Growth rates of microalgae encapsulated in calcium alginate as a possible indicator of the trophic state of aquatic ecosystems

Abstract

Growth rates of microalgae encapsulated in calcium alginate as a possible indicator of the trophic state of aquatic ecosystemsThere are many applications for encapsulated algae but the use as an indicator of the trophic state of aquatic environments has not been explored in-depth. In this paper, the effects of different nutrient concentrations in two encapsulated algae, Scenedesmus obtusus, and Parachlorella kessleri, were analyzed both in the laboratory (batch systems) and in field experiments; the latter were carried out in four wetlands in the city of Bogotá. Linear models with heterogeneous variance (LMHV) were used to assess differences in the algal growth rates under different nutrient concentrations, and multivariate general linear models (MGLM) were used to relate the influence of abiotic factors under field conditions. The laboratory results showed an increase in growth rates with higher nutrient concentrations, while the field results were less clear, but differences were observed in physical variables between the wetlands and the growth rates over time. The combined analysis revealed variability in the growth rates under field conditions, making it difficult to relate each wetland with a respective nutrient concentration. These results are preliminary, and more research is needed, but they suggest that encapsulated algae growth rates could be used to evaluate the trophic status of aquatic environments.