Influence of substratum surface roughness on periphytic algal community structure in a shallow tropical reservoir Influência da rugosidade do substrato sobre a estrutura da comunidade de algas perifíticas em reservatório raso tropical

AIM: This study aimed to evaluate the algal periphytic community structure on substrates with differing surface roughness in early and longer-term colonization; METHODS: Periphyton was sampled after 30 days (June 24 to July 24, 2008) and 5 days (July 07 to July 12, 2010) substrate exposure during dry season. Plastic slides were used as artificial substrate. Treatments were smooth surface (control), low roughness, medium roughness and high roughness. Samples were collected for limnological condition and periphyton (chlorophyll-a, AFDM, algal biovolume and density, species richness and diversity) analysis; RESULTS: Periphytic biomass, algal density and biovolume had no significant difference among treatments after 30 and 5 days colonization time. Taxonomic similarity was the lowest among treatments and the greatest difference occurred between control and treatments with roughness surface. Bacillariophyceae biovolume decreased with increasing surface roughness. Adherence forms, algal classes and species descriptors were significantly different after 5 days colonization time, especially in medium e high roughness surface. In the colonization advanced phase only species descriptors differ among treatments. Periphytic algae with pads and stalks for adherence decreased with increasing surface roughness. CONCLUSION: Substrate physical properties had little or no influence on periphyton biomass accumulation, total density and biovolume in this study, but algal assemblages were sensitive to changes in the microtopography. More studies are needed to increase understanding of the relation substrate-periphyton in tropical ecosystems. OBJETIVOS: Este estudo visou avaliar a estrutura da comunidade de algas perifíticas em substratos com diferentes graus de rugosidade na superfície na fase inicial e avan ada da coloniza o; MéTODOS: O perifíton foi amostrado após 30 dias de coloniza o (24 junho a 24 julho/2008) e 5 dias (07-12 de julho/2010) de exposi o do substrato no período seco. Laminas de plástico foram usadas como substrato artificial. Os tratamentos foram superfície lisa (controle), baixa, média e alta rugosidade. Foram coletadas amostras para analises das variáveis físicas e químicas e do perifíton (clorofila-a, MSLC, biovolume, densidade algal, diversidade e riqueza de espécies); RESULTADOS: A biomassa, densidade e biovolume algal n o apresentaram diferen a significativa entre os tratamentos na fase inicial e avan ada da coloniza o. A similaridade na composi o de espécies entre os tratamentos foi baixa e a maior diferen a ocorreu entre controle e tratamentos