Biology, physics and gravity interact to pum p organic carbon into the deep sea. The processes of fixa tion of inorganic carbon in organic matter during pho tosynthesis, its transformation by foodweb processes (trophodynamics), physical mixing, transport and grav itational settling are referred to collectively as the" bio logical pum p"(Figure 1). When the Global Ocean Flux Study (GOFS) began in 1984 in the US, followed in 1987 by the international Joint Global Ocean Flux Study (JGOFS), several ideas about the functioning of fhe bio logical pum p formed the conceptual core of the fledg ling program: