Cyst-based toxicity tests XV--application of ostracod solid-phase microbiotest for toxicity monitoring of...

A new "culture/maintenance-free" microbiotest has recently been developed for "direct-contact" toxicity determination of contaminated sediments. The 6-day Ostracodtoxkit F makes use of the neonates of the ostracod crustacean Heterocypris incongruens hatched from dormant eggs (cysts). The new low-cost assay has already been applied in three studies on river sediment from Flanders (Belgium) and from Canada and was found to perform comparably to the 10-day Hyalella azteca and Chironomus riparius tests in detecting and quantifying sediment toxicity. Taking into account that sediments are in fact underwater soils, the ostracod microbiotest was tentatively applied on 15 contaminated soils from Flanders (Belgium), and its sensitivity (based on mortality as the test criterion) was evaluated in comparison to the 28-day reproduction inhibition assay with the springtail Folsomia candida. The results revealed that the ostracod test species was as sensitive as or, in several samples, even more sensitive than the springtails. Leachate experiments on the same soil samples also showed that in most cases ostracod mortality was a result of the (nonsoluble) toxicants bound to the solid-phase particles, rather than of those that had dissolved in the water phase. Providing confirmation of these first findings through additional studies, the new culture/maintenance-free ostracod microbiotest seems to have good potential as a low-cost and user-friendly tool for routine toxicity monitoring of contaminated soils.