Relative importance of periphyton and phytoplankton in turbid and clear-vegetated shallow lakes from the Pampa Plain (Argentina): a comparative experimental study

SÁNCHEZ, MARÍA LAURA; PIZARRO, HAYDÉE; TELL, GUILLERMO; IZAGUIRRE, IRINA

HYDROBIOLOGIA

SPRINGER

Año: 2010 p. 271 - 280

0018-8158

This study analyzes the relative contribution of phytoplankton and periphyton in two shallow lakes from the Pampa Plain (Argentina) that represent opposite scenarios according to the Alternative Lake Equilibria Theory: a) a clear shallow lake with submerged macrophytes, b) a turbid shallow lake with high phytoplankton biomass. The temporal evolution of both algal communities was experimentally studied in each shallow lake using enclosures. The experiments focused on how these communities compete for light modifying their biomass and composition. Enclosures (by triplicate) were placed in each lake and they included: natural phytoplankton, artificial substrata (polycarbonate strips) with periphyton previously colonized until their mature stage, and clean artificial substrata to analyze periphyton colonization. In the clear vegetated shallow lake periphyton was dominant in terms of algal biomass: Chlorophyll a concentrations of the periphytic community were between 3 and 6 times higher than those of the phytoplankton community. Conversely, phytoplankton Chlorophyll a concentrations in the turbid lake were between 76 and 1325 times higher than the periphytic Chlorophyll a. In the turbid shallow lake, where light was limiting for the algal growth, the colonization of periphyton community was significantly lower than in the clear shallow lake. On the other hand, in the clear shallow lake, where limitation by nitrogen probably occurs, periphyton exhibited higher biomass, most likely due to their higher efficiency in nutrient recycling. The autotrophic index (ash free dry weight: Chlorophyll a ratio) ranged from 95 to 450 in the clear lake, and from 311 to 7578 in the turbid lake, suggesting that the periphyton of the latter included more heterotrophic components.