摘要:

In a letter published in Issues in Science and Technology, Revelle [1990] comments that one of the principal sinks for atmospheric carbon is probably phytoplankton production in the ocean. Revellegoes on to state (p. 21‐22).This process (that of phytoplankton growth and death, followed by settling of organic carbon out of the surface ocean to depth; the so‐called “biological pump”) could account for the sequestration of at least a billion tons of carbon of the total of five billion or six billion produced annually by fossil fuel consumption and biological a

ISSN:0886-6236    

DOI:10.1029/91GB01384

年代:1991

数据来源: WILEY

摘要:

In my reading and travels I frequently come across statements regarding the importance of biological cycles in the ocean to the uptake of CO2produced by fossil fuel burning and forest cutting. While these are often prefaced with an admission that physical processes are more important, the listener or reader comes away with a feeling that somehow biology has a very important role to play. This supposed importance is being used as a defense for the funding of a wide range of biologically oriented ocean programs. I challenge this defense.

ISSN:0886-6236    

DOI:10.1029/91GB01421

年代:1991

数据来源: WILEY

摘要:

Over the past decade it has become apparent that the atmosphere is a significant pathway for the transport of many natural and pollutant materials from the continents to the ocean. The atmospheric input of many of these species can have an impact (either positive or negative) on biological processes in the sea and on marine chemical cycling. For example, there is now evidence that the atmosphere may be an important transport path for such essential nutrients as iron and nitrogen in some regions. In this report we assess current data in this area, develop global scale estimates of the atmospheric fluxes of trace elements, mineral aerosol, nitrogen species, and synthetic organic compounds to the ocean; and compare the atmospheric input rates of these substances to their input via rivers. Trace elements considered were Pb, Cd, Zn, Cu, Ni, As, Hg, Sn, Al, Fe, Si, and P. Oxidized and reduced forms of nitrogen were considered, including nitrate and ammonium ions and the gaseous species NO, NO2, HNO3, and NH3. Synthetic organic compounds considered included polychlorinated biphenyls (PCBs), hexachlorocyclohexanes (HCHs), DDTs, chlordane, dieldrin, and hexachlorobenzenes (HCBs). Making this assessment was difficult because there are very few actual measurements of deposition rates of these substances to the ocean. However, there are considerably more data on the atmospheric concentrations of these species in aerosol and gaseous form. Mean concentration data for 10° × 10° ocean areas were determined from the available concentration data or from extrapolation of these data into other regions. These concentration distributions were then combined with appropriate exchange coefficients and precipitation fields to obtain the global wet and dry deposition fluxes. Careful consideration was given to atmospheric transport processes as well as to removal mechanisms and the physical and physicochemical properties of aerosols and gases. Only annual values were calculated. On a global scale atmospheric inputs are generally equal to or greater than riverine inputs, and for most species atmospheric input to the ocean is significantly greater in the northern hemisphere than in the southern hemisphere. For dissolved trace metals in seawater, global atmospheric input dominates riverine input for Pb, Cd, and Zn, and the two transport paths are roughly equal for Cu, Ni, As, and Fe. Fluxes and basin‐wide deposition of trace metals are generally a factor of 5‐10 higher in the North Atlantic and North Pacific regions than in the South Atlantic and South Pacific. Global input of oxidized and reduced nitrogen species are roughly equal to each other, although the major fraction of oxidized nitrogen enters the ocean in the northern hemisphere, primarily as a result of pollution sources. Reduced nitrogen species are much more uniformly distributed, suggesting that the ocean itself may be a significant source. The global atmospheric input of such synthetic organic species as HCH,PCBs, DDT, and HCB completely dominates their input via

ISSN:0886-6236    

DOI:10.1029/91GB01778

年代:1991

数据来源: WILEY

摘要:

