Expert answer:The upper 10 cm of sediment in the open ocean is i

  

Solved by a verified expert:Please read the following article:Whitman, W.B., Coleman, D.C., and Wiebe, W.J. (1998). Prokaryotes: The unseen majority. Proceedings of the National Academy of Sciences 95(2): 6578-6583.Note: You can find the above article in your iBoard course under Homework Assignment Instructions.Write a three to five page paper in which you summarize and reflect on this very important article that was one of the first to point out the magnitude of nutrients stored in microorganisms.The paper must be in proper APA format, have a references section, and site at least 2 peer reviewed articles. Please use AAU’s LIRN Library to search for these articles. You may utilize the Academic Resource Center (ARC) for a concise guide on how to use LIRN and for APA formatting guidelines.Proc. Natl. Acad. Sci. USAVol. 95, pp. 6578–6583, June 1998PerspectiveProkaryotes: The unseen majorityWilliam B. Whitman*†, David C. Coleman‡, and William J. Wiebe§Departments of *Microbiology, ‡Ecology, and §Marine Sciences, University of Georgia, Athens GA 30602portion of these cells are the autotrophic marine cyanobacteriaand Prochlorococcus spp., which have an average cellulardensity of 4 ϫ 104 cells͞ml (6). The deep (Ͼ200 m) oceanicwater contains 5 ϫ 104 cells͞ml on average. From globalestimates of volume, the upper 200 m of the ocean contains atotal of 3.6 ϫ 1028 cells, of which 2.9 ϫ 1027 cells areautotrophs, whereas ocean water below 200 m contains 6.5 ϫ1028 cells (Table 1).The upper 10 cm of sediment in the open ocean is includedin the oceanic habitat because, as a result of animal mixing andprecipitation, it is essentially contiguous with the overlyingwater column. Most of the marine sediment is found in thecontinental rise and abyssal plain, so the numbers of prokaryotes were calculated from an arithmetic average of thecellular densities in the studies cited by Deming and Baross(ref. 9; Table 1). The Nova Scotian continental rise wasexcluded from this calculation because of its unusual hydrology(10).There are fewer estimates of the number of prokaryotes infreshwaters and saline lakes (5). Given an average density of106 cells͞ml, the total number of cells in freshwaters and salinelakes is 2.3 ϫ 1026. This value is three orders of magnitudebelow the numbers of prokaryotes in seawater.In the polar regions, a relatively dense community of algaeand prokaryotes forms at the water–ice interface in annual seaice (11). In Antarctic sea ice, the estimated number of prokaryotes (2.2 ϫ 1024 cells) was based on the mean cell numbersof Delille and Rosiers (12) and the mean areal extent ofseasonal ice (13). If the population size in the Arctic is similar(14), the global estimate for both polar regions is 4 ϫ 1024 cells,only a fraction of the total number of prokaryotes.Soil. Soil is a major reservoir of organic carbon on earth andan important habitat for prokaryotes. Prokaryotes are anessential component of the soil decomposition subsystem, inwhich plant and animal residues are degraded into organicmatter and nutrients are released into food webs (15). Manystudies indicate that the number of prokaryotes in forest soilsis much less than the number in other soils. The total numberof prokaryotes in forest soil was estimated from detailed directcounts from a coniferous forest ultisol (16), which wereconsidered representative of forest soils in general (Table 2).For other soils, including grasslands and cultivated soils, thenumbers of prokaryotes appear about the same, e.g., thenumber of prokaryotes in Negev desert soil is comparable tothe number in cultivated soil (19). Therefore, the numbers ofprokaryotes in all other soils were estimated from the unpublished field studies of E. A. Paul for cultivated soils (cited in ref.18).Subsurface. The subsurface is defined here as terrestrialhabitats below 8 m and marine sediments below 10 cm. Fewdirect enumerations of subsurface prokaryotes have beenmade, largely because of the difficulty in obtaining uncontaminated samples. Nevertheless, circumstantial evidence suggeststhat the subsurface biomass of prokaryotes is enormous (20).For instance, groundwater from deep aquifers and formationABSTRACTThe number of prokaryotes and the totalamount of their cellular carbon on earth are estimated to be4–6 ؋ 1030 cells and 350–550 Pg of C (1 Pg ‫ 5101 ؍‬g),respectively. Thus, the total amount of prokaryotic carbon is60–100% of the estimated total carbon in plants, and inclusionof prokaryotic carbon in global models will almost doubleestimates of the amount of carbon stored in living organisms.In addition, the earth’s prokaryotes contain 85–130 Pg of Nand 9–14 Pg of P, or about 10-fold more of these nutrients thando plants, and represent the largest pool of these nutrients inliving organisms. Most of the earth’s prokaryotes occur in theopen ocean, in soil, and in oceanic and terrestrial subsurfaces,where the numbers of cells are 1.2 ؋ 1029, 2.6 ؋ 1029, 3.5 ؋1030, and 0.25–2.5 ؋ 1030, respectively. The numbers of heterotrophic prokaryotes in the upper 200 m of the open ocean,the ocean below 200 m, and soil are consistent with averageturnover times of 6–25 days, 0.8 yr, and 2.5 yr, respectively.