Developing Zebrafish Embryos as a Biomonitoring Tool for Evaluating the Ogeechee River system
Freshwater ecosystems are constantly subjected to environmental stressors that can have broad and lasting implications on the aquatic community. These stressors can result in consequences ranging from mass kills to abnormal developmental effects on the organisms living within the system. The ability to rapidly assess the health of a freshwater ecosystem using biomonitoring tools provides an early-stage opportunity to properly manage a potentially detrimental stressor. Recently, a major fish and organism kill occurred in a local freshwater system, the Ogeechee River. This study aimed to investigate utilizing zebrafish embryos as a biomonitoring tool for the Ogeechee River. Reaches of the river, with varying reported impairments, were randomly selected and surface water and sediment grab samples were taken at six different time points throughout the winter and summer months of 2014. For each sampling date, simultaneous experiments (one set with surface water only, one with water/sediment) were run to compare the two exposure strategies. The Fish Embryo Toxicity Test (FET) was run for 5 days to assess gross early developmental effects. The embryos were then euthanized at the end of the 5 days to assess stress-gene regulation to investigate effects on the molecular level. We found that the use of the water/sediment combination was the most effective exposure route. The embryos exposed to the FC/TWR (fecal coliform/trophic-weighted residue) water/sediment, 2 showed decreased hatching rate, increased malformations, and down regulation of certain antioxidant stress-genes compared to the other groups. These results support our hypothesis that if used with known impaired samples, zebrafish embryo bioassays are sensitive enough to detect consequential abnormalities on both the organismal and molecular level.