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Surface phytoplankton communities were linked with the carbon they export into the deep ocean by comparing 18 S rRNA gene sequence communities from surface seawater and individually isolated sinking particles. Particles were collected in sediment traps deployed at locations in the North Pacific subtropical gyre and the California Current. DNA was isolated from individual particles, bulk-collected trap particles, and the surface seawater. The relative sequence abundance of exported phytoplankton taxa in the surface water varied across functional groups and ecosystems. Of the sequences detected in sinking particles, about half were present in large (>300 μm), individually isolated particles and primarily belonged to taxa with small cell sizes (500 μm). The effect of particle degradation on the detectable 18 S rRNA gene community differed across taxa, and differences in community composition among individual particles from the same location largely reflected differences in relative degradation state. Using these data and particle imaging, we present an approach that incorporates genetic diversity into mechanistic models of the ocean’s biological carbon pump, which will lead to better quantification of the ocean’s carbon cycle.

Cell death drives the magnitude and community composition of phytoplankton and can result in the conversion of particulate organic carbon to dissolved organic carbon (DOC), thereby affecting carbon cycling in the aquatic food web. We used a membrane integrity probe (Sytox Green) to study the seasonal variation in the percentage of viable cells in the phytoplankton population in an estuary in the northern Baltic Sea for 21 months. The associated dissolved and particulate organic matter concentrations were also studied. The viable fraction of phytoplankton cells varied from

"A high-resolution study of the early- to late-summer progression in primary production and carbon export potential in the Atlantic Southern Ocean" is the Honours thesis of Amelia Deary, focusing on the switch from new- to regenerated production in the framework of the new production paradigm as defined by Dugdale and Goering (1967).As a consequence of the paucity of seasonally-resolved NPP and N uptake data for the Southern Ocean, many dynamics of biological C and N cycling are difficult to disentangle. Sampling at the beginning and end of a single growing season thus makes this study unique. Rates (bulk and size-fractionated) of net primary production (NPP) and N uptake (as NO3-and NH4+) were measured across the Atlantic Southern Ocean in early- (December) and late-summer (March) of the same year to investigate the evolution and drivers of phytoplankton N uptake dynamics and C export potential over the growing season.

The biological carbon pump exports carbon fixed by photosynthesis out of the surface ocean and transfers it to the deep, mostly in the form of sinking particles. Despite the importance of the pump in regulating the air‐sea CO2 balance, the magnitude of global carbon export remains unclear, as do its controlling mechanisms. A possible sinking flux of carbon to the mesopelagic zone may be via the mixed‐layer pump: a seasonal net detrainment of particulate organic carbon (POC)‐rich surface waters, caused by sequential deepening and shoaling of the mixed layer. In this study, we present a full year of daily small‐particle POC concentrations derived from glider optical backscatter data, to study export variability at the Porcupine Abyssal Plain (PAP) sustained observatory in the Northeast Atlantic. We observe a strong seasonality in small‐particle transfer efficiency, with a maximum in winter and early spring. By calculating daily POC export driven by mixed‐layer variations, we find that the mixed‐layer pump supplies an annual flux of at least 3.0 ± 0.9 g POC·m−2·year−1 to the mesopelagic zone, contributing between 5% and 25% of the total annual export flux and likely contributing to closing a gap in the mesopelagic carbon budget found by other studies. These are, to our best knowledge, the first high‐frequency observations of export variability over the course of a full year. Our results support the deployment of bio‐optical sensors on gliders to improve our understanding of the ocean carbon cycle on temporal scales from daily to annual., Key Points Gliders captured a full annual cycle of high‐frequency POC variability over the upper mesopelagic zoneSmall‐particle transfer efficiency displayed a strong seasonality, peaking in winter and early springThe data indicate a significant annual carbon supply to the mesopelagic zone by small particles through the mixed‐layer pump

