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811.
Methyl halides (monohalomethanes), especially methyl bromide, are known to contribute significantly to ozone destruction in the stratosphere. Budgets of natural and anthropogenic methyl bromide suggest that marine organisms may be the source of a significant proportion of the total global production. Since phytoplankton are abundant in surface waters, they are obvious candidates. Cultures of nine phytoplankton species were grown in CO2-enriched, nitrate-limited medium in sealed glass vessels. Species tested include Chaetoceros calcitrans, Isochrysis sp., Porphyridium sp., Synechococcus sp., Phaeodactylum tricornutum, Tetraselmis sp., Prorocentrum sp., Emiliania huxleyi and Phaeocystis sp. Methyl bromide (CH3Br) and methyl chloride (CH3Cl) concentrations were determined by bubbling the cultures with high-purity air, cryotrapping the effluent and analyzing it on a gas chromatograph with an electron capture detector. The Phaeocystis sp. samples were monitored with GCMS. Cell population, bacterial population, Chl a, pH, and nitrate concentration were monitored for periods of at least two weeks. CH3Cl was produced by all cultures. CH3Br was absent in Tetraselmis sp. and Isochrysis sp. cultures, but present in all the others. Methyl iodide (CH3I) was present in most cultures but could not be quantified due to analytical limitations. CH3I and CH3Br production was fastest in stationary phase and continued long after cell division had ceased. Axeic cultures of Phaeocystis sp. achieved almost identical production rates of CH3Cl and CH3Br as xenic cultures of the same species. Species from tropical waters had faster CH3Cl and CH3Br production rates than temperate species. Scaling the observed production rates using global standing stock estimates for Chl a and particulate nitrogen indicate that phytoplankton can account for only a fraction of the CH3Cl and CH3Br believed to be produced in the ocean. Calculations based on the estimated global biomass of Phaeocystis sp. and E. huxleyi blooms show that their contribution is insignificantly small. 相似文献
812.
Benthic Nutrient Recycling in Port Phillip Bay, Australia 总被引:8,自引:0,他引:8
W.M. Berelson D. Heggie A. Longmore T. Kilgore G. Nicholson G. Skyring 《Estuarine, Coastal and Shelf Science》1998,46(6):917-934
Benthic chamber measurements of the reactants and products involved with biogenic matter remineralization (oxygen, ammonium, nitrate, nitrite, phosphate, silicate, TCO2and alkalinity) were used to define solute exchange rates between the sediment and overlying water column of Port Phillip Bay, Australia. Measurements at various sites throughout the bay, conducted during the summers of 1994 and 1995, indicate that the variability in flux values within a site is comparable to year-to-year variability (±50%). Four regions of the bay were distinguished by sediment properties and the northern region was identified as having 3–30 times greater nutrient regeneration rates than the other regions. Benthic recycling accounted for 63 and 72% of the annualized N and P input, respectively, to the entire bay as determined by summing benthic, dissolved riverine, atmospheric and dissolved effluent sources. However, bay-wide sedimentary denitrification accounted for a loss of 63% of the potentially recyclable N. This fraction is higher than many other coastal regions with comparable carbon loading. Denitrification efficiency is apparently not enhanced by benthic productivity nor by bio-irrigation. The rate of bio-irrigation is negatively correlated with denitrification efficiency. Bio-irrigation was studied using radon-222 and CsCl spike injection chamber measurements. Radon fluxes from sediments in Port Phillip Bay were enhanced over the diffusive flux by 3–16 times. The modelled rate of loss of Cs from chamber water was positively correlated with radon flux enhancement results. Both methods identify regions within Port Phillip Bay that have particularly high rates of non-diffusive pore-water overlying water solute exchange. 相似文献
813.
The most important feature of the distribution of the alkalinity and calcium in the Sea of Japan—the increase in the potential
alkalinity with depth under the conditions when the waters are supersaturated in relation to calcium carbonate—is considered.
It is demonstrated that this fact cannot be accounted for by the reaction of the formation-dissolution of calcium carbonate.
