Colonization patters of autotrophic and heterotrophic microorganism on river benthic substrata

ROMANI, A.; ARTIGAS, J.; ADONIS GIORGI; SABATER, S.

Santiago de Compostela

Congreso; ASLO Meeting; 2005

River biofilms grown on any benthic wet surface (rocks, cobbles, sand, leaves, wood) are mainly composed by bacteria, algae, cyanobacteria, fungi and protozoa embedded in a polysaccharide matrix. This structure is highly dynamic biological layer which change its metabolism, thickness, density and composition depending on its own evolution and/or physical-chemical conditions. In rivers and streams biofilm attachment and detachment processes are frequent, collapse and recolonization can occur periodically. In his study, data on colonization processes, intensively monitored in the field from different river sites all over the world, are collected and analyzed by approaching sigmoid curves. The investigation is specially focused on the evolution of bacteria (cell number) and algae (as Chl-a) during the first colonization steps. In epilithic biofilms, algal growth favors bacterial growth and colonization. Algal and bacterial colonization tends to be faster to epixylic and epipsammic than for epilithic biofilms; algae are displaced by fungi and bacteria on leaves. In spite of the high range of sites and conditions, the calculated parameters for the colonization curves (r, K, Xo) are within a relatively short range.