A Comunidade planctónica e o estado trófico da Lagoa Nhambavale, província de Gaza

Abstract

The plankton community is a group of pelagic organisms that includes two categories: phytoplankton and zooplankton. Phytoplankton form the basis of the trophic chain in aquatic ecosystems and are primarily responsible for the production of dissolved oxygen in water. Zooplankton are responsible for the flow of nutrients and act as an intermediate link between producers and higher trophic levels. The Nhambavale lagoon is considered the most important for the locality of Chidemguele due to its size (35 km long) and the services it provides, such as tourism, fishing, and domestic water use. Due to the importance of this aquatic ecosystem, the present study was carried out with the aim of contributing to the knowledge of the ecology of the plankton community and the trophic state of the Nhambavale Lagoon. Sampling took place in 2021, during the dry season. The following physicochemical parameters were determined: water transparency, temperature, pH, salinity, dissolved oxygen concentration and conductivity. Regarding the biological parameters, plankton diversity and abundance were determined, and the distribution of plankton was related to the environmental parameters and the trophic state of the lagoon. 48 genera of phytoplankton were identified, grouped into 5 Divisions, namely Bacillariophyta (24), Chlorophyta (11), Cyanophyta (9), Dynophyta (3), Euglenophyta (1) and in the zooplankton group, 11 genera were identified, grouped into 3 Divisions, namely Rotifers (5), Cladocerans (4) and Copepods (2). In particular, the area designated as E was the one that presented the highest values ​​of diversity indices for phytoplankton and zooplankton. The Jaccard Similarity Index indicated that there is partial similarity between the plankton species in areas A and E. The ONE-WAY ANOVA test showed that there were significant differences between the plankton species in the sampling areas. The lagoon was classified as ultra-oligotrophic. Temperature, salinity, pH and dissolved oxygen appear to be the environmental parameters that influence the distribution of the plankton community. It is recommended that more similar studies be carried out over a longer period in order to capture possible changes in the two seasons and to obtain solid knowledge about the physical, chemical and biological conditions and, consequently, about the conservation status in order to develop appropriate management and conservation measures for this ecosystem(TRADUÇÃO NOSSA)