Marine carbon cycle

This experiment investigates the absorption of CO2 in a closed system to replicate open ocean buffering conditions without winds, currents, or temperature variations. A flask at STP (1 atm, 25°C) initially contains 0.5 L of air headspace (400 ppm CO2) and is modified to include 8 L of normal seawater (salinity 35 psu, alkalinity 2300 µmol/kg, pH 8.1, with flora, fauna, and nucleation sites). After increasing headspace CO2 to 800 ppm, the

Multiple sediment trap (MULTITRAP) arrays were deployed at 3 hydrographically and biologically distinct stations in the eastern North Pacific Ocean and used to evaluate experimentally the hypothesis that protozoan grazers are important in the diagenesis of sinking biogenic materials in the ocean. Measurements were made of adenosine triphosphate (ATP) concentrations and the abundances of bacteria and zooflagellates associated with sinking particles collected from in situ preserved and 2 sets of unpreserved (live) traps: one containing a selective eukaryote inhibitor (thiram) and the second without thiram which served as a live-control. Particulate organic carbon and nitrogen (POC and PON), NH:, NO;, NO;, dissolved organic nitrogen (DON), diatoms, and fecal pellets were quantified in live-control and live-thiram traps. In situ microbial production was estimated by measuring RNA and DNA synthesis in live-control and live-thiram traps pre-charged with 3H-adenine. Trap-collected bacteria and zooflagellates accounted for a low percentage of the total POC (2 to 11 % ) but a high percentage of the total microbial biomass (an estimated 25 to 2 100 % of total ATP). Zooflagellates were the principal protozoans collected and accounted for 2 to 25% of the total microbial biomass. Synthesis of RNA and DNA was observed at all stations and depths, indicating microbial growth in the live traps. ATP and microscopic analyses, however, independently confirmed that death rates exceeded growth rates on the sedimenting particles. Differences between the livecontrol traps (coupled microbial assemblage) and live-thiram traps (uncoupled assemblage, grazers inhibited) indicated slower decomposition and nutrient regeneration in the uncoupled system. In general, POC was higher and in the shallowest traps, NH: was lower, and DON was higher in the livethiram traps. Zooflagellates appear to strongly influence decomposition and nutrient recycling within the microbial assemblage associated with sedirnenting particles.

Recent observations in polar marine waters have shown that a large fraction of primary production may be lost to respiration by planktonic bacteria due to very low bacterial growth efficiencies in cold waters. Here we report that sea temperature may be a key factor (but not the only one) influencing the interaction between bacteria and primary production in North Atlantic and Arctic waters, suggesting that low primary production rates could not sustain bacterial carbon demand in the coldest Arctic waters. The use of freshly produced phytoplankton exudate by bacteria in early- and mid-summer was assessed, together with the bacterial uptake of dissolved inorganic nitrogen (DIN = nitrate and ammonium), in surface waters along a latitudinal gradient from the North Sea to the Arctic sea ice. Bacterial production was independent of the low primary production measured in the coldest waters. Under these conditions, heterotrophic bacteria can consume a large fraction of DIN and N-rich organi...

