, Volume 7, Issue 9, pp 1123-1132

The biodiversity of macrofaunal organisms in marine sediments

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Abstract

Marine sediments cover most of the ocean bottom, and the organisms that reside in these sediments therefore constitute the largest faunal assemblage on Earth in areal coverage. The biomass in these sediments is dominated by macrofauna, a grouping of invertebrate polychaetes, molluscs, crustaceans and other phyla based on size. Globally, only a small portion of marine habitats have been sampled for macrofauna, but sampled areas have led to global estimates of macrofaunal species number ranging from 500,000 to 10,000,000. Most of these species are undescribed, and global syntheses of patterns of individual taxa and biodiversity are few and based on limited samples. The significance of biodiversity in marine sediments to ecosystem processes is poorly understood, but individual species and functional groups are known to carry out activities that have global importance. Macrofaunal activity impacts global carbon, nitrogen and sulphur cycling, transport, burial and metabolism of pollutants, secondary production including commercial species, and transport of sediments. Documented extinctions of marine macrofauna are few, but the ramifications of species loss through habitat shrinkage and undocumented extinctions are unknown. Limited data suggest there is substantial functional redundancy in macrofauna within trophic groups but whether this redundancy is sufficient to allow species loss without significantly altering ecosystem processes is unknown. Sorely needed are experiments that test specific hypotheses on biodiversity, redundancy, and ecosystem processes as they relate to marine macrofauna.