The net primary productivity (NPP) of marine phytoplankton is ∼50 Pg C year–1, and roughly 10–20% of this NPP is exported out of the surface ocean as sinking particulate organic carbon (POC). Numerous mechanisms are hypothesized to control POC export out of the surface ocean but the relative importance of the various mechanisms remains poorly quantified on global scales. Here, we use a previously published satellite-based mechanistic model of POC export to examine the effects on global POC export of size-specific physical aggregation, size-specific and temperature-dependent zooplankton fecal pellet production, and size-specific and temperature-dependent non-grazing phytoplankton mortality. We test these mechanisms in different model configurations to determine if these processes improve the ability of the model to match POC export observations, and to assess the role of each process in controlling global POC export. We find that all model configurations predict that over 60% of the global POC export is from small zooplankton fecal pellets. All model configurations predict similar total POC export, and we find only small differences in the magnitude, timing, and geographical variations of total POC export. However, the fraction of total POC export due to sinking phytoplankton aggregates, and that due to the fecal pellets of large zooplankton, vary by more than a factor of two across the different model configurations. The POC export in all models is most sensitive to parameters controlling zooplankton fecal fluxes and non-grazing phytoplankton mortality. We compared zooplankton grazing rates predicted by the models to results of experimental data, and found that some models match the experimental grazing rates better than others, although data uncertainties remain large. More field measurements of bulk ecosystem rates (i.e., phytoplankton aggregation and zooplankton grazing), as well as explicit determinations of of the proportion of fecal matter to phytoplankton aggregation, will help to better constrain mechanistic models of global POC export.

Deep ocean microbial communities rely on the organic carbon produced in the sunlit ocean, yet it remains unknown whether surface processes determine the assembly and function of bathypelagic prokaryotes to a larger extent than deep-sea physicochemical conditions. Here, we explored whether variations in surface phytoplankton assemblages across Atlantic, Pacific and Indian ocean stations can explain structural changes in bathypelagic (ca. 4,000 m) free-living and particle-attached prokaryotic communities (characterized through 16S rRNA gene sequencing), as well as changes in prokaryotic activity and dissolved organic matter (DOM) quality. We show that the spatial structuring of prokaryotic communities in the bathypelagic strongly followed variations in the abundances of surface dinoflagellates and ciliates, as well as gradients in surface primary productivity, but were less influenced by bathypelagic physicochemical conditions. Amino acid-like DOM components in the bathypelagic reflected variations of those components in surface waters, and seemed to control bathypelagic prokaryotic activity. The imprint of surface conditions was more evident in bathypelagic than in shallower mesopelagic (200–1,000 m) communities, suggesting a direct connectivity through fast-sinking particles that escape mesopelagic transformations. Finally, we identified a pool of endemic deep-sea prokaryotic taxa (including potentially chemoautotrophic groups) that appear less connected to surface processes than those bathypelagic taxa with a widespread vertical distribution. Our results suggest that surface planktonic communities shape the spatial structure of the bathypelagic microbiome to a larger extent than the local physicochemical environment, likely through determining the nature of the sinking particles and the associated prokaryotes reaching bathypelagic waters., Spanish Ministry of Economy and Competitiveness (MINECO) through the Consolider-Ingenio program (Malaspina 2010 Expedition) (FEDER funds) CSD2008-00077 CTM2015-70340R CTM2015-65720-R CTM2015-69936-P RTI2018-101025-B-I00 UCE.PP2017.03 CTM2015-69392-C3-2-R, King Abdullah University of Science & Technology, Juan de la Cierva fellowship, GRAMMI project IJCI-2015-23505 RTI2018-099740-J-I00, Viera y Clavijo contract - ACIISI, ULPGC, Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) FONDAP-IDEAL15150003 FONDECYT-POSTDOCTORADO 3190369

Author(s): Morrow, RM; Ohman, MD; Goericke, R; Kelly, TB; Stephens, BM; Stukel, MR | Abstract: Predicting marine carbon sequestration in a changing climate requires mechanistic understanding of the processes controlling sinking particle flux under different climatic conditions. The recent occurrence of a warm anomaly (2014–2015) followed by an El Nino (2015–2016) in the southern sector of the California Current System presented an opportunity to analyze changes in the biological carbon pump in response to altered climate forcing. We compare primary production, mesozooplankton grazing, and carbon export from the euphotic zone during quasi-Lagrangian experiments conducted in contrasting conditions: two cruises during warm years - one during the warm anomaly in 2014 and one toward the end of El Nino 2016 – and three cruises during El Nino-neutral years. Results showed no substantial differences in the relationships between vertical carbon export and its presumed drivers (primary production, mesozooplankton grazing) between warm and neutral years. Mesozooplankton fecal pellet enumeration and phaeopigment measurements both showed that fecal pellets were the dominant contributor to export in productive upwelling regions. In more oligotrophic regions, fluxes were dominated by amorphous marine snow with negligible pigment content. We found no evidence for a significant shift in the relationship between mesozooplankton grazing rate and chlorophyll concentration. However, mass-specific grazing rates were lower at low-to-moderate chlorophyll concentrations during warm years relative to neutral years. We also detected a significant difference in the relationship between phytoplankton primary production and photosynthetically active radiation between years: at similar irradiance and nutrient concentrations, productivity decreased during the warm events. Whether these changes resulted from species composition changes remains to be determined. Overall, our results suggest that the processes driving export remain similar during different climate conditions, but that species compositional changes or other structural changes require further attention.

