Department of Ecology and Coastal Management, Institute of Marine Sciences of Andalusia (CSIC), 11510 Puerto Real, Cádiz, Spain; Centre for Functional Ecology (CFE), Department of Life Sciences, University of Coimbra, 3000-456 Coimbra, Portugal.
Central Department of Research (DCI), Ecuadorian Aquatic Ecotoxicology (ECUACTOX) Group, Universidad Laica Eloy Alfaro de Manabí (ULEAM), Manta, Ecuador; Departamento de Ciencias Biológicas, Universidad Técnica Particular de Loja (UTPL), Loja, Ecuador.
Sci Total Environ. 2018 Apr 1;619-620:906-915. doi: 10.1016/j.scitotenv.2017.11.170. Epub 2017 Nov 29.
Aquatic ecotoxicity assays used to assess ecological risk assume that organisms living in a contaminated habitat are forcedly exposed to the contamination. This assumption neglects the ability of organisms to detect and avoid contamination by moving towards less disturbed habitats, as long as connectivity exists. In fluvial systems, many environmental parameters vary spatially and thus condition organisms' habitat selection. We assessed the preference of zebra fish (Danio rerio) when exposed to water samples from two western Ecuadorian rivers with apparently distinct disturbance levels: Pescadillo River (highly disturbed) and Oro River (moderately disturbed). Using a non-forced exposure system in which water samples from each river were arranged according to their spatial sequence in the field and connected to allow individuals to move freely among samples, we assayed habitat selection by D. rerio to assess environmental disturbance in the two rivers. Fish exposed to Pescadillo River samples preferred downstream samples near the confluence zone with the Oro River. Fish exposed to Oro River samples preferred upstream waters. When exposed to samples from both rivers simultaneously, fish exhibited the same pattern of habitat selection by preferring the Oro River samples. Given that the rivers are connected, preference for the Oro River enabled us to predict a depression in fish populations in the Pescadillo River. Although these findings indicate higher disturbance levels in the Pescadillo River, none of the physical-chemical variables measured was significantly correlated with the preference pattern towards the Oro River. Non-linear spatial patterns of habitat preference suggest that other environmental parameters like urban or agricultural contaminants play an important role in the model organism's habitat selection in these rivers. The non-forced exposure system represents a habitat selection-based approach that can serve as a valuable tool to unravel the factors that dictate organisms' spatial distribution in connected ecosystems.
用于评估生态风险的水生生态毒性测定假设，生活在受污染生境中的生物被迫暴露于污染物中。这一假设忽略了生物通过向受干扰较小的栖息地移动来检测和避免污染的能力，只要存在连通性即可。在河流系统中，许多环境参数在空间上发生变化，从而影响生物对栖息地的选择。我们评估了斑马鱼（Danio rerio）在接触来自厄瓜多尔西部两条河流的水样时的偏好，这两条河流的干扰水平明显不同：Pescadillo 河（高度干扰）和 Oro 河（中度干扰）。我们使用一种非强制暴露系统，其中来自每条河流的水样根据其在野外的空间顺序排列，并连接起来，允许个体在样品之间自由移动，通过 D. rerio 测定栖息地选择来评估两条河流的环境干扰。暴露于 Pescadillo 河样品的鱼更喜欢靠近与 Oro 河汇合处的下游样品。暴露于 Oro 河样品的鱼更喜欢上游水域。当同时暴露于两条河流的样品时，鱼表现出对 Oro 河样品的相同的栖息地选择模式。鉴于两条河流是连通的，对 Oro 河的偏好使我们能够预测 Pescadillo 河鱼类数量的减少。尽管这些发现表明 Pescadillo 河的干扰水平更高，但测量的理化变量均与对 Oro 河的偏好模式没有显著相关性。栖息地偏好的非线性空间模式表明，其他环境参数，如城市或农业污染物，在该模式生物的栖息地选择中起着重要作用。非强制暴露系统代表了一种基于栖息地选择的方法，可以作为一种有价值的工具，用于揭示决定连通生态系统中生物空间分布的因素。
