The mean of net primary productivity (NPP) in aquatic and terrestrial ecosystems are 152 and 773 g dry mass m -2 yr -1 , respectively. The percentage of aquatic NPP to the total world NPP is 32.3%, and that of terrestrial NPP is 67.7%. It is obvious the net primary productivity in terrestrial ecosystems is much higher, about 5 times of that in aquatic ecosystems. Although the aquatic area is much large, two third of the world primary productivity is in terrestrial area.
According to the variation range of net primary productivity, aquatic and terrestrial ecosystems were divided into three levels. Among aquatic ecosystems, the low level group is the open ocean. And the middle level group includes lake and stream, continental shelf and upwelling ocean zones. The high level group includes estuaries, algal beds and reefs. In terrestrial ecosystems, the low level group is consisted of extreme deserts, rock, sand, ice; desert and semi-desert scrub, tundra and alpine, temperate grassland. The middle level group includes cultivated land, woodland and shrub land, savanna, boreal forest, temperate deciduous forest, temperate evergreen forest. The high level group only includes tropical seasonal forest, tropical rain forest, and swamp marsh http://www.cusabio.com/ .
Among aquatic ecosystems, the mean NPP in low, middle and high levels were 125g dry mass m -2 yr -1 , 360g dry mass m -2 yr -1 , 1800 g dry mass m -2 yr -1 , respectively. However, those in terrestrial ecosystems were 139g dry mass m -2 yr -1 , 863g dry mass m -2 yr -1 , 2091g dry mass m -2 yr -1 , respectively. For all three levels, the NPP in terrestrial ecosystems is higher than in aquatic ecosystems.
NPP is determined by two factors, the energy transferred by photosynthesis and the energy consumed by organism respiration. For primary producers, the respiration energy is about 30-40% of the production 3 . So the gross productivity, which described the energy conversion efficiency by photosynthesis, is higher than NPP. In this paper, I definite the energy utilization efficiency is the rate of available energy transferred by the ecosystem and accumulated in its production during a period time, so I only consider the “available energy” stored in the organisms. NPP is a form of available energy for the organisms in next trophic level, but the respiration energy is not available for use or transfer.
Although variation of NPP in ecosystems is obvious, from the global scale, the solar radiation energy entered into biosphere is about 0.8%, and the highest calculated solar energy conversion efficiency for primary producer is under 5% while it is under a ideal condition 3 . The energy utilization efficiency in aquatic ecosystems was 0.145%, 0.354% and 1.531% for low, middle and high NPP levels, respectively. Those in terrestrial ecosystems were 0.162%, 0.846% and 1.779%, respectively, obviously higher than aquatic ecosystems. So that, it could be concluded that the energy utilization efficiency in terrestrial ecosystems is higher than in aquatic ecosystems. So that the first step evidence is gotten for the hypothesis on “the biological community emerged in later geological era should has higher energy utilization efficiency than the community emerged earlier”.
Refer to this link: http://www.cusabio.com/ELISA-Kit/Guinea-pig-Apolipoprotein-B-APOB-ELISA-kit-1042034.html
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