The amount of shoot stem (i.e., woody part of the shoot) dry matter per unit shoot leaf dry matter (i.e., the shoot wood to leaf biomass ratio) has been reported to be lower in short shoots than in long ones, and this is related to the greater and earlier ability of short shoots to export carbon. This is important in fruit trees, since the greater and earlier carbon export ability of shoots with a lower wood to leaf biomass ratio improves fruit production. This ratio may vary with cultivars, training systems or plant age, but no study has previously investigated the possible effect of fruit production. In this study on two olive cultivars (i.e., Arbequina, with low growth rate, and Frantoio, with high growth rate) subject to different fruit production treatments, we found that at increasing fruit production, shoot length and shoot wood to leaf biomass ratio were proportionally reduced in the new shoots growing at the same time as the fruit. Specifically, fruit production proportionally reduced total new-shoot biomass, length, leaf area and average shoot length. With decreasing shoot length, shoot diameter, stem mass, internode length, individual leaf area and shoot wood to leaf biomass ratio also decreased. This may be viewed as a plant strategy to better support fruit growth in the current year, given the greater and earlier ability of short shoots to export carbon. Moreover, at the whole-tree level, the percentage of total tree biomass production invested in leaves was closely correlated with branching density, which differed significantly across cultivars. By branching more, Arbequina concentrates more shoots (thus leaves) per unit of wood (trunk, branches and root) mass, decreasing wood to leaf biomass ratio at the whole-tree level. Therefore, while, at the shoot level, shoot length determines shoot wood to leaf biomass ratio, at the canopy level branching density is also an important determinant of whole-tree wood to leaf biomass ratio. Whole-tree wood to leaf biomass ratio is likely to affect the canopy's ability to export carbon (i.e., towards fruits), as shoot wood to leaf biomass ratio affects the carbon export ability of the shoot.

Identificadors digitals: Digital object identifier for the 'European Research Council' (http://dx.doi.org/10.13039/501100000781) and Digital object identifier for 'Horizon 2020' (http://dx.doi.org/10.13039/501100007601) Unidad de excelencia María de Maeztu MdM-2015-0552 The long-term trend of increasing phytoplankton net primary production (NPP) in the Arctic correlates with increasing light penetration due to sea ice loss. However, recent studies suggest that enhanced stormy wind mixing may also play a significant role enhancing NPP. Here, we isolate the role of sea ice and stormy winds (hereafter high-frequency winds) using an eddy-permitting ice-ocean-biogeochemical model configured for the North Atlantic and the Arctic. In the model, the presence of high-frequency winds stimulates nutrient upwelling by producing an earlier and longer autumn-winter mixing period with deeper mixing layer. The early onset of autumn mixing results in nutrients being brought-up to near-surface waters before the light becomes the dominant limiting factor, which leads to the autumn bloom. The enhanced mixing results in higher nutrient concentrations in spring and thus a large spring bloom. The model also shows significant iron limitation in the Labrador Sea, which is intensified by high-frequency winds. The effect of sea ice loss on NPP was found to be regionally dependent on the presence of high-frequency winds. This numerical study suggests high-frequency winds play significant role increasing NPP in the Arctic and sub-Arctic by alleviating phytoplankton nutrient limitation and that the isolated effect of sea ice loss on light plays a comparatively minor role.

