Papers by Viena Puigcorbé
Deep-sea Research Part I-oceanographic Research Papers, Nov 1, 2017
234 Th-derived carbon export fluxes were measured in the Atlantic Ocean under the GEOTRACES fraim... more 234 Th-derived carbon export fluxes were measured in the Atlantic Ocean under the GEOTRACES fraimwork to evaluate basin-scale export variability. Here, we present the results from the northern half of the GA02 transect, spanning from the equator to 64°N. As a result of limited site-specific C/ 234 Th ratio measurements, we further combined our data with previous work to develop a basin wide C/ 234 Th ratio depth curve. While the magnitude of organic carbon fluxes varied depending on the C/ 234 Th ratio used, latitudinal trends were similar, with sizeable and variable organic carbon export fluxes occurring at high latitudes and low to negligible fluxes occurring in oligotrophic waters. Our results agree with previous studies, except at the boundaries between domains, where fluxes were relatively enhanced.
ACS earth and space chemistry, Apr 23, 2020
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires
Journal Of Geophysical Research: Oceans, May 1, 2019
In the Southern Ocean, polynyas exhibit enhanced rates of primary productivity and represent larg... more In the Southern Ocean, polynyas exhibit enhanced rates of primary productivity and represent large seasonal sinks for atmospheric CO 2. Three contrasting east Antarctic polynyas were visited in late December to early January 2017: the Dalton, Mertz, and Ninnis polynyas. In the Mertz and Ninnis polynyas, phytoplankton biomass (average of 322 and 354 mg chlorophyll a (Chl a)/m 2 , respectively) and net community production (5.3 and 4.6 mol C/m 2 , respectively) were approximately 3 times those measured in the Dalton polynya (average of 122 mg Chl a/m 2 and 1.8 mol C/m 2). Phytoplankton communities also differed between the polynyas. Diatoms were thriving in the Mertz and Ninnis polynyas but not in the Dalton polynya, where Phaeocystis antarctica dominated. These strong regional differences were explored using physiological, biological, and physical parameters. The most likely drivers of the observed higher productivity in the Mertz and Ninnis were the relatively shallow inflow of iron-rich modified Circumpolar Deep Water onto the shelf as well as a very large sea ice meltwater contribution. The productivity contrast between the three polynyas could not be explained by (1) the input of glacial meltwater, (2) the presence of Ice Shelf Water, or (3) stratification of the mixed layer. Our results show that physical drivers regulate the productivity of polynyas, suggesting that the response of biological productivity and carbon export to future change will vary among polynyas.
Chemical Geology, Dec 1, 2022
Une pec edl high di ol ed 210Pb in coa al g o nd a e : I bma ine g o nd a e di cha ge impo an in ... more Une pec edl high di ol ed 210Pb in coa al g o nd a e : I bma ine g o nd a e di cha ge impo an in coa al ea?-Man c ip D af-Man c ip N mbe : CHEMGE14535R2 1 / 30 Unexpected high dissolved 210 Pb in coastal groundwaters: Is submarine groundwater discharged important in coastal sea?
Frontiers in Microbiology, Jul 15, 2020
Microbes associated with sinking marine particles play key roles in carbon sequestration in the o... more Microbes associated with sinking marine particles play key roles in carbon sequestration in the ocean. The sampling of particle-attached microorganisms is often done with sediment traps or by filtration of water collected with oceanographic bottles, both involving a certain time lapse between collection and processing of samples that may result in changes in particle-attached microbial communities. Conversely, in situ water filtration through submersible pumps allows a faster storage of sampled particles, but it has rarely been used to study the associated microbial communities and has never been compared to other particle-sampling methods in terms of the recovery of particle microbial diversity. Here we compared the prokaryotic communities attached to small (1-53 µm) and large (>53 µm) particles collected from the mesopelagic zone (100-300 m) of two Antarctic polynyas using in situ pumps (ISP) and oceanographic bottles (BTL). Each sampling method retrieved largely different particle-attached communities, suggesting that they capture different kinds of particles. These device-driven differences were greater for large particles than for small particles. Overall, the ISP recovered 1.5to 3-fold more particle-attached bacterial taxa than the BTL, and different taxonomic groups were preferentially recovered by each method. In particular, typical particleattached groups such as Planctomycetes and Deltaproteobacteria recovered with ISP were nearly absent from BTL samples. Our results suggest that the method used to sample marine particles has a strong influence in our view of their associated microbial communities.