This study characterized ocean biological carbon pump metrics in the second iteration of the REgional Carbon Cycle Assessment and Processes (RECCAP2) project. The analysis here focused on comparisons of global and biome-scale regional patterns in particulate organic carbon (POC) production and sinking flux from the RECCAP2 ocean biogeochemical model ensemble against observational products derived from satellite remote sensing, sediment traps, and geochemical methods. There was generally good model-data agreement in mean large-scale spatial patterns, but with substantial spread across the model ensemble and observational products. The global-integrated, model ensemble-mean export production, taken as the sinking POC flux at 100 m (6.08 ± 1.17 Pg C yr 1), and export ratio defined as sinking flux divided by net primary production (0.154 ± 0.026) both fell at the lower end of observational estimates. Comparison with observational constraints also suggested that the model ensemble may have underestimated regional biological CO 2 drawdown and air-sea CO 2 flux in high productivity regions. Reasonable model-data agreement was found for global-integrated, ensemble-mean sinking POC flux into the deep ocean at 1,000 m (0.65 ± 0.24 Pg C yr 1) and the transfer efficiency defined as flux at 1,000 m divided by flux at 100 m (0.122 ± 0.041), with both variables exhibiting considerable regional variability. The RECCAP2 analysis presents standard ocean biological carbon pump metrics for assessing biogeochemical model skill, metrics that are crucial for further modeling efforts to resolve remaining uncertainties involving system-level interactions between ocean physics and biogeochemistry. Plain Language Summary Phytoplankton in the surface ocean create each year an amount of organic carbon approximately equivalent to all the annual photosynthesis by plants on land. A small fraction of this newly formed organic carbon is exported below the surface layer, and an even smaller amount makes it all the way to the deep ocean. The transport of organic carbon to the sub-surface ocean, called the biological carbon pump, influences the global-scale distributions of ocean nutrients, oxygen, and inorganic carbon as well as the amount of carbon dioxide in the atmosphere. The global rates and geographic patterns of photosynthesis and carbon flux out of the surface ocean have previously been constructed from ship measurements and satellite remote sensing. Here, we compare these observation-based estimates to a suite of three-dimensional numerical ocean models and find broadly similar results. The model simulations also capture aspects of the biological carbon pump deeper in the water column, where there are fewer direct constraints from field observations. Our comparison of observations and simulations identifies some deficiencies in the models that should be corrected in order to better simulate climate change impacts on the biological carbon pump.

Transparent exopolymer particles (TEP) have been reported as a significant fraction of organic microgels in different oceans. No TEP data have been published for the California Current region off Baja California that indicate the potential contribution of this reservoir to the carbon budget. We measured TEP in seawater samples, using the spectrophotometric method with alcian blue stain, and additional environmental and biological variables during 3 seasons at coastal stations between ~1.4 and 12.0 mi offshore, near 31ºN. Concentrations of TEP obtained with 0.45 µm pore size filters showed spatial and temporal distributions with a tendency to increase from offshore to nearshore and from winter to summer, respectively, ranging from undetectable values to 7.18 µg XG eq·mL–1 (median: 0.70). A significant positive correlation was observed between the concentration of TEP and bacterioplankton abundance (P < 0.05), and between total organic carbon and bacterioplankton abundance (P < ...

Since net zero targets have become a keystone of climate policy, more thought is being given to actively removing carbon dioxide from the atmosphere while con­tinu­ing to drastically reduce emissions. The ocean plays a major role in regulating the global climate by absorbing a large proportion of anthropogenic carbon dioxide emis­sions. As the challenges of land-based carbon dioxide removal (CDR) approaches are increasingly recognised, the ocean may become the new “blue” frontier for carbon removal and storage strategies in the EU and beyond. However, the ocean is not an “open frontier”; rather, it is a domain of overlapping and sometimes conflicting rights and obligations. There is a tension between the sovereign right of states to use ocean resources within their exclusive economic zones and the international obli­gation to protect the ocean as a global commons. The EU and its Member States need to clarify the balance between the protection and use paradigms in ocean governance when considering treating the ocean as an enhanced carbon sink or storage site.

The seabed of the Antarctic continental shelf hosts most of Antarctica's known species, including taxa considered indicative of vulnerable marine ecosystems (VMEs). Nonetheless, the potential impact of climatic and environmental change, including marine icescape transition, on Antarctic shelf zoobenthos, and their blue carbonassociated function, is still poorly characterised. To help narrow knowledge gaps, four continental shelf study areas, spanning a southern polar gradient, were investigated for zoobenthic (principally epi-faunal) carbon storage (a component of blue carbon), and potential environmental influences, employing a functional group approach. Zoobenthic carbon storage was highest at the two southernmost study areas (with a mean estimate of 41.6 versus 7.2 g C m − 2) and, at each study area, increased with morphotaxa richness, overall faunal density, and VME indicator density. Functional group mean carbon content varied with study area, as did each group's percentage contribution to carbon storage and faunal density. Of the environmental variables explored, sea-ice cover and primary production, both likely to be strongly impacted by climate change, featured in variable subsets most highly correlating with assemblage and carbon storage (by functional groups) structures. The study findings can underpin biodiversity-and climate-considerate marine spatial planning and conservation measures in the Southern Ocean.

