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Data from: Freshwater ecological quality assessment of the gold mining Mashcon watershed, Cajamarca - Peru

Citation

Mercado-Garcia, Daniel et al. (2022), Data from: Freshwater ecological quality assessment of the gold mining Mashcon watershed, Cajamarca - Peru, Dryad, Dataset, https://doi.org/10.5061/dryad.ngf1vhhwj

Abstract

These data were generated to investigate the aquatic community gradients across different types of anthropogenic impacts (reference, mining, rural and urban) and Andean environmental gradients (headwaters, midstream and downstream) in the Mashcon watershed. 

The macroinvertebrates' taxa abundance and abundance of traits modalities serve as biological values. The latter in combination with abiotic measurements of the freshwater habitats (i.e. physicochemical water quality and hydromorphology) constitute the ecological data.

The values were obtained from river sediments (macroinvertebrates collection), water samples for laboratory analyses, field protocols and in-situ water quality measurements at 40 sites, wherein 6 were downstream of the gold mine’s artificially recharged headwaters, 8 sites at near-pristine headwaters tributary streams, 14 sites at midstream rural areas and 12 sites at downstream urban areas (sample grouping information is shown in the Field_protocol.xlsx file).

Methods

Freshwater macroinvertebrates were collected with a standardized kick-sampling method, by simultaneously kicking and sweeping the river substrate using a hand-net (frame size 20 × 30 cm; mesh size 500 µm) to sample as many microhabitats as possible, and for 5 minutes at each location (Acosta et al., 2008). Macroinvertebrates were collected from the substrate samples and stored in 75% ethanol. The taxa were counted and identified at the family level by an expert taxonomist, except for the Acari subclass. The level of taxonomic resolution was selected for being sufficient to detect environmental and biodiversity gradients of freshwater macroinvertebrates communities (Mueller et al., 2013).

The macroinvertebrate taxa counts were complemented with traits information. Eight traits were selected according to the availability of databases of sufficient taxonomic resolution and suited to Andean ecosystems. Traits of macroinvertebrates were obtained from Tomanova et al. (2008), Tomanova and Usseglio-Polatera (2007) and Tachet et al. (2000). These consisted of five biological (maximal body size, food source, body form and respiration) and three ecological (mobility and attachment to substrates, feeding habits, saprobity and pH preferendum) traits. A traits matrix was created containing the modalities’ affinity scores for 43 taxa (supplementary ‘taxa-to-trait.xlsx’ file). Six families (Blephariceridae, Chordodidae, Curculionidae, Gripopterygidae, Hyalellidae and Hydrobiosidae) were excluded due to lacking traits information. A fuzzy coding procedure was applied to estimate the weighted traits abundance, allowing multiple affinities for certain taxa. For example, Baetidae feeds by scraping fine particulate organic matter, microphytes and microinvertebrates from surfaces, but it is also able to feed on deposited debris sometimes. Thus, considering the modalities ‘x’, ’y’ and ‘z’ for a given trait, and supposing there are 100 individuals of a taxon, and knowing that this taxon has an affinity of 3 for modality ‘x’, 1 for modality ‘y’ and no affinity for modality ‘z’; then the modality ‘x’ was given an abundance of 75 counts, modality ‘y’ 25 counts, and modality ‘z’ 0 counts. In addition, a dominant-trait coding procedure was applied to the initial traits matrix, disregarding the non-dominant trait modalities. In the above-mentioned Baetidae example, modality ‘x’ dominates the others, thus the dominant-trait approach assigns 100 counts for modality ‘x’. If more than one modality were equally dominant in a taxon, the affinity scores had to be assigned by equal fractions totaling 1, allocating equal counts to the equally dominant modalities. In both quantification methods, the abundance per sampling site was estimated by adding up the modality counts from each taxon.

Physicochemical measurements of temperature, conductivity, pH, turbidity, chlorophyll-a and dissolved oxygen (DO%) were taken using YSI® multiparameter probes. Hach-Lange® laboratory test kits were used for measuring chemical oxygen demand (COD), phosphorus, nitrate, nitrite and ammonium. Sulphates were measured with Hach® SulfaVer® 4 kits. Filtered (0.45 µm) freshwater samples were collected in 50 ml falcon tubes, and acidified to 1% HNO3 for dissolved metal analyses. The latter step was repeated without filtering for total metal analyses. A Thermo Fisher Scientific® iCAP 6000 ICP-OES® was used to measure concentrations of barium, copper, manganese and zinc. Geocoordinates and altitude were recorded using a Garmin eTrex® HC series GPS.

Funding

VLIRUOS, Award: ZEIN2013PR395

Consejo Nacional de Ciencia, Tecnología e Innovación Tecnológica, Award: 002-2016-FONDECYT