Seasonal effects of disturbance on a lake outlet algal assemblage
Robinson, C.T.; Rushforth, S.R.; Burgherr, P.
published: Apr 14, 2000
ArtNo. ESP141014802006, Price: 29.00 €
Streams flowing from lakes typically have high standing crops of filamentous algae and associated diatoms. Most outlet streams show more constant environmental conditions than other comparably-sized streams, as the lake ameliorates extreme fluctuations in flow, temperature, and water chemistry. We examined the recovery dynamics of periphyton following disturbance in a low elevation lake outlet in spring, summer, and winter. In each season, replicated 1 m2 areas were disturbed every 0 (not disturbed), 5, 10, and 30 days. After 30 days, each area was sampled and assessed for periphyton biomass, relative abundance of common algal taxa or groups (e. g. Cladophora glomerata (L.) KÜTZ. pennate diatoms), and diatom composition. Periphyton biomass of undisturbed areas was 4 x greater in spring and winter than in summer, probably due to seasonal changes in ambient light (i. e. canopy coverage) and temperature. Response to disturbance varied seasonally with recovery fastest in summer (< 10 days), intermediate in winter (< 30 days), and slowest in spring (> 30 days). Recovery primarily reflected increases in periphyton standing crops (i. e. growth of Cladophora) and seasonal changes in the abundance of some diatom species (e. g. Cocconeis placentula var. euglypta (EHR.) CL., Achnanthes minutissima KÜTZ., and Nitzschia dissipata (KÜTZ.) (Grun.)). Principal components analysis revealed that other diatom species also showed a change in abundance to frequent disturbance in spring and winter, but not in summer. Our results indicate that recovery of lake outlet periphyton assemblages following disturbance reflects seasonal differences in the abundances of specific taxa. The interplay between algal life histories and seasonal changes in environmental conditions play a strong role in the recovery dynamics of algal communities to physical disturbance.