Early chemical and ecotoxicological responses of the Varano lagoon (SE Italy) to a flood event

- Flood effects were evaluated in a poorly impacted Mediterranean coastal lagoon.
- The MOT-test, an innovative ecotoxicity test, was used as pre-screening tool.
- The MOT-test response was consistent with chemical data and input localization.
- Runoff resulting from the rainfall event caused a pollutant load in the lagoon.
- Results validate the approach adopted for the post-flood quality assessment.

The effects on coastal lagoons of floods resulting from intense rainfall need to be assessed using a multidisciplinary approach, able to describe in real time the occurrence of changes in sediment quality, anticipating risk situations. In the present study the effectiveness as pre-screening tool of the MOT-test, an innovative bioassay that uses sperm motility as endpoint, has been evaluated; its response has been compared with the sediment chemical characterization, in order to determine the effects of a flood event occurred in the Varano lagoon, a poorly anthropized Mediterranean coastal lagoon.The MOT-test effect percentages ranged from 10% to 30%, fully reflecting data from chemical analyses. Organic pollutants showed concentrations always below the critical levels. The highest metal values were found in the south-eastern area; however, only for few metals (mainly Cd), and in few sites, they reached the limits defined by the sediment quality guidelines; consistently, these sites are located in the area where a higher stressors' impact was expected and the highest MOT-test effect percentages were recorded.In conclusion, even if results exclude the occurrence of serious contamination events as a consequence of the flood, the runoff resulting from the intense rainfall event has caused a pollutant load in the lagoon, consistent with the localization of the main anthropogenic activities in the catchment area.Moreover, preliminary data indicate the validity of the approach adopted for the post-flood quality assessment, proving the usefulness of the MOT-test as early-screening tool in the case of extreme events.