Algal community analysis in a waste stabilisation pond

Our knowledge on the algal community structure in waste stabilisation ponds is limited and it is unclear how physical-chemical changes affect the algal community structure and the treatment performance of waste stabilisation ponds. In the present paper we studied the spatial distribution of the algal community in a waste stabilisation pond in Cuenca (Ecuador) and found that the distribution was associated with the BOD concentration of the system. At the upstream end of the facultative pond where the BOD value is relatively high (74 mg L−1), the community is dominated by motile algal species such as Euglena and Cryptophytes. More downstream, the algal community is more evenly distributed (G = 0.26 > 0.18) and also non-motile species such as Chlorophytes and Chrysophytes are present. Throughout the ponds, the reduction of motile algal species was associated with the decrease in BOD concentration. The dominance of Chlorophyta, Chrysophyta and Euglenophyta was highly associated with BOD concentration. Furthermore, it was concluded that the algal abundance (45541 cells mL−1), diversity (D = 0.85), evenness (G = 0.26) and richness (20.97) of the community in the maturation pond were higher than those of the facultative pond. The results of this research are valuable for a better understanding of the algae-based processes in waste stabilisation ponds.