Phytoplankton exudate release as an energy source for the growth of pelagic bacteria

The release of dissolved organic carbon (DOC) from phytolankton during photosynthesis, and the utilization of this carbon by planktonic bacteria, was studied using ¹⁴CO₂ and selective filtration. Natural sea water samples from a coastal area of the Northern Baltic Sea were incubated in the laboratory for detailed studies, and in situ for estimation of annual dynamics. In a laboratory incubation (at +1°C) the concentration of ¹⁴C-labelled dissolved organic carbon increased for about 2 h and then reached a steady state, representing about 0. 1% of the total DOC. Labelled organic carbon in the phytoplankton and bacterial fractions continued to increase almost linearly. The continuous increase in the bacterial fraction is thought to represent almost instantaneous utilization of the DOC released from the phytoplankton during photosynthesis. As an annual average, in 4 h in situ incubations, about 65% of the labelled organic carbon was found in the phytoplankton fraction (>3 m), about 27% in the bacterial fraction (0.2 to 3 m) and the remaining 8% as DOC (<0.2 m). Large variations in these percentages were recorded. The measured annual primary production was 93 g C m^-2 (March to December), and the estimated bacterial production due to phytoplankton exudates 29 g C m^-2. This represents a release of DOC of about 45% of the corrected annual primary production of 110 g C m^-2 (assuming a bacterial growth efficiency of 0.6).     

Comparison between the carbon-14 and oxygen consumption method for the determination of the activity of heterotrophic bacterial populations

The activity of the heterotrophic microbial population in the saline Lake Grevelingen (The Netherlands) and the Mediterranean Etang Salses Leucate (France) was determined by measuring the oxygen consumption rate, and the uptake of ¹⁴C-labelled glycollate, pyruvate and an amino acid mixture. The maximum uptake rate of the applied organic compounds in Lake Grevelingen was generally less than 10% of the carbon mineralization rate calculated from the oxygen consumption experiments. Only for pyruvate and glycollate higher values were found of about 30 to 40% with one exceptionally high value for pyruvate of 149%. However, these higher percentages were found in winter, when the activity of the heterotrophic microbial population was very low. In Etang Salses Leucate higher maximum uptake rates of the ¹⁴C-labelled compounds were found, relating this uptake to the oxygen consumption rate. Yet the maximum uptake rate is still always lower than 35% of the carbon mineralization calculated from the oxygen uptake rate. Taking into account that maximum uptake rates were considered, the results demonstrate that the uptake of ¹⁴C-labelled organic compounds represents a serious underestimation of the activity of the bacterial population in situ. The extent of the underestimation depends on the water type. It was concluded that the determination of the heterotrophic activity by measuring oxygen consumption rates offers a better insight into the carbon mineralization process in natural waters than the uptake experiments with ¹⁴C-labelled substrates.Communication no. 228 of the Delta Institute for Hydrobiological Research, Yerseke, The Netherlands     

Ecological energetics of the seaweed zone in a marine bay on the Atlantic coast of Canada. III. Energy transformations by sea urchins

An energy budget was constructed for a population of the sea urchin Strongylocentrotus droebachiensis in the nearshore area of St. Margaret's Bay, Nova Scotia, Canada. Of the 6 age classes identified, ages 1+and 2+accounted for about 1/2 the population energy flow. Population production efficiencies were: production/assimilation=0.28, production/consumption=0.04 to 0.13, and production/biomass=0.80. Although S. droebachiensis was the dominant herbivore in the seaweed bed, it utilized only 1 to 7% of seaweed production. As with other populations of sea urchins, however, it had a proportionately greater influence on seaweed biomass, and also presumably production, by clearing seaweed from large areas of substrate and maintaining it clear. Loss of dissolved organic matter, the only term in the energy budget not measured, was estimated by substracting the other terms in the energy budget from consumption. In laboratory individuals, this ranged from 40 to 80% of absorption (consumption-faeces). A critical review of energy budgets for 6 other species of marine benthic grazers also revealed large amounts of energy unaccounted for that might be attributed to loss of dissolved organic matter.Contribution to the International Biological Program CCIBP 192Bedford Institute Contribution.     

