Composición del sedimento del sistema afluente-laguna de oxidación-efluente, en una granja intensiva de Oncorhynchus mykiss / Sediment Composition of the System Affluent-Oxidation Pool-Effluent in an Intensive Farm of Oncorhynchus mykiss

Resumen El sedimento es la capa superficial del fondo en estanques o en lagunas de oxidación. Este se origina fundamentalmente por la deposición de sólidos en suspensión, nutrientes y partículas del suelo que están en contacto con el agua, y que son naturalmente producidos por la operación de las granjas. Su manejo y disposición se constituye actualmente en un imperativo técnico, dadas las implicaciones ambientales que tienen las descargas provenientes de cultivos piscícolas. Se realizó la caracterización general del sedimento en tres sectores de una granja intensiva de producción, afluente, laguna de oxidación y efluente, la cual incluyó cuatro parámetros, que fueron medidos en tres momentos diferentes. Los valores obtenidos fueron comparados mediante análisis de varianza de una vía con α = 0,05 como nivel de significancia. Además, cuando fue necesario se realizó una prueba de Tukey para precisar las diferencias. Aquello cobijó las medidas de fósforo disponible, materia orgánica, carbono orgánico y relación C: N. Las diferencias encontradas entre los sectores son una aproximación al efecto de la producción piscícola sobre la composición de los sedimentos.

Abstract Sediment is the surface layer in the bottom of ponds or oxidation pools. It is created basically due to the deposition of solids in suspension, nutrients, and soil particles that contact the water and are produced naturally in farming operations. Today, the management and arrangement are a must in technical issues due to the environmental implications generated by the discharges coming from fish cultures. The general characterization of the sediment was carried out in three sectors of an intensive production farm, affluent, oxidation pool, and effluent. It included four parameters that were measured in three different time points. Obtained values were compared using one-way variance analysis with α = 0.05 as the significance level. In addition, when necessary, a Tukey test was carried out to pin down the differences. It enabled us to find the measures of available phosphorus, organic matter, organic carbon, and the ratio C: N. the differences found between the sectors are approximate values to the effect of the fish production regarding the sediment composition.

The response of chironomid taxonomy- and functional trait-based metrics to fish farm effluent pollution in lotic systems.

The lotic habitats affected by trout farm waste are colonized with a particular invertebrate community of which chironomids are the most abundant group. However, there is little information available regarding how chironomid community structures respond to this type of pollution at the highest taxonomic resolution. Eight fish farms, together with their lotic systems as recipients, were used to test the variability of the chironomid community and its surrogates (taxonomic and functional metrics) across spatially arranged sampling sites to form a gradual decrease in the trout farm influence. The self organizing map (SOM) classified six different types of chironomid communities which were characteristic for both the control and affected habitats. The species indicator analyses listed 32 taxa as positive indicators of water pollution. The SOM and Kruskal-Wallis test revealed that the pattern of chironomid community structure obtained was mainly driven by six environmental parameters (Altitude, conductivity, distance from the outlet, hardness, HN4-N, NO3-N). Categorical principal components analysis (CATPCA) derived three models for each type of biotic metric, in which for diversity-, taxonomy- and functional feeding group-based metrics, the first two dimensions explained 55.2%, 58.3% and 55.4%, of the total variance respectively for 315 sampling sites. According to this analysis, the total number of taxa (S), abundance and the Shannon-Wiener index (H') (as a diversity metric), as well as the proportion of Tanypodinae (as taxonomic group) and grazers/scraper (GRA) and gatherer collector (GAT)(as FFG metrics), were related to the outlet distance gradient, thus showing great potential to be used in the multimetric approach in bioassessment.

Evaluation of oxidative stress biomarkers in the freshwater gammarid Gammarus dulensis exposed to trout farm outputs.

The current study reports a combined seasonal monitoring of the Crnica River watercourse using physico-chemical parameters and biomarkers measured in Gammarus dulensis with the aim of correlating the effects of pollution with the level of oxidative stress biomarkers in this amphipod. The pollution source is identified as a trout farm in the upper part of the Crnica River (Eastern Serbia). Physico-chemical water parameters and sediment trace element concentrations were measured in the Crnica River during three seasons. Three localities downstream [CR2, CR3, and CR4 (20 m, 400 m, and 1.3 km from the trout farm discharge, respectively)] were assessed in comparison with a reference location (CR1), 250 m upstream from the trout aquaculture in the Crnica River. Antioxidant biomarkers including the enzymes superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), glutathione reductase (GR), and glutathione-S-transferase (GST) were determined in pooled samples of G. dulensis. Our findings showed statistically different antioxidant enzyme levels in gammarids from the first downstream locality (CR2) compared to those from other three localities. The results indicate that oxidative stress occurred to some extent despite the assumed antioxidant induction as a result of exposure to elevated levels of some elements and changed water parameters, the effects seeming in part to be mediated by suppression of SOD and CAT (during summer and autumn); and by suppression of GPX and GR (during autumn) at the CR2 locality. The activity of GST in all seasons was higher at the CR2 locality than at the other localities, suggesting the presence of some permanent xenobiotic next to the aquaculture output. Seasonal difference in the physical and chemical water parameters and sediment trace element concentrations were observed. Overall, our results indicate a locality- and season-dependent antioxidant enzymes response in G. dulensis, pointing at progressively reduced deleterious effect of trout farm outputs with movement further downstream.

