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Dec 14

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Influence of fish in aquatic systems

Students:  Brian Allman, Muska Fahim, Megan May, Cody Roldan, and Ryan Edelen

Introduction:  What is the effect of fish on zooplankton abundance and composition?  How does addition of fish change an aquatic environment?  

Large zooplankton (cladocerans, copepods) would be reduced
Small zooplankton (rotifers) would be more abundant
Less dissolved oxygen
Reduced pH
Increase in bacteria
Increase in chlorophyll

Experimental design and methods:  

  • Six tanks, three with fish, three without fish.  
  • Purchased fish from pet store.  
  • Used water from Quarry Pond.  
  • Introduced four types of zooplankton into each tank - cladocerans, copepods, rotifers, nauplii.  
  • Added nitrogen and phosphorus to each tank one week before experiment began.
  • Measured chlorophyll, dissolved oxygen, conductivity, temperature, pH, nutrient analysis (P and N), bacterial abundance, zooplankton abundance. 

Addition of fish changed the aquatic environment.  There were increases in abundance of smaller zooplankton and bacteria.  Abundance of larger zooplankton (cladocerans, copepods) was reduced.  Dissolved oxygen content and pH decreased.  

Suggestions for future:  
Future projects should look into food availability for zooplankton, increasing sample size, using more clearly defined procedures, and using a more natural environment (soils, fish, other abiotic and biotic factors).