Transplantation of Microbenthic Algal Assemblages to Assess Structural and Functional Recovery After Diuron Exposure

The potential of microbenthic algal assemblages to recover after diuron exposure was investigated. Microbenthic algal assemblages (periphyton) were grown on glass slides in correspondence to a diuron-polluted and a diuron-free sampling site of a river. After 5 weeks of colonization, the impacted periphyton was transferred by translocating the colonized glass slides to the unpolluted site. To monitor the changes in functional and structural parameters and to assess recovery, both the transferred and the local reference periphyton were sampled at the day of transfer (t0) and 1, 3, and 5 weeks after the transfer (t1, t3, t5). Structural transitions of eukaryotic communities were characterized by denaturing gradient gel electrophoresis (DGGE) and functional ones were characterized by short-term incubation toxicity tests with diuron. As shown by Bray-Curtis similarity values based on DGGE band patterns, almost total structural recovery of the transferred periphyton took place 5 weeks after transfer. For the transferred periphyton, previous diuron exposure at the contaminated site induced the development of diuron tolerance, which decreased after 1 week and became very similar to the tolerance of the nonimpacted community after 5 weeks. It is concluded that 5-week-old eukaryotic periphyton communities are capable of restoring their structural and functional attributes after 5 weeks within a noncontaminated environment.