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Monterey Bay Studies

Monterey Bay Studies


Monterey Bay National Marine Sanctuary Project, 1999

Current-Winnowed Coarse-Grained Sediments at the Point Sur Pinnacles off Central California Yield a Diverse Microfauna

by Mary McGann


Coarse-grained sediments with a significant biogenic component were collected by SCUBA divers off Point Lopez (36=B001.2'N, 121=B034.9'W) and Slate Rock (36=B007.6'N, 121=B039.1'W) at water depths of 18 and 21 meters, respectively. These samples contain a diverse microfauna, including forty-five species of benthic and planktonic foraminifers. The benthic foraminiferal fauna is dominated by Cibicides fletcheri, Alveolophragmium columbiense, Rotorbinella turbinata, Trochammina pacifica, Cassidulina californica, C. tortuosa, and Rosalina globularis. Less abundant constituents include Planulina exorna, Cibicides lobatulus, Buccella frigida, Elphidiella crispum, Elphidium magellanicum and Trochammina kelletae. Many of these species exhibit an attached mode of life to either coarse-grained sediments or plants, a strategy which is well suited for the harsh conditions resulting from the swift currents in the area. The benthic foraminiferal fauna in these sediments is also quite distinct from any other found on the Monterey Bay shelf. Instead, it looks remarkably similar to the fauna collected from the turbulent waters of Cordell Bank to the north. As expected, only a few planktonic foraminifers were recovered from the Point Lopez and Slate Rock sediments due to the relatively shallow depth of these sites, as they prefer to live offshore in the open-ocean over the shelf break and slope. Planktonic foraminiferal species recovered include the upwelling-indicator species Globigerina bulloides and the warm-water indicating (right-coiling) form of Neogloboquadrina pachyderma.

This abstract is from Monterey Bay National Marine Sanctuary Symposium, Sanctuary Currents '97, Facets of Biodiversity, Poster Session, 1997.

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