Relative influence of direct and indirect environmental effects on sestonic chlorophyll-a concentration in Cerrado streams

Influência relativa de efeitos ambientais diretos e indiretos na concentração da clorofila-a planctônica em riachos do Cerrado

Abstract

Aim: Chlorophyll-a may be directly influenced by local variables and/or indirectly by land use and cover, once landscape modifications change limnological variables, which in turn affect the primary productivity of aquatic environments, e.g., streams. Therefore, the objective of this study was to determine the relative importance of the local and landscape environmental components and assess the direct and indirect effects of these variables on sestonic chlorophyll-a concentration in 30 Cerrado streams (Santa Teresa River basin).

Results

All aquatic environments were oligotrophic during the study period. Only the local variables were important to explain chlorophyll-a variation (R² = 0.27; P = 0.04). In addition, the path analysis showed that all variables used in the analysis influenced chlorophyll-a concentration more directly than indirectly. Conductivity was the most important variable to directly influence chlorophyll-a, followed by turbidity.

Conclusion

The large amount of remnant native vegetation in the basin indicates that the region studied is well preserved, which may explain the greater importance of local variables and the low effect of the landscape in explaining chlorophyll-a variation.

Keywords:
phytoplankton; conductivity; variation partitioning; landscape ecology; stream ecology