General Mechanisms for Inverted Biomass Pyramids in Ecosystems

TL;DR

This paper explores ecological models explaining the occurrence of inverted biomass pyramids in ecosystems, revealing key factors like prey growth and refuge size that influence these counterintuitive structures.

Contribution

It introduces three classes of predator-prey models that elucidate mechanisms generating inverted biomass pyramids, including well-mixing, refuges, and prey immigration.

Findings

Inverted biomass pyramids occur with high prey growth or immigration rates.

Refuge size impacts prey availability and predator-prey dynamics.

Models provide insights into ecological conditions leading to inverted pyramids.

Abstract

Although the existence of robust inverted biomass pyramids seem paradoxical, they have been observed in planktonic communities, and more recently, in pristine coral reefs. Understanding the underlying mechanisms which produce inverted biomass pyramids provides new ecological insights, and for coral reefs, may help mitigate or restore damaged reefs. We present three classes of predator-prey models which elucidate mechanisms that generate robust inverted biomass pyramids. The first class of models exploits well-mixing of predators and prey, the second class has a refuge (with explicit size) for the prey to hide, and the third class incorporates the immigration of prey. Our models indicate that inverted biomass pyramids occur when the prey growth rate, prey carrying capacity, biomass conversion efficiency, the predator life span, or the immigration rate of prey fish is sufficiently large. In the second class, we discuss three hypotheses on how refuge size can impact the amount of prey available to predators. By explicitly incorporating a refuge size, these can more realistically model predator-prey interactions than refgue models with implicit refuge size.