The biological carbon pump has been estimated to export ~5-15 Gt C yr 1 into the deep ocean, and forms the principal deep-sea food resource. Irregular, intense pulses of particulate organic carbon (POC) have been found to make up about one-third of the overall POC fluxes at a long-term deep-sea research station influenced by coastal upwelling of the California Current, Station M (34 � 50 0 N, 123 � W, 4000 m depth). However, the drivers of these pulses have been challenging to quantify. It has long been recognized that ocean currents can result in particles being advected while sinking to the point of collection by a sediment trap. Thus, a sediment trap time series can incorporate material from a dynamic catchment area, a concept sometimes referred to as a statistical funnel. This concept raises many questions including: what are the day-today conditions at the source locations of the sinking POC? And, how might such 'ocean weather' and related ecosystem factors influence the intense variation seen at the seafloor? Here we analyzed three-dimensional ocean currents from a Regional Ocean Modeling System (ROMS) model from 2011 to 2017 to trace the potential source locations of particles sinking at 1000, 100, and 50 m d 1 from an export depth of 100 m. We then used regionally tailored satellite data products to estimate export flux of POC from these locations. For the 100 m d 1 speed, the particles had origins of up to ~300 km horizontal distance from the sediment trap location, moored at Station M at 3400 m depth., and nearly 1000 km for the 50 m d 1 speed. Particle tracking indicated that, there was considerable inter-annual variation in source locations. Particle source locations tended to originate from the east in the summer months, with higher export and POC fluxes. Occasionally these locations were in the vicinity of highly productive ocean features nearer to the coast. We found significant correlations between export flux of organic carbon from the estimated source locations at 100 m depth to trap-estimated POC fluxes at 3400 m depth. These results set the stage for further investigation into sinking speed distributions, conditions at the source locations, and comparisons with mechanistic biogeochemical models and between particle tracking model frameworks.

Monthly hydrographic, primary production, bacterial production, and settling particulate carbon flux observations were collected between November 1995 and December 1997 at 10.5°N, 64.67°W within the Cariaco Basin, off Venezuela. Upwelling of Subtropical Underwater (SUW) started around October and lasted through approximately May of the following year. Wind speeds >7 m s−1 were observed between January and June, with weaker winds (<5 m s−1) between July and December. The upwelling cycle was therefore out of phase with that of the trade winds by 2–3 months. A seasonal cycle punctuated by transient extremes associated with subsurface ventilation events was observed in primary production. High bacterial activity and organic carbon recycling rates were observed near the oxic‐anoxic interface. Integrated primary production was 690 gC m−2 yr−1 in 1996 and 540 gC m−2 yr−1 in 1997. Settling carbon flux measured with sediment traps was about 5.6% of integrated primary production at 275 ...

Transparent exopolymer particles (TEP) have been reported as a significant fraction of organic microgels in different oceans. No TEP data have been published for the California Current region off Baja California that indicate the potential contribution of this reservoir to the carbon budget. We measured TEP in seawater samples, using the spectrophotometric method with alcian blue stain, and additional environmental and biological variables during 3 seasons at coastal stations between ~1.4 and 12.0 mi offshore, near 31ºN. Concentrations of TEP obtained with 0.45 µm pore size filters showed spatial and temporal distributions with a tendency to increase from offshore to nearshore and from winter to summer, respectively, ranging from undetectable values to 7.18 µg XG eq·mL–1 (median: 0.70). A significant positive correlation was observed between the concentration of TEP and bacterioplankton abundance (P < 0.05), and between total organic carbon and bacterioplankton abundance (P < ...

