SME
Oceanography · Problem type
Production passed up a food chain
Use this for “Phytoplankton make 150 g C/m² a year. With 10% passed up each step, how much reaches a carnivore three steps up the chain?”
Diagram
10% of 150 g C/m²/yr = 15 g C/m²/yr
10% of 15 g C/m²/yr = 1.5 g C/m²/yr
10% of 1.5 g C/m²/yr = 0.15 g C/m²/yr
10% of 0.15 g C/m²/yr = 0.015 g C/m²/yr
This is an example. Type your own values to start a new problem.
Pₜₒₚ (g C/m²/yr)
=
P (g C/m²/yr)
×
(
÷
100)
Formulas
Pₜₒₚ
=
P
×
(
E
100
)
n
0.15
=
150
×
(
10
100
)
3
Assumptions
•
Production is the carbon each level makes in a year under one square meter of sea, in g C/m²/yr.
•
The same efficiency E holds at every step up the chain, often 10–20% in the sea.
•
The rest (90% when E is 10%) goes to respiration or is lost as waste and dead matter at each step.
Step-by-step
WE KNOW
P = 150 g C/m²/yr, E = 10%, n = 3
FIND
production at the top (Pₜₒₚ)
Step 1 · Find production at the top (Pₜₒₚ)
Use Pₜₒₚ = P × (E ÷ 100)ⁿ
Each
step
up
keeps
E
%
of
the
production
below,
so
take
that
share
n
times.
Pₜₒₚ
=
150
×
(
10
100
)
3
Pₜₒₚ
=
150
×
0.1
3
Pₜₒₚ = 150 × 0.001
Pₜₒₚ
=
0.15
g
C/
m
2
/yr
Check
Put the numbers back in. Both sides should match.
0.15
=
150
×
(
10
100
)
3
✓
Topic check
See what you know: 5 questions on this topic
New questions each time. Pass to mark it complete.