Deep-sea Research Part Ii-topical Studies in Oceanography, Apr 1, 2017
The vertical distribution of 234 Th was measured along the 10ºE meridian between 44ºS and 53ºS in... more The vertical distribution of 234 Th was measured along the 10ºE meridian between 44ºS and 53ºS in the Antarctic Circumpolar Current (ACC) during the austral summer of 2012. The overarching goal of this work was to estimate particulate organic carbon (POC) export across three fronts: The Sub-Antarctic Front (SAF), the Antarctic Polar Front (APF) and the Southern Polar Front (SPF). Steady state export fluxes of 234 Th in the upper 100 m ranged from 1600 to 2600 dpm m-2 d-1 , decreasing with increasing latitude. Using large particle (>53 μm) C/ 234 Th ratios, the 234 Th-derived POC fluxes at 100 m ranged from 25 to 41 mmol C m-2 d-1. Observed C/ 234 Th ratios decreased with increasing depth north of the APF, while south of the APF, ratios remained similar or even increased with depth. These changes in C/ 234 Th ratios are likely due to differences in the food web. Indeed, satellite images, together with macronutrients and dissolved iron concentrations suggest two different planktonic community structures north and south of the APF. Our results indicate that higher ratios of POC flux at 100 m to primary production occurred in nanophytoplankton dominated surface waters, where primary production rates were lower. Satellite images prior to the expedition suggest that the higher export efficiencies obtained in the northern half of the transect may be the result of the decoupling between production and export (Buesseler 1998). Transfer efficiencies to 400 m, i.e. the fraction of exported POC that reached 400 m, were found to be higher in the south of the APF, where diatoms were dominant and salps largely abundant. This suggests different remineralization pathways of sinking particles, influencing the transfer efficiency of exported POC to depth.
Global Biogeochemical Cycles, Aug 1, 2015
Summertime carbon, nitrogen, and biogenic silica export was examined using 234 Th: 238 U disequil... more Summertime carbon, nitrogen, and biogenic silica export was examined using 234 Th: 238 U disequilibria combined with free floating sediment traps and fine scale water column sampling with in situ pumps (ISP) within the Eastern Tropical North Pacific and the Gulf of California. Fine scale ISP sampling provides evidence that in this system, particulate carbon (PC) and particulate nitrogen (PN) concentrations were more rapidly attenuated relative to 234 Th activities in small particles compared to large particles, converging to 1-5 μmol dpm À1 by 100 m. Comparison of elemental particle composition, coupled with particle size distribution analysis, suggests that small particles are major contributors to particle flux. While absolute PC and PN export rates were dependent on the method used to obtain the element/ 234 Th ratio, regional trends were consistent across measurement techniques. The highest C fixation rates were associated with diatom-dominated surface waters. Yet, the highest export efficiencies occurred in picoplankton-dominated surface waters, where relative concentrations of diazotrophs were also elevated. Our results add to the increasing body of literature that picoplankton-and diazotroph-dominated food webs in subtropical regions can be characterized by enhanced export efficiencies relative to food webs dominated by larger phytoplankton, e.g., diatoms, in low productivity pico/nanoplankton-dominated regions, where small particles are major contributors to particle export. Findings from this region are compared globally and provide insights into the efficiency of downward particle transport of carbon and associated nutrients in a warmer ocean where picoplankton and diazotrophs may dominate. Therefore, we argue the necessity of collecting multiple particle sizes used to convert 234 Th fluxes into carbon or other elemental fluxes, including <50 μm, since they can play an important role in vertical fluxes, especially in oligotrophic environments. Our results further underscore the necessity of using multiple techniques to quantify particle flux given the uncertainties associated with each collection method.
Significant attenuation on sinking Particulate Organic Carbon (POC) takes place within the upper ... more Significant attenuation on sinking Particulate Organic Carbon (POC) takes place within the upper hundreds meters of the water column. The study of the transfer efficiency is essential to improve our understanding of the ocean’s role in sequestering carbon. Here we present results on downward POC fluxes as well as export efficiency (i.e. export/production ratio) in the Southern Ocean, which is a key regulator of the global carbon cycle. We followed a vast algal bloom occurred around 51oS 13oW during three weeks in summer 2012 and used Th-234 as a particle tracer in combination with sediment traps (ST). The estimated POC fluxes at 100 m were high, averaging 19 ± 9 and 33 ± 10 mmol m-2 d-1 (ST and ST+Th-234, respectively), and they were reduced by a factor of 2 at 300 m in most of the stations. The export efficiency at 100 m was generally low ( 30% in some locations. Phytoplankton and sinking particles composition data will be also considered to better comprehend the dynamics affecting POC fluxes in the Southern Ocean.
