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Soft Sediment Fauna (Biotic Subclass)

Component: Biotic

Unique Identifier: 426

Biotic Setting Benthic/Attached Biota
Biotic Class Faunal Bed
Biotic Subclass Soft Sediment Fauna
Biotic Group Burrowing Anemones
Larger Deep-Burrowing Fauna
Small Surface-Burrowing Fauna
Soft Sediment Bryozoans
Clam Bed
Soft Sediment Crinoids
Mobile Crustaceans on Soft Sediments
Diverse Soft Sediment Epifauna
Echiurid Bed
Holothurian Bed
Hydroid Bed
Mussel Bed
Oyster Bed
Sand Dollar Bed
Scallop Bed
Pennatulid Bed
Larger Tube-Building Fauna
Small Tube-Building Fauna
Tunicate Bed
Tunneling Megafauna
Burrowing Urchins
Oligozoic Biota
Brachiopod Bed
Soft Sediment Brittle Stars
Mobile Mollusks on Soft Sediments
Sponge Bed
Starfish Bed
Sea Urchin Bed
Soft Sediment Basket Stars
Cephalochordates


Description
Definition Areas that are characterized by fine unconsolidated substrates (sand, mud) and that are dominated in percent cover or in estimated biomass by infauna, sessile epifauna, mobile epifauna, mobile fauna that create semi-permanent burrows as homes, or by structures or evidence associated with these fauna (e.g., tilefish burrows, lobster burrows). These animals may tunnel freely within the sediment or embed themselves wholly or partially in the sediment. In many cases, they will regularly leave their burrows, and may move rapidly or swim actively after doing so, but any animal that creates a semi-permanent home in the sediment can be classified as Soft Sediment Fauna. These animals may also move slowly over the sediment surface, but are not capable of moving outside of the boundaries of the classification unit within one day. Most of these fauna possess specialized organs for burrowing, digging, embedding, tube-building, anchoring, or locomotory activities in soft substrates. Biotic communities in the Soft Sediment Fauna subclass are identified with the term "Bed", to distinguish them from Attached Fauna biotic communities (which do not include the term "Bed").

Within Soft Sediment Fauna, the Biotic Group is identified as the biota making up the greatest percent cover or the greatest estimated biomass within the classified area. Biota present at lesser percent cover or estimated biomass values within the classified area may be identified as Co-occurring Elements (See Section 10.6.2) or (if not a CMECS Biotic Group) as Associated Taxa (See Section 10.3.1). Associated Taxa include rapid epifaunal predators such as crustaceans, fishes, and other nekton that are capable of leaving the boundaries of the classification unit within one day. Associated Taxa may be capable of digging into the sediment surface to feed or hide (e.g., portunid crabs) but do not construct a semi-permanent burrow as would define Soft Sediment Fauna. For practitioners who wish to better characterize Soft Sediment Fauna, the Community Successional Stage Modifier (Section 10.3.2, including Figure 10.1 and Table 10.3) is a helpful addition to classifying soft sediment fauna, and can be applied to almost every soft-sediment area. This modifier provides ecological and functional information, and adds an element of assessment.