Baixo Sabor: Phytoplankton - Ecological Monitoring Program [2016]

Sampling followed the procedures defined by the Portuguese National Water Authority in the protocol for sampling and analysis of phytoplankton quality element under the Water Framework Directive. In each sampling campaign, a two-step procedure was adopted. First (a) a water column profile for temperature and dissolved oxygen was perform using a multiparametric probe (b) the water transparency was measure using a Secchi disk (Secchi depth), and (c) the depth of the euphotic zone was estimated (2.5 x the Secchi Depth). Second, (a) water samples were collected, using an integrated water sampling device (hydrobios), from the surface to euphotic zone maximum depth; (b) samples were preserved in loco with Alkaline Lugol’s solution and transported in 48 hours to the laboratory. The samples were stored in a dark and cold place (1º to 4ºC) for a maximum period of 6 months. They were periodically examined and recompleted with Alkaline Lugol’s solution, whenever needed. In the lab, the analysis for identification (to the lower possible taxonomic level), quantification (cells/mL) and biovolume (mm3/m3) were carried out using sedimentation chambers and an inverted microscope (Utermöhl technique), as described in EN 15204:2006 (Water quality - Guidance standard on the enumeration of phytoplankton using inverted microscopy (Utermöhl technique)) and EN 16695:2015 (Water quality - Guidance on the estimation of phytoplankton biovolume).