This high efficiency of decomposition is due to the fact that the organisms carrying out the decomposition rely upon it as their sole source of chemical energy; in most of the open ocean, the heterotrophs only leave behind the organic matter that is too chemically resistant for it to be worth the investment to decompose. Figure 5.6.4 Nitrate, phosphate, and silicate profiles from an open-ocean location in the South Atlantic (52 o S, 35 o 13'58.8 W), north of South Georgia Island (image by PW . This connection is evident in multiple places. This zone starts at the bottom of the mesopelagic and stretches down to 4000 m (13,000 feet). The red cycle illustrates the fate of the majority of organic matter produced in the surface ocean, which is to be respired by heterotrophic organisms to meet their energy requirements, thereby releasing the nutrients back into the surface water where they can be taken up by phytoplankton once again to fuel regenerated production. The green cycle represents the internal respiration of phytoplankton themselves, that is, their own use of the products of photosynthesis for purposes other than growth. Oceans fix 80% of the total CO2 fixed by photosynthesis, yes, but they also unfix it at a similar rate. they should have accounted for 80% of the dry weight produced as well. Other important nutrients, such as phosphate and silica, show similar patterns to nitrate (Figure 5.6.4), and will be discussed in the section on primary production . The darkness can be interrupted, however, by some light caused by the organisms themselves. In other words, we tend to define "productivity" in terms of what is useful to us as a species, and algae are generally not useful. PDF The Process of Primary Production - University of Michigan This is significant as it determines the food supply for humans and other animals. Does it mean "O2 released from the oceans into the atmosphere, where it contributes to a growing surplus"? "Secondary production" (SP) typically refers to the growth rate of heterotrophic biomass. Because of their relative physiological simplicity, microzooplankton are thought to be highly efficient grazers that strongly limit the biomass accumulation of their prey. It 's because the ocean 's volume ( mostly open space ) in comparison to the amount of producers is massive . 5. Therefore, SP in the ocean is small in comparison to NPP. Open Ocean - Oceana As organic matter settles through the ocean interior and onto the seafloor, it is nearly entirely decomposed back to dissolved chemicals (Emerson & Hedges 2003, Martin et al. Browse other questions tagged, Start here for a quick overview of the site, Detailed answers to any questions you might have, Discuss the workings and policies of this site.
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