Atributos funcionais de diatomáceas perifíticas: uma abordagem para avaliação ambiental de reservatórios no semiárido

Abstract

Semi-arid reservoirs are influenced by several anthropic impacts (such as sewage discharges, hydrological, physical and chemical changes), and this interferes with the integrity of the water in these systems, often making their use for public supply, fish farming and leisure activities unfeasible. economic. Thus, it is important to evaluate the environmental quality of these systems, mainly using biological communities (peripheral diatoms), comparing metrics (density and biomass) to measure the level of environmental impact. In this context, we evaluated the environmental quality of different impact gradients based on a set of functional attributes and biological metrics (density and biomass) of peripheral diatoms. The study was carried out in four periods (June, September and December and March 2015), in the Poções, Sumé and Cordeiro reservoirs located in the state of Paraíba. Through Principal Component Analysis (PCA), the sites were classified into impact groups (less impacted, intermediate impact and severely impacted), and later related to biological metrics (density and biomass) to determine which one best characterized the gradients. Soon after, the functional attributes of the peripheral diatoms were selected and related to the environmental variables in each gradient of environmental impact. It was observed that biomass was more sensitive to variation in environmental gradients, with species segregation occurring in each gradient of environmental impact. In LD sites (less impacted sites), the species Rhopalodia gibba (28588.46 mm3cm-2) had the highest biomass, whereas in ID sites (intermediate impact sites), the most representative species was Nitzschia dissipata (102714.83 mm3cm -2), while in the SD sites (severely impacted) the largest biomass observed was of the species Gomphonema gracile (89412.84 mm3cm-2). Analyzing the size of the species, it was seen that the largest sizes had a high contribution on the LD sites, while the smallest sizes were present on the sites with the greatest environmental impact (ID and SD). Through RLQ, we observed negative relationships between cell sizes and higher temperatures on LD sites. Positive relationships occurred at the ID sites, between ammonia and water transparency with species with feathered symmetry, as well as negative relationships between centric symmetry and the values of ammonia and water transparency. Still on the ID sites, chlorophyll-a showed a positive relationship between centric species, however, it also had negative relationships with feathered species and raphe. In the SD sites, species with mucilaginous pads and rods showed a positive relationship with depth, and also had a negative relationship with the redox potential. And chlorophyll-a showed a positive relationship with smaller cell sizes. It is concluded that the reservoirs varied when the level of environmental degradation, with these environments being characterized with less impact, intermediate impact and severely impacted. The attributes related to cell sizes and forms of adhesion are the main descriptors of the ecological condition of these systems, being useful in ecological assessments. In addition, it is noticed that biomass is a metric sensitive to the levels of environmental impact, indicating that its use in environmental assessment is important. The need to monitor these systems is evidenced with the proposal of means that minimize the environmental impacts that they are subject.