An annual carbon budget for the kelp Laminaria longicruris

Oxygen evolution and uptake by whole thalli of the large marine alga Laminaria longicruris de la Pylaie were measured for 24 h, once every 2 weeks for a year, using large chambers to incubate the plants on the sea bed. Diel rates of photosynthesis and respiration were calculated from these measurements and continuous light measurements were used to extrapolate the data between observation dates. The resulting estimates were combined with measurements of growth and carbon content to give an annual carbon budget for a typical mature plant. Annual net assimilation was 6.8 mgC per cm² of frond surface (71 cal cm^-2). Approximately 45% of this appeared in the production of new frond tissue, and a further 12% was accounted for by storage of carbon in mature frond tissue. About 8% was needed for stipe growth, and the remaining 35% was assumed to be lost as dissolved organic carbon. Diel net photosynthetic rates reached a maximum in June and July and were negative only in November, indicating an ability to produce a photosynthetic surplus throughout winter. In early winter the plants drew on stored reserves to supplement photosynthesis in providing carbon for growth, but from January onwards photosynthesis provided more than enough carbon for growth.     

Nitrogen assimilation by phytoplankton and other microorganisms in the surface waters of the central North Pacific Ocean

Assimilation rates of ¹⁵N-labelled ammonium, urea, and nitrate by plankton in the upper euphotic zone were measured in 2 summer, 2 winter, and 1 spring cruise in the central North Pacific Ocean. Average rates of ammonium plus urea assimilation could not be determined precisely, but were estimated to be 7 to 25 g-at. N m^-3 day^-1. Indirect evidence suggested that non-photosynthetic microorganisms contributed to these rates. Nitrate assimilation was negligible in the upper waters considered in this report (above the chlorophyll maximum and the nutricline). Potential, nitrate-saturated rates were in the range 1 to 8 g-at. N m^-3 day^-1. Seasonal comparison showed lowest rates of both carbon and nitrogen assimilation rates per chlorophyll a in winter.     

Sedimentation and benthic mineralization of organic detritus in a Norwegian fjord

The supply of particulate material to the sea-bed as well as the oxygen consumption and the redox potential of the sea-bed were measured during a one-year period (1979/1980) at 60 and 90 m depth in the inner part of a west Norwegian fjord, Fanafjorden. At both sites, uniform sedimentation rates of total particulate material (825 and 885 g m^-2 yr^-1, respectively) and particulate inorganic material (576 and 616 g m^-2 yr^-1, respectively) were found. The sedimentation rates of particulate organic carbon (96 and 107 g m^-2 yr^-1, respectively) and particulate organic nitrogen (10 and 12 g m^-2 yr^-1, respectively) were low in winter, higher in summer and autumn, with maxima in May/June, reflecting similar maxima in the phytoplankton biomass in the area, with 6 to 8 wk delay. The oxygen consumption of the sea-floor was lowest in winter/spring and highest in summer. Thirtytwo and 38 g C m^-2 yr^-1 (respiration quotient=0.85) were metabolized by the sediment at 60 and 90 m, respectively. The simultaneous measurements of sedimentation rates and sediment oxygen uptake throughout a whole year demonstrated that the benthic mineralization is governed by the sedimentation over a longer time-scale, but that seasonal imbalances do occur. A box-model of the flux of particulate organic carbon to the sediment surface is presented, and includes the relevant processes and some quantitative estimates.     

Isotopic composition (C & N) of the suspended particles and N uptake by phytoplankton in a shallow tropical coastal lagoon

