Macroinvertebrate biomass was highest at an intermediate riparian ecotone complexity with an adequate supply of organic matter and incident light. Fish biomass followed the same trend, being lowest in heavily shaded areas and in open channels without riparian vegetation (range: 1-4.5 g m-2), but highest in ecotones of intermediate complexity (range: 1.6-92.8 g m-2). The cascading effect of invertebrate density depletion, which was inversely related to fish biomass, was observed seasonally. (Wiley InterScience)

The complexity and biological importance of riparian ecotones depend on the extent to which the system is self-regulating, which depends in turn on geology, physiography, climate, vegetation, human activity and the age of the system. (Fish and riparian ecotones – a hypothesis)

A common example of ecotones is estuaries—the transitional area between rivers and the oceans. The variety of species found in an estuary is much higher than in the river or in the shallow sea-water. (BASICS OF ECOLOGY & LIFE SUPPORT SYSTEMS)