Rittenburg Bank is approximately 50 kilometers (31 mi) off the Marin County coast and lies at depths ranging from approximately 50 to 150 meters. Rittenburg Bank has a high density of sponges at its northwest region, 184 sponges per 1000 m2, consisting of at least nine taxa of sponges. There are at least 35 taxa of fishes with a density of 139 fish per 1000 m2 and six taxa of anthozoans (corals), with a density of 138 anthozoans per 1000 m2. In October 2012, the sanctuary explored and mapped Rittenburg Bank. Rittenburg Bank has higher density of sponges in comparison to Cochrane Bank and Farallon Escarpment. The habitat at Rittenburg Bank appears to be highly suitable for corals and sponges, with 10.1% being rugose, hard substrate. Many small corals and sponges were observed, suggesting recent recruitment to the coral and sponge populations. Dr. Gary Williams, California Academy of Sciences, identified a new species of gorgonian coral from material collected during a 2012 survey. High densities of large sponges were observed in areas of highest rugosity and were not likely to have been impacted by bottom trawls. A reduction in trawl effort (a consequence of fishery closures in the region enacted in the 2000's) may have contributed favorably to the abundance and condition of corals and sponge observed on the Bank. The multibeam bathymetry, acoustic backscatter, and sea floor character data are publicly available online through the United States Geological Survey (USGS) website, and described in detail in Dartnell et al. 2014.
A technical report (PDF, 3Mb), summarizing the characterization of these this area can be found at this link. Minimum count and distribution data are available on line at the Essential Fish Habitat Data Catalog.