UV sensitivity of planktonic net community production in ocean surface waters

The net plankton community metabolism of oceanic surface waters is particularly important as it more directly affects the partial pressure of CO2 in surface waters and thus the air-sea fluxes of CO2. Plankton communities in surface waters are exposed to high irradiance that includes significant ultraviolet blue (UVB, 280-315 nm) radiation. UVB radiation affects both photosynthetic and respiration rates, increase plankton mortality rates, and other metabolic and chemical processes. Here we test the sensitivity of net community production (NCP) to UVB of planktonic communities in surface waters across contrasting regions of the ocean. We observed here that UVB radiation affects net plankton community production at the ocean surface, imposing a shift in NCP by, on average, 50% relative to the values measured when excluding partly UVB. Our results show that under full solar radiation, the metabolic balance shows the prevalence of net heterotrophic community production. The demonstration of an important effect of UVB radiation on NCP in surface waters presented here is of particular relevance in relation to the increased UVB radiation derived from the erosion of the stratospheric ozone layer. Our results encourage design future research to further our understanding of UVB effects on the metabolic balance of plankton communities. Key Points UV sensitivity of planktonic NCP ©2014. American Geophysical Union. All Rights Reserved.This research was funded by the projects RODA (CTM-2004-06842-CO3-O2) and ATOS (POL2006-00550/CTM), Humboldt-2009 project (CTM2008-02497-E), MEDEICG (CTM2009-07013), and the Malaspina-2010 expedition project funded by the CONSOLIDER Ingenio-2010 program (CSD2008-00077), all funded by the National Plan of R + D of the Spanish Ministry of Science and Innovation. A.R.d.G. was supported by the EU Marie Curie EST project Metaoceans (MEST-CT-2005-019678)Peer Reviewe

Poor correlation between phytoplankton community growth rates and nutrient concentration in the sea

Nutrient availability is one of the major factors regulating marine productivity and phytoplankton community structure. While the response of phytoplankton species to nutrient variation is relatively well known, that of phytoplankton community remains unclear. We question whether phytoplankton community growth rates respond to nutrient concentration in a similar manner to phytoplankton species composing the community, that is, following Monod's model. Data on in situ marine community growth rates in relation to nutrient concentration and the behaviour of a simple multi-species community model suggest that community growth rate does not respond to nutrient concentration according to the Monod equation. Through a simulation study we show this can be explained as a consequence of changes in size structure. Marine biogeochemical models must not parameterize phytoplankton community growth rate response to nutrient concentration using a single Monod equation but rather involve different phytoplankton functional groups each with different equation parameters.Versión del editor3,859

O impacto do upwelling de Cabo Frio sobre os processos metabólicos do plâncton: revisão bibliográfica

Núcleo de Pesquisa em Biodiversidade Marinha da Universidade de São Paulo (NP-BioMar/USP

Comparing marine primary production estimates through different methods and development of conversion equations

Numerous studies have compared the rates of primary production using various techniques at specific locations and times. However, these comparisons are local and cannot be used to compare or scale rates of primary production using different methods across ocean basins or seasonal time scales. Here, we quantify the range in rates of primary production derived using different techniques and provide equations that allow conversions of estimates between different methods. We do so on the basis of a compilation of data on volumetric estimates of primary production rates concurrently estimated with at least two different methods. We observed that the comparison of estimates of marine phytoplankton primary production derived from different methods reveals very large variations between methods. The highest primary production estimates are derived using the 18O method, which may provide the best and more generally applicable estimate of gross primary production (GPP). The regression equations presented in this work provide the best available approach to convert data across methods and therefore integrate and synthesize available and future data derived using different methods

Consequences of UV-enhanced community respiration for plankton metabolic balance

The net community production (NCP) of plankton communities affects their role as sources or sinks of atmospheric CO2. Most estimates of NCP have been made by enclosing communities in bottles, generally glass borosilicate, that remove ultraviolet (UV)B and part of UVA wavelengths. A series of experiments were conducted to test whether NCP values from communities incubated excluding UVB (+ part of UVA) radiation (i.e., in glass borosilicate) differ from those of communities receiving the full solar radiation spectrum (i.e., incubated with quartz bottles) and to explore the effect of UV radiation on the respiration rates and bacterial production in these communities. Plankton NCP tended to be 43% lower, on average, when the rates were measured under full solar radiation than when UVB (+ part of UVA) was removed. Dark respiration was significantly enhanced after exposure to the full solar spectrum for most communities, showing lower values when previously incubated in a light environment free of UVB (−50%) or in the dark (−62%). Bacterial production was inhibited by natural sunlight but increased, as observed for community respiration, when transferred to the dark. Communities previously exposed to full solar spectrum showed the greatest increase in bacterial production when allowed to recover in the dark. The net result of these responses were an increase in community respiration and decline in net community production over 24 h, indicating that UVB radiation plays a major role in the metabolic balance of the ocean's surface ecosystem

