Department of Geosciences, Federal University of São João del-Rei, São João del-Rei, Minas Gerais, Brazil.
Department of Chemical Analytics and Biogeochemistry, Leibniz-Institute for Freshwater Ecology and Inland Fisheries, Berlin, Germany.
Sci Total Environ. 2021 Feb 10;755(Pt 2):142660. doi: 10.1016/j.scitotenv.2020.142660. Epub 2020 Oct 2.
Fatty acids (FAs) and their metrics have been used to detect and assess the impacts of urbanization and agriculture on aquatic ecosystems. Here, we investigated whether seston FAs are also useful to characterize and understand early-stage aquaculture impacts in a large tropical reservoir (Furnas Reservoir, SE Brazil). We tested the hypothesis that single FAs, as well as selected FA metrics in the seston fraction, are efficient markers of net-cage fish farming effects. In general, fish farming had only minor effects on standard water chemical variables, mainly small increases in ammonium, nitrate, and dissolved organic nitrogen concentrations. By increasing concentrations of several polyunsaturated FAs, early-stage fish farming improved sestonic food quality in the more oligotrophic branch of the reservoir under drought conditions. However, in general, increases in concentrations of bacterial FAs, due to fish farming, suggested organic matter (OM) subsidies from non-ingested and non-assimilated fish feed. In the more eutrophic reservoir branch, seston FA profiles suggested that fish farming caused an increase of low-quality food resources, such as cyanobacteria. Thus, background impact levels may determine the biochemical responses of tropical reservoirs to fish farming. Higher contributions of potentially sewage-derived and bacterial FAs during drought conditions, especially at reference sites of the more oligotrophic branch, suggested that drought shifted OM inputs towards anthropogenic sources, thereby overwriting land-use related differences between reservoir branches and homogenizing their environmental conditions. In conclusion, FA variables were useful to evaluate and understand environmental conditions, as well as the effects of early-stage fish farming and drought, and should be considered in impact assessments in tropical lentic ecosystems.
脂肪酸（FAs）及其指标已被用于检测和评估城市化和农业对水生生态系统的影响。在这里，我们研究了在一个大型热带水库（巴西东南部的富纳斯水库）中，水藻中的脂肪酸是否也可用于描述和理解早期水产养殖的影响。我们检验了这样一个假设，即水藻中的单一脂肪酸（FAs）以及特定的 FA 指标可以有效地作为网箱养鱼影响的标志物。总的来说，鱼类养殖对标准的水化学变量的影响较小，主要是铵、硝酸盐和溶解有机氮浓度略有增加。在干旱条件下，早期鱼类养殖通过增加几种多不饱和脂肪酸的浓度，改善了贫营养分支中水体食物质量。然而，总的来说，由于鱼类养殖，细菌脂肪酸浓度的增加表明有来自非摄入和非同化鱼饲料的有机物质（OM）的补充。在富营养化程度较高的水库分支中，水藻脂肪酸组成表明鱼类养殖导致低质量食物资源的增加，如蓝藻。因此，背景影响水平可能决定了热带水库对鱼类养殖的生化响应。在干旱条件下，特别是在贫营养分支的参考点，潜在的污水衍生和细菌脂肪酸的贡献增加，表明 OM 输入偏向于人为来源，从而掩盖了水库分支之间与土地利用有关的差异，并使它们的环境条件趋于一致。总之，脂肪酸变量可用于评估和了解环境条件，以及早期鱼类养殖和干旱的影响，在评估热带静水生态系统的影响时应予以考虑。