The spatial distribution of the C/N ratios and variations in δ¹³C and δ¹⁵N of suspended particulate matter were used to characterise their source in Asia’s largest brackish water lagoon, Chilika, India. In addition, the significance of re-mineralised nutrients in the primary productivity of the shallow lagoon was also determined through quantification of the subsurface nitrogen uptake conditions at two relatively stable locations in the lagoon. The results indicated that the influence of terrestrial organic matter was the maximum in the northern sector and was relatively limited at the central and southern part of the lagoon. In situ ¹⁵N uptake experiments (daytime) under biogeochemically stable conditions revealed that the N uptake by phytoplankton ranged between 0.24 and 1.01?mM?m^?3?h^?1 during pre-monsoon and post-monsoon seasons. New production and regenerated production in the shallow lagoon was also estimated by calculating f-ratios (ratio of nitrate assimilation by phytoplankton to total nitrogenous nutrient assimilation, have been estimated), which varied from 0.52 in the post-monsoon to 0.38 in the pre-monsoon. Lowering of the f-ratio from post- to pre-monsoon indicated a dominance of mineralisation over the new production.     

Feeding biology of the brackish-water oncholaimid nematode Adoncholaimus thalassophygas

The brackish-water inhabiting nematode Adoncholaimus thalassophygas (De Man, 1876) may be classified as an omnivore and predator according to the gut contents of the adults. A series of ¹⁴C experiments was conducted to investigate the feeding potential of labelled microorganisms and dissolved ¹⁴C glucose. The observed consistent failure to incorporate ¹⁴C from labelled microorganisms, and its consistent success with dissolved ¹⁴C glucose suggests that dissolved organic matter may be more important than microorganisms as a food source for his nematode. This corresponds also with direct observations of living worms which showed very little uptake of particulate food other than that originating from predation. Defecation and mean gulping rates were low and, therefore, ¹⁴C glucose uptake from solution can hardly be explained by the assumption that large amounts of water are swallowed and passing through the gut. By means of mucus secretion, A. thalassophygas forms compact agglutinations of detrital sediment which are sites of enhanced microbial activity. We suggest that hatched juveniles feed primarily on dissolved organic matter released by the intensive microbial activity within this habitat. Adults retain the ability to utilize dissolved organic matter, and supplement their diet by scavenging on carcasses and occasional predation. Thus, the biology of oncholaimid nematodes may be characterized by an intimate linkage to microbial metabolism, although they do not appear to feed directly upon microorganisms.     

Energy relations of the bivalve Mercenaria mercenaria on an intertidal mudflat

Measurements of the filtration rate and oxygen consumption of the bivalve Mercenaria mercenaria (L.) have been made using flowing water systems, and then combined with growth and survivorship data to construct an energy budget for a tidal-flat population in Southampton Water. Estimated consumption (1292 kcal m^-2 year^-1) is mainly deposited as faeces and pseudofaeces (759 kcal) or excreted (160 kcal); 29% (374 kcal) is assimilated, of which 241 kcal are used for respiration, 72 kcal for flesh production and 61 kcal for gamete production. M. mercenaria contributes significantly to other trophic groups in Southampton Water; predators remove an estimated 55 kcal m^-2 year^-1, and 829 kcal pass to the scavenger/decomposer chain.     

Plankton of the fladen ground during FLEX 76 III. Vertical distribution,population dynamics and production of Calanus finmarchicus (Crustacea: Copepoda)

Samples taken in the northern North Sea with the Continuous Plankton Recorder (CPR), the Undulating Oceanographic Recorder (UOR), the Longhurst Hardy Plankton Recorder (LHPR) and by our colleagues from other participating Institutes during the Fladen Ground Experiment (FLEX 76) were used to describe the vertical distribution and population dynamics of Calanus finmarchicus (Gunnerus) and to provide estimates of the production and carbon budget of the population from 19 March to 3 June, 1976. Total production of the 19 March to 3 June, 1976. Total production of the nauplii and copepodite stages (including adults), during the exponential growth phase in May, was estimated to be in the range of 0.49 to 0.91 g C m^-2 d^-1 or 29.0 to 55 g dry wt m^-2 (14.5 to 27.8 g C m^-2) for the three successive 10 d periods in May. Two gross growth efficiencies (K ₁) (20 and 34%), together with the lower value of C. finmarchicus production, were used to calculate the gross ingestion levels of algae as 2.45 and 1.44 g C m^-2 d^-1 (73.5 and 43.2 g C m^-2 over the May period). These ingestion levels, together with the algae ingested by other zooplankton species, are greater than the estimated total phytoplankton production of 45.9 g C m^-2 over the FLEX period. A number of factors are discussed which could explain the discrepancies between the production estimates. One suggestion is that the vertical distribution of the development stages of this herbivorous copepod and their diel and ontogenetic migration patterns enable it to efficiently exploit its food source. Data from the FLEX experiment indicated that the depletion of nutrients limited the size of the spring bloom, but that it was the grazing pressure exerted by C. finmarchicus which was responsible for the control and depletion of the phytoplankton in the spring of 1976 in the northern North Sea.JONSDAP Contribution No. 51     

