Arsenic Pollution Measured with an online Monitoring System using Daphnia

Abstract

Arsenic is a common pollutant in many water reservoirs around the world and is the cause of human mortality in many countries. The microcrustacean Daphnia can be cultured easily and is sensitive to many toxic substances including As. This bioindicator is the basis of the Daphniatox instrument which uses computerized image analysis of swimming organisms in real time. Fourteen endpoints are evaluated including motility, swimming velocity, orientation with respect to light or gravity as well as several cell size and form parameters. Using automatic track analysis of a large number of organisms warrants high statistical signifi cance. In a vertical swimming fl ask Daphnia shows pronounced gravitaxis moving upward and downward while in a horizontal fl ask the organisms swim in random directions. Exposure for up to 72 h to 0-10 mg/L NaAsO 2 (corresponding to 0-77.5 μM As) according to the standard NBR 12713 protocol showed an EC 50 value of 5.97 mg/L for motility after an exposure time of 7 h and 4.82 mg/L after 26 h. Comparably, the EC 50 value for velocity was 5.32 mg/L after an exposure time of 7 h and after 26 h it was 3.05 mg/L. As expected, the length of the organisms did not change over the exposure time because of their rigid exoskeleton, but the circularity which corresponds to the area divided by the perimeter squared decreased which is interpreted to be due to a release of water. The results indicate that this method provides a reliable, fast and inexpensive test for arsenic toxicity in drinking water from wells and reservoirs.

Trophic-Level Interactive Effects of Phosphorus Availability on the Toxicities of Cadmium, Arsenic, and Their Binary Mixture in Media-Exposed Scenedesmus acutus and Media and Dietary-Exposed Daphnia pulex

“…There are currently no studies that explain why there may be an increase in responses of the selective behavioral parameters induced by dietary-As exposure in a media/environment with limited P condition. However, in the study by Häder and Erzinger, they observed differential effects (decrease or no effect) on the 14 swimming behavioral end points of D. magna exposed to media As.…”

“…magna exposed to media As. Häder and Erzinger attributed the reduction in swimming behavior to oxidative stress and partly to feeding since the organisms were not fed during the experimental period. The responses in selective behavioral parameters of D.…”

“…pulex. We investigated these two freshwater sentinel species because both organisms are very sensitive to environmental pollution and are essential bioindicators for ecological risk assessment and environmental biomonitoring. , Furthermore, data from this study will inform decision makers of the need to incorporate complex ecological interactions, elemental cycling, and interactive effects of natural stressors such as resource limitation and contaminant stressors in their decision-making process for setting realistic target concentrations for environmental contaminants.…”