The vertical distribution and temporal changes in aggregate abundance and sizes were measured in the Ross Sea, Antarctica between 2002 and 2005 to acquire a more complete understanding of the mechanisms and rates of carbon export from the euphotic layer. Aggregate abundance was determined by photographic techniques, and water column parameters (temperature, salinity, fluorescence, transmissometry) were assessed from CTD profiles. During the first three years the numbers of aggregates increased seasonally, being much more abundant within the upper 200 m in late summer than in early summer from 50 to 100 m (12.5 L–1 in early summer vs. 42.9 L–1 in late summer). In Year 4 aggregate numbers were substantially greater than in other years, and average aggregate abundance was maximal in early rather than late summer (177 vs. 84.5 L–1), which we attributed to the maximum biomass and aggregate formation being reached earlier than in other years. The contribution of aggregate particulate organic carbon to the total particulate carbon pool was estimated to be 20%. Ghost colonies, collapsed colonies of the haptophyte Phaeocystis antarctica, were observed during late summer in Year 4, with maximum numbers in the upper 100 m of ca. 40 L–1. Aggregate abundance, particulate organic carbon and ghost colonies all decreased exponentially with depth, and the rate of ghost colony disappearance suggested that their contribution to sedimentary input was small at the time of sampling. Bottom nepheloid layers were commonly observed in late summer in both transmissometer and aggregate data. Late summer nepheloid layers had fluorescent material within them, suggesting that the particles were likely generated during the same growing season. Longer studies encompassing the entire production season would be useful in further elucidating the role of these aggregates in the carbon cycle of these regions.

Emissions of nitrogen (N) from anthropogenic sources enrich marine waters and promote planktonic growth. This newly synthesised organic carbon is eventually exported to benthic waters where aerobic respiration by heterotrophic bacteria results in the consumption of dissolved oxygen (DO). This pathway is typical of marine eutrophication. A model is proposed to mechanistically estimate the response of coastal marine ecosystems to N inputs. It addresses the biological processes of nutrient-limited primary production (PP), metazoan consumption, and bacterial degradation, in four distinct sinking routes from primary (cell aggregates) and secondary producers (faecal pellets, carcasses, and active vertical transport). Carbon export production ( P E ) and ecosystems eXposure Factors (XF), which represents a nitrogen-to-oxygen ‘conversion’ potential, were estimated at a spatial resolution of 66 large marine ecosystem (LME), five climate zones, and site-generic. The XFs obtained range from 0.45 (Central Arctic Ocean) to 15.9 kg O 2 kg N −1 (Baltic Sea). While LME resolution is recommended, aggregated P E or XF per climate zone can be adopted, but not global aggregation due to high variability. The XF is essential to estimate a marine eutrophication impacts indicator in Life Cycle Impact Assessment (LCIA) of anthropogenic-N emissions. Every relevant process was modelled and the uncertainty of the driving parameters considered low suggesting valid applicability in characterisation modelling in LCIA.

The depth-attenuation of sinking particulate organic carbon (POC) is of particular importance for the ocean's role in the global carbon cycle. Numerous idealized flux-versus-depth relationships are available to parameterize this process in Earth System Models. Here we show that these relationships are statistically indistinguishable from available POC flux profile data. Despite their quantitative similarity, we also show these relationships have very different implications for the flux leaving the upper ocean, as well as for the mechanisms governing POC flux. We discuss how this tension might be addressed both observationally and in modeling studies.

Author(s): Ohman, MD | Abstract: This contribution provides an introduction to a sequence of five papers (CCE I- CCE V) that describe the impact of the Warm Anomaly of 2014–15 and El Nino 2015–16 on the pelagic food web of the southern California Current Ecosystem. These contributions analyze the influence of these two warm water perturbations on satellite-based measures of ocean fronts, export efficiency out of the euphotic zone, copepod egg production, mesozooplankton community structure, and a synthesis of primary production, mesozooplankton grazing, and gravitational fluxes of organic carbon.

It is recognized that anthropogenic factors have had a major impact on carbon fluxes from land to the ocean during the past two centuries. However, little is known about how future changes in climate, atmospheric CO2, and land use may affect riverine carbon fluxes over the 21st century. Using a coupled hydrological‐biogeochemical model, the Dynamic Land Ecosystem Model, this study examines potential changes in dissolved inorganic carbon (DIC) export from the Mississippi River basin to the Gulf of Mexico during 2010–2099 attributable to climate‐related conditions (temperature and precipitation), atmospheric CO2, and land use change. Rates of annual DIC export are projected to increase by 65% under the high emission scenario (A2) and 35% under the low emission scenario (B1) between the 2000s and the 2090s. Climate‐related changes along with rising atmospheric CO2 together would account for over 90% of the total increase in DIC export throughout the 21st century. The predicted increase in DIC export from the Mississippi River basin would alter chemistry of the coastal ocean unless appropriate climate mitigation actions are taken in the near future., Key Points DIC export is projected by using a process‐based land ecosystem modelFuture DIC would largely increase under a high emission scenarioClimate change would dominate DIC export over the 21st century

