Results

I recorded their total body length (from the head to the end of the tail), body width (the widest part of their body), and head width (across their eyes or the widest part of their head) to the nearest mm. I used a linear regression to test the relationship between fertilizer concentration and the average head length, average body width, and average total body length. Additionally a t-Test was conducted to compare each concentration to one another.

Methods After the zebrafish spawned each morning, the eggs were collected from the marble dishes and placed in 15 mL petri dishes containing either a control or experimental solution. The control was artificial spring water, while the experimental trials contained a solution of Scott’s fertilizer ranging from 2000x, 4000x, 5000x, and 10000x, where X = the EPA 10 µg/L safety standard. Approximately 10-15 eggs were placed per dish. Once the embryos hatched, they were sacrificed with MS-222 and preserved in 70% ethanol.

Introduction

Eutrophication is the process by which excess nutrients, particularly nitrogen and phosphorous, enter a water body causing an abnormal increase in algal growth (an algal bloom) on the water’s surface. Ultimately these blooms die off and bacteria move in to consume them. During this process the bacteria consume oxygen leading to the formation of a hypoxic zone, which is harmful to animals. Inorganic nitrogen pollution can also impair the ability of aquatic animals to survive, grow and reproduce as a result of direct toxicity of inorganic nitrogenous compounds (Camargo et al 2006). After reviewing existing nutrient criterions directed by the Everglades Forever Act, the EPA and the Florida Department of Environmental Protection (FDEP) set a total phosphorous (TP) and total nitrogen (TN) limit of 10 µg/L (Payne et al., 2012). This is the total percent nitrogen safety standard set for human consumption, however, how will these levels impact aquatic biota? I hypothesized that zebrafish embryos exposed to fertilizer runoff conditions would have a dose-dependent response to fertilizer that will include retarded growth.

Methods

Zebrafish, Danio rerio, were used as the test subject. Adult zebrafish were acclimated to a 10-gallon tank covered with black plastic to prevent light from penetrating through to the tank. This set up was crucial to acclimating the zebrafish to a fourteen-hour day, ten-hour night to replicate their natural spawning schedule. Since adult fish are known to consume freshly laid eggs, three finger bowls full of glass marbles were placed on the bottom of the aquarium to catch the eggs.

Results

The Effect of Fertilizer Runoff Conditions on the Development of Danio rerio Embryos

Erica Gillespie, Department of Biology, Stetson University, DeLand, FL

Results

Conclusion

•Based on my results, there is a threshold response instead of a dose-dependent relationship between specific fertilizer concentrations and the embryonic development.•The threshold response occurs after 2000x on the average total body length and average total body width. •If runoff conditions reduce the ability of a species to mature reproductively, or in size, there could be an issue in repopulating a diminishing species. •My experiment may have focused on Danio rerio but if hypoxic zone formation or excess nutrients in general impact development, there may be future issues to take into consideration.• Future studies could focus on how the retardation in growth affects the maturation of zebrafish and impacts their reproductive ability.

Acknowledgements I thank my advisor, Dr. Gibbs, for her help throughout the entire process. Additionally, I thank the Stetson Biology Department for their use of the laboratories and access to the tools to complete my experiment.

Lit Cited

Camargo J., Alonso A., Salamanca A. (2005). Nitrate toxicity to aquatic animals: a review with new data for freshwater invertebrates. Chemosphere. 58 (9): 1255-1267.

Payne G., Weaver K., Xue S. (2012). Chapter 2C: Status of Phosphorousand Nitrogen in the Everglades Protection Area. 2012 South Florida Environmental Report. 1 (2): 2C-1 – 2C-30).

Results

Figure 1. There is no statistically significant dose-dependent relationship between the fertilizer concentrations and the average

head width. The T-test was >0.05, therefore there is not a statistically significant difference between fertilizer concentration

doses on the average head width.

Figure 2. There is no statistically significant dose-dependent relationship between the fertilizer concentrations and the average

total body length. Based on the T-test (T < 0.05), there was a threshold response after 2000x

Figure 3. There is no dose-dependent relationship between the fertilizer concentrations and average body width (mm). There is a threshold response occurring after 2000x according to the T-Test

Value < 0.05

Control15 mL

Spring Water

2000x 0.02=g/L

4000x0.04 g/L

5000x0.05 g/L

10000x0.1 g/L