influência da salinidade na estrutura taxonômica e funcional da comunidade fitoplanctônica em reservatórios tropicais

Abstract

Knowing the mechanisms (processes) that regulate the structure of communities helps in the production of more effective strategies for the management of aquatic ecosystems, since the increase/reduction of diversity is related to the functioning of ecosystems. As a way of measuring changes in biodiversity, taxonomic and functional approaches are applied, the latter being able to demonstrate complementary responses, due to its connection with the characteristics that determine the growth, reproduction and survival of species. Currently, in the context of climate change, which has the potential to intensify the salinization process in freshwater ecosystems, there is an effort to determine the mechanisms that control spatial and temporal changes in communities. Salinity can act as an environmental filter, selecting the functional characteristics of the species, in addition, within the reservoirs of the semi-arid region, the increase in water intake and the particularities of the region make these environments susceptible to the salinization event, which consequently can affect the ecosystem services provided by these water bodies. Therefore, the present study aims to evaluate the variation in the taxonomic and functional structure of the phytoplankton community along a salinity gradient in tropical reservoirs. Our hypothesis is that salinity has greater relative importance in the dry season, with the gradient promoting a decrease in taxonomic and functional diversity. In addition to selecting tolerant species, such as cyanobacteria, which have filamentous morphology and heterocytes as functional characteristics. The taxonomic and functional responses of thirteen reservoirs distributed on the Borborema plateau in the rainy and dry season were evaluated in relation to their salt concentrations, in addition, diversity metrics and the Threshold Indicator Taxa Analysis (TITAN) analysis were performed for taxonomic patterns and functional. As a result, salts had greater relative importance in the dry season only for functional patterns, salinity also had negative effects for most taxonomic and functional metrics. In addition to selecting as positive indicators of the salinity gradient, the species of the Chlorophyceae group. And as indicative functional characteristics, the salts selected unicellular species of smaller sizes with silicified wall, replacing colonies, filamentous of larger sizes. These results highlight the need to consider the salinization process of water bodies intended for public supply, as this process can alter the base organisms in the aquatic food chain.