Microbial respiration in the aphotic zone of the Ross Sea (Antarctica)

Azzaro, Maurizio; Ferla, Rosabruna La; Azzaro, F.

doi:10.1016/j.marchem.2005.09.011

Cited by 22 publications

(20 citation statements)

References 57 publications

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“…If respiration is weak relative to the rate of NPP, the mechanism causing a reduction in depth‐integrated drawdown with increasing MLD is limited; in fact, deficit concentrations might be mixed to depth and persist, leading to apparent increases in depth integrals with increasing mixing depth. Prior work in the Ross Sea has shown bacterial respiration to be low, relative to rates of NPP [ Craig et al , 1999; Azzaro et al , 2006], thus this explanation seems plausible. It is not clear how to reconcile this finding, however, with the inference that respiration is of comparable magnitude to NCP (see below).…”

Section: Resultsmentioning

confidence: 82%

Vertical structure, seasonal drawdown, and net community production in the Ross Sea, Antarctica

et al. 2011

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[1] We calculate net community production (NCP) during summer [2005][2006] and spring 2006 in the Ross Sea using multiple approaches to determine the magnitude and consistency of rates. Water column carbon and nutrient inventories and surface ocean O 2 /Ar data are compared to satellite-derived primary productivity (PP) estimates and 14 C uptake experiments. In spring, NCP was related to stratification proximal to upper ocean fronts. In summer, the most intense C drawdown was in shallow mixed layers affected by ice melt; depth-integrated C drawdown, however, increased with mixing depth. DO 2 /Ar-based methods, relying on gas exchange reconstructions, underestimate NCP due to seasonal variations in surface DO 2 /Ar and NCP rates. Mixed layer DO 2 /Ar requires approximately 60 days to reach steady state, starting from early spring. Additionally, cold temperatures prolong the sensitivity of gas exchange reconstructions to past NCP variability. Complex vertical structure, in addition to the seasonal cycle, affects interpretations of surface-based observations, including those made from satellites. During both spring and summer, substantial fractions of NCP were below the mixed layer. Satellite-derived estimates tended to overestimate PP relative to 14 C-based estimates, most severely in locations of stronger upper water column stratification. Biases notwithstanding, NCP-PP comparisons indicated that community respiration was of similar magnitude to NCP. We observed that a substantial portion of NCP remained as suspended particulate matter in the upper water column, demonstrating a lag between production and export. Resolving the dynamic physical processes that structure variance in NCP and its fate will enhance the understanding of the carbon cycling in highly productive Antarctic environments.

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Section: Resultsmentioning

confidence: 82%

Vertical structure, seasonal drawdown, and net community production in the Ross Sea, Antarctica

et al. 2011

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“…Furthermore the ETS assay offers sensitivity and resolution levels as well as data acquisition rates that are not attainable with incubation-based methods. It is a sensitive biochemical assay especially suited for estimating the community respiration of organisms in the meso-and bathypelagic waters [12,14,[56][57][58][59]. Moreover, it facilitates the collection of large temporal and spatial data sets rendering it suitable for oceanographic surveys.…”

Section: Resultsmentioning

confidence: 99%

Prokaryotic abundance and heterotrophic metabolism in the deep Mediterranean Sea

Ferla

Azzaro

Caruso

et al. 2010

Advances in Oceanography and Limnology

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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.

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“…Such evidence highlighted POC as the main organic fuel in the RS biological pump. The oxidation rate, fuelling the dissolved organic fraction, was not measured by sediment traps (Jiao et al 2010, Legendre et al 2015, but it was a smaller fraction, here in the RS, than it was in other oceans (Azzaro et al 2006).…”

Section: Introductionmentioning

confidence: 88%

“…The ETS assay allowed an estimation of the maximum velocity (Vmax) of the dehydrogenases transferring electrons from their physiological substrates (NADH, NADPH and succinate) to a terminal electron acceptor (O 2 ) through their associated electron transfer system. Details on our ETS measurements in Antarctic and peri-Antarctic areas have been described previously (Azzaro et al 2006, Crisafi et al 2010. Briefly, subsamples (from 2 to 20 l) were pre-filtered through a 250-µm mesh-size net and concentrated on GF/F-glass-fibre filters (nominal pore diameter 0.7 µm) at reduced pressure (< 1/3 atm).…”

Section: Ets Measurements and Relative Ratesmentioning

confidence: 99%

“…Catalano et al (2006) confirmed that, in spring-summer periods, about 90% of the total carbon derived from new production was exported via higher trophic levels. Comparing the oxidation and sinking of organic matter through the deep water found that, according to sediment-traps estimates, 63% of organic carbon, remineralized to CO 2 by microbial respiration, originated in the particulate organic matter (POC) pool (Azzaro et al 2006). Such evidence highlighted POC as the main organic fuel in the RS biological pump.…”

Section: Introductionmentioning

confidence: 99%

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Microbial metabolic rates in the Ross Sea: the ABIOCLEAR Project

Azzaro¹,

Packard²,

Monticelli³

et al. 2019

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The Ross Sea is one of the most productive areas of the Southern Ocean and includes several functionally different marine ecosystems. With the aim of identifying signs and patterns of microbial response to current climate change, seawater microbial populations were sampled at different depths, from surface to the bottom, at two Ross Sea mooring areas southeast of Victoria Land in Antarctica. This oceanographic experiment, the XX Italian Antarctic Expedition, 2004-05, was carried out in the framework of the ABIOCLEAR project as part of LTER-Italy. Here, microbial biogeochemical rates of respiration, carbon dioxide production, total community heterotrophic energy production, prokaryotic heterotrophic activity, production (by 3H-leucine uptake) and prokaryotic biomass (by image analysis) were determined throughout the water column. As ancillary parameters, chlorophyll a, adenosine-triphosphate concentrations, temperature and salinity were measured and reported. Microbial metabolism was highly variable amongst stations and depths. In epi- and mesopelagic zones, respiratory rates varied between 52.4–437.0 and 6.3–271.5 nanol O2 l-1 h-1; prokaryotic heterotrophic production varied between 0.46–29.5 and 0.3–6.11 nanog C l-1 h-1; and prokaryotic biomass varied between 0.8–24.5 and 1.1–9.0 µg C l-1, respectively. The average heterotrophic energy production ranged between 570 and 103 mJ l-1 h-1 in upper and deeper layers, respectively. In the epipelagic layer, the Prokaryotic Carbon Demand and Prokaryotic Growth Efficiency averaged 9 times higher and 2 times lower, respectively, than in the mesopelagic one. The distribution of plankton metabolism and organic matter degradation was mainly related to the different hydrological and trophic conditions. In comparison with previous research, the Ross Sea results, here, evidenced a relatively impoverished oligotrophic microbial community, throughout the water column.

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Microbial respiration in the aphotic zone of the Ross Sea (Antarctica)

Cited by 22 publications

References 57 publications

Vertical structure, seasonal drawdown, and net community production in the Ross Sea, Antarctica

Vertical structure, seasonal drawdown, and net community production in the Ross Sea, Antarctica

Prokaryotic abundance and heterotrophic metabolism in the deep Mediterranean Sea

Microbial metabolic rates in the Ross Sea: the ABIOCLEAR Project

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