Seasonal growth and productivity ofMacrocystis integrifolia in British Columbia,Canada

The seasonal growth rates and nitrogen and carbon fluxes were estimated for two subtidalMacrocystis integrifolia Bory kelp forests in British Columbia, Canada from changes in population structure through time. Mean relative growth rates of the forests varied from a high of 4.3% d^-1 to a low of-3.6% d^-1. Mean net assimilatioon rates of carbon (a photosynthesis analog) varied from a high of 0.66 g C m^-2 of foliage d^-1 to a low of-0.87 g C m^-2 d^-1. The leaf area index ranged from 0.3 to 11.9. Annual carbon input on a foliage area basis was calculated at 250 g C m^-2 yr^-1. Annual carbon input to the forest was estimated at 1 300 g C m^-2 of ocean bottom yr^-1. The yearly nitrate nitrogen input to the forest was estimated at 60 g N m^-2 of ocean bottom yr^-1. The net ecosystem production varied from-520 to +31 g C m^-2 of ocean bottom yr^-1. The intra-forest, inter-forest and seasonal variabilities of these productivity parameters are discussed.     

Seasonal variations in nitrogen-fixation (acetylene reduction) and sulphate-reduction rates in the rhizosphere of Zostera noltii: nitrogen fixation by sulphate-reducing bacteria

Nitrogen-fixation (acetylene reduction) rates were measured over an annual cycle in meadows of the seagrass Zostera noltii Hornem in the Bassin d'Arcachon, south-west France, between March 1994 and February 1995, using both slurry and whole-core techniques. Measured rates using the slurry technique consistently overestimated those determined on whole cores, probably due to the release of labile organic carbon sources as a result of root damage during preparation of the slurries. Thus, the whole-core technique may provide a more accurate estimate of in situ activity, since disturbance of physicochemical gradients of oxygen, sulphide, nutrients and the relationship between the plant roots and the rhizosphere microflora is minimised. Rates measured by the whole-core method were 1.8- to 4-fold greater (dependent upon season) in the light than those measured during dark incubations, indicating that organic carbon diffusing from the plant roots during photosynthesis was an important factor in regulating nitrogen fixation in the rhizosphere. Additions of sodium molybdate, a specific inhibitor of sulphate-reducing bacteria (SRB) inhibited acetylene-reduction activity by >80% as measured by both the slurry and whole-core techniques throughout the year, inferring that SRB were the dominant component of the nitrogen-fixing microflora. A mutualistic relationship between Z. noltii and nitrogen-fixing SRB in the rhizosphere, based on the exchange of organic carbon and fixed nitrogen is proposed. Acetylene- and sulphate-reduction rates showed distinct summer peaks which correlated with a reduced availability of ammonium in the sediment and the annual growth cycle of Z. noltii in the basin. Overall, these data indicate that acetylene reduction (nitrogen fixation) activity in the rhizosphere of Z. noltii was regulated both by the availability of organic carbon from the plant roots and maintenance of a low NH ₄ ⁺ concentration in the vicinity of the plant roots due to efficient assimilation of NH ₄ ⁺ by Z. noltii during the growth season. Nitrogenfixation rates determined from acetylene-reduction rates measured using the whole-core technique ranged from 0.1 to 7.3 mg N m^-2d^-1, depending on season, and were calculated to contribute between 0.4 and 1.1 g N m^-2yr^-1, or 6.3 to 12% of the annual fixed nitrogen requirement of Z. noltii.     

