The bright side of a weed: Daphnia as a biosensor on the assessment of cyanotoxins (saxitoxins) phytoremediation by the invasive water hyacinth (Pontederia crassipes)

Author(s): Mauro Vilar
Email (s):
Institution or organization of origin: Federal University of Rio de Janeiro
Country: Brazil


Cyanobacterial blooms are a worldwide issue mainly due to cyanotoxins that compromise water quality and affect aquatic organisms. Several methods are employed on contaminants remediation in water, but the use of aquatic plants has proven to be a promising ecofriendly alternative. Although invasive, the water hyacinth (Pontederia crassipes) has been reported removing several pollutants and improving water quality. Thus, we aimed to indirectly assess the phytoremediation of saxitoxins by the water hyacinth, through toxicity tests with the tropical zooplankton Daphnia laevis. Phytoremediation experiment was carried out with a nutrient-enriched culture medium contaminated with extract of the saxitoxin-producing cyanobacterium Raphidiopsis raciborskii at a saxitoxin equivalent concentration of 100 µg L-1. Plants (n=4) were incubated in beakers with contaminated medium and before/after 7 days it was tested for toxicity in Daphnia. 96h-toxicity assays were run to test whether the water hyacinth was able to reduce medium toxicity. Neonates were placed in tubes and tested for the medium and its controls incubated with and without plants. Overall, the contaminated medium caused a 15-37% reduction in Daphnia survival. However, in the presence of plants, only a 1.8% reduction in survival was observed, indicating that the water hyacinth improved the quality of the medium. Similarly, in the absence of saxitoxins the animals showed a 95% survival. A higher somatic growth rate was also displayed by the zooplankter when kept in the medium treated with the plant. In conclusion, assays with D. laevis suggested that the water hyacinth was able to improve the medium quality.

View the author’s explanation: