Biogeochemical Cycles
Adapted by Carrie Jones and Jamie Church for 9-12 Marine Science class
A. Standards (Ocean Literacy standards)
1. The ocean has one big ocean with many features
2. The ocean and life in the ocean shape the features of the Earth
4. The ocean makes Earth habitable
5. The ocean supports a great diversity of life and ecosystems
6. The ocean and humans are inextricably connected
B. Performance Objectives
Following completion of this lesson, students will be able to:
 Understand how nutrient cycles throughout the oceans
 Understand that nutrients are essential for life
 Apply nutrient cycling to a closed ecosystem and how it will affect the living
things in it
 Journal about the progress of their ecosystem
 Assess how their ecosystem survived by concepts of nutrient cycling
C. Lesson Plan
1. Concept Exploration
Set-up stations around the room or outside representing different areas of an
ecosystem where nitrogen (or you may choose a different nutrient) enters or
exits an area. We used atmosphere, surface water, rain water, groundwater,
fertilizer, soils, ocean, live animals, dead plants and animals, animal waste and
live plants as our stations. You will need 11 dice and a stamp or different
colored marker for each station. Introduce nitrogen, where it is found and
why it is important. Explain that the students are playing the role of a
nitrogen atom and they are traveling through a nitrogen cycle based on dice
rolls. They will mark on a passport where they traveled (see attached
worksheet). Afterwards, ask them to diagram how they traveled.
http://www.windows.ucar.edu/teacher_resources/nitrogen_activity.pdf
2. Concept Introduction
Nitrogen is part of the biogeochemical cycles. Most of the nitrogen is in the
atmosphere and all living things need nitrogen. Although the nitrogen cycle is
very complex, it is probably the most important nutrient cycle because it is
usually the most limiting factor for plants, is very soluble and is the most
mobile (http://www.ag.ohio-state.edu/~prec/soil/n_cycle.htm). Nitrogen is
transformed through nitrification, denitrification, mineralization and fixation
by bacteria. When in the form of ammonia, it is highly toxic to fish. Excess
of nutrients can lead to contamination and/or eutrophication. Many human
influences have affected this cycle and thus the organisms in the water where
it is concentrated and needed for organisms to grow are highly affected.
Explain that when setting up an aquarium, you must establish the bacteria
and nutrients before putting the animals in it. There are different types of
filtration systems that contain the bacteria needed. You also need a clean hard
surface for the bacteria to live on.
3. Concept Application
Students will apply what they learned about nutrient cycling and
aquariums to set-up their own closed ecosystem. Purchase or collect a hardy
freshwater fish. We used guppies since they are cheap, easy to get from any
pet store, are sexually dimorphic, have short gestation periods and give live
birth. This also gives you the opportunity to explain concepts of ecology and
reproduction. You will need some type of container with a lid such as a pickle
jar or large plastic pretzel jar, freshwater plants, gravel and sand. Provide
pond water and they will choose if they want to use tap, pond or filter the
pond water with a coffee filter. The students should get in groups of 2-3
students.
A couple days before you bring in the guppies, they will need to set up
their jars. This is an inquiry-based project. The students will decide how to
set-up their jars and how much of what materials they will use. Give them a
rationale sheet asking what substrate they used (gravel or sand), how much
and why, how many plants and what type of water (tap, pond or filtered pond)
and why. The students can use a mixture of any or all materials, let them
decide! They must leave the lids off after they set-up their jars so the gases
may dissolve out if they used tap water. They also need to choose a location
in the room. Explain if they put it by a window, the plants may survive better,
however the biggest stressor for fish is temperature change. After their
ecosystems have had a few days to establish, they will put the guppies in, 4-5
guppies per group (1 male, 4 females) and close the lid. The most important
thing is to not open the lid until the experiment is done. Everyday, the
students will make close observations and record them in a journal for a
couple of weeks. They should record behaviors of the fish, health of the
plants, if any babies are born, if the fish are seen eating the plants and if the
fish are near the top, bottom, etc.
D. Review/Evaluation
Assess the students understanding through having them write a paper explaining
how their closed ecosystem sustained itself through nutrient cycling. They need to
include terms such as nitrifying bacteria, photosynthesis, decomposition and
consumption. They should hypothesize if they think their substrate, plants, placement
or what type of water the used contributed to the success/failure of their ecosystem,
animals and if they had any babies.
Sources:
http://www.windows.ucar.edu/teacher_resources/nitrogen_activity.pdf
http://www.ag.ohio-state.edu/~prec/soil/n_cycle.htm