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In the English Channel the producers hold less biomass than the consumers above them. What explains that inversion?
APhytoplankton are unusually unproductive
BPhytoplankton are eaten and replaced fast
CZooplankton store energy for many years
DZooplankton feed on two trophic levels
Answer & Solution
Correct answer: B. Phytoplankton are eaten and replaced fast
1. Biomass is the mass present at the moment of measurement, not the mass produced over time.
2. In the English Channel the primary producers measure 4 grams per square meter.
3. The primary consumers measure 21 grams per square meter, so the pyramid is inverted.
4. The producers there are phytoplankton, which are grazed almost as fast as they appear.
5. That high turnover keeps their standing biomass tiny at any one instant.
6. They reproduce quickly enough to support the whole level above them anyway.
7. So the inversion is not caused by low productivity, which is the trap this sets.
8. Long term storage by zooplankton is not what creates the pattern either.
_Source: OpenStax Biology 1e (CC BY 4.0), Chs 44 and 46, section 46.2 Energy Flow through Ecosystems_
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