Pristine reef - Shark-dominated. Source.
Top predator biomass in pristine coral reefs is described to be between 54% and a whopping 85%, meaning that the resulting classical trophic pyramid of biomass is inverted, thus seemingly contradicting the rule that the biomass of prey must be larger than that of the predators because most of the energy gets lost whenever it is moving up through the food chain.
The prevailing explanation for this apparent paradox, is that the lower trophic levels have a much higher turnover rate whereas the top is much slower both in metabolism and reproduction. In fact, if instead of simply taking a snapshot and looking at biomass, one were to to plot the same data over time by depicting a productivity pyramid, one would once again obtain a standard, non-inverted shape.
But is this really the whole story.
- Coral reefs are not closed
This is specially true for those remote islands that feature important influxes both from the open ocean (= plankton but also larger, often migratory transients) and from the deep, the latter especially at night. This means that the effective available biomass of prey may in fact be much larger than merely the local residents.
- The range of those predators may encompass multiple ecosystems.
Research shows that many reef Sharks are resident during the day but disperse during the night, likely in order to forage. Thus, those islands may merely act as anchor points during periods of relative inactivity during the day, whereas feeding may happen both on the reef but also offshore and deeper - once again meaning that for those Sharks, the effective biomass of available prey may well be much larger than what can be deducted by merely observing what lives on those reefs.
And if so, how would the resulting trophic pyramid look like?
Just sayin'! :)
Just sayin'! :)
When researching the above, I've stumbled across this inspirational TED talk by Enric Sala.
Oldie but goodie - enjoy!