Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
9479729 | Deep Sea Research Part I: Oceanographic Research Papers | 2005 | 17 Pages |
Abstract
Although the organization patterns of fauna in the deep sea have been broadly documented, most studies have focused on the megafauna. Bivalves represent about 10% of the deep-sea macrobenthic fauna, being the third taxon in abundance after polychaetes and peracarid crustaceans. This study, based on a large data set, examined the bathymetric distribution, patterns of zonation and diversity-depth trends of bivalves from the Porcupine Seabight and adjacent Abyssal Plain (NE Atlantic). A total of 131,334 individuals belonging to 76 species were collected between 500 and 4866Â m. Most of the species showed broad depth ranges with some ranges extending over more than 3000Â m. Furthermore, many species overlapped in their depth distributions. Patterns of zonation were not very strong and faunal change was gradual. Nevertheless, four bathymetric discontinuities, more or less clearly delimited, occurred at about 750, 1900, 2900 and 4100Â m. These boundaries indicated five faunistic zones: (1) a zone above â¼750Â m marking the change from shelf species to bathyal species; (2) a zone from â¼750 to 1900Â m that corresponds to the upper and mid-bathyal zones taken together; (3) a lower bathyal zone from â¼1900 to 2900Â m; (4) a transition zone from â¼2900 to 4100Â m where the bathyal fauna meets and overlaps with the abyssal fauna and (5) a truly abyssal zone from approximately 4100-4900Â m (the lower depth limit of this study), characterized by the presence of abyssal species with restricted depth ranges and a few specimens of some bathyal species with very broad distributions. The â¼4100Â m boundary marked the lower limit of distribution of many bathyal species. There was a pattern of increasing diversity downslope from â¼500 to 1600Â m, followed by a decrease to minimum values at about 2700Â m. This drop in diversity was followed by an increase up to maximum values at â¼4100Â m and then again, a fall to â¼4900Â m (the lower depth limit in this study).
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Geology
Authors
Celia Olabarria,