The deep sea includes habitats around the Channel Islands that extend from 30 to greater than 200 meters over the continental shelf and slope and well over 1000 meters in canyons. Over 90 percent of deep-water benthic habitats in the sanctuary consist of fine sands in shallow regions, grading into silt and clay-dominated sediments in deeper regions (Science Applications International Corporation 1986; Thompson et al. 1993). These soft-bottom particulates are derived from terrestrial runoff and decaying plankton. Coarse sediments occur near Point Conception, and north of San Miguel Island (Blake and Lissner 1993). Fine sediments occur on the sill at the western end of the
Santa Barbara Channel, and in the Santa Barbara Basin. Most of the deep-water hard bottom substrates are low-relief reefs less than 1 meter in height; some reefs have 1- to 5-meter-high features and may take the form of boulder and bedrock outcroppings. Hard bottom habitat is often found on the highest parts of undersea ridges, banks, and pinnacles such as those found off the northwest end of San Miguel Island. Because light rapidly disappears below 50 meters, offshore benthic habitats do not support marine algae. Invertebrates can, however, be found in these habitats and include sponges, anemones, cup corals, black coral, sea fans, bryozoans, feather stars, brittle stars, sea stars, and lamp shells. Demersal fishes are common, especially various species of rockfish. Due to the difficulty in studying very deep habitats, little is known about these areas in the sanctuary. However, recent submersible studies have begun to reveal the important associations between these diverse fish and invertebrate communities (Tissot et al. 2006).
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