A white Secchi disk with a diameter of 30 cm with a lead weight at the bottom was used during the field campaign aboard the R/V Dallaporta between 14 and 27 March 2021. At selected station the Secchi disk depth was recorded as a relative measure of water clarity, detailed approach is presented in open-access (Garaba et al., 2015; Wernand, 2011). The Secchi disk is lowered until it is no longer visible and the depth at which it disappers is recorded from the surface. The measurements is then used to describe water clarity as clear or turbid using the Secchi disk depth in meters as an index. Stations were located in the Po Delta and coastal waters of the Northen Adriatic Sea.

The PoPLAST 2021 cruise on R/V Dallaporta was financed by the Consiglio Nazionale delle Ricerche.