Effects of Pesticide on Blue Crabs

Adult Blue Crabs in fish tanks prior to exposure.

Adult Blue Crabs in fish tanks prior to exposure.

Adult Juvenile Blue Crabs in fish bowls after initial exposure.

Adult Juvenile Blue Crabs in fish bowls after initial exposure.

 

Who We Are

Nicole, Kelly, Amanda, Lisa and Maribel

What We Did

Prior to the experiment we had to ensure all fish tanks and bowls were properly cleaned and free of chemicals. We had to clean the fish bowls, trash cans for sea water, and fish tanks, rinse filters, and clean bubblers. We also labeled the fish tanks. We made sea water. Once preparation was complete the adult blue crabs were purchased then they were placed in their own fish tanks. Each crab needed to have their length measured and also identify their gender. Next, Kelly calculated the number of pours needed for the experiment. We then poured the correct amount of sea water into a trash can so that she could then apply the correct amount of pesticide needed for the blue crabs that were going to be exposed. There were multiple rounds of experimentation conducted. For each experiment there were three groups of crabs: controlled, exposure, and acute. Data was collected at hour 0 (righting time, time to flip, eye coordination, and behavior and coordination)  to have baseline data, then the crabs were exposed to the pesticide and  re-assesed at hour 1 then 12, 24, 48, and 96 hours and data was collected each time. After, the desired exposure time of the blue crabs to the pesticide was complete the crabs were then taken to a hatchery and were each placed in a flume to see if they could still find a source of food.

Measuring a juvenile crab

Measuring a juvenile crab

The adults needed to have cardboard placed around their fish bowl for their own safety so that they would not have an additional stressor from their own reflection.

The adults needed to have cardboard placed around their fish bowl for their own safety so that they would not have an additional stressor from their own reflection.

What We Learned

  • How to properly time a crab’s righting and flip time.
  • How to make sea water and use a refractometer to ensure proper salinity level for the blue crabs.
  • The increased rain fall altered the ocean’s salinity water and affected the blue crabs behavior .
  • When a crab molts its shell the crab is exposed and soft. The crab actually molts his whole shell including the claws.
  • Exposure to pesticide does alter both adult and juvenile’s eye response and their behavior and coordination negatively.
  • New Vocabulary
    • Abdominal swipe – when a crab covers its abdomen with its claw.
    • Righting time – once a crab is placed on their back  how long it takes them to return to a normal position

Questions We Have

  • Who would be less affected by the exposure pesticide adult or juvenile crabs?
  • Why does the salinity of the water greatly alter the crab’s behavior?
  • What makes one crab more aggressive than another ?
  • What are the the effects of acute exposure of pesticide versus long-term exposure of pesticide on blue crabs?

Connections to Teaching

Science TEKS 4th grade

§112.15. Science, Grade 4

(b) Knowledge and skills.

(2) Scientific investigation and reasoning. The student uses scientific inquiry methods during laboratory and outdoor investigations. The student is expected to:

(A) plan and implement descriptive investigations, including asking well-defined questions, making inferences, and selecting and using appropriate equipment or technology to answer his/her questions;

(B) collect and record data by observing and measuring, using the metric system, and using descriptive words and numerals such as labeled drawings, writing, and concept maps;

(C) construct simple tables, charts, bar graphs, and maps using tools and current technology to organize, examine, and evaluate data;

(D) analyze data and interpret patterns to construct reasonable explanations from data that can be observed and measured;

(E) perform repeated investigations to increase the reliability of results; and

(F) communicate valid, oral, and written results supported by data.

(4) Scientific investigation and reasoning. The student knows how to use a variety of tools, materials, equipment, and models to conduct science inquiry. The student is expected to:

(B) use safety equipment as appropriate, including safety goggles and gloves.