Biogeochemical Cycles:
The Development of an

Abstract This lab consisted of several weeks of work involving monitoring the changes that took place in an ecosystem. Our aquatic ecosystem consisted of a small plastic container with several organisms such as snails, elodea, crustaceans and algae filled with water and rocks covering the bottom. The environment remained unmodified for 2 weeks, spending time underneath an isolated heating cart in order to provide a control group on which to examine the changes that took place in the container. The change that occurred was a result of our own modifications, in which we added 1 mL of a nitrogen solution three times starting in week 3. This resulted in an algal bloom as expected, but also influenced other aspects of the environment such as the elodea. This relates back to our studies of the nitrogen cycle in which fertilizers, which are rich in nitrogen, through run off often creates large algal blooms. This shows that nitrogen is often an important component in growth of organisms as it acts as a limiting factor since it is an essential part of DNA, the base unit of all life.

Background Biogeochemical cycles are processes in which compounds and substances go through. They are the movement of matter through a system through compounds being used or reused. A chemical reaction is a change in state from one form of compound into a new form of compound through biological, geological, and chemical processes (Carolina Biological Supply Company). Each step of a cycle involves some sort of chemical reaction. These cycles again prove that matter is not created or destroyed, but only changed. There are many biogeochemical cycles such as the Water Cycle, the Nitrogen Cycle, the Sulfur Cycle, the Carbon Cycle, and the Phosphorus Cycle. The water cycle. In aquariums, the water cycle is very evident, especially with evaporation. The hydrological cycle involves many complex parts. Evaporation is when water vapor evaporates from the ground and from bodies of water due to heat. Evapotranspiration refers to the summation of evaporation and transpiration, water transpired from plants. Water vapor then condenses into a liquid, forming clouds (Carolina Biological). Water then falls to the Earth as precipitation, and can form dew near the ground. Most of the water flows downhill as runoff (above ground or underground), eventually returning to the seas as slightly salty water (Enchanted Learning). The nitrogen cycle. Bacteria are a key component of the nitrogen cycle. They help cycle compounds through the ecosystem. A main step in the nitrogen cycle, which is performed by bacteria, is nitrogen fixation. In this step, N2 or nitrogen gas is converted into NH3, or ammonia. These bacteria can be found in the soil, in aquatic environments, and in the roots of plants (Carolina Biological). Many other nitrogen cycle processes include bacteria converting ammonia into nitrites or nitrates. Animals release nitrogen into the environment through excrement. In aquatic environments, some bacteria convert nitrogenous compounds back into nitrogen gas through denitrification. Then, N2 is converted into ammonia.

Works Cited:
Carolina Biological, Supply Company. "Carolina Biogeochemical Cycles for AP Environmental
Science." Student Guide.
Enchanted, Learning. "The Water Cycle." THE EARTH.

Materials
Aquarium
Aquarium Lid
Gravel
Springwater
Permanent Marker
Elodea
Mixed crustaceans
Mixed Green Algae
Pond Snails
2 Pipets
4 Nitrate/Nitrite Strips
4 pH test strips
4 Hydrogen sulfide test strips
Graduated Cylinder
Vial
Color Charts
2mL AgNo3

Methods/Procedures
Set-Up Procedure
1. Spread the gravel evenly across the bottom of the aquarium.
2. Use the graduated cylinder to measure spring water to fill the aquarium. Add water until the aquarium is three-quarters full of water. Record the