Electrochemical standardization of the dehydrogenase assay used in the estimation of respiration rates

A primary coulometric titration is proposed as a standardization technique for the succinate dehydrogenase assay used in the estimation of respiration rates in marine plankton. The coulometric method, which is shown to be simple, accurate, and reproducible, eliminates the difficulties of using a chemical reducing agent. An alternative method using polarography is also discussed

Respiration predicted from an Enzyme Kinetic Model and the Metabolic Theory of Ecology in two species of marine bacteria

12 pages, 8 figures, 5 tablesRespiratory oxygen consumption is the result of a cell's biochemistry. It is caused by enzymatic activity of the respiratory electron transfer system (ETS). However, in spite of this understanding, respiration models continue to be based on allometric equations relating respiration to body size, body surface, or biomass. The Metabolic Theory of Ecology (MTE) is a current example. It is based on Kleiber's law relating respiration (R) and biomass (M) in the form, View the MathML source, where C is a constant, Ea is the Arrhenius activation energy, k is the Boltzmann constant for an atom or molecule, and T is the temperature in Kelvin. This law holds because biomass packages the ETS. In contrast, we bypass biomass and model respiration directly from its causal relationship with the ETS activity, R = f (ETS). We use a biochemical Enzyme Kinetic Model (EKM) of respiratory oxygen consumption based on the substrate control of the ETS. It postulates that the upper limit of R is set by the maximum velocity, Vmax, of complex I of the ETS and the temperature, and that the substrate availability, S, modulates R between zero and this upper limit. Kinetics of this thermal-substrate regulation is described by the Arrhenius and Michaelis–Menten equations. The EKM equation takes the form View the MathML source where Rg is the molar gas constant and K is the Michaelis–Menten constant. Here, we apply the EKM and the MTE to predict a respiration time-profile throughout the exponential, steady state, and nutrient-limited phases of the marine bacteria Pseudomonas nautica and Vibrio natriegens in acetate-based cultures. Both models were tested by comparing their output with the measured RO2 time-profile. The MTE predicted respiration accurately only in the exponential growth phase, but not during the nutrient limitation part of the stationary phase. In contrast, the EKM worked well throughout both physiological phases as long as the modeled substrates fall with the declining carbon source. Results support the theoretical bases of the EKM. We conclude that the EKM holds promise for predicting respiration at the different physiological states and time-scales important to microbiological studiesFinancial support was provided by the Universidad de Las Palmas de Gran Canaria (ULPGC), the Spanish Ministry of Education and Science, the Graduate Program in Oceanography at the ULPGC, ICM-CSIC, and the research grants MODIVUS (CTM2005-04795/MAR), EXOME (CTM 2008-01616), and OITHONA (CTM2007-60052). T. Packard was supported by contract EXMAR SE-539 10/17 (Proyecto Estructurante en Ciencias Marinas). This is contribution #200906 from the Bigelow Laboratory for Ocean SciencesPeer reviewe

Prokaryotic abundance and heterotrophic metabolism in the deep Mediterranean Sea

A synthesis of field data carried out in the Mediterranean Sea are presented, aimed at contributing to the knowledge of three prokaryotic-mediated processes and their implications on the Carbon cycle. The distribution of exoenzymatic activities, secondary production and respiration rates was studied together with the prokaryotic abundances. Particular attention was paid to the meso- and bathypelagic layers which play an important role in the Mediterranean carbon cycle. The study is noteworthy because of its large spatial scale spanning the entire Mediterranean Sea over 4 years. In addition, two Atlantic stations in front of the Gibraltar Strait were investigated. The longitudinal distribution of prokaryotic activities and abundance along the MED showed different trends along the depthlayers. In particular, higher exoenzymatic rates were detected in the Eastern basin compared to the Western one; carbon respiration rate showed patterns variable with the sampling periods in the epipelagic and bathypelagic layers, while a consistent Westwards decreasing trend at the mesopelagic layers occurred. Specific enzyme activities per cell showed high values in the deepest layers for leucine aminopeptidase. Comparison with Carbon respiration rate data collected before the 2000s showed changing patterns of microbial heterotrophic processes in the Mediterranean Sea

Metabolic Responses of Subtropical Microplankton After a Simulated Deep-Water Upwelling Event Suggest a Possible Dominance of Mixotrophy Under Increasing CO2 Levels

In the autumn of 2014, nine large mesocosms were deployed in the oligotrophic subtropical North-Atlantic coastal waters off Gran Canaria (Spain). Their deployment was designed to address the acidification effects of CO2 levels from 400 to 1,400 mu atm, on a plankton community experiencing upwelling of nutrient-rich deep water. Among other parameters, chlorophyll a (chl-a), potential respiration (Phi), and biomass in terms of particulate protein (B) were measured in the microplankton community (0.7-50.0 mu m) during an oligotrophic phase (Phase I), a phytoplankton-bloom phase (Phase II), and a post-bloom phase (Phase III). Here, we explore the use of the Phi/chl-a ratio in monitoring shifts in the microplankton community composition and its metabolism. Phi/chl-a values below 2.5 mu L O-2 h(-1) (mu g chl-a)(-1) indicated a community dominated by photoautotrophs. When Phi/chl-a ranged higher, between 2.5 and 7.0 mu L O-2 h(-1) (pg chl-a)(-1) , it indicated a mixed community of phytoplankton, microzooplankton and heterotrophic prokaryotes. When Phi/chl-a rose above 7.0 mu L O-2 h(-1) (mu g chl-a)(-1), it indicated a community where microzooplankton proliferated (>10.0 mu L O-2 h(-1) (mu g chl-a)(-1)), because heterotrophic dinoflagellates bloomed. The first derivative of B, as a function of time (dB/dt), indicates the rate of protein build-up when positive and the rate of protein loss, when negative. It revealed that the maximum increase in particulate protein (biomass) occurred between 1 and 2 days before the chl-a peak. A day after this peak, the trough revealed the maximum net biomass loss. This analysis did not detect significant changes in particulate protein, neither in Phase I nor in Phase III. Integral analysis of Phi/chl-a and B, over the duration of each phase, for each mesocosm, reflected a positive relationship between 4) and pCO(2) during Phase II [alpha = 230.10-5 mu L O-2 h(-1) L-1 (patm CO2)(-1) (phase-day)(-1), R-2 = 0.30] and between chl-a and pCO(2) during Phase III [alpha = 100.10(-5) Ag chl-a L-1 (mu atmCO(2))(-1) (phase-day)(-1), R-2 = 0.84]. At the end of Phase II, a harmful algal species (HAS), Vicicitus globosus, bloomed in the high pCO(2) mesocosms. In these mesocosms, microzooplankton did not proliferate, and chl-a retention time in the water column increased. In these V globosus-disrupted communities, the (Phi/chl-a ratio [4.1 +/- 1.5 /mu L O-2 h(-1) (mu g chl-a)(-1)] was more similar to the Phi/chl-a ratio in a mixed plankton community than to a photoautotroph-dominated one

Nitrate reductase measurements in upwelling regions : I. Significance of the distribution off Baja California and Northwest Africa

Analyse de l'Écosystème des "Upwellings", Deuxième Conference : Analysis of Upwelling Systems, Second Conference, 28-30 May 1973, Marseille.-- 7 pages, 10 figures, 2 tablesPeer reviewe

Respiration, mineralization, and biochemical properties of the particulate matter in the southern Nansen Basin water column in April 1981

12 pages, 4 figures, 5 tablesDeterminations of the activity of the respiratory electron transport system (ETS), during the FRAM III expedition permit us to estimate oxygen utilization rates (RO2) from the surface to 2000 m under the polar pack ice in the Nansen Basin just north of Svalbard (83°N, 7°E) during April 1981. We found RO2 at in situ temperatures ranging from 20 pM O2 min-1 just below the ice to 0.2 pM O2 min-1 at 2000 m. These rates are low compared to most other ocean regions, but they could decrease particulate organic carbon and nitrogen by 76% and 74%, respectively, over a period of ∼6 months. The RO2 calculations based on measurements made at 0 °C yielded a power function of RO2 vs. depth (Z) of RO2=67Z-0.5534. When this RO2 profile was superimposed on a more recent oxygen utilization rate profile made using the 3He-3H-AOU method (OUR), in the same vicinity of the Nansen Basin during 1987 (OUR=52Z-0.4058, [Zheng, Y., Schlosser, P., Swift, J.W., Jones, E.P., 1997. Oxygen utilization rates in the Nansen Basin, Arctic Ocean: implications for new production. Deep Sea Research I 44, 1923-1943]), the agreement of the two profiles was close. On one hand, this was to be expected because RO2 is the biological basis of OUR, on the other hand, it was a surprise because the methodologies are so different. Nitrate mineralization obtained from ETS activities also compared favorably with calculations based on the data of Zheng et al. [1997. Oxygen utilization rates in the Nansen Basin, Arctic Ocean: implications for new production. Deep Sea Research I 44, 1923-1943]. Chlorophyll ranged from 6 ng L-1 at 5 m to 0.06 ng L-1 at 2000 m. Particulate organic carbon (POC) decreased from 0.93 μM C just below the ice to less than 0.4 μM C at 500 m. Particulate organic nitrogen (PON) was not detectable below 70 m, however in the upper 70 m it ranged from 0.16 to 0.04 μM N. The C/N mass ratio over these depths ranged from 5.8 to 11.3. Annual carbon productivity as calculated to balance the total water column respiration was 27 g C m-2 y-1. The integrated respiration rate between 50 and 4000 m suggests that exported production and carbon flux from the 50 m level was 24 g C m-2 y-1. These are minimal estimates for the southern Nansen Basin because they are based on measurements made at the end of the Arctic winter. © 2007 Elsevier Ltd. All rights reservedWe acknowledge Institut Ciències del Mar (CSIC), CICYT project MAR98-0932, BIOHAB project EVK3-1999-00072, TURFIREN2002-01591/Mar), MICROROL (CICYT LTM 2004-02575/Mar), and NSF Grants DPP-825744, OPP-0125399 (J. Swift, PI) and OPP-0125306 for financial support. This is contribution No. 200510 from the Bigelow Laboratory from Ocean Sciences. ReferencesPeer Reviewe

