Shell preservation of Limacina inflata in surface sediments of the Central and South Atlantic


Over 300 surface sediment samples from the Central and South Atlantic Ocean and the Caribbean Sea were investigated for the preservation state of the aragonitic test of Limacina inflata. Results are displayed in spatial distribution maps and are plotted against cross-sections of vertical water mass configurations, illustrating the relationship between preservation state, saturation state of the overlying waters, and overall water mass distribution. The microscopic investigation of L. inflata (adults) yielded the Limacina dissolution index (LDX), and revealed three regional dissolution patterns. In the western Atlantic Ocean, sedimentary preservation states correspond to saturation states in the overlying waters. Poor preservation is found within intermediate water masses of southern origin (i.e. Antarctic intermediate water (AAIW), upper circumpolar water (UCDW)), which are distinctly aragonite-corrosive, whereas good preservation is observed within the surface waters above and within the upper North Atlantic deep water (UNADW) beneath the AAIW. In the eastern Atlantic Ocean, in particular along the African continental margin, the LDX fails in most cases (i.e. less than 10 tests of L. inflata per sample were found). This is most probably due to extensive “metabolic” aragonite dissolution at the sediment-water interface combined with a reduced abundance of L. inflata in the surface waters. In the Caribbean Sea, a more complex preservation pattern is observed because of the interaction between different water masses, which invade the Caribbean basins through several channels, and varying input of bank-derived fine aragonite and magnesian calcite material. The solubility of aragonite increases with increasing pressure, but aragonite dissolution in the sediments does not simply increase with water depth. Worse preservation is found in intermediate water depths following an S-shaped curve. As a result, two aragonite lysoclines are observed, one above the other. In four depth transects, we show that the western Atlantic and Caribbean LDX records resemble surficial calcium carbonate data and delta13C and carbonate ion concentration profiles in the water column. Moreover, preservation of L. inflata within AAIW and UCDW improves significantly to the north, whereas carbonate corrosiveness diminishes due to increased mixing of AAIW and UNADW. The close relationship between LDX values and aragonite contents in the sediments shows much promise for the quantification of the aragonite loss under the influence of different water masses. LDX failure and uncertainties may be attributed to (1) aragonite dissolution due to bottom water corrosiveness, (2) aragonite dissolution due to additional CO2 release into the bottom water by the degradation of organic matter based on an enhanced supply of organic matter into the sediment, (3) variations in the distribution of L. inflata and hence a lack of supply into the sediment, (4) dilution of the sediments and hence a lack of tests of L. inflata, or (5) redeposition of sediment particles.

Supplement to: Gerhardt, Sabine; Henrich, Rüdiger (2001): Shell preservation of Limacina inflata (Pteropoda) in surface sediments from the Central and South Atlantic Ocean: a new proxy to determine the aragonite saturation state of water masses. Deep Sea Research Part I: Oceanographic Research Papers, 48(9), 2051-2071

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Metadata Access
Creator Gerhardt, Sabine; Henrich, Rüdiger
Publisher PANGAEA
Publication Year 2001
Rights Creative Commons Attribution 3.0 Unported;
OpenAccess true
Resource Type Supplementary Publication Series of Datasets; Collection
Format application/zip
Size 3 datasets
Discipline Earth System Research
Spatial Coverage (-79.145W, -38.468S, 15.480E, 20.920N); Walvis Ridge; Angola Basin; Guinea Basin; Equatorial Atlantic; Brazil Basin; Romanche fracture zone; Cape Basin; Hunter Channel; Eastern Rio Grande Rise; Northern Rio Grande Rise; Kongo delta; Northern Guinea Basin; West Angola Basin; Mid Atlantic Ridge; East Brazil Basin; Amazon Fan; Niger Sediment Fan; Kongo sediment fan; off Kunene; Namibia Continental Margin; Namibia continental slope; South African margin; Uruguay continental margin; Argentine Basin; Rio Grande Rise; Santos Plateau; Northern Brasil-Basin; Western Equatorial Atlantic; Sierra Leone Rise; South of Cape Verde Islands; NE-Brazilian continental margin; off Rio Paraiba do Sul; off Macaé; Continental Slope off Rio Paraiba do Sul; off Rio Doce; south of Abrolhos Bank; eastern Abrolhos Bank; Northern Cape Basin; Continental slope off Brazil; Northeast Brasilian Margin; Midatlantic Ridge; Ceara Rise; Guayana continental slope; Ascencion Island; Mid-Atlantic Ridge; Northwestern Vema Channel; Atlantic Ocean
Temporal Coverage Begin 1959-04-21T00:00:00Z
Temporal Coverage End 1998-05-25T02:43:00Z