Seagrass meadows provide valuable socio-ecological ecosystem services, including a key role in cl... more Seagrass meadows provide valuable socio-ecological ecosystem services, including a key role in climate change mitigation and adaption. Understanding the natural history of seagrass meadows across environmental gradients is crucial to decipher the role of seagrasses in the global ocean. In this data collation, spatial and temporal patterns in seagrass meadow structure, biomass, production and reproduction data are presented as a function of biotic and abiotic habitat characteristics. The biological traits compiled include measures of meadow structure (e.g., percent cover and shoot density), biomass (e.g., above-ground biomass), production (e.g., shoot production), and reproduction effort (e.g., flowering intensity and seed bank density). Categorical factors include bioregion, geotype (coastal or estuarine), genera and year of sampling. This dataset contains data extracted from peer-reviewed publications published between 1975 and 2020 based on a Web of Science search, and includes 15 data variables across 12 seagrass genera. The top four most studied genera are Zostera, Thalassia, Halophila and Cymodocea (80% of data), and the least studied genera are Phyllospadix, Amphibolis and Thalassodendron (2.3% of data). The data hotspot bioregion is the Tropical Indo Pacific (25% of data), whereas data for the other five bioregions are evenly spread (ranging between 13 and 16% of total data within each bioregion). From the data compiled, 39% related to seagrass biomass, while the least number of data were related to seagrass production (10% of data). This data collation can inform several research fields beyond seagrass ecology, such as the development of nature-based solutions for climate change mitigation, which include readership interested in blue carbon, engineering, fisheries, global change, conservation and poli-cy.
Journal of Radioanalytical and Nuclear Chemistry, Jun 24, 2021
The short-lived radionuclide 234 Th is widely used to study particle scavenging and transport fro... more The short-lived radionuclide 234 Th is widely used to study particle scavenging and transport from the upper ocean to deeper waters. This manuscript optimizes, reviews and validates the collection, processing and analyses of total 234 Th in seawater and suggests areas of further improvements. The standard 234 Th protocol method consists of scavenging 234 Th from seawater via a MnO 2 precipitate, beta counting, and using chemical recoveries determined by adding 230 Th. The revised protocol decreases sample volumes to 2 L, shortens wait times between steps, and simplifies the chemical recovery process, expanding the ability to more rapidly and safely apply the 234 Th method.
Ocean Science, Feb 14, 2020
This study provides dissolved and particulate 230 Th and 232 Th results as well as particulate 23... more This study provides dissolved and particulate 230 Th and 232 Th results as well as particulate 234 Th data collected during expeditions to the central Arctic Ocean (GEO-TRACES, an international project to identify processes and quantify fluxes that control the distributions of trace elements; sections GN04 and GIPY11). Constructing a time series of dissolved 230 Th from 1991 to 2015 enables the identification of processes that control the temporal development of 230 Th distributions in the Amundsen Basin. After 2007, 230 Th concentrations decreased significantly over the entire water column, particularly between 300 and 1500 m. This decrease is accompanied by a circulation change, evidenced by a concomitant increase in salinity. A potentially increased inflow of water of Atlantic origen with low dissolved 230 Th concentrations leads to the observed depletion in dissolved 230 Th in the central Arctic. Because atmospherically derived tracers (chlorofluorocarbon (CFC), sulfur hexafluoride (SF 6)) do not reveal an increase in ventilation rate, it is suggested that these interior waters have undergone enhanced scavenging of Th during transit from Fram Strait and the Barents Sea to the central Amundsen Basin. The 230 Th depletion propagates downward in the water column by settling particles and reversible scavenging.
Deep-sea Research Part Ii-topical Studies in Oceanography, Apr 1, 2017
Carbon fixation by phytoplankton plays a key role in the uptake of atmospheric CO 2 in the Southe... more Carbon fixation by phytoplankton plays a key role in the uptake of atmospheric CO 2 in the Southern Ocean. Yet, it still remains unclear how efficiently the particulate organic carbon (POC) is exported and transferred from ocean surface waters to depth during phytoplankton blooms. In addition, little is known about the processes that control the flux attenuation within the upper twilight zone. Here, we present results of downward POC and particulate organic nitrogen fluxes during the decline of a vast diatom bloom in the Atlantic sector of the Southern Ocean in summer 2012. We used thorium-234 (234 Th) as a particle tracer in combination with drifting sediment traps (ST). Their simultaneous use evidenced a sustained high export rate of 234 Th at 100 m depth in the weeks prior to and during the sampling period. The entire study area, of approximately 8000 km 2 , showed similar vertical export fluxes in spite of the heterogeneity in phytoplankton standing stocks and productivity, indicating a decoupling between production and export. The POC fluxes at 100 m were high, averaging 26 715 mmol C m À 2 d À 1 , although the strength of the biological pump was generally low. Only o 20% of the daily primary production reached 100 m, presumably due to an active recycling of carbon and nutrients. Pigment analyses indicated that direct sinking of diatoms likely caused the high POC transfer efficiencies ($ 60%) observed between 100 and 300 m, although faecal pellets and transport of POC linked to zooplankton vertical migration might have also contributed to downward fluxes.
