Biological pump

The biological pump, in its simplest form, is the ocean’s biologically driven sequestration of carbon from the atmosphere to the deep sea. It is the part of the oceanic carbon cycle responsible for the cycling of organic matter formed by phytoplankton during photosynthesis (soft-tissue pump), as well as the cycling of calcium carbonate (CaCO3) formed by certain plankton and mollusks as a protective coating (carbonate pump).

Overview

The biological pump can be divided into three distinct phases, the first of which is the production of fixed carbon by planktonic phototrophs in the euphotic (sunlit) surface region of the ocean. In these surface waters, phytoplankton use carbon dioxide (CO₂), nitrogen (N), phosphorus (P), and other trace elements (barium, iron, zinc, etc.) during photosynthesis to make carbohydrates, lipids, and proteins. Some plankton, (e.g. coccolithophores and foraminifera) combine calcium (Ca) and dissolved carbonates (carbonic acid and bicarbonate) to form a calcium carbonate (CaCO₃) protective coating.