How stable versus fluctuating suspended sediments affect fish behavior
摘要
Suspended sediments in aquatic habitats are a natural phenomenon but concentrations are increasing due to human development. Sediments in water can shape aquatic ecosystems through both physical effects on environmental structure and direct impacts on the organisms within them. Much of the existing literature on the effects of suspended sediments on animals focuses on stable sediment level exposures and short-term impacts; however, sediment levels frequently fluctuate in nature and can remain in suspension for extended periods, making it difficult to extrapolate these results to the natural world. Here, we used kaolin clay to evaluate the effects of a long-term (2-week) suspended sediment exposure on normal zebrafish (Danio rerio) behavior under both stable and fluctuating sediment conditions. We also assayed zebrafish foraging and color preferences using a separate, acute, 2-day sediment exposure. Fish decreased their movement rates over the 2-week exposure as they acclimated to experimental conditions; however, fish experiencing fluctuating sediment levels acclimated more slowly and maintained higher movement rates compared to fish experiencing consistent visibility levels. Two-week sediment exposure also generally interfered with social hierarchy establishment. During the short-term exposure study, fish took 198–350% longer to find and consume food at our highest level of suspended sediment (~ 40 NTU). Our results demonstrate that zebrafish acclimate well to suspended sediments but that long-term observation is necessary to observe the full impacts of suspended sediments on behavior over time. Our results also demonstrate the need for further research on the effects of fluctuating environmental conditions on ecosystems, particularly fluctuating sediment levels.