Comunidade fitoplanctônica da lagoa do Tabapuá, Caucaia (Ceará, Brasil)

Abstract

Phytoplankton has great importance for the aquatic ecosystem, being the main primary producer. It is found in the most diverse environments, from those freshwater to the marine ones, having great influence the physical, chemical and biological factors in its composition. The objective of this work was to verify the composition of the phytoplankton community of the Tabapuá Laker, Caucaia/CE, analyzing the species qualitatively and determining the diversity, richness and equability, as well as the trophic index of the lagoon. The collections were monthly, from March to October 2018. The plankton net was used, filtered 100 L, concentrated to 10 mL and analyzed 0.1 mL in Labec. Water was also collected for determination of physical and chemical parameters (water temperature and transparency, pH, dissolved oxygen, ammonia, nitrite and phosphorus). The results showed that the Tabapuá Laker presents stable and normal levels of the physical and chemical patterns, except for the depth, because during the drought period there was a marked reduction of its water volume. It was observed an increase in the amount of phytoplankton during the dry period, probably due to the reduction of macrophytes, such as the aguapé, which in the rainy season completely covered the lagoon surface. The diversity and species richness of the phytoplankton was low, a non-significant equability and dominance of Pediastrum simplex. In general, the lagoon presented good water quality and considered oligotrophic.