Responses of aquatic macrophytes to anthropogenic pressures: comparison between macrophyte metrics and indices.

Macrophyte responses to anthropogenic pressures in two rivers of Central Spain were assessed to check if simple metrics can exhibit a greater discriminatory and explanatory power than complex indices at small spatial scales. Field surveys were undertaken during the summer of 2014 (Duraton River) and the spring of 2015 (Tajuña River). Aquatic macrophytes were sampled using a sampling square (45 × 45 cm). In the middle Duraton River, macrophytes responded positively to the presence of a hydropower dam and a small weir, with Myriophyllum spicatum and Potamogeton pectinatus being relatively favored. Index of Macrophytes (IM) was better than Macroscopic Aquatic Vegetation Index (MAVI) and Fluvial Macrophyte Index (FMI) in detecting these responses, showing positive and significant correlations with total coverage, species richness, and species diversity. In the upper Tajuña River, macrophytes responded both negatively and positively to the occurrence of a trout farm effluent and a small weir, with Leptodictyum riparium and Veronica anagallis-aquatica being relatively favored. Although IM, MAVI, and FMI detected both negative and positive responses, correlations of IM with total coverage, species richness, and species diversity were higher. Species evenness was not sensitive enough to detect either positive or negative responses of aquatic macrophytes along the study areas. Overall, traditional and simple metrics (species composition, total coverage, species richness, species diversity) exhibited a greater discriminatory and explanatory power than more recent and complex indices (IM, MAVI, FMI) when assessing responses of aquatic macrophytes to anthropogenic pressures at impacted specific sites.

Comparative study of the effects of a small-scale trout farm on the macrozoobenthos, potamoplankton, and epilithic diatom communities.

Trout farms are one of the major sources of pollution of highland streams and rivers, which are very sensitive ecosystems otherwise scarcely influenced by human activities. A trout farm with low annual production was chosen for comparative monitoring of its effects on the macrozoobenthos, epilithic diatom, and potamoplankton communities in the receiving stream. Research was conducted every 2 months during a period of 1 year (one control point and three localities downstream from the farm). The fish farm discharge induced moderate alteration of environmental factors in the receiving watercourse, viz., significant increase of the ionized and un-ionized ammonia fraction, dissolved oxygen concentration, and biological oxygen demand. Species richness and Simpson's diversity index did not change in any of the communities. Correspondent analysis of potamoplankton community composition clearly showed trout farm effects, thereby indicating the need for reevaluation of saprobic valence values for potamoplankton species. The complete lack of influence of the trout farm discharge on the epilithic diatom community is probably due to absence of significant changes of phosphorus concentration in the receiving stream. Effects of the trout farm on the macrozoobenthos community were further characterized by 14 additional indices. The percentages of Chironomidae larvae, shredders, and total collectors; ratio of shredders to collectors; and the family biotic index are suggested as candidates for future multimetric index for measuring of trout farm influence.

The trout farm effect on Dinocras megacephala (Plecoptera: Perlidae) larvae: Antioxidative defense.

Trout production represents a major agricultural activity in Serbia. Organic compounds are drained into the environment, usually without previous sedimentation, thus affecting the stream biota. Considering that biological monitoring is commonly based on aquatic macroinvertebrates as target organisms, the authors used larvae of Dinocras megacephala to estimate trout farm effects on the mass of the larvae and their antioxidative defense in pollution stress conditions. Four locations were chosen along the channel of the Raska River, 2 upstream (L1, L2) and 2 downstream (L3, L4) from the trout farm outlet. Basic physical and chemical water parameters were measured. Superoxide dismutase (SOD) and catalase (CAT) activity changes were analyzed to determine the level of oxidative stress caused by the increase of organic compounds originating from the trout farm. Dissolved oxygen concentration decreased from the upstream to downstream locations. Furthermore, the concentration of ionized ammonia was almost 10 times higher at the downstream locations than at the upstream locations. Larval mass, as well as CAT activity, was significantly higher at L3 compared with the other 3 locations. Activity of SOD was significantly higher at L3 than at L1. The results indicate that higher concentrations of organic compounds from the trout farm induce clear changes in the status of the antioxidant defense of D. megacephala larvae. Environ Toxicol Chem 2016;35:1775-1782. © 2015 SETAC.