Marine snow aggregates often dominate carbon export from the surface layer to the deep ocean. Therefore, understanding the formation and properties of aggregates is essential to the study of the biological pump. Previous studies have observed a relationship between phytoplankton growth phase and the production of transparent exopolymer particles (TEP), the sticky particles secreted by phytoplankton that act as the glue during aggregate formation. In this experimental study, we aim to determine the effect of phytoplankton growth phase on properties related to aggregate settling. Cultures of the diatom Thalassiosira weissflogii were grown to four different growth phases and incubated in rotating cylindrical tanks to form aggregates. Aggregate excess density and delayed settling time through a sharp density gradient were quantified for the aggregates that were formed, and relative TEP concentration was measured for cultures before aggregate formation. Compared to the first growth phase, later phytoplankton growth phases were found to have higher relative TEP concentration and aggregates with lower excess densities and longer delayed settling times. These findings may suggest that, although particle concentrations are higher at later stages of phytoplankton blooms, aggregates may be less dense and sink slower, thus affecting carbon export.

The magnitude and composition of the sinking-particle flux were studied over the northern Mid-Atlantic Ridge (MAR) from June 2007 to July 2010. Four moorings equipped with dual sediment traps, 100 m and 1000 m above the sea floor, sampled regions north and south of the Charlie Gibbs Fracture Zone (between 49°N and 54°N) and east and west of the MAR. Biogenic data were coupled with satellite estimates of primary production and modelled particle source to assess the variability in export flux. Large variations were found in the seasonality, chemical composition, magnitude and source of sinking particulate material between mooring sites. The northern moorings recorded both greater mean primary production and greater particle mass flux than the southern moorings, although, the large inter-annual variability within the sites exceeded inter-site differences. While estimates of primary production and organic carbon fluxes are comparable to other investigations of this type, they are notably lower than previous estimates for the abyssal plain of the North Atlantic. The deeper traps consistently recorded a higher mass flux compared to the shallower traps. However, we suggest that the overall flux recorded by the shallower traps was reduced by trapping inefficiency, which in the light of the low current velocities, may largely be due to the physical nature of the sinking material. Although deep-trap flux estimates may be more susceptible to errors due to re-suspended and advected material from nearby topography, mass flux and current velocity are not linked. In addition, the relatively low aluminium concentration of the deep-trap material indicates that this contribution is relatively small. The organic carbon flux to the NE, NW, SE and SW station was 0.8, 1.2, 1.1 and 1.1 g m−2 y−1 respectively, corresponding to an export flux of 0.6% over this region of the MAR.

Vertical distributions of dissolved organic carbon (DOC), nitrogen (DON) and phosphorous (DOP) were studied in the Southern Adriatic basin in two contrasting periods: autumn (high stratification) and winter (high extent of mixing). These data provide the first observations of dissolved organic matter (DOM) stoichiometry in a key area of the Mediterranean Sea. DOC and DON values are similar to those reported for other areas of the Mediterranean Sea as well as for tropical and temperate regions of the oceans. Surface DOP values are about one order of magnitude lower than those reported for the oceanic waters, confirming the low availability of P in the Mediterranean Sea. Consequently, surface DOM (C:N:P =1189-1411:86-88:1) has higher proportions of C and N with respect to P than in the oceans. DOM stoichiometry in the deep waters of the Southern Adriatic ranged between 993:85:1 and 1693:108:1, indicating a depletion of DOC (or an elevation of DON and DOP) with respect to the old western Mediterranean deep waters. This finding can be explained by the young age of the water masses in the Southern Adriatic, which can mask the effect of mineralization. Our data clearly show that physical processes (water mass circulation, deep water formation and extent of stratification) affect both distribution and stoichiometry of DOM. Finally, we discuss the role of the Adriatic Sea in maintaining the high N:P ratio observed in the Eastern Mediterranean Sea. (C) 2012 Elsevier Ltd. All rights reserved.

