Abstract
This study evaluated the influence of physical, chemical and physico-chemical variables of water on the biomass of periphyton community and verified the differences between six sampling sites over the course of São Mateus river: two upstream of the city of São Mateus, Espírito Santo State (E1, E2), two along (E3, E4), and two downstream of the city (E5, E6). The periphyton was collected from roots of Eichhornia crassipes (Mart.) Solms. Samplings were undertaken every week in September and October 2010. The periphyton biomass was estimated through chlorophyll ‘a’, biovolume, dry mass, ash-free dry mass, and ash. Higher values of chlorophyll ‘a’ were found at E1, while the total biovolume featured greater values in E4 and E3. Regarding the values of periphyton dry mass, the inorganic fraction was higher at sites along and downstream of the city of São Mateus. The variation of periphyton biomass was influenced by the availability of nutrients (phosphorus and nitrogen) and turbidity, as evidenced by the CCA. The results suggest that the input of allochthonous material, especially from human activities (fish farming and discharge of domestic and industrial wastewater), has changed the water quality (as pointed out by the PCA), as well as the communities present.
Highlights
Rivers are open aquatic ecosystems, with unidirectional flow, continuous from headwaters to the mouth, strongly influenced by natural characteristics, which integrates with the adjacent terrestrial environments, forming a more balanced functional unit (MARGALEF, 1983)
Biological Sciences impacted by events located at distinct points of the basin which results in a serial discontinuity (MARQUES et al, 2003; SILVA et al, 2010), where human interference like the construction of reservoirs and discharge of wastewater of any nature, disrupts the river gradient in relation to environmental conditions, changing biotic and abiotic processes (WARD; STANFORD, 1983; WARD; STANFORD, 1995), disrupting the predicted continuum of the system (BRIGANTE; ESPINDOLA, 2003)
On biological communities several researches have been performed in Brazil to evaluate periphyton biomass (FELISBERTO; RODRIGUES, 2005; LEANDRINI; RODRIGUES, 2008; FERRAGUT et al, 2010; MARTINS; FERNANDES, 2011), through determining total dry weight, ash free dry weight (= organic matter), photosynthesizing pigments and total biovolume
Summary
Rivers are open aquatic ecosystems, with unidirectional flow, continuous from headwaters to the mouth, strongly influenced by natural characteristics, which integrates with the adjacent terrestrial environments, forming a more balanced functional unit (MARGALEF, 1983). On biological communities several researches have been performed in Brazil to evaluate periphyton biomass (FELISBERTO; RODRIGUES, 2005; LEANDRINI; RODRIGUES, 2008; FERRAGUT et al, 2010; MARTINS; FERNANDES, 2011), through determining total dry weight, ash free dry weight (= organic matter), photosynthesizing pigments and total biovolume. These data are excellent bases for debates about the organic/inorganic characteristic of the periphyton, as well as its heterotrophic or autotrophic status, besides allowing discussions on the real importance of this community in aquatic ecosystems. The biovolume, when compared with density data, permits to evaluate the actual contribution of algae with larger or smaller size in the dynamic processes of the system (FERNANDES; ESTEVES, 2011)
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