Can Top-Down and Bottom-Up Forces Explain Phytoplankton Structure in a Subtropical and Shallow Groundwater Connected Lake?

FRAU D.; DEVERCELLI M.; JOSÉ DE PAGGI S.; SCARABOTTI P.; MAYORA G.; BATTAUZ Y.; SENN M.

MARINE AND FRESHWATER RESEARCH

CSIRO PUBLISHING

Lugar: Collingwood; Año: 2015 vol. 66

1323-1650

Bottom-Up and Top-Down control of phytoplankton is one of the most important hypothesis that explains and predicts aquatic community structure. Our aim was to elucidate if predation and resource limitation can control phytoplankton composition and abundance in a subtropical shallow lake with groundwater connection to the river system. During 12 months, the lake was sampled at three points. Physico-chemical parameters, phytoplankton and zooplankton were sampled fortnightly, while fish every 3 months. The results showed that Euglenophyta dominated the total biovolume followed by Dinophyta and Cryptophyta. As to species composition, Chlorophyta was the dominant group (80 species recorded) followed by Cyanobacteria (26 species recorded). RDA analysis indicated that temperature and nitrate nitrite concentration mainly explained biovolume changes with zooplankton predation not having any measurable effect on phytoplankton during the high water period (HW). During low waters period (LW) Top-Down by fish was more important. At higher taxonomic resolution (species biovolume), phosphorus was other controlling factors. We concluded that phytoplankton in this lake is mainly regulated by hydrological changes as a macrofactor which affects nutrient availability and other environmental conditions. Even though Bottom-Up Top-Down forces do not have a central effect, we found evidence of positive nutrient influences at HW and fish effect at LW.