Temperature dependence of planktonic metabolism in the subtropical North Atlantic Ocean

The temperature dependence of planktonic metabolism in the subtropical North Atlantic Ocean was assessed on the basis of measurements of gross primary production (GPP), community respiration (CR) and net community production (NCP), as well as experimental assessments of the response of CR to temperature manipulations. Metabolic rates were measured at 68 stations along three consecutive longitudinal transects completed during the Malaspina 2010 Expedition, in three different seasons. Temperature gradients were observed in depth and at basin and seasonal scale. The results showed seasonal variability in the metabolic rates, the highest rates being observed during the spring transect. The overall mean integrated GPP / CR ratio was 1.39 ± 0.27 decreasing from winter to summer, and the NCP for the subtropical North Atlantic Ocean during the cruises exhibits net autotrophy (NCP > 0) in about two-thirds (66%) of the total sampled communities. Also, we reported the activation energies describing the temperature dependence of planktonic community metabolism, which was generally higher for CR than for GPP in the subtropical North Atlantic Ocean, as the metabolic theory of ecology predicts. Furthermore, we made a comparison of activation energies describing the responses to in situ temperature in the field (EaCR = 1.64 ± 0.36 eV) and those derived experimentally by temperature manipulations (EaCR = 1.45 ± 0.6 eV), which showed great consistency

