Hotspots of benthic biodiversity

Key players and environmental factors

In coastal areas and along continental shelves and slopes, rich benthic communities, such as coral reefs or sponge beds, may thrive in spite of nutrient- and food-impoverished waters. This paradox of flourishing benthic life on the one hand, and low pelagic production on the other, has puzzled marine ecologists for decades. The high productivity and biodiversity of benthic hotspots may be related to: the creation of habitat, intense recycling of materials, and the ability of the suspension-feeder dominated communities to act as a large filter, removing particulate and dissolved materials from the water passing across their complex surface. Near-reef plankton depletions suggest that planktivores may provide a key to the paradox in shallow waters, and similar mechanisms may apply to deep coral and sponge communities. Biophysical interactions including plankton enrichments near fronts, density currents and tidal bores may play an important role in fuelling benthic productivity, where cascading of seasonally productive surface waters and retention of advected food may account for high densities of corals and sponges in otherwise impoverished waters (see Figure). The mechanisms of plankton supply to epibenthic communities in polar, temperate and tropical waters, and susceptibilities of the key species and communities to climatic changes, is a central theme of our research.