Despite their size, prokaryote (bacteria and archaea) biomass is estimated to represent between 15 and 30% of total living biomass 1,2. Prokaryotes play major roles in marine ecosystems and in global biogeochemical cycling 3,4. Molecular phylogenetic approaches have revolutionised microbiology and have revealed that the complexity of microbial life is orders of magnitude greater than previous estimates based on cultivation-based approaches 5. This highlights how little we currently know about the microbial world and the clear potential of this vast untapped resource for human application. Here we present the first in-depth analysis of microbial community diversity and composition in the Irish Sea. The western Irish Sea is characterised by distinct hydrographic conditions, resulting in summer stratified offshore deeper waters and settling of fine mud, while well-mixed waters and coarser sediment type dominate in the south and coastal regions. We wished to assess whether these factors play a role in prokaryote abundance and diversity.

h i g h l i g h t s Discrete method for the determination of Fe(II) in snow and firn. Fe(II) record from Dome C (Antarctica) and the Holtedahlfonna glacier (Svalbard). Identification of the Pinatubo/Cerro Hudson volcanic eruption. Preliminary investigation of processes that can influence Fe speciation in firn.

In open regions of the Ross Sea, the role of the microbial community in the turnover of organic matter has scarcely been investigated; indeed, very little is known on how microbial distribution and functional diversity respond to environmental conditions and hydrographic structures. During the austral summer of 2017, two pelagic areas of the Ross Sea [the Drygalski Ice Tongue and the nearby Terra Nova Bay polynya (A area), and the continental Shelf Break area near Cape Adare (C area)] were studied at selected depths [surface, Deep Chlorophyll Maximum (DCM), Circumpolar Deep Water (CDW), deep waters]. Trophic properties [nutrient concentrations, particulate (POC), dissolved organic carbon (DOC) and its optically significant fraction (CDOM) were measured, together with the main hydrological variables. Microbial community abundance [total prokaryotes, living, dead, and actively respiring fraction, high- and low nucleic acid cells (HNA and LNA), pico- and nano-eukaryotes, culturable het...

The oceans’ uptake of anthropogenic carbon dioxide (CO2) decreases seawater pH and alters the inorganic carbon speciation – summarized in the term ocean acidification (OA). Already today, coastal regions experience episodic pH events during which surface layer pH drops below values projected for the surface ocean at the end of the century. Future OA is expected to further enhance the intensity of these coastal extreme pH events. To evaluate the influence of such episodic OA events in coastal regions, we deployed eight pelagic mesocosms for 53 days in Raunefjord, Norway, and enclosed 56–61 m3 of local seawater containing a natural plankton community under nutrient limited post-bloom conditions. Four mesocosms were enriched with CO2 to simulate extreme pCO2 levels of 1978 – 2069 μatm while the other four served as untreated controls. Here, we present results from multivariate analyses on OA-induced changes in the phyto-, micro-, and mesozooplankton community structure. Pronounced diff...

In open regions of the Ross Sea, the role of the microbial community in the turnover of organic matter has scarcely been investigated; indeed, very little is known on how microbial distribution and functional diversity respond to environmental conditions and hydrographic structures. During the austral summer of 2017, two pelagic areas of the Ross Sea [the Drygalski Ice Tongue and the nearby Terra Nova Bay polynya (A area), and the continental Shelf Break area near Cape Adare (C area)] were studied at selected depths [surface, Deep Chlorophyll Maximum (DCM), Circumpolar Deep Water (CDW), deep waters]. Trophic properties [nutrient concentrations, particulate (POC), dissolved organic carbon (DOC) and its optically significant fraction (CDOM) were measured, together with the main hydrological variables. Microbial community abundance [total prokaryotes, living, dead, and actively respiring fraction, high- and low nucleic acid cells (HNA and LNA), pico- and nano-eukaryotes, culturable het...

