresholds with growth. The potential for competition between sympatric stoneflies for prey is discussed.

Drumming is first described for five North American stonefly species, Acroneuria evoluta, Doroneuria baumanni, Isoperla namata, Chernokrilus misnomus, and Pictetiella expansa. Signals of Acroneuria lycorias, Phasganophora capitata and Isoperla signata are further described. Drumming was not recorded from Amhinemura delosa. Signals of A. evoluta are the most complex yet recorded in Plecoptera. Doroneuria baumanni, P. expanse, C. misnomus and P. capitata have 2-way exchanges. Male D. baumanni produce two prolonged beats by rubbing the hammer on the substratum; male-female signals are non-overlapping in the first two species and overlapping in the latter two. Female P. capitata answered with an unusually long sequence of beats. Two male Isoperla species produced monophasic calls without female answers. Female A. lycorias answered taped male signals with monophasic signals like all observed females.