Taiga or boreal forest environments are a poorly understood component of the global CH4budget. Results from a 1‐year study of CH4fluxes at a range of representative floodplain and upland taiga sites in the Bonanza Creek long term ecological research area show that soil consumption of atmospheric CH4was the dominant process. Methane emission occurred only sporadically in the earliest successional stages in the floodplain system; all other floodplain and upland sites were net CH4consumers. Our results suggest that upland and floodplain taiga soils are an atmospheric CH4sink of up to 0.8 Tg yr−1. Point‐source bogs and fens are the only important CH4‐emitting sites i

ISSN:0886-6236    

DOI:10.1029/91GB01303

年代:1991

数据来源: WILEY

摘要:

Increased world demand for rice production may lead to an increase in methane emission to the atmosphere and future global warming. One suggested way to reduce methane emission is to discourage the practice of incorporating previous crop residue prior to planting rice, since the residue may enhance methane emission from flooded rice fields. This concept is supported by data from a 2‐year study of flooded rice fields on two different soil types in Texas. In 1990, rice stubble from 1989 was incorporated into both soils. Seasonal methane emission from a Lake Charles clay field increased from 15.9 g m−2in 1989 to 31.0 g m−2 in 1990. In the Beaumont clay field, seasonal methane emission increased from 4.5 to 11.4 g m−2. While methane emission increased between 1989 and 1990, grain yield dropped by 2100 and 840 kg ha−1in the Lake Charles and Beaumont fields, respectively. Visual inspection at harvest indicated that the 1990 rice yield decrease resulted from grain abortion, presumably caused by the rice cultivar's sensitivity to soil anaerobiosis. The calculated amount of organic carbon not translocated to grain was comparable to the estimated amount of organic carbon required for the increased methane emission. We hypothesize that labile carbon in straighthead susceptible rice cultivars can "leak" from roots damaged by excessively anaerobic soil and be metabolized to its equivalent in methane. These data suggest that minimizing incorporation of crop residue prior to planting can decrease methane emission from flooded rice and reduce the potential for yield loss, particularly with some cultivars and in soils with low rates of seepage and pe

ISSN:0886-6236    

DOI:10.1029/91GB01304

年代:1991

数据来源: WILEY

摘要:

Previously published data on vertical fluxes of particulate carbon (PC), nitrogen (PN), organisms (MICRO), and extracted adenosine triphosphate (ATP) into screened sediment traps (335 μm) from the VERTEX 5 and ADIOS I programs are reexamined as they relate to biogeochemical cycling and oceanic productivity. The four stations discussed represent an oligotrophic to mesotrophic gradient in total primary production (PT), ranging from 245 to 1141 mg Cm−2d−1and a gradient in PC flux from the euphotic zone, ranging from 12 to 164 mg Cm−2d−1for particles<335 μm in diameter. Vertical fluxes of PC, PN, MICRO, and ATP decreased as negative power functions of depth with significantly higher depth‐dependent losses for ATP fluxes. The flux of intact biota (free, particle‐associated, and some active “swimmers,” measured microscopically and by extracted ATP) decreased rapidly in the upper 200 m, contributing as much as 52.4% at the most productive station and as little as 1.6% to the flux of PC at oligotrophic stations, remaining relatively constant or increasing slightly (to 3.4 ‐ 9.6% PC flux) between 200 and 2000 m. Multiple regression analyses, expressing fluxes as functions of depth and PTor new production, PN, demonstrated that MICRO and ATP fluxes were more dependent on PT, PN, and depth than bulk PC or PN fluxes. The present analysis illustrates that while sinking particulate organic matter (POM) undergoes rapid attrition in the upper water column, the fluxes of sedimenting biota decrease at even higher rates. Findings support the hypothesis that in oceanic waters, POM sinking from the euphotic zone rapidly becomes a poor habitat for associated microbes, and mechanisms other than remineralization by attached microbes must be invoked to explain observed fluxes and attrition rates. This study also supports the hypothesis that the vertical flux of intact organisms is a more sensitive and less ambiguous record of upper ocean processes than bulk flux measurements of total mass, PC, or PN. Therefore time‐resolved measurement of the flux of biota may be useful in estimating PTand PNin

ISSN:0886-6236    

DOI:10.1029/91GB01543

年代:1991

数据来源: WILEY