The first floristic study of freshwater dinoflagellates (Dinophyceae) in Colombia

The first comprehensive study of dinoflagellate flora and their related environmental variables in reservoirs, swamps, and an insular lake of Colombia is presented. Fourteen Colombian water bodies were assessed. In each, water temperature, electric conductivity, oxygen saturation, turbidity, and apparent color were the physical and chemical variables measured. Twelve dinoflagellate taxa were recorded, indicating a considerable richness compared to similar surveys. Ensembles recovered showed a spatial structuration mediated by the type of the water bodies (reservoirs and swamps); environmental variables and species richness explained equally the differences among the water bodies. The dinoflagellate flora showed altitudinal segregation, with intermediate altitude systems displaying the highest richness values. A brief discussion about the geographical distribution of the species collected is offered. The study contributes to the knowledge of the ecological aspects of dinoflagellate flora and outlines preliminary biodiversity tendencies of ensembles in tropical water systems.

Evaluation of physical and chemical variables of organic substrates in a hydroponic system for strawberry (Fragaria ananassa Duch)

This project is presented as an innovative and clean alternative that optimizes the use of small areas for strawberry (Fragaria ananassa Duch) production in the department of Nariño. This research was conducted at the Centro Internacional de Producción Limpia Lope -SENA- Regional Nariño, with the aim of evaluating physical and chemical variables of organic substrates such as coconut fiber, rice husk, and their mixtures for strawberry (Fragaria ananassa Duch) variety Albión production in a hydroponic system. Six treatments and four repetitions were performed; the treatments were 100% rice husk, 70% rice husk and 30% coconut fiber mixture, 50% of each of the substrates used, a mixture of 70% coconut fiber and 30% rice husk, 100% coconut fiber, and a control in soil with plastic cover. A comparative analysis was made between the average values obtained in the initial stage and the final stage of the experiment, evaluating physical and chemical properties such as bulk density, real density, gravimetric moisture, granulometry, pH, and electrical conductivity. The experiment showed that taking initial and final measurements of the substrates allows adequate monitoring for optimal crop development since a substrate with a high percentage of particles in the sieve <0.25, electrical conductivities greater than 2000 µS.cm-1, and an increase in bulk density can produce salinization and compaction, negatively impacting the crop.

Macroinvertebrates responses based on chemical and physical variables in urban streams

The Land uses and occupations around small watersheds generate negative impacts such as deterioration of water quality, environmental simplification, reduced availability of habitats for species, and loss of biodiversity. Benthic macroinvertebrates are an important aquatic community and are widely used in environmental monitoring actions in aquatic ecosystems, including urban streams, which are still little studied in Brazil. In our study, an urban headwater basin (Monjolinho River Basin) was studied on the benthic community structure, together with the physical and chemical variables of the water, as an environmental monitoring tool calculated by RHDEP, TSI, BMWP indexes and abundance-biomass curves. The results showed a gradient of environmental quality, where the best environments are a consequence of preserving the vegetation cover. These environments (Espraiado and Canchim) present groups sensitive to environmental degradation (Ephemeroptera, Plecoptera and Trichoptera), greater diversity and a better structure in the respective benthic macroinvertebrate assemblages. Among the streams sampled, one is very clean, four are moderately polluted, and one is severely polluted. Thus, considering that these streams’ waters are essential for public supply, actions to clean up and recover degraded environments are urgent and a priority.

Predictive Models to Estimate Carbon Stocks in Agroforestry Systems

This study aims to assess the carbon stock in a pasture area and fragment of forest in natural regeneration, given the importance of agroforestry systems in mitigating gas emissions which contribute to the greenhouse effect, as well as promoting the maintenance of agricultural productivity. Our other goal was to predict the carbon stock, according to different land use systems, from physical and chemical soil variables using the Random Forest algorithm. We carried out our study at an Entisols Quartzipsamments area with a completely randomized experimental design: four treatments and six replites. The treatments consisted of the following: (i) an agroforestry system developed for livestock, (ii) an agroforestry system developed for fruit culture, (iii) a conventional pasture, and (iv) a forest fragment. Deformed and undeformed soil samples were collected in order to analyze their physical and chemical properties across two consecutive agricultural years. The response variable, carbon stock, was subjected to a boxplot analysis and all the databases were used for a predictive modeling which in turn used the Random Forest algorithm. Results led to the conclusion that the agroforestry systems developed both for fruit culture and livestock, are more efficient at stocking carbon in the soil than the pasture area and forest fragment undergoing natural regeneration. Nitrogen stock and land use systems are the most important variables to estimate carbon stock from the physical and chemical variables of soil using the Random Forest algorithm. The predictive models generated from the physical and chemical variables of soil, as well as the Random Forest algorithm, presented a high potential for predicting soil carbon stock and are sensitive to different land use systems.