Recentemente, as águas interiores (i.e. lagos, reservatórios, banhados, etc.) foram reconhecidas como um compartimento ativo e importante do ciclo global do carbono. O balanço de carbono nos ecossistemas aquáticos permite avaliar o metabolismo dos mesmos e caracterizar estados de fonte ou sumidouro. O aporte de carbono terrestre possui um papel importante no metabolismo e na dinâmica dos ecossistemas aquáticos, portanto, a melhor compreensão dos processos que atuam na ciclagem e transporte do carbono terrestre para os corpos de água é necessária. O objetivo deste trabalho é conectar os processos do ciclo do carbono nas fases terrestre e aquática em bacias hidrográficas, com vistas à análise integrada do balanço de carbono em águas interiores. Um modelo distribuído para simulação da dinâmica de carbono em bacias hidrográficas, denominado MGB-IPH-C, foi desenvolvido e acoplado ao modelo MGB-IPH que simula os processos hidrológicos. O MGB-IPH-C foi estruturado em dois módulos principais: balanço no solo e balanço na água. O modelo foi aplicado na bacia hidrográfica do rio Ijuí, situada no planalto meridional gaúcho, com foco nas sub-bacias do Taboão e Turcato, no rio Potiribu. Nessas duas sub-bacias, dados mensais de vazão, carbono orgânico e carbono inorgânico foram utilizados para quantificar a exportação fluvial e auxiliar no ajuste do modelo. Recently, inland waters (i.e., lakes, reservoirs, wetland, etc.) were acknowledged as an active, important compartment of the global carbon cycle. The carbon balance in aquatic ecosystems allows evaluating their metabolism and characterizing the states of source or sinks. The terrestrial carbon input plays a major role in the metabolism and dynamics of aquatic ecosystems, and thus it would be necessary to understand more about the processes that are at play in cycling and transporting terrestrial carbon to the water bodies. The purpose of this study is to connect the carbon cycle processes in the terrestrial and aquatic phases in river basins, with a view to the integrated analysis of the carbon balance in inland waters. A distributed model to simulate carbon dynamics in river basins, called MGB-IPH-C, was developed and coupled to the MGB-IPH model that simulates the hydrological processes. MGB-IPH-C was structured into two main models: balance in soil and balance in water. The model was applied in the Ijuí River basin, located in the southern plateau of Rio Grande do Sul, focusing on the Taboão and Turcato sub-basins in the Potiribu river. In these two sub-basins, monthly data on flow, organic carbon and inorganic carbon were used to quantify fluvial export and help adjust the model.

International audience; Northeast Atlantic mode waters (NEAMW) are formed by subduction in a region which is a strong sink of atmospheric CO2. The mechanisms underlying this sink were thoroughly examined in the frame of the POMME experiment, which covered the 2001 seasonal cycle with particular focus on meso to sub-mesoscales. The biological and physical data collected during POMME were used to initialize, constrain and evaluate a regional, 4.5 km-resolution, bio-physical model simulation of the 2001 seasonal cycle in the region of NEAMW formation. We used this model to examine the contribution of sub-mesoscales on the annual budget of carbon export below the mixed-layer and on NEAMW biogeochemical characteristics. This is done by comparing a high-resolution (eddy) simulation at 4.5 km resolution with a high-diffusivity (non-eddy) simulation where the only change is a stronger eddy diffusivity. We found that the model mixed-layer depth is more stratified and closer to reality in the eddy simulation. This result confirms with observational data the proposed mechanism of restratification of the upper ocean driven by sub-mesoscales. We found that the phytoplankton bloom and the subduction of NEAMW display strong contrasts at the sub-mesoscale. Nevertheless, the mean intensity of the bloom and of the subsequent biological pump are only marginally modified by sub-mesoscales (less than 5%), while the intensity of the physical pump (subduction of carbon) is moderately reduced (−10%) in the non-eddy experiment. Moreover, the biogeochemical and thermodynamical characteristics of NEAMW are substantially affected, with, in particular, a wider range of densities and biogeochemical characteristics biased toward winter conditions in the eddy simulation. These differences ensued essentially from lateral induction across sub-mesoscale filaments, which is found to contribute to subduction before seasonal stratification, i.e. before the effective subduction period.

