Dataset - Manuscript "Density of Limnoperna fortunei larval stages in a cascade of subtropical reservoirs"

Description

This data set was used in the manuscript "Density of Limnoperna fortunei larval stages in a cascade of subtropical reservoirs: spatiotemporal variation and environmental influences," which is being submitted for publication.

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Samplings were conducted monthly from December 2018 to November 2019 at five points in each large Hydroelectric Power Plants (Campos Novos, Barra Grande, Machadinho, Itá, and Foz do Chapecó) located at the upper Uruguay River region, that together form a cascading system. Water temperature, electrical conductivity, dissolved oxygen concentration, and pH were measured in situ at each point with a multiparameter meter (YSI-85). In addition, water transparency was evaluated using a Secchi disk, the euphotic zone depth (Zeu) was estimated by multiplying the Secchi depth by 2.7, and the maximum depth (Zmax) was the total depth obtained “in situ.” Water samples were collected to determine the concentrations of dissolved cations and anions and the total phosphorus and nitrogen. The quality control of water chemicals followed the Standard Methods for the Examination of Water and Wastewater (APHA, 2012), with duplicates for each sample. For ion concentrations, the water samples were filtered (glass fiber filter Whatman GF/F, nominal porosity of 0.7 μm) and preserved with thymol for subsequent analysis using a flow injection analysis (FIA). Absorbance measurements, as well as the recording of the electronic spectra of the aqueous solutions of TP and TN, were performed in a Micronal B502 spectrophotometer, following the methodology of Valderrama (1981). The precipitation was presented as the accumulated precipitation seven days before the sampling day. Limnoperna fortunei larvae samples were collected by horizontal trawls (30 cm diameter) using a 68 µm mesh opening, with a calibrated flowmeter attached between the center and the rim of the mouth, to estimate the volume of water filtered. Samples (n=285) were analyzed and fixed with buffered formaldehyde (with borax and sugar) at a final concentration of 4.0 % since 15 were lost. The different larval stages were identified, separated according to size and larval shell type, and quantified. Plankton samples were collected monthly, concomitantly with water samples. Real-time PCR protocols for L. fortunei quantification were applied to detect the species in e-DNA.

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