A PALEOLIMNOLOGICAL STUDY OF TUGULNUIT LAKE, BRITISH-COLUMBIA, CANADA, WITH SPECIAL EMPHASIS ON RIVER INFLUENCE AS RECORDED BY CHIRONOMIDS IN THE LAKES SEDIMENT

Sediments from Tugulnuit Lake in the Okanagan Valley of British Columb ia, Canada, were examined for chironomid assemblages. The chironomid s tratigraphy obtained encompasses the last 4000 to 5000 years and sugge sts a warm and fairly stable climate typical for a temperate lake at l ow-to mid-elevation. This is indicated by the even distribution of war m-water taxa, such as Cladopelma, Dicrotendipes, Polypedilum, Pentaneu rini, Stempellina, Stempellinella/Zavrelia and Pseudochironomus throug hout the core. Very few cold-water taxa occurred in the sediments. How ever, stream inputs have had a major impact on Tugulnuit Lake. Sandy s ediments and the appearance of Simuliidae and stream-inhabiting chiron omid taxa (e.g., Brillia/Euryhapsis, Eukiefferiella/Tvetenia, Rheocric otopus) indicate that a stream intruded into the current lake's basin ca. 3800 yr Before Present (BP). Sediments deposited prior to, and aft er, the stream's intrusion show a distinctly different chironomid asse mblage exhibiting chironomid taxa more typical for lentic habitats. Th is result indicates that chironomids can serve to detect past stream i n fluences on lake environments. Thus, rheophilic chironomids preserve d in lake cores provide a new alternative for reconstructing stream pa laeoenvironmental records.