Monthly hydrographic, primary production, bacterial production, and settling particulate carbon flux observations were collected between November 1995 and December 1997 at 10.5ЊN, 64.67ЊW within the Cariaco Basin, off Venezuela. Upwelling of Subtropical Underwater (SUW) started around October and lasted through approximately May of the following year. Wind speeds Ͼ7 m s Ϫ1 were observed between January and June, with weaker winds (Ͻ5 m s Ϫ1) between July and December. The upwelling cycle was therefore out of phase with that of the trade winds by 2-3 months. A seasonal cycle punctuated by transient extremes associated with subsurface ventilation events was observed in primary production. High bacterial activity and organic carbon recycling rates were observed near the oxic-anoxic interface. Integrated primary production was 690 gC m Ϫ2 yr Ϫ1 in 1996 and 540 gC m Ϫ2 yr Ϫ1 in 1997. Settling carbon flux measured with sediment traps was about 5.6% of integrated primary production at 275 m and about 1.7% at 1225 m, with no seasonality in the proportion of vertical flux to primary production. In total, between 10 and 11 gC m Ϫ2 yr Ϫ1 were delivered to the bottom sediment of Cariaco, which suggests that between 4 ϫ 10 5 and 1 ϫ 10 6 t of C yr Ϫ1 were delivered to sediments within the upwelling area of the Cariaco Basin. This represents permanent sequestration of carbon previously entrained in the North Atlantic gyre in the area of formation of SUW. Results suggests that upwelled inorganic nitrogen, rather than nitrogen fixation, is responsible for the large productivity and particulate carbon settling flux in the Cariaco Basin.

In open regions of the Ross Sea, the role of the microbial community in the turnover of organic matter has scarcely been investigated; indeed, very little is known on how microbial distribution and functional diversity respond to environmental conditions and hydrographic structures. During the austral summer of 2017, two pelagic areas of the Ross Sea [the Drygalski Ice Tongue and the nearby Terra Nova Bay polynya (A area), and the continental Shelf Break area near Cape Adare (C area)] were studied at selected depths [surface, Deep Chlorophyll Maximum (DCM), Circumpolar Deep Water (CDW), deep waters]. Trophic properties [nutrient concentrations, particulate (POC), dissolved organic carbon (DOC) and its optically significant fraction (CDOM) were measured, together with the main hydrological variables. Microbial community abundance [total prokaryotes, living, dead, and actively respiring fraction, high- and low nucleic acid cells (HNA and LNA), pico- and nano-eukaryotes, culturable het...

Transparent exopolymer particles (TEP) have been reported as a significant fraction of organic microgels in different oceans. No TEP data have been published for the California Current region off Baja California that indicate the potential contribution of this reservoir to the carbon budget. We measured TEP in seawater samples, using the spectrophotometric method with alcian blue stain, and additional environmental and biological variables during 3 seasons at coastal stations between ~1.4 and 12.0 mi offshore, near 31ºN. Concentrations of TEP obtained with 0.45 µm pore size filters showed spatial and temporal distributions with a tendency to increase from offshore to nearshore and from winter to summer, respectively, ranging from undetectable values to 7.18 µg XG eq·mL–1 (median: 0.70). A significant positive correlation was observed between the concentration of TEP and bacterioplankton abundance (P < 0.05), and between total organic carbon and bacterioplankton abundance (P < ...