Incorporation of organic aggregates by marine mussels

Two marine mussels, Geukensia demissa (Dillwyn) and Mytilus edulis (L.) collected in 1990 in Old Silver Beach, Falmouth, Massachusetts, incorporated nitrogen when fed ¹⁵N-labelled organic aggregates produced from dissolved organic nitrogen released by the brown sea-weed Fucus vesiculosis. Uptake of ¹⁵N on the aggregate diet was linear over the course of 24 h, and unincorporated ¹⁵N was eliminated from the gut after 48 h. Both species of mussels incorporated approximately five times more N when they were fed organic aggregates than when they were fed either ¹⁵N-labelled dissolved organic material (DOM) or particulate detritus, both of which were also derived from the seaweed. Nitrogen uptake was greatest in controls fed the diatom Thalassiosira weissflogii; mussels fed phytoplankton incorporated seven times more nitrogen than those fed aggregates. However, aggregates could supply an estimated 7 to 14% of the N requirements for both mussels, whereas DOM or particulate detritus could only supply 1 to 3%. These data provide evidence that a food web pathway exists from primary producer to released dissolved organic nitrogen to microbial organic aggregate to metazoan consumer, and, further, that it can be more important in a detrital food web than either particulate detritus or DOM.     

Effect of boundary layer transport on the fixation of carbon by the giant kelp Macrocystis pyrifera

The uptake of inorganic carbon into the thallus of Macrocystis pyrifera (L.) C. Ag. requires first that the inorganic carbon pass through the water medium to the plant surface. This transfer of inorganic carbon to the thallus must take place through a boundary layer. Experiments in water tunnels indicate that the boundary layer adjacent to the M. pyrifera blade may be turbulent in water speeds as low as 1 cm sec^-1. Photosynthetic output of the blade can be increased by a factor of 300% by increasing water speeds over the blade surface from 0 to 4 cm sec^-1. This is consistent with a decrease in the thickness of the boundary layer. Above 4 cm sec^-1, the assimilation of carbon was limiting. The assimilation of carbon is generally known to follow Michaelis-Menten-like kinetics. Combining the two uptake steps into an overall model of carbon uptake agrees well with photosynthetic data obtained from M. pyrifera under varying conditions of water speed and bicarbonate concentrations in the laboratory. The ecological and morphological consequences of these findings are discussed.     

Spatial variation of growth and gonadal developments of Maurolicus muelleri in the Norwegian Sea and in a Norwegian fjord

The epibenthic megafauna of the high-Arctic Northeast Greenland shelf was investigated by means of seafloor photography and Agassiz trawl catches. At 54 stations in water depths between 40 and 770 m, sequences of color slides, each depicting about 1 m² of the seafloor, were obtained along photographic transects of about 100 to 600 m length. The photographs were quantitatively analyzed for abundance of epibenthic organisms identified by comparison with specimens collected from trawl catches. Megabenthic biomass was estimated by multiplying density values with averge body mass figures. For five dominant brittle star species, the population oxygen uptake and, thus, organic carbon mineralization potential were approximated by applying individual respiration rates of average-sized specimens to density figures. Multivariate analyses of the megabenthic species distribution revealed a distinct depth zonation. Shallow shelf banks (<150 m), characterized by coarse sediments, many stones and boulders as well as negative bottom water temperatures, housed a rich epifauna (30 to 340 ind m^–2, 1.8 to 10.5 g AFDW m^–2), strongly dominated (80 to 98% by numbers) by the brittle stars Ophiocten sericeum and Ophiura robusta. The oxygen uptake by brittle stars ranged from 0.4 to 95 mol O₂ m^–2 h^–1 (i.e., assuming a respiratory quotient of 0.8, an organic carbon mineralization of 0.1 to 21.9 mg C m^–2 d^–1). At the bank flanks sloping to the shelf troughs (100 to 580 m), finer sediments prevailed, stones were rare, and bottom water temperatures were positive due to the inflow of Atlantic water. Compared to bank sites, total epibenthic abundances as well as carbon mineralization by brittle stars were roughly ten times and total biomass about four times smaller. In deep shelf depressions as well as at the continental slope (200 to 770 m), stones were completely lacking, and sediments very fine. Epibenthic standing stock and carbon mineralization were one to two orders of magnitude lower than on the banks. The estimation of brittle star oxygen uptake indicates that a considerable portion of the organic carbon produced in the polynya and partitioned to the benthos may be remineralized by epibenthic bank assemblages.     

