Left: Dover sole on sand, Cordell Bank National Marine Sanctuary, CA, USA.

摘要: ECOLOGICAL TRAITS: Medium to coarse-grained, unvegetated and soft minerogenic sediments show moderate levels of biological diversity. The trophic network is dominated by consumers with very few in situ primary producers. Interstitial microalgae and planktonic algae are present, but larger benthic primary producers are limited either by substrate instability or light, which diminishes with depth. In shallow waters, where light is abundant and soft substrates are relatively stable, this group of systems is replaced by group M1. 1, which is dominated by vascular marine plants. In contrast to those autochthonous systems, subtidal sand beds rely primarily on allochthonous energy, with currents generating strong bottom flows and a horizontal flux of food. Sandy substrates tend to have less organic matter content and lower microbial diversity and abundance than muddy substrates (M1. 8). Soft sediments may be dominated by invertebrate detritivores and suspensionfeeders, including burrowing polychaetes, crustaceans, echinoderms and molluscs. Suspension-feeders tend to be most abundant in high-energy environments where waves and currents move sandy sediments, detritus, and living organisms. The homogeneity and low structural complexity of the substrate exposes potential prey to predation, especially from pelagic fish. Large bioturbators, such as dugongs, stingrays and whales, may also be important predators. Consequently, many benthic animals possess specialised traits that enable other means of predator avoidance, such as burrowing, shells or camouflage.KEY ECOLOGICAL DRIVERS: The substrate is soft, minerogenic, low in …