Respiration and vertical carbon flux in the Gulf of Maine water column

23 pages, 6 figures, 10 tablesThe transport of carbon from mean surface waters to the deep sea is a critical factor in calculations of planetary carbon cycling and climate change. This vertical carbon flux can be calculated by integrating the vertical profile of the seawater respiration rate but is rarely done because measuring seawater respiration is so difficult. However, seawater respiratory oxygen consumption is the product of the combined activity of all the respiratory electron transfer systems in a seawater community of bacterioplankton, phytoplankton, and zooplankton. This respiratory electron transfer system (ETS) is the membrane bound enzymatic system that controls oxygen consumption and ATP production in all eukaryots and in almost all bacteria and archaea. As such, it represents potential respiratory oxygen consumption. Exploiting this, we measured plankton-community ETS activity in water column profiles in the Gulf of Maine to give the potential-respiration of the water column. To interpret these potentials in terms of actual seawater respiration we made use of previous measurements of respiratory oxygen consumption and ETS activity in the Gulf of Maine to calculate a ratio of respiratory potential to actual respiration. Armed with this ratio we calculated seawater respiration depth profiles from the ETS activity measurements. These profiles were characterized by: (1) high oxygen consumption rates in the euphotic zone; (2) subsurface maxima near the subsurface chlorophyll maxima (SCM); (3) rapid declines associated with thermoclines; (4) low declining rates below 50 m; (5) and elevated values occasionally near the bottom. Sea surface values ranged from 229 to 489 pmol O2, min-1 L-1. Euphoric zone maximum values ranged from 457 to 682 pmol O2 min-1 L-1 while the minimum values below 70 m ranged from 10 to 27 pmol O2 min-1 L-1. A depth-normalized power function described the respiratory profiles between their maxima and minima. Integrating these respiratory oxygen consumption profiles from the respiratory maximum to the near bottom minimum, we calculated carbon flux profiles. The vertical carbon fluxes through the 30 m, 50 m, and 100 m levels were 3.09 ± 1.55, 1.76 ± 0.96, and 0.93 ± 0.68 μmol C min-1 m-2, respectivelyWe acknowledge the Institut Ciències del Mar, CICYT project MAR98-0932, BIOHAB project EVK3-1999-00072, and ONR contract N00014-02-1-4094 for financial supportPeer Reviewe

Nitrate reductase activity in upwelling regions : II. Ammonia and lifht dependence

Analyse de l'Écosystème des "Upwellings", Deuxième Conference : Analysis of Upwelling Systems, Second Conference, 28-30 May 1973, Marseille.-- 11 pages, 20 figures, 2 tablesPeer reviewe

Zooplankton ETS activity and respiration in the Catalan Sea (Western Mediterranean)

4 páginas, 6 figuras, 1 tabla.-- Contribución a "Topics in marine biology, Ros J.D. (ed.)Zooplankton biomass, ETS activity and direct measurements of respiration were compared in a study of the Catalan Sea during the summer stratification period, in and around the deep chlorophyll maximum. The pattern of vertical distribution of zooplankton biomass differed from that found on previous cruises, but some trends in the horizontal were similar (minimum inte rated values coinciding with ascending deep waters). Over the Catalan shelf the ETS activity averaged 0.09 meq h-1 l-1. The potential respiration, stoichiometrically calculated from the ETS activity, is 0.5 m1O2 h-1 l-l. Seaward of the frontal system on the shelf the rates decreased 50% and then increased to 0.5 m1O2 h-1 l-l on the eastern side of the divergence that occurs in the middle of the Catalan Sea. The zooplankton ETS activity did not increase in the chlorophyll maximum. A comparison of the ETS activity in the net and bottle samples suggests a difference in the capture efficiencies by both sampling methods. Physiological measurements of respiration were made on board and compared with ETS activity. A wide range of respiration/ETS ratio (1.60-3.38) was found; the correlation coefficient of respiration on ETS activity was 0.64This work has been supported by the US-Spanish Committee for Scientific and Technological Cooperation (grant CCA 8411/54), the CAICYT (Comisión Asesora para la Investigación Científica y Técnica) gant PR 84-0067, and the Institut de Ciències del Mar de Barcelona, CSICPeer reviewe