Abstract
The trophic plasticity of most fish species of Astyanax Baird & Girard, 1854 in response to environmental changes and resource availability is high. This work evaluates the differences in the trophic characteristics of two congeneric species, Astyanaxtaeniatus (Jenyns, 1842) and Astyanaxlacustris (Lütken, 1875), in Rio das Velhas Basin, which is highly impacted by the discharge of sewage from the Metropolitan Region of Belo Horizonte (MRBH). Eight sites were sampled and grouped into three regions: upper course (two sites upstream of the MRBH); middle course (three sites located in the middle portion of the Rio das Velhas, region with greater influence of the MRBH), and lower course (three sites downstream of the MRBH). Samples of fish and food resources were collected from all sites to obtain the isotopic composition of nitrogen (δ15N) and carbon (δ13C), and the stomach contents of the two species was analized. The most common items in the stomach of A.lacustris and A.taeniatus, respectively, were from plants and insects, followed by algae/periphyton (especially at the low course of Rio das Velhas). In contrast, stable isotope analyses indicated that algae (in polluted sites) and periphyton (in least-disturbed sites) were best assimilated both species. Both analyses indicated that the trophic niches of the two species overlap more in more polluted sites relative to less polluted sites. Astyanaxtaeniatus and A.lacustris only presented different isotopic composition of carbon and nitrogen in the upper course of the Rio das Velhas, probably in response to the greater diversity of food items consumed by each species. In the other regions, the species presented similar isotopic signatures, with δ15N and δ13C notably enriched in the most polluted regions (middle and low course). Our results suggest that pollution acts by increasing trophic niche overlap of these species, altering the type of resources most assimilated, and promoting a greater enrichment of δ15N in fish and resources.
Highlights
In many developing countries, a large proportion of untreated raw sewage is released into aquatic environments (Macedo and Sipaúba-Tavares 2010), increasing the load of organic matter and pollutants in rivers, which are considered as the main drivers of artificial eutrophication in these environments (Tundisi and Tundisi 2008)
In Upper RV, A. lacustris feed more on plant remnants, aquatic insects and detritus, while A. taeniatus feed on sediments and insect remnants
In the middle RV, A. lacustris maintained its diet based on plant remnants, there was an increase of insect remnants
Summary
A large proportion of untreated raw sewage is released into aquatic environments (Macedo and Sipaúba-Tavares 2010), increasing the load of organic matter and pollutants in rivers, which are considered as the main drivers of artificial eutrophication in these environments (Tundisi and Tundisi 2008). Environmental pollution of aquatic systems may homogenize the type of resources available to organisms in higher trophic levels. This process of homogenization in aquatic systems has been described in several taxonomic groups such as diatoms, zooplankton and macroinvertebrates (Lougheed et al 2008). Such changes in the balance of available resources may affect the food web since changes in nutritional composition or abundances of basal food sources can induce shifts in primary consumers or even their exclusion (Hall 2004). The effects of this homogenization of producer communities on upper trophic levels remains unclear
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