The responses of North Pacific intermediate and deep water ventilation and ocean biogeochemical properties to northern North Atlantic glacial freshwater perturbations are evaluated with a coupled atmosphere-ocean general circulation model MIROC and an earth system model of intermediate complexity LOVECLIM. When the Atlantic meridional overturning circulation (AMOC) is weakened as a result of the North Atlantic freshwater discharge, both models simulate subthermocline and intermediate water warming in the Pacific Ocean. The sensitivities of the Pacific meridional overturning circulation (PMOC) to AMOC weakening differ significantly between the two models. MIROC simulates a small enhancement of the deep sinking branch of the PMOC in the North Pacific. On the contrary, the LOVECLIM freshwater experiment exhibits intensified deep water formation in the North Pacific, associated with a maximum transport change of 19 Sv. Despite the significant differences in ocean circulation response, both models successfully reproduce high-oxygen and low-nutrient conditions of intermediate and deep waters, in accordance with sediment core based paleoproxy reconstructions from the North Pacific and Bering Sea during Heinrich event 1. Emergence of younger intermediate and deep water in the North Pacific can be partly attributed to an overall enhanced mixing as well as intensified overturning circulation of the subpolar North Pacific. Our models simulate broad features observed in several paleoproxy data of the Pacific Ocean: biological production decrease in northern Japan, cooling in the western North Pacific Ocean, and the southward shift of the Pacific intertropical convergence zone.

Monthly hydrographic, primary production, bacterial production, and settling particulate carbon flux observations were collected between November 1995 and December 1997 at 10.5ЊN, 64.67ЊW within the Cariaco Basin, off Venezuela. Upwelling of Subtropical Underwater (SUW) started around October and lasted through approximately May of the following year. Wind speeds Ͼ7 m s Ϫ1 were observed between January and June, with weaker winds (Ͻ5 m s Ϫ1) between July and December. The upwelling cycle was therefore out of phase with that of the trade winds by 2-3 months. A seasonal cycle punctuated by transient extremes associated with subsurface ventilation events was observed in primary production. High bacterial activity and organic carbon recycling rates were observed near the oxic-anoxic interface. Integrated primary production was 690 gC m Ϫ2 yr Ϫ1 in 1996 and 540 gC m Ϫ2 yr Ϫ1 in 1997. Settling carbon flux measured with sediment traps was about 5.6% of integrated primary production at 275 m and about 1.7% at 1225 m, with no seasonality in the proportion of vertical flux to primary production. In total, between 10 and 11 gC m Ϫ2 yr Ϫ1 were delivered to the bottom sediment of Cariaco, which suggests that between 4 ϫ 10 5 and 1 ϫ 10 6 t of C yr Ϫ1 were delivered to sediments within the upwelling area of the Cariaco Basin. This represents permanent sequestration of carbon previously entrained in the North Atlantic gyre in the area of formation of SUW. Results suggests that upwelled inorganic nitrogen, rather than nitrogen fixation, is responsible for the large productivity and particulate carbon settling flux in the Cariaco Basin.

Monthly hydrographic, primary production, bacterial production, and settling particulate carbon flux observations were collected between November 1995 and December 1997 at 10.5ЊN, 64.67ЊW within the Cariaco Basin, off Venezuela. Upwelling of Subtropical Underwater (SUW) started around October and lasted through approximately May of the following year. Wind speeds Ͼ7 m s Ϫ1 were observed between January and June, with weaker winds (Ͻ5 m s Ϫ1) between July and December. The upwelling cycle was therefore out of phase with that of the trade winds by 2-3 months. A seasonal cycle punctuated by transient extremes associated with subsurface ventilation events was observed in primary production. High bacterial activity and organic carbon recycling rates were observed near the oxic-anoxic interface. Integrated primary production was 690 gC m Ϫ2 yr Ϫ1 in 1996 and 540 gC m Ϫ2 yr Ϫ1 in 1997. Settling carbon flux measured with sediment traps was about 5.6% of integrated primary production at 275 m and about 1.7% at 1225 m, with no seasonality in the proportion of vertical flux to primary production. In total, between 10 and 11 gC m Ϫ2 yr Ϫ1 were delivered to the bottom sediment of Cariaco, which suggests that between 4 ϫ 10 5 and 1 ϫ 10 6 t of C yr Ϫ1 were delivered to sediments within the upwelling area of the Cariaco Basin. This represents permanent sequestration of carbon previously entrained in the North Atlantic gyre in the area of formation of SUW. Results suggests that upwelled inorganic nitrogen, rather than nitrogen fixation, is responsible for the large productivity and particulate carbon settling flux in the Cariaco Basin.

