1) The study tested the effects of different concentrations of fertilizer runoff on zebrafish embryo development by exposing embryos to control spring water or solutions with fertilizer at concentrations of 2000x, 4000x, 5000x, and 10000x of the EPA safety standard. 2) The results found no dose-dependent relationship between fertilizer concentration and average head width, total body length, or body width, but instead a threshold response occurred after 2000x concentration for body length and width. 3) The conclusion is that a threshold response rather than dose dependency was observed, and future studies should examine impacts on zebrafish maturation and reproduction.

1. 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
Control
15 mL
Spring Water
2000x
0.02=g/L
4000x
0.04 g/L
5000x
0.05 g/L
10000x
0.1 g/L