O:N atomic ratio as a tool to describe zooplankton metabolism

Mayzaud, Patrick; Conover, RJ

doi:10.3354/meps045289

Cited by 298 publications

(216 citation statements)

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“…Distinct mechanisms can be employed to maintain the internal homeostasis and the adequate level of energy expenditure, varying from behavioral changes to shifts of distinct metabolic pathways (ECHEVARRÉA et al, 1993;ROCHA et al, 2001 CONOVER, 1988). Our data suggest a metabolism depending mainly on proteins shifting to a dependence on a mixture of proteins and lipids.…”

Section: Discussionmentioning

confidence: 78%

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Metabolic rates of the antarctic amphipod Gondogeneia antarctica at different temperatures and salinities

et al. 2013

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A B S T R A C TChanges in environmental factors may deeply affect the energy budget of Antarctic organisms as many of them are stenothermal and/or stenohaline ectotherms. In this context, the aim of this study is to contribute to knowledge on variations in the energy demand of the Antarctic amphipod, Gondogeneia antarctica as a function of temperature and salinity. Experiments were held at the Brazilian Antarctic Station "Comandante Ferraz", under controlled conditions. Animals collected at Admiralty Bay were acclimated to temperatures of 0°C; 2.5°C and 5°C and to salinities of 35, 30 and 25. Thirty measurements were made for each of the nine combinations of the three temperatures and three salinities, totalling 270 measurements. Metabolic rates were assessed by oxygen consumption and total nitrogenous ammonia excretion, in sealed respirometers. When acclimated to salinities 30 or 35, metabolic rates at 0°C and 2.5°C were very similar indicating a possible mechanism of metabolic compensation for temperature. At 5.0°C, however, metabolic rates were always higher. Lower salinities enhanced the effects of temperature on metabolism and ammonia excretion rates. The physiological adaptations of individuals of G. antarctica suggest adaptive mechanisms for energy saving, adjusted to an environment with stable conditions of temperature and salinity. Little is known about the joint effects of salinity and temperature and this study is an important contribution to the understanding of the mechanism of polar organisms in their adaptation to both factors. R E S U M OAlterações ambientais podem modificar a alocação de energia dos organismos, principalmente dos ectotermos estenotérmicos e/ou estenohalinos. Nesse contexto, este trabalho contribui com o conhecimento da demanda de energia do anfípode antártico Gondogeneia antarctica em função da temperatura e da salinidade. Experimentos foram realizados na Estação Antártica Brasileira "Comandante Ferraz", em condições laboratoriais controladas. Animais coletados na Baía do Almirantado foram aclimatados a temperaturas de 0°C; 2.5°C e 5°C e salinidades de 35, 30 and 25. Foram realizadas trinta medições para cada uma das nove combinações das três temperaturas com as três salinidades, totalizando 270 medições. As taxas metabólicas foram estimadas por meio do consumo de oxigênio e excreção de amônia, em câmaras respirométricas seladas. Quando aclimatados a salinidades 30 ou 35, as taxas metabólicas a 0°C e 2.5°C foram semelhantes indicando possível mecanismo de compensação térmica, nessa faixa de variação dos fatores. A 5.0°C, no entanto, as taxas metabólicas foram sempre mais elevadas. Baixas salinidades potencializaram os efeitos da temperatura no consumo de oxigênio e na excreção de produtos nitrogenados. Os resultados estão relacionados a mecanismos adaptativos para economia de energia em indivíduos G. antarctica, ajustados a um ambiente que tem condições estáveis de temperatura e de salinidade. Pouco se sabe sobre os efeitos conjugados da salinidade e temperatura nos organismos e...

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Section: Discussionmentioning

confidence: 78%

“…The ratio between oxygen consumed and nitrogen excreted (O:N) was calculated for each group of the 9 combinations of temperature and salinity, using the adjusted data (MAYZAUD, 1973;MAYZAUD;CONOVER, 1988). The O:N ratio gives an indication of the kind of substrate that is being used for catabolism in a particular condition.…”

Section: Methodsmentioning

confidence: 99%

Metabolic rates of the antarctic amphipod Gondogeneia antarctica at different temperatures and salinities

et al. 2013

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“…For all species, the O:N ratio was not significantly different between treatments, indicating that there was no shift in metabolic substrate in use response to exposure to CO 2 . An O:N ratio below a value of 16 indicates that protein is the primary fuel source for catabolism whereas a ratio of 50-60 is indicative of a diet balanced between lipid and protein catabolism (Mayzaud and Conover 1988). Tropical pteropod species O:N ranged on average between 20-40 suggesting that protein fueled a significant portion of their catabolism.…”

Section: Speciesmentioning

confidence: 99%

The metabolic response of pteropods to acidification reflects natural CO<sub>2</sub>-exposure in oxygen minimum zones

2012

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Abstract. Shelled pteropods (Thecosomata) are a group of holoplanktonic mollusks that are believed to be especially sensitive to ocean acidification because their aragonitic shells are highly soluble. Despite this concern, there is very little known about the physiological response of these animals to conditions of elevated carbon dioxide. This study examines the oxygen consumption and ammonia excretion of five pteropod species, collected from tropical regions of the Pacific Ocean, to elevated levels of carbon dioxide (0.10 %, 1000 ppm). Our results show that pteropods that naturally migrate into oxygen minimum zones, such as Hyalocylis striata, Clio pyramidata, Cavolinia longirostris and Creseis virgula, were not affected by carbon dioxide at the levels and duration tested. Diacria quadridentata, which does not migrate, responds to high carbon dioxide conditions with reduced oxygen consumption and ammonia excretion. This indicates that the natural chemical environment of individual species may influence their resilience to ocean acidification.

