Habitat fragmentation caused by contaminants: Atrazine as a chemical barrier isolating fish populations

Abstract

Information on how atrazine can affect the spatial distribution of organisms is non-existent. As this effect has been observed for some other contaminants, we hypothesized that atrazine-containing leachates/discharges could trigger spatial avoidance by the fish Poecilia reticulata and form a chemical barrier isolating upstream and downstream populations. Firstly, guppies were exposed to an atrazine gradient in a non-forced exposure system, in which organisms moved freely among the concentrations, to assess their ability to avoid atrazine. Secondly, a chemical barrier formed by atrazine, separating two clean habitats (extremities of the non-forced system), was simulated to assess whether the presence of the contaminant could prevent guppies from migrating to the other side of the system. Fish were able to avoid atrazine contamination at environmentally relevant concentrations (0.02 μg L), below those described to cause sub-lethal effects. The AC (atrazine concentration causing avoidance to 50% of the population) was 0.065 μg L. The chemical barrier formed by atrazine at 150 μg L (concentration that should produce an avoidance around 82%) caused a reduction in the migratory potential of the fish by 47%; while the chemical barrier at 1058 μg L (concentration that produces torpidity) caused a reduction in the migratory potential of the fish by 91%. Contamination by atrazine, besides driving the spatial distribution of fish populations, has potential to act as a chemical barrier by isolating fish populations. This study includes a novel approach to be integrated in environmental risk assessment schemes to assess high-tier contamination effects such as habitat fragmentation and population displacement and isolation.

Effects of climate and land-use changes on fish catches across lakes at a global scale

“…By combining Eqs. (6)- (8) and re-arranging α coefficients, we developed the conditional probabilistic distribution for CATCH expressed as…”

“…Among lake ecosystem services, fisheries are especially vulnerable to environmental changes because fish are ectothermic and fish distribution is usually limited by structural 6 , thermal 7 , and chemical 8 barriers. Environmental changes driven by climate and land-use changes have been linked to major shifts in fish catches (CATCHs) and species composition in many lakes around the world, such as lakes Erie 9 , Kinneret 10 , Naivasha 11,12 , Peipsi 13 , and Victoria 14 , as well as the collapse of Aral Sea fisheries 15 .…”

Spatial avoidance as a response to contamination by aquatic organisms in nonforced, multicompartmented exposure systems: A complementary approach to the behavioral response

“…Because each concentration forming the gradient can be measured at the end of the assays, the avoidance or preference response can be associated with a given concentration within the gradient. However, the one‐dimensional structure prevents any other type of connectivity between compartments than in‐line (horizontal) displacement, although more complex scenarios such as chemical fragmentation of a habitat can also be simulated (Araújo et al ).…”

Not Only Toxic but Repellent: What Can Organisms’ Responses Tell Us about Contamination and What Are the Ecological Consequences When They Flee from an Environment?

“…This is of great importance if static systems (without peristaltic pumps) are used, as it is difficult to maintain the gradient for a long time when the fish are swimming continuously. Avoidance studies with fish have also been performed with different contaminants such as: tuna fish processing plant effluent [72], triclosan [73], atrazine [74], river samples [75,76], bisphenol [77], copper [78,79], fipronil and 2,4-D [80], dairy wastewater [76], among others. In the study by Araújo et al [71], the avoidance response was assessed during very short exposure periods, sometimes not exceeding 4 h. In almost all cases, the avoidance initially observed (e.g., after 30 min) was similar to the avoidance at different periods during the remaining hours of the experiment.…”