Cylindrospermopsis raciborskii in the coastal wetland of Anzali

A study on Cylindrospermopsis raciborskii was undertaken in the Anzali Lagoon, a shallow coastal wetland, during the growth seasons in spring and summer of 1992 and 2005. Water samples were collected on a monthly basis from four sampling stations for quantitative and qualitative analyses of phytoplankton species. A Ruthner sampler was used to collect water samples from a depth of 20 cm for the quantitative analyses of phytoplankton while water samples for the identification of plankton species were collected from the entire water column using a plankton net sampler with a mesh size of 25 microns. All samples were fixed in 2% formalin solution. C. raciborski, a freshwater species of the subtropical and pantropical regions was observed in the samples along with 19 other cyanophyta species. Masses of C. raciborskii consisted of filaments that were cylindrical, straight and narrowed towards the end. Cells were cylindrical or barrel shaped 2.5-12(16) × (1.7)2-4 μm. The cross walls were narrow, end cells conical or round. Heterocytes were drop-like with ovoid or pointed terminals. Akinetes were cylindrical or ovoid (7)8.5 - 18(22) μm. Formation of blooms is a distinctive feature of this species and populations of this species produce a kind of cyanotoxin. This species was found abundantly in the western region of the Anzali Lagoon where the pH was above 8. The species C. raciborskii comprising more than 70% of the species composition in the months of July and August was considered the dominant species in this region of the Anzali Lagoon. Owing to the lack of proper environmental management policies, a large amount of sewage (industrial, agricultural and domestic) enters the Anzali Lagoon everyday causing an increase in the organic load and eutrophication of this lagoon thus providing favorable conditions for the occurrence of heavy blooms of C. raciborskii. This will ultimately result in the mass mortality of aquatic organisms.