The distribution of dissolved organic carbon (DOC) concentration across coastal waters was characterized based on the compilation of 3510 individual estimates of DOC in coastal waters worldwide. We estimated the DOC concentration in the coastal waters that directly exchange with open ocean waters in two different ways, as the DOC concentration at the edge of the shelf break and as the DOC concentration in coastal waters with salinity close to the average salinity in the open ocean. Using these estimates of DOC concentration in the coastal waters that directly exchange with open ocean waters, the mean DOC concentration in the open ocean and the estimated volume of water annually exchanged between coastal and open ocean, we estimated a median ± SE (and average ± SE) global DOC export from coastal to open ocean waters ranging from 4.4 ± 1.0 Pg C yr to 27.0 ± 1.8 Pg C yr (7.0 ± 5.8 Pg C yr to 29.0 ± 8.0 Pg C yr) depending on the global hydrological exchange. These values correspond to a median and mean median (and average) range between 14.7 ± 3.3 to 90.0 ± 6.0 (23.3 ± 19.3 to 96.7 ± 26.7) Gg C yr per km of shelf break, which is consistent with the range between 1.4 to 66.1 Gg C yr per km of shelf break of available regional estimates of DOC export. The estimated global DOC export from coastal to open ocean waters is also consistent with independent estimates of the net metabolic balance of the coastal ocean. The DOC export from the coastal to the open ocean is likely to be a sizeable flux and is likely to be an important term in the carbon budget of the open ocean, potentially providing an important subsidy to support heterotrophic activity in the open ocean., This is a contribution to the >Malaspina 2010 Expedition> consolider project funded by the Spanish Ministry of Economy and Competitivity (reference CONSOLDER2008-00077). C.B. was funded by a scholarship from the government of the Balearic Islands, a Juan de la Cierva fellowship from the Spanish Ministry of Economy and Competitivity and a research fellow scholarship from the Australian Research Council --discovery projects--120101778

Estimates of dissolved organic carbon (DOC) release by marine macrophyte communities (seagrass meadows and macroalgal beds) based on in situ benthic chambers from published and unpublished are compiled in this study. The effect of temperature and light availability on DOC release by macrophyte communities was examined. Almost 85% of the seagrass communities and all of macroalgal communities examined acted as net sources of DOC. Net DOC fluxes in seagrass communities increase positively with water temperature. In macroalgal communities net DOC fluxes under light exceeded those under dark condition, however, this trend was weaker in seagrass communities. Shading of a mixed seagrass meadow in The Philippines led to a significant reduction on the net DOC release when shading was maintained for 6 days compared to only 2 days of shading. Net DOC fluxes increased with increasing community respiration, but were independent of primary production or net community production. The estimated global net DOC flux, and hence export, from marine macrophytes is about 0.158 ± 0.055 or 0.175 ± 0.056 Pg C year−1 depending on the global extent of seagrass meadows considered., This work was funded by the European Commission projects EUROTROPH (contract EVK3-CT-2000-00040), PREDICT (contract IC18-CT98-0292), M&M's (contract EVK3-CT-2000-00044), the Spanish Plan of I+D (REN2001-4977-E) and IBIS project, co-financed by European Social Fund and the Greek Ministry of Development-GSRT.

Spatial and seasonal distribution patterns of suspended particulate matter, particulate organic carbon (POC), particulate nitrogen, chlorophyll a and phytoplankton abundance and biomass were analysed along two transects in the southern Adriatic and northern Ionian Seas. Moreover, 2 years of samples collected by sediment traps at one selected station for each transect are used to assess the variability of fluxes of biogenic (organic carbon, total nitrogen, carbonates, biogenic silica) and lithogenic constituents. According to the low suspended matter concentration, the two study areas can be considered as representative of oligotrophic systems. The availability of diverse nutrient forms (inorganic or organic), due to the different water column structure and circulation dynamics, affected the structure of phytoplankton communities. Along the Adriatic transect, the influence of waters coming from the northern Adriatic was evident at the surface of the western stations. The phytoplankton community was mainly represented by diatoms and nanoflagellates. In the northern Ionian, particulate matter concentration decreases with respect to the Adriatic stations (st. A1) and the community was dominated by nanoflagellates (54% in cell number), and coccolithophorids (26%). In the southern Adriatic, the vertical mixing convection related to the climatic variability, supplying inorganic nutrients in the upper layers from the deep, represents the dominant process, increasing primary production and downward fluxes of particulate matter in early spring. Higher mass fluxes measured at the bottom are likely due to horizontal and advective contributions of material originated in the shelf area and transported into the basin by mesoscale circulation. Vertical fluxes in the Ionian mainly depend on production processes occurring in the photic layer, such as spring and autumn blooms, controlled by the seasonal mixing and dynamics of the water column. Fluxes are characterised by discontinuous and short-time events correlated with the end phase of micro-phytoplankton blooms. At both stations, the low carbon export (less than 4% of primary productivity) indicates high carbon utilisation and/or high degradation efficiencies of particulate organic matter, i.e. fast recycling in the upper water column.