DIURNAL RECRUITMENT PATTERNS IN ALGAE - EFFECTS OF LIGHT CYCLES AND STRATIFIED CONDITIONS

The diel pattern in algal habitat shift between sediment and water was recorded above (shallow site) and below (deep site) the thermocline i n a stratified, unproductive forest lake. Migrating algae were caught in funnel traps, and the net transport was calculated Diel recruitment patterns varied temporally within site and spatially between sites. F or most species, recruitment and sinking was low at the deep site duri ng stratification. When stratification began to break down in August, the migratory activity increased at the deep site, suggesting that til e stratified conditions affected algal migration behavior. Although li ght obviously affected algal migration, recruitment often deviated fro m consistent diel patterns, indicating that simple Light-dark cycles a re not sufficient to explain algal migratory patterns. Instead, the st udy suggests that some algal species have receptors able to detect sev eral environmental variables, including light and variables associated with stratified conditions. Hence, some algal species, but not others , may be able to optimize resource needs by properly adjusting the tim ing for recruitment from the sediment surface in relation to the risk of being trapped below the euphotic zone by a thermocline not possible to penetrate.