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Copyright of Acta Universitaria is the property of Universidad de Guanajuato/Acta Universitaria and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of ESPOCH Congresses: The Ecuadorian Journal of S.T.E.A.M. is the property of Knowledge E DMCC and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Fipronil and imidacloprid currently represent approximately one third of the global insecticide market. In the present study, the environmental risk (ERA) of fipronil and imidacloprid in the postlarvae of the river shrimp (Cryphiops caementarius, Molina 1782) was evaluated. Short-term toxicity bioassays were performed based on LC50 (mean lethal concentration) (mortality) and EC50 (mean effective concentration) (swimming hypoactivity). PNEC (Predicted Concentration with No Known Effect) and available environmental standards for PEC (Expected Environmental Concentration) were calculated for fipronil and imidacloprid to determine risk quotient (RQ). Imidacloprid was more at risk for the aquatic environment than fipronil for the lethal response (mortality) and sublethal response (swimming hypoactivity). The observed risk difference between the two insecticides could be due to their different modes of action. C. caementarius should be considered as a sensitive species when defining an environmental quality standard for the conservation of the aquatic environment. Therefore, it is recommended to continue monitoring the presence of these insecticides in coastal freshwater bodies, and to reduce the use of fipronil and imidacloprid in the agricultural crops that use them. [ABSTRACT FROM AUTHOR]

The aim was to quantify the level of pollution with metals in sediments of the Bustillos Lagoon and to compare two methods of digestion (agua regia and peroxide). Fifteen random points were selected, and samples were collected at the top (0-10 cm) and below (10-20 cm). The analysis was performed in a ICPOES quantifying chromium (Cr), iron (Fe), lithium (Li), magnesium (Mg), manganese (Mn), nickel (Ni), zinc (Zn), cobalt (Co), cooper (Cu), lead (Pb) and strontium (Sr). An ANOVA was carried out considering a 2x2 factorial arrangement. The results showed statistical differences for the digestion method (P<0.05), but no differences was noted for depth (P>0.05) neither for the interaction (P>0.05). It is concluded that the sediments of the Bustillos ecosystem do not represent a hazard because the metals Cr, Fe, Mn, Ni, Zn, Cu and Pb were not above the international and national standards and the metals Li, Mg, Co and Sr do not have standards. [ABSTRACT FROM AUTHOR]

The distribution and abundance of fish is influenced by multiple factors at temporal and spatial scales, and their community composition represent good river integrity indicators. The main objective of this study was to describe the composition and structure of fish assemblages along the Anchique river sub-basin (that drains to Magdalena river), and to test the hypothesis that these communities vary temporally and spatially. For this, four sites (E1, E2, E3 and E4) were sampled along the river (from river birthplace to Magdalena river), during the periods of high and low waters, in 2014. In each site, longitudinal transects (100 m long x 2 m wide, 60 min) were established and fishing was made with both electrofishing and trawl (10 m x 1 m, 0.05 m) nets. Fish samples were fixed and transported to the laboratory for posterior taxonomic identification with the use of keys; fish diversity and structure composition were calculated with the use of standard models. Besides, substrate composition and environmental variables were also considered. A total of 652 fish belonging to 36 species were recorded; high water showed higher values (325 fish with 32 species) than low water period (300 fish with 31 species). Siluriformes was dominant (51 %), followed by Characiformes (32 %), Gymnotiformes (5 %), Cyprinidontiformes and Cichliformes (6 %). Most abundant families were Characidae (28.3 %; 9 spp.), Loricariidae (23.4 %; 8 spp.) and Trichomycteridae (15.0 %; 2 spp.). Kruskal-Wallis test indicated that there is no significant difference among some environmental variables at the temporal level. The values of structural complexity and substrate composition indices showed that E4 had the highest values (0.8), followed by E1 (0.6), and E2 and E3 (0.4). Moreover, E4 had the highest richness and diversity, according to Hill's number. The canonical correspondence analysis showed that the substrate, and the complexity and width of the river channel, had a significant influence on fish composition and distribution. The fish community richness and diversity did not change temporarily, but did spatially, which could be related to the different structural features of sampling sites. Rev. Biol. Trop. 66(1): 336-351. Epub 2018 March 01. [ABSTRACT FROM AUTHOR]

Results of the present paper are concerned with evaluating pollutant contributions to aquatic ecosystems according to the products processed in Cuban fishing facilities. The captures in 1955-1999 were between 3 950 and 23 970 t/year in 12 years of sampling, with BOD between 56 and 342 t/year and of DQO between 111 and 676 t/year. The principal nutrient was total nitrogen, followed by total phosphorous and finally ammonia-nitrogen, representing a total contribution of 136,3; 52,7 and 18,0 t/year respectively in those 12 years. The report culminates with the possible affectations caused by polluted water discharges to the ecosystem, recommending the use of the information offered in this document with the objective to elaborate future plans allowing the establishment of environmental management programs. [ABSTRACT FROM AUTHOR]

The construction of major dams in the Colorado River has produced a drastic effect on the amount of fresh water entering the Colorado River Delta. After 1935 there was a dramatic decrease in fresh-water input, causing ecological impacts and a decrease of organisms in the natural habitat. We carried out six spatial samplings during a period ofno fresh-water inflow to the delta, in June, August and November 1989, and February, April and June 1990; during each sampling, a 24-hourtime series was conducted at one station and seawater samples were taken every two hours. Also, in May 1991 we carried out an eight-day time series, taking samples of seawater at 08:00, 12:00 and 16:00 hours. The objective was to estimate phytoplankton abundance, chlorophyllconcentration and primary productivity during a period of no fresh-water input. In the spatial distribution, the chlorophyll a concentrations and phytoplankton abundance were higher on the Baja California side than on the Sonora side, with concentrations of 2.6-18.2 mg m-3 and 1.8-12.7 mg m-3 and of 274 and 166 cells mL-1, respectively. In the time series, the dinoflagellates weremore abundant than the diatoms. The primary production showed a tendency to decrease from August 1989 to June 1990, with values of 15.0 to 0.5 mgC m-3 h-1. The primary productivity values in the time series presented a tendency to increase during the tide transition, reaching values of 76 mgC m-1 h-1. The variations of chlorophyll concentration, phytoplankton abundance and primary productivity were strongly influenced by the effects caused by the tidal currents. [ABSTRACT FROM AUTHOR]