A sound resolution to the food paradox in the sea

Abstract

The average concentrations of biota in the ocean are generally low, presenting a critical problem for ocean consumers. In seminal experimental work in the 1970s, Lasker demonstrated that animals fed the average food concentrations measured using nets and pumps do not survive, presenting a paradox for life in the sea. Active acoustics, in contrast to more traditional tools, allow us to sample a wide range of animals at high spatial and temporal resolution. Employing a variety of platforms including ships, profilers, moorings, and autonomous vehicles to deploy acoustic sensors, often guided by the predators themselves, we find that instead of being relatively devoid of life, the ocean is peppered with narrow hot spots of activity. These features, often missed with traditional sampling tools, exist from the surface ocean to the deep sea, the tropics to the poles, in animals ranging from plankton and fish to squid and whales. These small patches of plenty have impacts on ecosystems disproportionate to their contribution to the total biomass. Small aggregations provide the key to solving experimentally demonstrated feeding paradoxes as well providing a mechanism for evolution in an apparently isotropic environment where there are no obvious barriers to gene flow, Hutchinson’s “Paradox of Plankton.”