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Oligozoic Biota (Biotic Group)

Component: Biotic

Unique Identifier: 543

Biotic Setting Benthic/Attached Biota
Biotic Class Faunal Bed
Biotic Subclass Soft Sediment Fauna
Biotic Group Oligozoic Biota
Biotic Community Anoxic Oligozoic Bed
Meiofaunal Bed
Bacterial Bed

Definition Zones that are devoid of macrofauna, larger fauna, and microbial mats, i.e., where no evidence of larger multicellular life can be detected when a sufficient area of the substrate is sampled to deliver sub-millimeter resolution, and where microbial communities are not visible to the naked eye. Interstitial meiofauna, however, may be present or inferred. It is inappropriate to identify this biotic group with sampling methods that are not capable of sub-millimeter resolution and cannot detect infauna that may reside below the surface in soft sediments. Sampling methods which can resolve this biotic group include retrieval of substrate followed by sieving with < 0.5 millimeter mesh size and stereoscopic examination, and sediment profile imaging with cameras that provide sub-millimeter resolution at the faceplate. This biotic group is found in areas of extremely high stress (e.g., anoxic zones, highly toxic areas, and high-energy pebble or cobble beaches) where conditions cannot support larger multicellular life. Oxic areas of subtidal mineral sands are generally sparsely colonized by multicellular organisms (e.g., haustoriid amphipods, syllids and other small polychaetes) and are not considered Oligozoic Biota.