Soft-bodied benthic algae in pristine Brazilian streams: from acid to karst¹

ABSTRACT

This study evaluated soft-bodied benthic algae from seven streams located in protected areas of central Brazil (Parque Nacional de Brasília, Parque Nacional da Chapada dos Veadeiros and Parque Estadual de Terra Ronca), and related them to abiotic factors. We addressed the following questions: A) how algal community structure in Cerrado streams is influenced by the marked seasonality typical of the region; and B) how karst geology influences algal communities in Parque Estadual de Terra Ronca, as compared to streams in other Cerrado areas. Samples were collected between 2012 and 2013 from a single site in each stream, and upstream and downstream of caves present in Parque Estadual de Terra Ronca. Altogether, 159 taxa were recorded. Algal community structure varied significantly among sites, but not between seasons, despite relatively lower abundances during the rainy season, likely due to a negative influence of the faster currents in streams during this period. Some alkaliphilic species were observed only at sites near caves (e.g. the cyanobacterium Tolypothrix distorta), while acidophilic taxa were more frequent in the other streams (e.g. desmids and Cyanobacteria such as Scytonema caldarium, Hapalosiphon stuhlmannii and Stigonema ocellatum). We observed a rare green alga, Microthamnion kuetzingianum, and reported the cyanobacterium Rivularia aquatica for the first time in Brazil.

Keywords:
abiotic variables; biodiversity; Cerrado; Cyanobacteria; lotic systems; periphyton; soft-bodied algae; pristine streams; Zygnematophyceae