RELATIONSHIP BETWEEN ALGAE IN SUSPENSION AND PERIPHYTON IN TWO COLORADO MOUNTAIN STREAMS

V. V. Vavilova, W. M. Lewis, Jr. , and R. Dufford. CIRES, University of Colorado, Boulder CO 80309

The rates at which algae in mountain streams enter the water column were quantified and compared with the abundance of attached algae and current velocity. We estimated abundance and species composition in algal drift. The suspended algae were heterogeneously distributed on different spatial scales. Average algal drift increased 100 times from headwaters downstream and coincided with an increase in percentage of filter-feeding insect larvae. The ratio of attached algae to algae in water column dropped about 100-fold from the headwaters, while water velocity decreased to one third. Species similarity between attached and suspended algae at particular points ranged from 6% to over 90%; morphotype similarity ranged from 17% to 100%. Thin elongated and cylindrical cells were most likely to enter the water column. A simple model detachment was developed.