Patterns in ocean metabolism: rates, balance and controls

[eng] The balance between the gross primary production (GPP) and the community respiration (CR) in oceanic ecosystems has been the subject of much discussion and controversy in the scientific community. The expanded observational basis resulting from these debates provided an opportunity to elucidate patterns in the metabolic balance in the Ocean, including examination of the magnitude of the differences in rates derived by different methods and describe the scaling among different metrics of plankton metabolic rates, evaluate regional and global variability in plankton metabolism and determine the threshold gross primary production separating heterotrophic from autotrophic communities. We analyse also here environmental parameters such as irradiance or water temperature that play an important role in controlling the metabolic balance of planktonic communities. We show here that the metabolism of plankton communities varies greatly across different oceanic regions with heterotrophic plankton communities more prevalent in the continental shelf consistent with high allochthonous inputs to the coastal ocean. The existence of a threshold of GPP of, on average 1.1 mmol O2 m-3 d-1 , separating less productive from more productive is exposed also here, providing evidence that less productive planktonic communities tend to be net heterotrophic. We report also in this work the evidence that the compensation depth for plankton community metabolism averages 36 ± 9 m. Furthermore, a threshold temperature of 23.5 ºC has been exposed here for a P/R ratio of 1, indicative of metabolic balance. The results presented in this dissertation reveal, in summary, important patterns of metabolic balance for planktonic communities across the ocean, their rates and controls. Continuing to explore the oceans and evaluating the metabolic balance of their planktonic communities is fundamental considering the major role planktonic community play in the global carbon cycle.[cat] L'equilibri entre la producció primària bruta (GPP) i la respiració de la comunitat (CR) en els ecosistemes oceànics ha estat objecte de molta discussió i controvèrsia en la comunitat científica. L’àmplia base d'observació resultant d'aquests debats ens proporciona l'oportunitat d'aclarir els patrons en l'equilibri metabòlic a l'oceà, inclòs l’estudi de la magnitud de les diferències en les taxes obtingudes per diferents mètodes i descriure l'escala entre els diferents mesures de taxes metabòliques de plàncton, avaluar la variabilitat regional i global en el metabolisme del plàncton i determinar el llindar que separa la producció primària bruta de les comunitats heterotròfiques i autotròfiques i la irradiància llindar necessària per equilibrar la producció primària i la respiració. S'analitzen també els paràmetres ambientals com ara la llum o la temperatura de l'aigua que juguen un paper important en el control de l'equilibri metabòlic de les comunitats planctòniques. Hem demostrat que el metabolisme de les comunitats planctòniques varia enormement entre diferents regions oceàniques. Les comunitats de plàncton heteròtrofes són freqüents a la plataforma continental de conformitat amb elevada aportació alòctona a l'oceà costaner. L'existència d'un llindar de GPP de mitjana 1.1 mmol O2 m-3 d-1 , que separa els menys productius dels més productius s'exposa també aquí, proporcionant evidència que les comunitats planctòniques menys productivess tendeixen a ser netament hetertròfiques. Es presenta també en aquest treball l'evidència que la profunditat de compensació pel metabolisme de la comunitat de plàncton és de 36 ± 9 m. D'altra banda, un llindar de temperatura de 23.5 º C s'ha exposat aquí per obtenir una relació P / R de 1, indicatiu de balanç metabòlic. Els resultats presentats en aquesta tesi revelen, en resum, importsants patrons d'equilibri metabòlic important per a les comunitats planctòniques a través de l'oceà, els seus tipus i controls. Continuar estudiant els oceans i l'avaluació del balanç metabòlic de les seves comunitats planctòniques és fonamental considerant l'important paper que juga la comunitat planctònica en el cicle global del carboni.[fra] L’équilibre entre la production primaire brute (GPP) et la respiration (CR) de la communauté planctonique dans les écosystèmes océaniques a fait l’objet de multiples discussions et de controverses au sein de la communauté scientifique. La large base de données provenant de ces débats a permis d’élucider les tendances de l’équilibre métabolique dans l’océan qui inclut l’examen de l’ampleur des différences au sein des taux métaboliques dûes à différentes méthodes, la description de l’échelle de différence des taux du métabolisme planctonique, l’évaluation de la variation régionale et globale du métabolisme, la détermination de la limite de GPP séparant les communautés hétérotrophes d’autotrophes. On a analysé également dans ce travail les paramètres environnementaux telle que la lumière et la température de l’eau qui jouent un rôle important dans le contrôle de l’équilibre métabolique de la communauté planctonique. On a montré que le métabolisme de la communauté planctonique varie de manière importante le long des différentes régions océaniques où les communautés planctoniques hétérotrophes sont plus répandues sur le plateau continental en accord avec les forts apports allochtones de l’océan côtier. L’existence d’une limite de GPP, en moyenne de 1.1 mmol O2 m-3 d-1 , séparant les communautés moins productives des plus productives a été exposée ici, apportant l’évidence que les communautés planctonique les moins productives tendent à être hétérotrophes. On a rapporté également dans ce travail l’évidence que la profondeur de compensation pour la communauté planctonique environnée 36 ± 9 m. De plus, une limite de température de 23.5 ºC a été montrée ici pour un rapport P/R de 1, indiquant un équilibre métabolique. Les résultats présentés dans ce manuscrit révèlent, en résumé, d’importantes tendances de l’équilibre métabolique de la communauté planctonique au travers les océans, leurs taux et leurs contrôles. L’exploration des océans et l’évaluation de l’équilibre métabolique des communautés planctoniques sont fondamentales si on considère le rôle majeur de la communauté planctonique dans le cycle global du carbone

Temperature dependence of planktonic metabolism in the ocean

10 páginas, 6 figuras, 2 tablas.Standard metabolic theory predicts that both respiration and photosynthesis should increase with increasing temperature, albeit at different rates. However, test of this prediction for ocean planktonic communities is limited, despite the broad consequences of this prediction in the present context of global ocean warming. We compiled a large data set on volumetric planktonic metabolism in the open ocean and tested the relationship between specific metabolic rates and water temperature. The relationships derived are consistent with predictions derived from metabolic theory of ecology, yielding activation energy for planktonic metabolism consistent with predictions from the metabolic theory. These relationships can be used to predict the effect of warming on ocean metabolism and, thus, the role of planktonic communities in the flow of carbon in the global ocean.Esta es una contribución al proyecto CONSOLIDER “Malaspina 2010” financiado por el Ministerio de Ciencia e Innovación del Gobierno español (ref. CSD2008-00077) y el Metaoceans Marie Curie Early Stage Research Network (019678–2), financiado por el Sexto Programa Marco de la Unión Europea.Peer reviewe

