FOSSIL PIGMENTS AS INDICATORS OF PHOTOTROPHIC RESPONSE TO SALINITY AND CLIMATIC-CHANGE IN LAKES OF WESTERN CANADA

High performance liquid chromatography was used to quantify changes in fossil pigments among 111 saline lakes in British Columbia and to rec onstruct past changes in phototrophic communities in three closed-basi n prairie lakes. Redundancy analysis of survey data demonstrated that pigment concentrations were greatest in deep stratified lakes but were unaffected by ion concentrations, pH, or conductivity. Algal standing crop las chlorophyll) was correlated (r = 0.21-0.33, P < 0.01) only w ith fossil measures of total algal abundance (beta-carotene, pheophyti n a). In contrast, redundancy analysis demonstrated that relative abun dance (%) of fossil carotenoids varied with lake chemistry. Lutein-zea xanthin (from green algae, cyanobacteria) and diatoxanthin (diatoms) r eplaced fucoxanthin (diatoms, chrysophytes, dinoflagellates) as salini ty increased, while alloxanthin (cryptophytes) and myxoxanthophyll (co lonial cyanobacteria) were most common in lakes with low Ca2+ and high dissolved organic carbon contents. Ordinations of surficial sediments suggested that post-deposition degradation did not alter the relation between pigment abundance and environmental characteristics. Fossil p rofiles of chlorophyll b and lutein-zeaxanthin also recorded climatic signals from Antelope and Kenosee lakes. These findings suggest that f ossil pigments are well preserved in saline lakes and are capable of r ecording phototrophic community response to changes in salinity and cl imate.