Indian Ocean carbonate saturation

Figure 4 Comparison of carbonate saturation profiie for the eastern equatorial Indian Ocean with measurements of foraminiferal fragmentation and carbonate content (weight-%) from depth-distributed modern sediment samples in this region. The saturation horizon with respect to caicite (ACOa " = 0) occurs iocaiiy in the water column at a depth of 3800 m. This level corresponds with both the foraminiferai iysociine and carbonate iysociine as recognized in the sediments. The carbonate compensation depth (CCD) in this region is found at a depth of approximateiy 5000 m. increased foraminiferal fragmentation and decreases in sedimentary carbonate content are the resuit of dissoiution and carbonate ioss beiow the iysociine. Carbonate saturation data are from GEOSECS Station 441 (5°2 S, 91°47 E Takahashi et al. 1980) modern sediment data are from Peterson and Prell (1985).

Halyminine, isolated from the species Halymenia por-phyroides, is a particularly original sphingosine, with a saturated cyclononadecane (Bano, Uddin, and Ahmad, 1990), while the species Halymenia durivilliae, harvested aroimd the Andaman and Nicobar Islands (Indian Ocean), contains a sphingosine similar to the previous one, but without a carbon cycle (Rao and Saayanarayana, 1994). 

North Atlantic to 500 m in the North Pacific. This reflects an increasing addition of CO2 to deep waters as meridional overturning circulation moves them from the Atlantic to the Indian and then to the Pacific Ocean. Thus, as a water mass ages, it becomes more corrosive to calcium carbonate. Since aragonite is more soluble than calcite, its saturation horizon lies at shallower depths, rising from 3000 m in the North Atlantic to 200 m in the North Pacific. 

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