In open regions of the Ross Sea, the role of the microbial community in the turnover of organic matter has scarcely been investigated; indeed, very little is known on how microbial distribution and functional diversity respond to environmental conditions and hydrographic structures.
During the austral summer of 2017, two pelagic areas of the Ross Sea [the Drygalski Ice Tongue and the nearby Terra Nova Bay polynya (A area), and the continental Shelf Break area near Cape Adare (C area)] were studied at selected depths [surface, Deep Chlorophyll Maximum (DCM), Circumpolar Deep Water (CDW), deep waters]. Trophic properties [nutrient concentrations, particulate (POC), dissolved organic carbon (DOC) and its optically significant fraction (CDOM) were measured, together with the main hydrological variables. Microbial community abundance [total prokaryotes, living, dead, and actively respiring fraction, high- and low nucleic acid cells (HNA and LNA), pico and nano-eukaryotes, culturable heterotrophic bacteria], composition, and metabolism (as whole community and as isolated bacteria) were also assessed. Through a multidisciplinary dataset, this study highlighted the variable response of microbial abundance, diversity, and metabolism of the microbial community to the changing local environmental conditions of the Ross Sea. Different forces, such as organic matter inputs (mostly of detrital nature) released from the Drygalski glacier in the A area, and a coastal-to-offshore gradient in the C area, coexisted within this extreme ecosystem. This resulted in a significant spatial segregation of the edaphic parameters, and of the microbial community distribution and metabolic activity patterns.

Tabernacle Baptist Church) for your unconditional love, support, and encouragement through this journey of faith and endurance. I could not have done this without you! Phillipians 1:6 Being confident of this very thing, that he which hath begun a good work in you will perform it until the day of Jesus Christ Galatians 6:9 And let us not be weary in well doing: for in due season we shall reap, if we faint not. I extend my deepest gratitude to Dr. Robert Byrne, my research advisor, for being not only a brilliant scientist but a humble, patient, and humorous educator. His support, encouragement, and mentorship over the years have been invaluable. I thank my committee (Dr.

Cultivating coccolithophore algae for carbon sequestration is discussed. Coccolithophores have been major calcium carbonate producers in the world’s oceans for about 250 million years. Today, they account for about a third of the total marine CaCO3 production by coating their single cells externally with plates of microcrystalline CaCO3. The possibility that these algae could be used to trap atmospheric CO2 with existing technology has not been widely considered. There is scope for both high technology cultivation in bioreactors and low technology cultivation in terraced raceway ponds or lagoons on tropical coastal sites. The latter could produce a sludge of pure CaCO3 as a feedstock for cement production in place of the fossilised limestone currently used (cement production accounts for around 8% of industrial fossil CO2 emissions). On the high seas coccolithophores naturally produce extensive blooms, which emit the volatile gas dimethyl sulfide to the atmosphere, where it promotes...

Here we explore strategies of resource utilization and allocation of algal versus terrestrially derived carbon (C) by lake bacterioplankton. We quantified the consumption of terrestrial and algal dissolved organic carbon, and the subsequent allocation of these pools to bacterial growth and respiration, based on the δ(13)C isotopic signatures of bacterial biomass and respiratory carbon dioxide (CO2). Our results confirm that bacterial communities preferentially remove algal C from the terrestrially dominated organic C pool of lakes, but contrary to current assumptions, selectively allocate this autochthonous substrate to respiration, whereas terrestrial C was preferentially allocated to biosynthesis. The results provide further evidence of a mechanism whereby inputs of labile, algal-derived organic C may stimulate the incorporation of a more recalcitrant, terrestrial C pool. This mechanism resulted in a counterintuitive pattern of high and relatively constant levels of allochthony (~...

