Feedback Mechanisms Between Degradation and Primary Production in the Marine Pelagic Environment

Abstract

Carbon sequestration in the terrestrial biosphere is mainly a question of accumulating organic material in biomass or in its undegraded remains, since degradation of organic material in terrestrial systems will normally lead to a more or less instantaneous release of CO₂ to the atmosphere. In terms of increased sequestration, the most relevant aspect of degradative processes may then seem primarily to be the question of how degradation may be restrained. While the marine system is partly analogous, there is the important difference that the deep ocean constitutes a huge reservoir where carbon can be stored for extended periods away from contact with the atmosphere, irrespective of whether it is in organic or inorganic form. Transport processes moving material between the upper layer where primary production occurs, and the ocean’s interior, are therefore an essential component of carbon sequestration in the marine system. In large areas of the world’s oceans, primary production in the upper, photic zone is assumed to be limited by the availability of mineral nutrients such as nitrogen, phosphorus or iron. Microbial degradation of organic material interferes closely with the cycling of such mineral nutrients.