Data of mollusk communities from intermittent rivers in Brazilian semiarid region
Description
Studies on reservoirs in the Brazilian semiarid region identify that the most important factors for the community structuring of these animals are the hydroperiod and its related variables (precipitation, depth, and water temperature) (Almeida et al., 2018; Okumura & Rocha, 2020; Silva et al., 2020b). Therefore, these factors, as well as anthropic impacts, should also structure mollusk communities, in intermittent rivers. It is also assumed that seasonality similarly influences the community structure when analyzing intermittent rivers from the same hydrographic basin. In this sense, the objective of this study is to investigate the influence of determining factors for environmental heterogeneity, linked to the irregularity of hydroperiods and the state of conservation of intermittent rivers in the Brazilian semiarid region, on the structure and dynamics of limnic mollusk communities. When analyzing the data, our results showed that the environmental heterogeneity, characteristic of semiarid regions and that is generated by the irregularity of the hydroperiods, does not contribute to a high species richness and that the communities of limnic mollusks of intermittent rivers in these regions are shaped by the association of environmental heterogeneity with alterations anthropic consequences resulting from the multiple uses of the margin and bed of the rivers. Additionally, the high abundance of M. tuberculata and B. straminea species in the analyzed rivers, influenced by the previously mentioned factors, reinforces attention to problems related to species invasion and the maintenance of the cycle of parasites of medical importance, respectively. Our results also show that it is necessary to expand ecological studies in the semiarid region, since many aspects of the dynamics of mollusk communities, historically accepted as a standard, are singular in this region due to the dynamism and the extreme changes to which they are subject in short periods of time.
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The study was conducted in the southwestern region of Piauí, Brazil. Sampling was performed specifically on the Itaim River near Itainópolis (07º26'49"S; 41º28'42" W) and the Guaribas River near Picos (07º04'37"S; 41º28'01" W). Sampling was conducted monthly at five points along the middle section of each river, within urban areas, spanning from October 2017 to September 2019. Three samples were collected at each point. The distance between the points was approximately 100 m, and between the samples approximately 2 m, to ensure data independence. Samples were collected 1 m from the bank, using a 21 cm diameter sieve with a 0.3 cm mesh, attached to a wooden rod. To remove the samples, the sieve was immersed five times until each point sediment. The procedures for collecting and transporting the mollusks were performed with Authorizations for Activities with Scientific Purposes (Nos 60423-1, 60423-2, 60423-4, 60423-5, and 74421-1, 74421-2, 74421-3) emitted by Biodiversity Authorization and Information System (SISBIO). All species were registered in the National System for the Management of Genetic Heritage and Associated Traditional Knowledge (SISGEN: ACECD6D). The Rapid Assessment Protocol (RAP) was applied for each collection point during the sampling. This protocol attributed a score to characteristics observed on the riverbank and bed. This determined one of the four conservation states: natural (score 68-90), with reduced alterations (41-67), with moderate alterations (28- 40), or with extreme alterations (0-27) in each month of sampling. As additional data, we measured surface temperature and water column depth at each collection point respectively with a precision thermometer and a measuring tape attached to a wooden rod. To evaluate the effect of precipitation on mollusk communities, the volume of rainfall accumulated 30 days before sampling was considered using data from the public platform of the National Institute of Meteorology (INMET), the Agricultural Decision Support System (SISDAGRO), in Picos’ meteorological station (C).