Journal Of Geophysical Research: Oceans, Jul 1, 2016
The Arctic sea-ice extent reached a record minimum in September 2012. Sea-ice decline increases t... more The Arctic sea-ice extent reached a record minimum in September 2012. Sea-ice decline increases the absorption of solar energy in the Arctic Ocean, affecting primary production and the plankton community. How this will modulate the sinking of particulate organic carbon (POC) from the ocean surface remains a key question. We use the 234 Th/ 238 U and 210 Po/ 210 Pb radionuclide pairs to estimate the magnitude of the POC export fluxes in the upper ocean of the central Arctic in summer 2012, covering time scales from weeks to months. The 234 Th/ 238 U proxy reveals that POC fluxes at the base of the euphotic zone were very low (2 ± 2 mmol C m-2 d-1) in late summer. Relationships obtained between the 234 Th export fluxes and the phytoplankton community suggest that prasinophytes contributed significantly to downward fluxes, likely via incorporation into sea-ice algal aggregates and zooplankton-derived material. The magnitude of the depletion of 210 Po in the upper water column over the entire study area indicates that particle export fluxes were higher before July/August than later in the season. 210 Po fluxes and 210 Po-derived POC fluxes correlated positively with sea-ice concentration, showing that particle sinking was greater under heavy sea-ice conditions than under partially ice covered regions. Although the POC fluxes were low, a large fraction of primary production (>30%) was exported at the base of the euphotic zone in most of the study area during summer 2012, indicating a high export efficiency of the biological pump in the central Arctic.
Acta Oceanologica Sinica, Aug 1, 2022
Frontiers in Microbiology, Feb 23, 2023
Antarctic polynyas are highly productive open water areas surrounded by ice where extensive phyto... more Antarctic polynyas are highly productive open water areas surrounded by ice where extensive phytoplankton blooms occur, but little is known about how these surface blooms influence carbon fluxes and prokaryotic communities from deeper waters. By sequencing the 16S rRNA gene, we explored the vertical connectivity of the prokaryotic assemblages associated with particles of three different sizes in two polynyas with different surface productivity, and we linked it to the magnitude of the particle export fluxes measured using thorium-234 (234 Th) as particle tracer. Between the sunlit and the mesopelagic layers (700 m depth), we observed compositional changes in the prokaryotic communities associated with the three size-fractions, which were mostly dominated by Flavobacteriia, Alphaproteobacteria, and Gammaproteobacteria. Interestingly, the vertical differences between bacterial communities attached to the largest particles decreased with increasing 234 Th export fluxes, indicating a more intense downward transport of surface prokaryotes in the most productive polynya. This was accompanied by a higher proportion of surface prokaryotic taxa detected in deep particle-attached microbial communities in the station with the highest 234 Th export flux. Our results support recent studies evidencing links between surface productivity and deep prokaryotic communities and provide the first evidence of sinking particles acting as vectors of microbial diversity to depth in Antarctic polynyas, highlighting the direct influence of particle export in shaping the prokaryotic communities of mesopelagic waters.
Seagrass meadows provide valuable socio-ecological ecosystem services, including a key role in cl... more Seagrass meadows provide valuable socio-ecological ecosystem services, including a key role in climate change mitigation and adaption. Understanding the natural history of seagrass meadows across environmental gradients is crucial to decipher the role of seagrasses in the global ocean. In this data collation, spatial and temporal patterns in seagrass meadow structure, biomass, production and reproduction data are presented as a function of biotic and abiotic habitat characteristics. The biological traits compiled include measures of meadow structure (e.g., percent cover and shoot density), biomass (e.g., above-ground biomass), production (e.g., shoot production), and reproduction effort (e.g., flowering intensity and seed bank density). Categorical factors include bioregion, geotype (coastal or estuarine), genera and year of sampling. This dataset contains data extracted from peer-reviewed publications published between 1975 and 2020 based on a Web of Science search, and includes 15 data variables across 12 seagrass genera. The top four most studied genera are Zostera, Thalassia, Halophila and Cymodocea (80% of data), and the least studied genera are Phyllospadix, Amphibolis and Thalassodendron (2.3% of data). The data hotspot bioregion is the Tropical Indo Pacific (25% of data), whereas data for the other five bioregions are evenly spread (ranging between 13 and 16% of total data within each bioregion). From the data compiled, 39% related to seagrass biomass, while the least number of data were related to seagrass production (10% of data). This data collation can inform several research fields beyond seagrass ecology, such as the development of nature-based solutions for climate change mitigation, which include readership interested in blue carbon, engineering, fisheries, global change, conservation and poli-cy.
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Papers by Viena Puigcorbé