Measuring Biomass
• Biomass can be calculated by measuring the mass of carbon that an organism contains or by the draw mass of its tissue per unit area per unit time
• The dry mass is the total mass of an organism without any water. The water content in different organism greatly varies therefore a dry mass is more beneficial than a wet mass in reference to biomass
• In measuring the dry mass, a sample of an organism is dried (usually in an oven at a low temperature). This mass is then measured every day until the sample reaches a constant mass, this means that all the water has been removed. Approximately 50% of the total mass of the dry mass is carbon. Now that the dry mass is known multiply the figure to give the dry mass (biomass) of the total population or the area being investigated. The typical units for dry mass is kg m-2
• Biomass varies over a period of time, it is useful to carry out multiple biomass test over a time. The typical unit is kg m-2 yr-1
Calorimetry
• Burning the chemical energy is a sample can also give an estimate to the biomass using a calorimeter
• The heat output determines how much energy is given off and thus how much energy was contained
• A sample of the dry biomass is burnt under a known volume of water, where the change in the temperature of the water is therefore calculated for the chemical energy of the dry biomass
Primary Production
• Gross Primary Production (GPP) is the total amount of chemical energy produced from light energy by plants in a given area over a given time
• Respiratory loss (R) is the approximate 50% of the gross primary production which is lost to the environment as heat when the plant respires
• Net Primary Production (NPP) is the remaining chemical energy
NPP = GPP – R
• NPP energy allows the plant to grow and reproduce as well as being the energy which is able to move up the trophic levels
Net Production in Consumers
• Consumers get their energy by the consumption of plant (primary) material or animals which have eaten plant materials
• Not all of the chemical energy is transferred to the next trophic level as around 90% of it is lost over different ways:
o Not all of the animal/plant is eaten such as bones or cellulose is digested
o Energy is wasted in the animal moving
o Energy is wasted in maintain homeostasis
o Etc
• Net Product is the amount of energy after the energy has been lost, the remaining amount is stored in the consumers biomass and is therefore available for the next trophic level
N = I – (F + R)
N = net production
I = Chemical energy in ingested food
F = Chemical energy lost in faeces and urine
R = Energy lost through respiration

Efficiency of Energy Transfer
• Energy transfer can be measured by comparing the net production of energy for the current trophic level to the previous trophic level:
Net production of trophic level x 100
Net production of previous trophic level
• Energy transfer generally becomes more efficient the higher up the trophic level is, this is greatly to do with plants being greatly indigestible however the consumer being an animal has a greater proportion of chemical energy it can transfer as more of it digestible