A new concept explaining the alkalinity distribution in the sea is proposed. According to it, the biological pump is the basic
process responsible for the alkalinity transport from the euphotic layer into the interior of the sea. Photosynthesis is the
driving force for this process. The role of the active element transporting the alkalinity is not calcium carbonate, as has
been claimed elsewhere, but extracellular polysaccharides (EPSs) produced by phytoplankton. EPSs bind to calcium and other
cations to form transparent exopolymer particles (TEPs). The proposed conception makes it possible to explain the following:
(a) the vertical flux of calcium carbonate that is independent of the super-saturation—undersaturation state of the ambient
water regarding calcium carbonate; (b) the existence of the calcium carbonate flux regardless of the nature of the plankton
skeletons; (c) the nonstoichiometric ratio between the alkalinity and calcium fluxes. 相似文献
814.
I. G. Boyarskikh S. A. Khudyaev S. G. Platonova S. P. Kolotukhin A. V. Shitov T. A. Kukushkina O. V. Chankina 《Izvestiya Atmospheric and Oceanic Physics》2012,48(7):747-760
Local geophysical and geochemical anomalies affect the polymorphism of taste variations, berry shape, and content of some biologically active substances in Lonicera caerulea leaves in the tectonically active Altai Mountains (Dzhazator River basin). 相似文献
815.
通过对菲律宾皮纳图博(Pinatubo)火山1991年6月爆发前后南海表层沉积物及沉降颗粒物中的硅藻丰度及群落组成进行分析,试图揭示皮纳图博火山爆发对南海硅藻生长的影响.研究发现,火山爆发后南海沉积物中硅藻相对丰度显著减少,原因主要在于皮纳图博火山喷发物大量沉积于南海深海,显著提高了南海沉积速率,同时稀释了沉积物中生源... 相似文献
816.
Oceanology - In November 2020, the invasive ctenophore Beroe ovata Bruguière, 1789 was recorded in samples of gelatinous zooplankton from the northern and central parts of the Caspian Sea. The... 相似文献
817.
Oceanology - Thermohaline anomalies in the upper 300-m layer at stations of the so-called “hundred-mile” ship sections over the line “coastal zone of Gelendzhik–central part... 相似文献
818.
Fedorov V. M. Frolov D. M. Velasco Herrera V. M. N. Soon W. W.-H. Cionco R. G. 《Izvestiya Atmospheric and Oceanic Physics》2021,57(10):1239-1253
Izvestiya, Atmospheric and Oceanic Physics - On the basis of calculations of insolation and insolation characteristics, taking into account changes in solar activity, the causes of global climatic... 相似文献
819.
Chechin D. G. Artamonov A. Yu. Bodunkov N. E. Zhivoglotov D. N. Zaytseva D. V. Kalyagin M. Yu. Kouznetsov D. D. Kounashouk A. A. Shevchenko A. M. Shestakova A. A. 《Izvestiya Atmospheric and Oceanic Physics》2021,57(5):526-532
Izvestiya, Atmospheric and Oceanic Physics - The growing relevance of the use of unmanned aerial vehicles (UAVs) for studying turbulence in the atmospheric boundary layer (ABL) is associated with... 相似文献
820.
This study describes an automatic berthing system with mooring lines. It is designed to be berthed by using mooring device on the upper deck of a ship. It is to berth once maintaining parallel with the quay by controlling both forward and aft breast lines. Berthing method is used through length adjustment of mooring lines connected between ship and quay by controlling the angular velocity and the torque of hydraulic motor in mooring device. The study is conducted under three changing conditions of draft, such as even-keel, rise of the gravity center and trim to stern. Variables affecting berthing stability are determined based on the control performance of each condition. Bond graphs method is used to model the system. Controller is designed as PID control method of reference-model algorithm. The control program is composed of synchronous control system based on the equations derived with the numerical analysis. The tank test is conducted to verify the usefulness of the control program. 相似文献