Surface-film microbial populations: diel amino acid metabolism,carbon utilization,and growth rates

Microheterotrophic dissolved free amino acid (DFAA) utilization, and microbial community and bacterial community carbon production and growth were studied using ³H-labeled organics as tracers in marine surface-film and subsurface (10 cm) waters off Baja California in November 1983. DFAA utilization was generally more rapid during the day (0.14 to 0.38 nM h^-1) than at night (0.04 to 0.14 nM h^-1) in surface-film and subsurface waters, but the percent of utilized amino acid which was respired was always greater during the night (22 to 57%) compared to the day (14 to 18%). Utilization of DFAA-carbon was estimated to range from 0.3 to 5.3 g C l^-1 d^-1 for all stations studied. In six of the 8 samples examined, the percentage of microbial carbon accounted for by the bacterial component of the population (1.4 to 5.9%) was strikingly similar to the percentage of microbial carbon production accounted for by bacterial carbon production (1.9 to 5.1%). In all of these six samples, total microbial specific-growth rates and bacterial specific-growth rates were approximately equivalent (0.9 to 2.2 d^-1 for the microbial community; 0.7 to 1.9 d^-1 for bacteria). The two exceptions were samples apparently influenced by transient flagellate populations migrating into the surface or subsurface waters at night. These observations support the conclusion that surface films contain unique and highly active microbial populations.     

Plankton of the fladen ground during FLEX 76 II. Population dynamics and production of Thysanoessa inermis (Crustacea: Euphausiacea)

Samples taken in the northern North Sea with the Continuous Plankton Recorder (CPR), the Undulating Oceanographic Recorder (UOR) and the Longhurst-Hardy Plankton Recorder (LHPR) during the Fladen Ground Experiment in 1976 (FLEX 76) are used to describe the vertical distribution and population dynamics of Thysanoessa inermis (Krøyer) and to provide estimates of the production and carbon budget of the population from 19th March to 3 June 1976. Spawning occurred in late April and early May, in near synchronisation with the start of the spring bloom of phytoplankton. Eggs, nauplii and calyptopes reached maximum abundance in succession, and furciliae were numerous when sampling ceased in early June. Adults increased in length from a mean of 12.1 mm in mid-March to 17.5 mm in early June and the estimated production was 2.40 mg m^-3 over the 74 d period. Total carbon ingested by the population of T. inermis was estimated to be 10 mg C m^-2 d^-1 in the upper 100m which was only 1.5% of the daily primary production of 0.68 gC m^-2 measured over the FLEX period 26 March to 4 June 1976. The grazing by T. inermis on the phytoplankton population was assumed to have little effect on the control and depletion of the spring phytoplankton bloom during FLEX 77.JOSDAP Contribution No. 50     

Benthic response to sedimentation of a spring phytoplankton bloom: Process and budget

The response of benthos to sedimentation of the spring phytoplankton bloom in the Kiel Bight (Western Baltic Sea) is described in terms of biomass (ATP) and activity (heat production and ETS-activity). Input of the bloom (11.5 g C m^-2) over a period from March 25 to April 19, 1980 to the sediment surface was in the form of cells and fresh phytodetritus as indicated by low C/N ratios (7) and high energy charge values (0.78). Benthic microbial activity was immediately stimulated by this input as heat production doubled and the activity of ETS tripled over winter values within 12 d in the absence of a significant increase in ambient temperature. A comparison of the two activity parameters suggests that anaerobic metabolism is more important during the winter (February and March) than after input of the bloom. Meiofauna was not able to take part in the first activity outburst. Benthic ATP-biomass (excluding macrofauna) doubled in late April due to microbial production, and doubled again in early May when meiofauna started reproductive activity. For macrofauna a general statement was not possible, although the sediment surface feeder Macoma baltica commenced a build up of glycogen and lipid resources immediately following bloom input whereas Nephtys ciliata, feeding on sediment and small macrofauna, showed a less pronounced and delayed effect from this input. An energy budget based on heat production measurements was calculated. A daily heat loss of the benthic community of 21.7 KJ m^-2 d^-1 (35.5 KJ m^-2 d^-1) was found, when a depth of 3 cm sediment (5 cm) was assumed. Heat production of macrofauna contributed less than 5% of this activity. The input of the bloom was burned within 21 (13) d. Preliminary estimations for an annual budget suggest that the vertical transport of particulate organic matter via sedimentation can only explain 25% (15%) of the benthic activity in the shallow water ecosystem of the Kiel Bight. This indicates the presence of other sources of organic carbon such as benthic primary production or other transport processes providing carbon to the sediments.Publication No. 384 of the Joint Research Program of Kiel University (Sonderforschungsbereich 95)     

Reassessment of the Ocean-To-Atmosphere Flux of Carbon Monoxide

Abstract

Carbon monoxide (CO) in the surface sea waters is produced predominantly by photochemical processes, oxidized by micro-organisms and outgassed to the atmosphere. to assess carbon monoxide flux from the oceans to the atmosphere, the photochemical production and microbial oxidation of carbon monoxide in the oceanic mixed-layer was investigated during several oeanographic cruises and in the laboratory. the photoproduction rate of carbon monoxide was found to be well correlated to the concentration of dissolved organic carbon (DOC) in coastal and open ocean surface waters. Taking a global average carbon monoxide production rate of 10 ± 2 nmole litre^?1 (mg DOC hr)^?1 in the surface open ocean water, and 25 ± 7 nmole litre^?1 (mg DOC hr)^?1 in coastal sea water, at cloud-free summer solar noon, the photochemical production of carbon monoxide in the global oceans is estimated to be at a rate of 1200 ± 200 Tg CO y^?1. the microbial carbon monoxide turnover time in the mixed-layer was observed to range from hours in a coastal estuary to 16 days in the Pacific along 1057deg; W in dark incubations. Natural sunlight can largely inhibit the microbial consumption of carbon monoxide in surface water. On a global scale, microbial consumption is responsible for the loss of less than 10% of photochemical produced carbon monoxide in the surface ocean. Field measurements have shown that the net transport of carbon monoxide from the euphotic zone to the underlying deeper ocean water is limited and that the overall life time in surface sea waters is less than 3-4 hours. When combined, these field measurements with the photoproduction and microbial consumption rates obtained, we estimate the oceanic flux to the atmosphere is about 1000 ± 200 Tg CO y^?1, which represents the largest single source of atmospheric carbon monoxide.     

Carbon budget for the spring bloom in Auke Bay,Alaska

This paper describes a carbon budget for the spring phytoplankton bloom in Auke Bay, a subarctic bay in southeastern Alaska. The budget was constructed using semiweekly data on carbon production, particulate carbon in the water column, and cumulative sedimentation of carbon, chlorophyll a, and pheopigments. From these measured parameters, seasonal carbon consumption, utilization, and import/export terms were derived. The chlorophyll and pheopigment data were used to partition carbon sinking out of the photic zone between phytoplankton cells and fecal material. The difference between total carbon production and carbon available for consumption was attributed primarily to carbon import/export related to advection of water masses into and out of the bay. Separate budgets were developed for each of five sampling years (1985–1989). An average of 130±16 g C/m² were produced by phytoplankton during each spring. Our model suggests that an average of 70% of this carbon was available for consumption by grazers within the bay; the remaining 30% is assumed to have been exported from the bay by advective transport. Of the available (non-exported) carbon, an average of 55% was consumed by grazers, 34% sank out of the photic zone in the form of uneaten algae, and about 11% remained at the end of the sampling period in the form of phytoplankton standing stocks. Overall, about 27% of the carbon produced each spring in Auke Bay (35 gC/m²) was used for growth and respiration by first-order consumers within the bay.