Can zooplankton species be used as indicators of trophic status and ecological potential of reservoirs?

The European Water Framework Directive implements the policies to achieve a good ecological status of all European waterbodies. To determine the ecological potential in freshwater environments, abiotic (morphology, physical and chemical variables) and biotics (algae, fishes, etc.) metrics are used. Despite their importance in trophic web, zooplankton was not included as one of the Biological Quality Elements (BQE) to determine the water quality. In the present research, we studied the zooplankton species that can be considered as indicators of trophic status and ecological potential for more than 60 water reservoirs. The data were obtained from more of 300 samples collected during 10 years from reservoirs at Ebro River watershed, which is the largest basin in Spain. According to their physicochemical and biological elements, the trophic status and ecological potential of these reservoirs were established. More than 150 zooplankton species were identified during the study. The results from this research indicate that species that are related with low water quality are: Acanthocyclops americanus, Ceriodaphnia spp., Daphnia cucullata, Daphnia párvula, Diaphanosoma brachyurum, Brachionus angularis, Keratella cochlearis and Phompolyx sulcata. An indicator of moderate quality was Bosmina longirostris, while Daphnia longispina, Ascomorpha ovalis and Ascomorpha saltans were considered as indicators of good water quality. The data obtained suggest that zooplankton species can be used as a valuable tool to determine the water quality status and should be considered, in a near future, as one more of the BQE within the WFD metrics.

Morphology and Ecological Characteristics of Paracyclops Novenarius Reid, 1987: A Cyclopoid Copepod Inhabiting a Highly Contaminated Aquifer in Central-North of Mexico

This work reports the freshwater copepod Paracyclops novenarius, in a water body with high arsenic concentrations. Morphologic analysis, abundances, body size of the copepod and physical and chemical variables of the water (including arsenic concentrations) were evaluated in two different climatic seasons (rainy and dry). Morphological analysis showed that the high arsenic concentrations do not affect the morphology of P. novenarius, including all its development and adult instars. The highest abundances of this species were found in the dry season for all development stages, with values ​​of 1.51 and 1.50, 4.46, 0.21 ind/L-1, for nauplii, copepodites, females, and males, respectively. However, these values are lower than other aquatic systems of the region and the world, without polluting agents. The highest arsenic concentration was found in the dry season (58 mg/L-1) and the lowest during the rainy (54.5 mg/L-1). The body size of the analyzed organisms was larger in rainy compared to dry, with an average of 637.2 ± 42 µm for females and 650 ± 37 µm for males. A Mann-Whitney U test showed significant differences in lengths by season and by arsenic concentration (U = 1284.5, U = 1284.5; p < 0.05). The results of this study could provide information for environmental impact assessments on aquatic systems.

FIRST EVIDENCE OF POTENTIAL TOXIC CYANOBACTERIA IN THE WATER-SEDIMENT INTERFACE OF A TROPICAL DRINKING WATER RESERVOIR

The Nostocales and Chroococcales cyanobacteria can produce potent cyanotoxins and survive in deep zones of aquatic ecosystems by the formation of morphologically distinguishable resistance structures and temporarily latent colonies in sediments. The purpose of this study was to determine the presence and density of Nostocales and Chroococcales with toxic potential in the water-sediment interface. During four samplings in three locations of the drinking water reservoir Riogrande II, some physical and chemical variables and chlorophyll a concentration of different spectral groups were measured, density of cyanobacteria was established by conventional microscopy, and mcyD and mcyE genes were detected by PCR. The environmental factors correlated with the abundance of cyanobacteria in the water-sediment interface were pH, total phosphorus, and iron. The highest chlorophyll concentration was provided by Chlorophyceae, while chlorophyll from the cyanobacteria spectral group fluctuated between 0.07 and 3.6 mg/L in field samples. About 86 % of the total cells number corresponded to the Microcystis complex while the Nostocales represented just 3.35 %. It was possible to find evidence for cyanobacteria with toxic potential in the three sampling points through the detection of the mcyD and mcyE genes. The presence of these cyanobacteria is possibly related to their life cycle and the resuspension processes caused by the way river water enters the reservoir. Additionally, this is the first evidence that demonstrates the importance of the water-sediment interface as a reservoir of cyanobacteria with toxic potential, since they can recolonize the water column in ecosystems that supply drinking water.

