A Survey on a Persistent Greenish Bloom in the Comacchio Lagoons (Ferrara, Italy)

Abstract

The Comacchio lagoonal system has been affected for years by a persistent phytoplanktonic bloom which makes the waters greenish. Surveys carried out from April 1995 to February 1996 showed that this bloom was caused by a Synechococcus sp. and by an Eustigmatophycean belonging to the genus Nannochloropsis . However, while the Synechococcus sp. was mainly present in the summer, Nannochloropsis was always present with constant density values. Moreover, this species shows many ultrastructural features and a pigment composition similar to those of Nannochloropsis spp. and reproduces by autospores. The 18S rRNA gene sequence of this strain is identical to those of five strains of Nannochloropsis gaditana . In this paper, besides phytoplankton (including picophytoplankton), we also report the data of the main chemico-physical parameters. Among them, the salinity and nutrient values showed an anomalous seasonal trend.