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“…This is also supported by the annual variation in the O:N ratio (oxygen consumed/excreted nitrogen) which can vary by a factor of 3, in winter up to 16, in summer (Brockington 2001). Values around 3 usually indicate the exclusive use of proteins as the energy substrate, while values between 20 and 25 indicate that protein fuels of 50% metabolic substrate and above 25 the presence of other energy combustibles (Ikeda & Hing Fay 1981, Mayzaud & Conover 1988. The principal events involved in the seasonal metabolism of L. elliptica are shown in Figure 1.…”

Section: Nitrogen Metabolismmentioning

confidence: 85%

NITROGEN METABOLISM OF THE ANTARCTIC BIVALVE Laternula elliptica (KING & BRODERIP) AND ITS POTENTIAL USE AS BIOMARKER

2007

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The Antarctic marine environment is characterized by the extreme seasonality of the primary production in the water column and the low but stable temperatures. Both are considered the main factors in the adaptative evolution of Antarctic ectothermic organisms. Studies about physiological and biochemical processes of the cold-adapted species revealed the presence of antifreeze glycoproteins in the biological fluids and cold-adapted proteins. The low and stable temperatures have resulted in the appearence of enzymes with high catalytic efficiency and the absence of the thermal stress proteins in some Antarctic fishes. The austral winter promotes a seasonal food shortage, submitting the benthic ectotherms to long periods of starvation. This is particularly true for the organisms that depend on phytoplankton as their primary source of food. The Antarctic marine environment also presents areas of high copper concentrations on the sediment surface as well as cadmium in the water column. The bivalve Laternula elliptica, a circumpolar species, has been proposed as bioindicator for long term monitoring of heavy metals in the shallow waters of Antarctica due to its capacity to accumulate metals, especially cadmium and zinc. Like other Antarctic ectothermic organisms, L. elliptica changes its metabolism from aerobic to anaerobic as a function of temperature, being 6 ºC critical and 9 ºC lethal. This bivalve also shows a marked seasonality in its metabolism, with low oxygen consumption in winter as compared to summer. It is speculated that it enters into a dormancy state during the austral winter as it apparently retracts its siphons below the sediment surface. The apparent supression of the water pumping by the siphons during winter forces L. elliptica to mobilize its energy reserves, using the siphon proteins as its principal source of energy (ratio of oxygen consumption/excreted nitrogen = 3.0). Even during summer, when the high food supply stimulates the bivalve growth, the metabolism is mainly protein based. (O:N ratio = 16). The excretory nitrogen metabolism of this bivalve is typically ammoniotelic, characterized by the excretion of almost 90% of nitrogen in the form of ammonia and 10% as urea. Probably, the urea excreted arises from the hydrolysis of the proteic aminoacid L-arginine by arginase in order to maintain the tissue levels of that aminoacid. In such case, the presence of this enzyme in the kidney tissues may be related to the physiological constraints caused by the retraction of the siphons and the requirements for the excretion of this nitrogen compound during the austral winter. Studies with the renal arginase of this bivalve showed a high metabolic tolerance to the metallic cations Cu, Zn, Fe and Cd, when compared to the arginase behavior of other bivalves such as Dreissena polymorpha. The present work covers the life history of this bivalve, its potential use as a biomarker and its adaptations to the extreme marine environment conditions in Antarctica. Key-words: Antarctica, benthos, Laternula ...

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O:N atomic ratio as a tool to describe zooplankton metabolism

Cited by 298 publications

References 29 publications

Metabolic rates of the antarctic amphipod Gondogeneia antarctica at different temperatures and salinities

Metabolic rates of the antarctic amphipod Gondogeneia antarctica at different temperatures and salinities

The metabolic response of pteropods to acidification reflects natural CO<sub>2</sub>-exposure in oxygen minimum zones

NITROGEN METABOLISM OF THE ANTARCTIC BIVALVE Laternula elliptica (KING & BRODERIP) AND ITS POTENTIAL USE AS BIOMARKER

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O:N atomic ratio as a tool to describe zooplankton metabolism

Cited by 298 publications

References 29 publications

Metabolic rates of the antarctic amphipod Gondogeneia antarctica at different temperatures and salinities

Metabolic rates of the antarctic amphipod Gondogeneia antarctica at different temperatures and salinities

The metabolic response of pteropods to acidification reflects natural CO&lt;sub&gt;2&lt;/sub&gt;-exposure in oxygen minimum zones

NITROGEN METABOLISM OF THE ANTARCTIC BIVALVE Laternula elliptica (KING & BRODERIP) AND ITS POTENTIAL USE AS BIOMARKER

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The metabolic response of pteropods to acidification reflects natural CO<sub>2</sub>-exposure in oxygen minimum zones