Introduction

Abstract

Marine fronts are part of the structural complexity of the sea; they are narrow boundaries separating different water masses. Fronts are caused by diverse forcing and occur throughout the world ocean at several spatial and temporal scales. Unlike terrestrial ecotones, they show high biological production, affecting pelagic and benthic organisms of all trophic levels; consequently they are important for fisheries. Solar energy stimulates biological production in the entire biosphere, but in the sea it needs to be complemented by auxiliary energy to replenish plant nutrients; a significant quantity of mechanical energy becomes available for biological production at fronts. Global change is redistributing auxiliary energy in the oceans; consequently fronts are ideal sites for early monitoring of global change effects. Fronts also provide retention mechanisms for plankton in the highly dispersive marine environment; and become landmarks and beacons important for migrations or meeting of some species in a traceless realm.

On almost any ocean there is day after day when scarcely a bird, beast, or fish appears to break the monotony, and contrasted with this, here and there a few minutes or hours of teeming abundance, when every field of the binoculars shows a dozen birds or a hundred, and porpoises, orcas, or that cynosure of all passengers’ eyes, “real whales,” are seen on every hand. Why should things be so badly arranged?

(Brooks 1934)