Applicability of DNA-based identifications for the WFD-guided monitoring using macroinvertebrates: a large-scale DNA metabarcoding study for implementing routine ecological status assessments in Iberian rivers

Over the last decade, remarkable improvements have been made in the field of metabarcoding-based tools for routine ecological status assessments. However, important issues are yet to be solved to fulfil the European Water Framework Directive (WFD) requirements and standards. These limitations, which include problems related to e.g. the lack of a complete COI macroinvertebrate barcode database available for the Iberian Peninsula Murria 2020, or the scarce recovery of specific taxa due to DNA extraction and/or PCR amplification bias, are especially difficult to overcome for routine freshwater macroinvertebrate monitoring. For that purpose, a large-scale study is on going to test how metabarcoding data can infer existing macroinvertebrate morphotaxonomy-based biotic indexes and ecological status of Iberian rivers. Freshwater macroinvertebrates were selected as a Biological Quality Element and identified by using both morphological and metabarcoding approaches. The mitochondrial gene for cytochrome c oxidase subunit I (COI) was used as a DNA Barcode. Taxonomic coverage, taxonomic composition metrics and ecological status obtained from both approaches were analysed. Physical and chemical variables obtained during the routine biomonitoring, as well as other ecological parameters including biodiversity indexes, were also assessed. Multivariate data analysis of these environmental and biotic data obtained from both approaches were compared. Results seem to support the hypothesis Kuntke 2019 that the DNA-metabarcoding approach might deliver similar quality assessments results to the morphological approach, though some refinement must be done at the different steps of the process prior to establish a reliable procedure allowing the alternative use of both methods giving similar results for the ecological status classes marked by the WFD.

Variability in Environmental Conditions Strongly Impacts Ostracod Assemblages of Lowland Springs in a Heavily Anthropized Area

The Po river plain (Northern Italy) hosts artificial, lowland springs locally known as fontanili, which provide important ecosystem services in an area dominated by intensive agricultural activities. Here we present a study carried out in 50 springs. Each spring was visited once from October 2015 to January 2016. The sampled sites were selected to include springs studied in 2001 and 2004, to evaluate changes in water quality and ostracod assemblages that possibly occurred over a period of 10–15 years, and explore the relationships between ostracod community composition and water physical and chemical variables. Our results showed a decrease in the chemical water quality especially, in springs south of the Po river, evidenced by high nitrate levels. Most of the studied springs showed a relevant decrease in dissolved reactive silica, probably related to recent transformations of either agricultural practices or crop typology. Ostracods were mostly represented by common and tolerant species, and communities were characterized by low alpha diversity and high species turnover. Water temperature and mineralization level were the most influential variables in structuring the ostracod communities. We stress the need to implement conservation and restoration measures for these threatened ecosystems, to regain their role as ecosystem services providers.

Environmental factors driving phytoplankton biomass and diversity in a tropical reservoir

We determined the spatial and temporal variation of phytoplankton biomass and diversity in 10 fortnightly sampling journeys verifying five sampling sites in El Peñol-Guatapé reservoir located in Antioquia, Colombia. In situ and ex situ physical and chemical variables were measured and phytoplankton samples were taken. Richness was dominated by Chlorophyta and biomass by Dinophyta. This variable was higher in the transition zone while in the riverine zone it showed average values, the lowest were registered in the lacustrine zone. Diversity was lower in the riverine zone, but it increased considerably in the transition zone and in the lacustrine zone where it showed similar values. At the vertical scale, biomass and diversity did not vary widely. Biomass showed a differential response to the effect of precipitation changes and water levels in the reservoir zones. Due to the low variability in environmental conditions, diversity was homogeneous time-wise. These results suggest that factors related to the hydrodynamic such as precipitation and water level resulting from the dam operation and inflow have a slight influence on the temporal variations of phytoplankton biomass and structure. There was a direct relationship between these attributes and physical variables such as turbidity and nutrients concentration at spatial scale while at the vertical scale, mixing patterns and the influence of the wind explained the absence of the vertical gradient of biomass and phytoplankton structure.