No abstract

The study of phytoplanktonic organisms has grown in recent times, as a consequence of its importance in several aquatic ecosystems, both in continental and marine environments. In stabilization ponds, for example, they act in the biological treatment of sewage. These ponds are an eutrophic environment, characterized by a considerable growth of phytoplankton. To study the phytoplankton composition in such ponds, samples were collected in a facultative pond in a sewage treatment station, located in Barbalha (Ceará State, Brasil), from March/2006 to January/2007. The samples were analyzed in vivo and fixed, then indexes of abundancy, frequency, diversity and equitability were calculated. Cyanophyta, Euglenophyta, Bacillariophyta and Chlorophyta species were identified. The most abundant species and present in all samples were Planktothrix isothrix (Skuja) Komárek et Komárková. and Microcystis aeruginosa (Kütz) Kütz., which are both toxic species. In both dry and rainy seasons, variation of the phytoplankton composition wasn't observed and the high presence of P. isothrix resulted in a low diversity. The phytoplankton groups observed are typical of eutrophic environments.

Macrophytes play several roles in aquatic ecosystems, including the provision of habitat for many aquatic organisms, especially the periphyton.

Studies considering the functional traits of organisms, populations, and communities functional indices increase the understanding of many factors on ecosystem functioning. Here, we analyze the predation effect (by fi sh) on zooplankton functional diversity and the effects of biomass and density of periphytic algae on zooplankton feeding type trait and body size. We expect that intense predation by fi sh on zooplankton leads to higher values of zooplankton functional diversity and that food resource will be positively related to the abundance of zooplankton trait and body size.For that, microcosms were established (T1-fi sh-absence, and T2-fi sh-presence, both with periphytic algae as food). We observed that fi sh presence decreased zooplankton functional diversity through modifi cations in the availability of nutrients and algae, through the middle-out effect. We also observed that body size had a negative relationship with the food resource, reaffi rming that high food availability in subtropical lakes is linked to small-bodied zooplankton. The raptorial copepods covariate positively with the periphytic algae, which was an alternative food resource and, in this case, the main form of carbon input into the system. In this study, omnivorous fi sh reduced zooplankton functional traits, which can alter the energy stock and energy fl ow in aquatic ecosystems.

Aim A taxonomic study of the species of the genus Cosmarium Corda ex Ralfs (Desmidiaceae) was conducted in two lentic environments of the Upper Paraná River Floodplain (Garças and Patos lakes). Methods The samples were collected in November 2016. Two petioles of Eichhornia azurea (Sw) Kunth were sampled and analyzed qualitatively. Results Six species, nine varieties, and three forms were identified, with five taxa being common to both lakes, nine in Garças Lake, and four in Patos Lake. Of this, thirteen species represent the first records for the floodplain environment. Conclusion This study contributes to the knowledge of the biodiversity of this region, providing support for future ecological studies and biomonitoring.