Periphytic diatoms exhibit a longitudinal gradient in a large subtropical shallow lake

Abstract

Some limnological differences among 3 areas in Mangueira Lake, Brazil, a large shallow oligo-mesotrophic system under continuous wind influence, were related to the wind action and influenced diatom community structure. Our goal was to investigate if wind and precipitation influence the attached communities, producing a heterogeneous diatom distribution along the lake. Sampling was performed in summers 2006 and 2008 at the North, Center, and South points of the lake. Biofilms were scraped from natural substrata for quantitative analyses; 17 species were considered abundant. The South is characterized by high transparency and high pH and is influenced by continuous wind perturbation (NE direction), both in frequency and intensity. The diatom community was characterized by low-profile guild and pioneer life-forms, which are resistant to physical disturbances. The North is shallow with high humic acids because of its proximity and interaction with the wetland, and it was characterized by high-profile and motile guilds. Interannual spatial variation was registered due the influence of continuous precipitation before the 2008 sampling date, which made the lake more homogeneous than it was in 2006. The Center acted as a transition point, which was more similar to the North in 2006 and more similar to the South in 2008. The longitudinal gradient was generated due to abiotic characteristics of the North and the South. The diatom community exhibited a longitudinal gradient N→S, and the diatom life-forms and ecological guilds were a useful tool for examining spatial heterogeneity.