Impacts of bay floor disturbances on benthic habitats in San Francisco Bay

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Greene, H. G., Vallier, T. L., Bizzarro, J. J., Watt, S., & Dieter, B. E. (2007). Impacts of bay floor disturbances on benthic habitats in San Francisco Bay. Special Paper - Geological Association of Canada, (47), 401-419.
TitleImpacts of bay floor disturbances on benthic habitats in San Francisco Bay
AuthorsG. Greene, L. Vallier, J. Bizzarro, S. Watt, E. Dieter
AbstractApproximately 120 km2 of San Francisco Bay were mapped using archived multibeam bathymetry data and another ∼40.5 km2 were mapped using recently acquired sidescan sonar data. Imagery was collected in several parts of San Francisco Bay, typically between 10 and 30 m. These data were interpreted into potential habitat types and further evaluated for natural (normally-) and human-induced disturbances. Ninety-one distinct potential habitats were identified, of which 74 were composed of soft, 12 of mixed, and 5 of hard, substrates. Bay floor sediment samples, collected by the US Geological Survey and the National Ocean Survey of the National Oceanic and Atmospheric Administration, were used to document substrate composition and document ("ground-truth") habitat interpretations. The sedimentological history of the region extends back to approximately 10 Ma with the initiation of a major sediment depocentre in the tectonic graben formed between the Hayward-Calaveras and San Andreas fault zones. Modern sedimentation from fluvial input and tidal scouring and deposition has resulted in a dynamic and complex bay floor. Strong currents have produced large sediment waves and dune fields, rippled sediment patches, and scoured channel floors and walls. Soft habitats composed primarily of mud and/or sand dominate the region, whereas hard rocky and mixed habitats are relatively rare and occur mainly in shallow areas adjacent to peninsulas and islands. Anthropogenic effects such as dredge material and debris-fields, borrow pits, dredged channels, and blasted bedrock knolls and normal disturbances such as sand waves are distinctly displayed in the data covering ∼63.5 km2 of area and delineated on the habitat maps. With the increasing demand for construction aggregate and development in the greater San Francisco Bay area, and the need to maintain and expand dredged channels and lower bedrock knolls to allow the safe passage of deeper draft vessels, many potential habitats will be impacted.
JournalSpecial Paper - Geological Association of Canada
Start page401
End page419
Subjectsbathymetric survey, bedrock, benthic environment, current, depocenter, dredging, environmental disturbance, habitat type, mapping method, seafloor mapping, substrate, California, North America, San Francisco Bay, United States