Compensation irradiance for planktonic community metabolism in the ocean

9 páginas, 5 figuras, 2 tablas.The light compensation irradiance for planktonic metabolic balance, defined as the irradiance where gross planktonic primary production equals community respiration, is an important property describing ecosystem dynamics. Planktonic communities receiving irradiances above the compensation irradiance or compensation depth (i.e., the depth at which the compensation irradiance is received) are autotrophic and act as CO2 sinks, whereas those at lower irradiances or located deeper in the water column act as CO2 sources. However, this property is undefined for heterotrophic communities in which metabolic balance is not set by light availability. The compensation irradiance for planktonic metabolism in the ocean was quantified experimentally and calculated using data available in the literature to assess its variability and possible controls. Gross primary production by the oceanic planktonic communities examined here meet their respiratory requirements at irradiances of about 1.1 ± 0.4 mol quanta m−2 d−1 and tend to be autotrophic above a depth of 36 ± 9 m, on average. The depth of nitracline is closely correlated with the compensation depth for community metabolism across the studied areas, but the compensation depth tends to be located above the depth of the nitracline. This is expected from the facts that the underlying, net heterotrophic communities should act as sources of inorganic nutrients and that the nitracline cannot develop within the mixed layer where the compensation depth is often located. These results imply that the planktonic communities examined extending from 36 m depth, on average, to the bottom of the euphotic layer tend to be heterotrophic, acting as CO2 and inorganic nutrient sources.Esta investigación ha sido financiada gracias a los proyectos RODA (CTM-2004-06842-CO3-O2) y ATOS (POL2006-00550/CTM), proyecto Humboldt-2009 (CTM2008-02497-E), y la expedición del proyecto Malaspina-2010 financiado por el programa CONSOLIDER Ingenio-2010(CSD2008-00077), todos ellos subvencionados por el Plan Nacional de I+D del Ministerio de España de Ciencia e Innovación. Aurore Regaudie-de-Gioux ha sido financiada por el programa de la Unión Europea Marie Curie EST, proyecto Metaoceans (MEST-CT-2005-019678).Peer reviewe

Thresholds of gross primary production for the metabolic balance of marine planktonic communities

8 pages, 1 figure, 1 table.-- Full-text available Open Access at the journal site.The notion that less productive marine planktonic communities tend to be heterotrophic was tested by synthesizing reported estimates of the relationships between the net community production or community respiration and gross primary production (GPP), allowing calculation of the threshold GPP separating less productive, heterotrophic communities from more productive, autotrophic ones. A total of 35 estimates of the threshold GPP were assembled, derived from reports of comparative analyses of individual regions (Mediterranean Sea, Atlantic Ocean, Southern Ocean, Pacific Ocean, and Indian Ocean) and global comparative analyses for open-ocean and coastal environments, time-series analyses of changes in planktonic metabolism at individual locations, experimental manipulations in mesocosms, and a semi-empirical modeling exercise. Planktonic communities of the open ocean and continental shelf showed threshold GPP values ranging 30-fold, from 0.34 mmol O2 m-3 d-1 to 9.45 mmol O2 m-3 d-1, with those for estuarine and coastal locations reaching 50.60 mmol O2 m-3 d-1. Antarctic and ultra-oligotrophic ecosystems showed the lowest threshold GPP values (<2.2 mmol O2 m-3 d-1), with a general consistency across approaches for a given ecosystem. Plankton community respiration in the absence of or under low primary production is not negligible and is supported by semi-labile dissolved organic carbon. The analysis of GPP thresholds suggests that allochthonous organic inputs to the less productive regions of the ocean must be in the order of mmol O2 m-3 d-1, consistent with recent estimates of allochthonous inputs of organic carbon to the ocean.This research was supported by project "COCA: Flujo de carbono en la región Canaria: acoplamiento entre exportación costera y demanda oceánica", "RODA: Remolinos oceánicos y deposición atmosférica: efectos biológicos y biogeoquímicos en aguas del Atlántico Este", "ATOS: Atmospheric inputs of organic carbon and pollutants to the polar ocean: Rates, significance and Outlook", and the "Malaspina 2010" CONSOLIDER project funded by the Spanish Ministry of Science and Innovation, and the integrated project Thresholds and the EUR-OCEANS network of excellence funded by the European Commission. A. R. d. G was supported by the METAOCEANS Marie Curie Network, of FP 6 of the European Commission.Peer reviewe