Carbonate compensation depth

The calcite and aragonite compensation depth refers to a line of depth in the ocean below which lime in the form of calcite and aragonite dissolves completely. Cause is the increase in carbon dioxide concentration in the water with increasing water depth. For calcite, this line is 3500-5000 m for aragonite 3000-3500 m.

The partial dissolution begins below the Lysokline, which is about 300 to 800 m above the calcite compensation line.

Background

Both inland waters and seas generally have a gradient with depth increasing concentration of dissolved carbon dioxide. In the seas, this gradient is ongoing, while it originates in inland waters with the changing seasons and disappears (see lake ecosystem ). Its cause is biogenic, that is, caused by the processes of life. Near the surface, carbon dioxide is bound as biomass through photosynthesis by algae and distributed to the food chain. So can fall as rain particles into the deeper water layers of the organic carbon. There, this biomass is usually destroyed by bacteria again and respired to carbon dioxide. So it happens gradually in depth to a CO2 - enrichment and thus to said gradient.

With a correspondingly high concentration of CO2 reacts now all calcium carbonate according to the following equation to dissolved calcium bicarbonate:

And the temperature and residence time, caused by a different water mixture, affect the reaction. Accordingly, different is the position of the two compensation depth in the oceans. Furthermore, the depth of change in the course of history.

Calcite compensation depth

As calcite compensation depth (CCD, of Engl. " Calcite compensation depth" ) is defined as the depth of the sea is dissolved from the sämtliches calcite in the water. The CCD varies 3500-5000 m water depth. Above this depth, so is a saturated solution of calcium carbonate (lime) the introduction of added lime is precipitated and is deposited on the seabed. Below the CCD can be found hence no more limescale but only lime-free sediments based on silicate. Priority should be mentioned here the red Tiefseeton and sediments from soda silica ( opal ). The latter arise from the housings of micro-organisms such as diatoms or radiolarians ( Radiolarienschlamm ).

Aragonite compensation depth

Aragonite is more soluble in water than calcite. Accordingly, already in a lower water depth fail no more aragonite and thus come as a sedimentary rock in question. Analogously, one can now take a aragonite compensation depth ( ACD, of Engl. " Aragonite compensation depth" ) to determine which, apart from the solubility, the same laws as the calcite compensation depth follows. It is to settle 3000-3500 m depth.