Abstract
The Caatinga is a semi-arid biome in northeast Brazil. The Paraguaçú River is located in the Caatinga biome, and part of its course is protected by the National Park of Chapada Diamantina (PNCD). In this study we evaluated the effect of PNCD protection on the water quality and microbial community diversity of this river by analyzing water samples obtained from points located inside and outside the PNCD in both wet and dry seasons. Results of water quality analysis showed higher levels of silicate, ammonia, particulate organic carbon, and nitrite in samples from the unprotected area compared with those from protected areas. Pyrosequencing of the 16S rRNA genes revealed that Burkholderiales was abundant in samples from all three sites during both seasons and was represented primarily by the genus Polynucleobacter and members of the Comamonadaceae family (e.g., genus Limnohabitans). During the dry season, the unprotected area showed a higher abundance of Flavobacterium sp. and Arthrobacter sp., which are frequently associated with the presence and/or degradation of arsenic and pesticide compounds. In addition, genes that appear to be related to agricultural impacts on the environment, as well as those involved in arsenic and cadmium resistance, copper homeostasis, and propanediol utilization, were detected in the unprotected areas by metagenomic sequencing. Although PNCD protection improves water quality, agricultural activities around the park may affect water quality within the park and may account for the presence of bacteria capable of pesticide degradation and assimilation, evidencing possible anthropogenic impacts on the Caatinga.
Highlights
The Caatinga is a semi-arid biome located in the northeast of Brazil (3–17°S to 35–45°W)
Our results showed that levels of silicate, ammonia, particulate organic carbon (POC), and nitrite were higher in samples from the unprotected area, whereas levels of dissolved organic carbon (DOC), total nitrogen, orthophosphate, and total phosphorus were higher in samples from the protected areas (Table 1; S1–S3 Figs), allowing the segregation of the samples into two groups (Fig 2)
Samples obtained in the unprotected area were clustered according to season, with the vectors for POC and ammonia grouping samples obtained during the wet season, and vectors for silicate, nitrite, and nitrate grouping samples obtained during the dry season (Fig 2)
Summary
The Caatinga is a semi-arid biome located in the northeast of Brazil (3–17°S to 35–45°W) It occupies almost 900,000 km of the Brazilian territory and is characterized by its vegetation during the dry season, when the leaves fall and white tree trunks and shrubs remain in the landscape [1, 2]. The Paraguaçú River, which is a typical Caatinga river, shows high seasonal volume fluctuations This river supplies water for agricultural and mining activities, as well as several cities. The National Park of Chapada Diamantina (PNCD) was created in 1985 This park, which protects part of the Paraguaçú River course, is surrounded by agricultural land, some of which is in direct contact with the Paraguaçú River
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