Mesocosms (Practical 5)
Understanding:
• Ecosystems have the potential to be sustainable over long periods of time
Ecosystems describe the interaction between biotic components (i.e. communities) and abiotic components (i.e. habitat)
They are largely self-contained and have the capacity to be self-sustaining over long periods of time
There are three main components required for sustainability in an ecosystem:
Energy availability – light from the sun provides the initial energy source for almost all communities
Nutrient availability – saprotrophic decomposers ensure the constant recycling of inorganic nutrients within an environment
Recycling of wastes – certain bacteria can detoxify harmful waste byproducts (e.g. denitrifying bacteria such as Nitrosomonas)
Skill:
• Setting up sealed mesocosms to try to establish sustainability
Mesocosms are enclosed environments that allow a small part of a natural environment to be observed under controlled conditions
A terrarium is a small transparent container (e.g. glass or plastic) in which selected plants (or animals) are kept and observed
Making a Self-Sustaining Terrarium
A terrarium can be created using a glass or plastic bottle with a lid, according to the following steps:
Building a verdant foundation
Add a bottom layer of pebbles, gravel or sand – this layer exists for drainage (smaller vessels require thinner rock layers)
Add a second thin layer of activated charcoal – this will prevent mold and help to aerate the soil
Spread a thin cover of sphagnum moss (or use an organic coffee filter) to create a barrier between the lower layers and soil
The final layer is the pre-moistened growing medium (i.e. potting mix)
Selecting the right plants
Ideally, choose plants that are both slow growing and thrive in a bit of humidity (e.g. most ferns, club moss, etc.)
Inspect the plant thoroughly for any signs of disease or insects before introducing to the terrarium
Maintaining appropriate conditions
Ensure the terrarium is placed in a location that provides a continuous source of light
Locate the terrarium in a place that does not experience fluctuating temperature conditions (i.e. avoid direct sunlight)
Do not initially over-water the plants – once the right humidity is established, a terrarium can go months without watering
Occasional pruning may be required – however, as level of soil nutrients decrease, plant growth should slow down
Some pictures of the making of the mesocosm: