The relationship between community respiration and ETS activity in the ocean

We have studied the relationship between community respiration(R) and enzymatic activity of the electron transport system(ETS) in upper ocean microbial communities (<225 µm)from different oceanic regions. In all except one of the regions,R and ETS were significantly positive correlated. This supportsthe hypothesis that ETS can be widely used to estimate planktonrespiration in natural marine communities (Packard, T.T., Adv.Aquat Microbiol, 3,207–261, 1985). A regression equationwas obtained between all the R and ETS data studied, to deriverespiration from ETS activity. This equation yields a mean errorin the prediction of ±34%, similar to the errors obtainedapplying the equations at each area, but lower than the errorobtained when using the mean R:ETS ratio to determine respiration(±45%). Our results suggest that the use of the ETS-Ralgorithm, along with measurements of ETS activity in seawater,facilitates the estimation of seawater respiratory oxygen consumptionon the mesoscale. This means that by using this approach onecould extend our knowledge of oceanic respiration over largetemporal and spatial scales, and begin to use respiration, notonly productivity, in addressing carbon balance problems inthe upper ocean.     

Respiratory ETS activity of plankton in the northwestern Alboran Sea: seasonal variability and relationship with hydrological and biological features

Respiratory electron transport system (ETS) activity was measuredin plankton samples (<200 µm) collected in the NW AlboranSea. Sampling was carried out during seasonal cruises (summerand autumn 2003 and winter and spring 2004) in 12 stations locatedin transects off the coast of Malaga (southern Spain). Thiswork reports for the first time seasonal variations of the Arrheniusactivation energy (Ea) as well as being the first study to addressCO₂ balance in the NW Alboran Sea. These variations were relatedto changes in the phytoplankton community assemblage, whichcould ultimately be caused by the seasonal variability of hydrologicalconditions. ETS activity was significantly higher in summer,coinciding with a higher chlorophyll a (Chl a) concentrationand relatively high levels of particulate organic matter. TheETS:Chl a_total ratios were low during the four seasons, suggestinga high contribution of autotrophic phytoplankton to the respiratoryactivity of planktonic community. Respiratory CO₂ production(RCP) calculated from ETS activity ranged from 4.6 to 28.1 mgC m^–3 day^–1 during the four cruises. Chl a-specificRCP was lower than the maximum photosynthetic rates reportedin the literature for the studied area, suggesting that primaryproduction (PP) and respiration in the water column might beunbalanced.     

Respiratory electron transport activity of microplankton in the Weddell Sea during early spring: influence of the ice cover and the ice edge

Summary The activity of the respiratory electron transport system (ETS) of the microplankton (<240 m size) was measured in the Northern Weddell Sea during EPOS 1, in the Close Pack Ice (CPI), and in the ice edge (Outer and Inner Marginal Zones, OMIZ and IMIZ). During early spring the activity increased with time and in the pack ice-open water direction. The temporal trend was more obvious than the spatial one. ETS activity ranged from 0.01 to 1.25 ml O₂ m^–3 h^–1 under the ice and from 0.1 to 1.6 ml O₂ m^–3 h^–1 in the open water at the ice edge. Depth-integrated ETS activity in the upper 300 m ranged from 13 to 130 ml O₂ m^–2h^–1. 60% to 80% of the activity took place above 100 m in the OMIZ in the prebloom conditions at the end of the cruise. ETS/Chl a ratios showed the importance of microheterotrophs under the ice, versus a greater phytoplankton dominance in the ice edge-open water zone. The carbon-specific activity reached a maximum (0.43 day^–1) in the innermost zone of the CPI where bacteria dominated. Respiratory activity under the ice is important in producing the oxygen deficit observed, due to the negative balance between photosynthesis and respiration. The ETS activity was at the lower range of that found in the region in summer and is comparable to that measured in other oligotrophic, stratified systems in oceanic areas.Data presented here were collected during the European Polarstern Study (EPOS) sponsored by the European Science Foundation     

Pigment Composition of a Novel Oxygenic Photosynthetic Prokaryote Containing Chlorophyll d as the Major Chlorophyll

The principal pigment found in the majority of oxygenic photosyntheticorganisms is known to be chlorophyll a. However, we isolateda new oxygenic photosynthetic prokaryote that contained chlorophylld as a predominant pigment with chlorophyll a being a minorpigment. Chlorophyll d had previously been noted but its naturaloccurrence and function remained unclear. Cells of the new prokaryotehad an absorption maximum at red region of 714–718 nmdue to chlorophyll d absorption, but no characteristic absorptionpeak of chlorophyll a around 680 nm was observed. Chlorophylld of the new organism was identified spectrophotometricallyin several solvents and its chemical structure was confirmedby NMR and FABMS analysis. The cell also contained a chlorophyllc-like pigment, zeaxanthin and a-carotene but not chlorophyllb and ß-carotene. The content of chlorophyll d accountedfor more than 2% of the cell dry weight, while the content ofchlorophyll a was less than 0.1%. The chlorophyll a/d ratioremained between 0.03 and 0.09 under different culture conditions.The light absorption characteristics and the high content ofchlorophyll d along with the small content of chlorophyll aindicated the existence of a new light utilization mechanisminvolving chlorophyll d. (Received October 7, 1996; Accepted December 16, 1996)     

Respiratory electron transport system (ETS) activity in Spanish reservoirs: relationships with nutrients and seston

We examined the relationship between potential respiration rates,as measured by electron transport system (ETS) activity, standardizedat a defined temperature (ETS2O). and nutrients and sestonicparticles in a set of 101 Spanish reservoirs spannin a widerange of limnological characteristics. ETS activity ranged from0.009 to 31 31 µmol e^- 1^–1 h^–1 Among the nutrients,it was significantly correlated only with phosphorus, and onlyduring the stratification period. During this period, the bestregressor of ETS2O was the concentration of chlorophyll a (Chla),whereas during the mixing period the best regressor was particulateorganic nitrogen (PON), suggesting a greater contribution ofnon-algal sestonic particles to total metabolism. Both the meanETS20:PON ratio and the mean Chla:PON ratio increased systematicallywith increasing PON, indicating a lower relative contnbutionof detrital particles to total seston as trophic state increased.In contrast, the mean ETS20:Chla ratio was constant across therange of Chla. Vertical profiles of ETS2O. Chla and PON weremore coherent during the stratification period. when subsurfaceand metalimnetic peaks were frequent, than during the mixingperiod.     

Oxygen consumption in the marine bacterium Pseudomonas nautica predicted from ETS activity and bisubstrate enzyme kinetics

The respiratory O₂ consumption in aerobic bacterial cultureshas been modeled from the time profiles of the in vitro activityof the respiratory electron transfer system (ETS), the bacterialprotein and the concentration of the carbon source in the cultures.The model was based on the concept of bisubstrate kinetic controlof the ETS throughout the exponential, steady-state and senescentphases of the cultures. In the exponential phase, the measuredrates of O₂ consumption and the in vitro ETS activity were closelycoupled, but in the senescent phase, they were uncoupled. Thein vitro ETS activity remained high even after the culture'scarbon source was exhausted, while the O₂ consumption fell tolow levels. Based on the hypothesis that this uncoupling wascaused by limitation of the intracellular ETS substrates (NADHand NADPH), a semi-empirical model incorporating a bisubstrateenzyme kinetics algorithm was formulated and fitted to the observationsof the experiments. The model predicted the rate of O₂ consumptionthroughout the different phases of the cultures with an r² >0.92 (n = 9, P < 0.001) using physiologically realistic Michaelisand dissociation constants. These results suggest that planktonrespiration in the field could be assessed more accurately thanbefore by measuring the intracellular ETS substrates (NADH andNADPH), in addition to ETS activity, in plankton.     

Factors affecting phytoplankton production over the Campbell Plateau, New Zealand

The Campbell Plateau, which covers approximately 600,000 km²at depths ranging from 0–500 m on the rises to 1500 mat the plateau edge, possibly encompasses a unique combinationof bathymetric and hydrological features. Nutrients are in good supply and do not limit primary production.Over areas deeper than 450 m chlorophyll a concentrations aregenerally low but are greater where the stability of the surfacewaters is greater. Chlorophyll a reaches maximum concentrationsin areas shallower than 500 m (e.g., Pukaki Rise and BountyPlateau). Water over the Campbell Plateau generally has low stability,the result presumably of bathymetrically induced mixing andthe turbulent meteorological regime. Phytoplankton-poor wateris apparently introduced into this area where water column stabilityis insufficient to support rapid phytoplankton growth. Shallowbathymetric features appear to confine the phytoplankton nearthe surface and enhance phytoplankton production. It is postulated that current speed and direction is responsiblefor the skewness of the relationship between bottom depth andthe distribution of chlorophyll a and differences between eachbathymetric feature.     

Studies on the absorption spectra of chlorophyll a in aqueous dispersions of lipids from the photosynthetic membranes

The absorption spectra of chlorophyll a were studied in aqueousdispersions of four major lipid components present in the thylakoidmembranes. Chlorophyll a in aqueous dispersions of uncharged galactolipidsrevealed two absorption bands, at 670 and 745 nm, when the molecularratio of chlorophyll to lipid was higher than 0.2. The latterband may be due to the formation of microcrystals of chlorophylla. Chlorophyll a in aqueous dispersions of negatively chargedlipids revealed a single absorption band at 670 nm. However,chlorophyll a was decomposed during measurement in these lipiddispersions. The absorption spectra of chlorophyll a in aqueous dispersionsof mixture of galactolipid and charged lipid were apparentlysimilar to those of chlorophyll a in the charged lipid dispersion.Chlorophyll a, however, was not decomposed in these aqueousdispersions of lipid mixtures. It is concluded that the presence of both galactolipid and chargedlipid are necessary to reconstruct the state of chlorophylla dissolved in the lipid phase in the thylakoid membranes. The red absorption band of chlorophyll a in the reconstructedsystem composed of chlorophyll a, charged and uncharged lipids,appeared at 670 nm with a half bandwidth of 22 nm. Analysisof the absorption spectrum in the fourth derivative and thecurve-fitting methods indicated that the red band was composedmainly of a single band with a peak at 670–671 nm. ¹ Present address: Department of Biology, College of GeneralEducation, University of Tokyo, Komaba, Meguro-ku, Tokyo 153,Japan. (Received October 13, 1977; )     

Respiratory electron transport activity in plankton of the Weddell and Scotia Seas during late spring — early summer: relationships with other biological parameters

Summary As a means to estimate potential oxygen consumption, profiles of elctron transport system (ETS) activity were made along three transects across the Weddell-Scotia Confluence zone (WSC) and the marginal ice zone (which overlapped in part) during the EPOS leg 2 cruise of the RV Polarstern. The integrated ETS activity between 0 and 100 m depth (referred to in situ temperatures) ranged from 261 meq (mili-electron equivalents) m^–2 day^–1 in the WSC to 45 meq m^–2 day^–1 in the southernmost stations at 62° S. The temporal changes in the overall distribution of ETS activity were small compared with the spatial variations. The main feature of the ETS activity distribution was the presence of maxima located in the WSC, coinciding with peaks of phytoplankton biomass. Different relationships between ETS and chlorophyll a concentration in these maxima appeared to be related to diatom or flagellate dominance. Vertically integrated ETS activities were significantly correlated with chlorophyll a and paniculate organic carbon concentrations, primary production and bacterial thymidine uptake.Data presented here were collected during the European Polarstern Study (EPOS) sponsored by the European Science Foundation     

Distribution of chiorophylls and phaeopigments in the Northwestern Atlantic Ocean

During a cruise in the Northwestern Atlantic the distributionsof chlorophylls and phaeopigments were investigated in relationto mesoscale features by high-performance liquid chromatography.Samples were collected from hydrographic Stations and from twoContinuous underway sampling systems fished simultaneously atthe surface (2 m) and at deeper (30–90 m) depths. Highestpigment concentrations were associated with the transitionalzones between Slope Water, the Gulf Stream and Northern SargassoSea. Chlorophyll b occurred in 47% of the samples analyzed andthe dominant chlorophyll a degradation product was phaeophorbidea. Chlorophyllide a was usually found at low concentrationsand phaeophytin a levels were undetectable. Concentrations ofthe various chlorophylls and their degradation products wereused to infer Changes in taxonomic composition, phytoplanktonbiomass and zooplankton grazing pressure across several frontalzones.     

The size distribution of phytoplankton and participate organic matter in the Equatorial Atlantic Ocean: importance of ultraseston and consequences

The size fractionation of paniculate matter (<200, <35,<3 and <1 µm) has been measured in the EquatorialAtlantic Ocean at different stations. Chlorophyll a, phaeophytin,particulate carbon, nitrogen and phosphorus have been analysed.Primary production by ¹⁴CO₂ uptake was also measured with prescreeningtechnique. It appears from this study, that the pariculate matter has avery small size: 40–60% of the chlorophyll passed through1 µm Nucleopore filter, and 75–90% of the paniculatecarbon and nitrogen passed through 3 µm Nucleopore filterin offshore waters. From the atomic ratio C/N, C/P and C/chla, and primary productionvalues, the <3 µm fraction would be mainly constitutedby inactive photosynthetic organisms or partides of detritus.The 3–35 µm fraction, in contrast, would be principallyactive phytoplankton.     

Plankton community respiration in Bransfield Strait (Antarctic Ocean) during austral spring

Community respiration (R) was determined in Bransfield Straitfrom oxygen changes in water samples incubated in borosilicatebottles maintained at in situ temperature. The respiratory electrontransport system (ETS) activity of seawater communities wasalso measured from the same samples. Both data sets were relatedby the regression equation: log R (mg O₂ m^–3 day^–1)=0.462+0.730xlogETS activity mg O₂ m^–3 day^–1) (r=0.80, n=23). Fromthis equation and 37 ETS activity depth profiles, we calculatedthe integrated (0–100 m) community respiration as beingin the range 1.2–4.5 g O₂ m^–2 day^–1 (mean=2.2).These values do not differ significantly from other publishedresults for the Arctic and Antarctic Oceans. Assuming a respiratoryquotient of unity, the areal respiration ranges between 0.45and 1.69 g C m^–2 day^–1 (mean=0.8). This would representan important sink for the primary production reported for BransStrait. The spatial distribution of community respiration showedhigher values associated with the warmer and phytoplankton-richwaters outflowing from Gerlache Strait into Bransfield Strait,and with the front that separates Bellingshausen Sea watersfrom Weddell Sea waters. We suggest that this pattern of distributionmay be related to the transport of organic matter by the BransfieldCurrent along the front.     

Contribution of the different planktonic microbial assemblages to ETS activity in the Ligurian frontal area: north-west Mediterranean Sea

Spatial and size distribution of micro-organisms and their ETSactivity has been investigated in Ligurian Sea surface watersalong the Nice-Calvi transect across frontal areas from 18 to37 km offshore (TOMOFRONT 1 and 2 cruises, April 1988 and April-May1989 respectively). Aplastidic and plastidic nanoflagellatesand aplastidic picoflagellates were present in numbers closeto 0.25 x 10⁴ cells ml^–1, whereas plastidic picoflagellatesaccounted for about half this number. Correlations have beenevidenced between plastidic and aplastidic micro-organisms withinthe same size group, suggesting that they belong to a well-definedecosystem. The highest correlation between total ETS activityand abundance of the considered size groups was observed fornanoflagellates (r = 0.94, n = 22, and r = 0.90, n = 22 foraplastidic and plastidic cells respectively). The importanceof the role of nanoflagellates in surface waters, with respectto the overall ETS activity, was supported by results from sizefractionation which assigned to the 3–10 µm sizerange a 73.3% contribution to overall ETS activity. Resultsemphasize analysing global ETS activity of natural samples inorder to derive relationships between the different populationspresent in the sampled water. It is suggested that couplingflow cytometry to the ETS approach should be very helpful inthat respect.     

Can phaeopigments be used as markers for Daphnia grazing in Lake Constance?

The formation of chlorophyll a degradation products was measuredwith natural phytoplankton from Lake Constance and Daphnia magnaand native Daphnia as grazers in grazing experiments duringspring bloom conditions using high-pressure liquid chromatography(HPLC). Chlorophyll a start concentrations were between 1.2and 16.3 µg l^–1; phaeopigment weights constituted5% of chlorophyll a weight. Only phaeophorbide a was a markerfor Daphnia grazing; concentrations of other phaeopigments (phaeophytina, chlorophyllide a and two unidentified phaeopigments) didnot increase during Daphnia grazing. Conversion efficiencies(chlorophyll a to phaeophorbide a) were between 0 and 43% ona weight basis, and between 0 and 65% on a molar basis. Conversionefficiencies were highest at high grazer density (40 Daphnial^–1) and after a 24 h exposure time. Grazing by microzooplanktonprobably led to the formation of the two unidentified phaeopigments.In Lake Constance, Daphnia density was significantly positivelycorrelated with the phaeophorbide a/chlorophyll a ratio whenit was <5000 Daphnia m^–3. However, when higher Daphniadensities were included in calculations, then Daphnia densitywas positively, but insignificantly, correlated with the phaeophorbidea/chlorophyll a ratio. This suggests that when the level offood per Daphnia is low, then grazing is more efficient withless production of phaeophorbide a and a higher production ofcolourless products.     

The productive and optical status of the oligotrophic waters of the Southern Aegean Sea (Cretan Sea), Eastern Mediterranean

Primary production, pigment concentrations and spectral measurementsof downwelling irradiance were made at four stations in fourseasons (spring, summer, autumn, winter) during 1994 in thewaters of the South Aegean Sea (Cretan Sea), Eastern Mediterranean.Rates of production were determined using in Situ incubationtechniques and included measurements at the surface microlayer.Depth-integrated values averaged over season were 5.66 mg Cm^–2 h^–1 for primary production and the correspondingchlorophyll (Ch1) a and phaeophytin (Phaeo) a values had meansof 4.87 and 1.21 mg m^–3 respectively. The assimilationratio remained very low (mean over season: 1.19 mg C mg^–2Chl a h^–1 as did the Phaeo a/Chl a ratio (mean over season:0.24). The annual production for the area was estimated to yield24.79 g C m^–2 year^–1. Primary production and Chla estimates showed statistically significant seasonal, spatialand depth variations. The spectral values of the attenuationcoefficient Kd (     

Effect of Irradiance on Chlorophyll Estimation with the Minolta SPAD-502 Leaf Chlorophyll Meter

Leaf chlorophyll content may be used as an indirect indicatorof crop nitrogen status. Chlorophyll meter values (SPAD values)taken with the Minolta SPAD-502 chlorophyll meter in the shadeplantOxalis acetosellaL. and in winter wheat (Triticum aestivumL.)varied by 15 and 8%, respectively, with variation in irradiance.The lowest SPAD-values were measured at high irradiance. Duringa natural night-day-night cycle SPAD values for winter wheatwere lowest in the middle of the day, highest at low irradianceat dusk and dawn and intermediate in darkness before dawn andafter dusk. The results indicate that irradiance during measurementshould be considered when using the Minolta SPAD-502 chlorophyllmeter for the estimation of crop N-status.Copyright 1998 Annalsof Botany Company Chlorophyll meter, nitrogen, irradiance,Oxalis acetosellaL.,Triticum aestivumL., winter wheat.     

Respiration and respiratory electron transport activity in marine phytoplankton: growth rate dependence and light enhancement

Respiratory electron transport system (ETS) activity and actualoxygen consumption rates were measured in batch cultures offour species of marine phytoplankton, in two different growthstages: exponential or log-phase (L) and stationary phase (S).The L cultures showed higher ETS activity and respiration ratesthan the S cultures of the same species. Among the L cultures,the higher respiration and ETS activity corresponded to thosehaving higher growth rates. The carbon-specific ETS activityand the carbon-specific respiration (h^–1) showed a cleardependence on growth rates. Samples subjected to short (10 min)exposures to high, oversaturating irradiances (1000 µEm^–2 s^–1) displayed enhanced ETS activity and respiration.The experiments show that, under the light regime at which thealgal cells grow, the respiratory ETS activity and actual oxygenconsumption in phytoplankton are strongly related to growthrate and that short, high irradiance exposures enhance boththe respiratory enzyme activity and their actual oxygen consumption.     

Spatial distribution of Euphausia pacifica (Euphausiacea: Crustacea) in the Yellow Sea

Euphausia pacifica were collected in the Yellow Sea in summer(August, 1997) and winter (February, 1998), and their distributionwas investigated in terms of the developmental stages in relationto environmental factors (temperature, salinity and chlorophylla). In summer, the water column was highly stratified with athermocline between 10–30 m depth, whereas the water columnwas well mixed in winter. Seasonal variation in temperaturewas large, ranging between 6.3 and 28.8°C in summer and3.9 and 12.2°C in winter. Chlorophyll a concentration changedlittle seasonally but a high concentration was observed in coastalareas. Salinity in the two seasons varied little spatio-temporally.In the studied area and sampling period, E.pacifica was themost dominant euphausiid species (99.7 and 99.8% in summer andwinter, respectively), and comprised adults and juveniles (74.6%in summer and 41.9% in winter), furcilia (17.5 and 44.9%) andcalyptopis (7.9 and 13.1%). The spatial distribution of theE.pacifica population varied seasonally depending on developmentalstage and appeared to be related primarily to the seawater temperatureand secondly to the chlorophyll a concentration, but not tosalinity. In summer, adults were abundant in areas below 10°C,and furcilia and calyptopis above 9°C. In winter, adultswere confined to areas between 7 and 10°C, and furciliaand calyptopis, to areas between 6 and 8°C. Furcilia andcalyptopis were concentrated in the vicinity, or at the centerof chlorophyll a-rich water masses, whereas adults seemed toavoid those water masses.     

Metabolic changes associated with biofilm formation in an undisturbed Mediterranean stream

Respiratory activity (ETS), ectoenzymatic activity (-glucosidase and -xylosidase) and photosynthetic ¹⁴C-bicarbonate incorporation in the biofilm were measured in a shaded stream during a colonization sequence (43 days) on artificial substrates (unglazed clay tiles) and compared with older (aged) tiles. In the first five days bacterial densities and ectoenzyme activities showed a sharp increase. After two weeks, algal density, chlorophyll and productivity increased moderately. Chlorophyll did not reach similar values to those of the aged biofilms until the last day of colonization. Photosynthetic activity seemed to be relevant to the heterotrophs metabolism during substrate colonization, as could be deduced from the significant correlation between -glucosidase and ¹⁴C-bicarbonate incorporation, algal cell densities and chlorophyll. Respiratory activity (ETS) decreased in the older biofilms, accordingly to their higher algal and bacterial density. Younger biofilms (up to 8 days old) showed higher ETS activity per cell, indicating a fast response of microorganisms to substrate availability.     

Dynamics of microplankton communities at the ice-edge zone of the Lazarev Sea during a summer drogue study

Microzooplankton grazing and community structure were investigatedin the austral summer of 1995 during a Southern Ocean Drogueand Ocean Flux Study (SODOFS) at the ice-edge zone of the LazarevSea. Grazing was estimated at the surface chlorophyll maximum(5–10 m) by employing the sequential dilution technique.Chlorophyll a concentrations were dominated by chainformingmicrophytoplankton (>20 µm) of the genera Chaetocerosand Nitzschia. Microzooplankton were numerically dominated byaloricate ciliates and dinoflagellates (Protoperidinium sp.,Amphisoleta sp. and Gymnodinium sp.). Instantaneous growth ratesof nanophytoplankton (<20 µm) varied between 0.019and 0.080 day^–1, equivalent to between 0.03 and 0.12 chlorophylldoublings day^–1. Instantaneous grazing rates of microzooplanktonon nanophytoplankton varied from 0.012 to 0.052 day^–1.This corresponds to a nanophytoplankton daily loss of between1.3 and 7.0% (mean = 3.76%) of the initial standing stock, andbetween 45 and 97% (mean = 70.37%) of the daily potential production.Growth rates of microphytoplankton (>20 µm) were lower,varying between 0.011 and 0.070 day^–1, equivalent to 0.015–0.097chlorophyll doublings day^–1. At only three of the 10 stationsdid grazing by microzooplankton result in a decrease in microphytoplanktonconcentration. At these stations instantaneous grazing ratesof microzooplankton on microphytoplankton ranged between 0.009and 0.015 day^–1, equivalent to a daily loss of <1.56%(mean = 1.11%) of initial standing stock and <40% (mean =28.55%) of the potential production. Time series grazing experimentsconducted at 6 h intervals did not show any diel patterns ofgrazing by microzooplankton. Our data show that microzooplanktongrazing at the ice edge were not sufficient to prevent chlorophylla accumulation in regions dominated by rnicrophytoplankton.Here, the major biological routes for the uptake of carbon thereforeappear to be grazing by metazoans or the sedimentation of phytoplanktoncells. Under these conditions, the biological pump will be relativelyefficient in the drawdown of atmospheric CO₂.