It is generally accepted that most of the oceanic CaCO 3 production is biogenic, whereas homogeneous, inorganic CaCO 3 nucleation and precipitation from seawater is inhibited by the presence of other seawater constituents, including dissolved organic carbon. Notwithstanding, heterogeneous CaCO 3 precipitation (HCP) from supersaturated seawater onto solid surfaces is well documented, evidence for HCP in the open-ocean settings has not been convincingly demonstrated. In this study, we provide evidence for inorganic CaCO 3 precipitation in the water column of the Red Sea and in the neighboring Gulf of Aqaba. The evidence includes a decrease in alkalinity and dissolved inorganic carbon (DIC) at a 1.7:1 ratio along the southward route of Red Sea deep-water, and an alkalinity deficiency in the Gulf of Aqaba deepwater. These observations are made after correcting alkalinity and DIC for changes in nutrient content and salinity and are therefore not the result of mixing, respiration or photosynthesis. We suggest that the interaction between seawater and suspended solids, providing precipitation nuclei, resulted in HCP and accounted for the above-mentioned observations. We base this suggestion on: 1. time-series measurements in the Gulf of Aqaba, showing abrupt alkalinity decrease following the entrainment of large amounts of solids; 2. incubation experiments confirming that suspension of Gulf of Aqaba sediments in seawater induces a decrease in alkalinity; 3. precipitation of inorganic aragonite needles within the pores of the skeleton of a local coral. Based on the data presented here, we postulate that HCP may occur in parts of the ocean that receive a substantial influx of solid particles, and areas subject to frequent dust storms. Hence, HCP may be an overlooked pathway in the oceanic CaCO 3 cycle.

Spring phytoplankton blooms are important events in Shelf Sea pelagic systems as the increase in carbon production results in increased food availability for higher trophic levels and the export of carbon to deeper waters and the sea-floor. It is usually accepted that the increase in phytoplankton abundance and production is followed by an increase in plankton respiration. However, this expectation is derived from field studies with a low temporal sampling resolution (5-15 days). In this study we have measured the time course of plankton abundance, gross primary production, plankton community respiration, respiration of the plankton size classes (> 0.8 µm and 0.2-0.8 µm) and bacterial production at ≤5 day intervals during April 2015 in order to examine the phasing of plankton autotrophic and heterotrophic processes. Euphotic depth-integrated plankton community respiration increased five-fold (from 22 ± 4 mmol O 2 m −2 d −1 on 4th April to 119 ± 4 mmol O 2 m −2 d −1 on 15th April) at the same time as gross primary production also increased five-fold, (from 114 ± 5 to 613 ± 28 mmol C m −2 d −1). Bacterial production began to increase during the development of the bloom, but did not reach its maximum until 5 days after the peak in primary production and plankton respiration. The increase in plankton community respiration was driven by an increase in the respiration attributable to the > 0.8 µm size fraction of the plankton community (which would include phytoplankton, microzooplankton and particle attached bacteria). Euphotic depth-integrated respiration of the 0.2-0.8 µm size fraction (predominantly free living bacteria) decreased and then remained relatively constant (16 ± 3-11 ± 1 mmol O 2 m −2 d −1) between the first day of sampling (4th April) and the days following the peak in chlorophyll-a (20th and 25th April). Recent locally synthesized organic carbon was more than sufficient to fulfil the bacterial carbon requirement in the euphotic zone during this productive period. Changes in bacterial growth efficiencies (BGE, the ratio of bacterial production to bacterial carbon demand) were driven by changes in bacterial production rates increasing from < 30 ± 14% on 4th April to 51 ± 11% on 25th of April. This study therefore shows a concurrent rather than a phased increase in primary production and community respiration attributable to cells > 0.8 µm during the development of the spring bloom, followed 5 days later by a peak in bacterial production. In addition, the size fractionated respiration rates and high growth efficiencies suggest that free living bacteria are not the major producers of CO 2 before, during and a few days after this shelf sea spring phytoplankton bloom.

A suite of lipid biomarkers were investigated from surface sediments and particulate matter across hydrographically distinct zones associated with the western Irish Sea gyre and the seasonal bloom. The aim was to assess the variation of organic matter (OM) composition, production, distribution and fate associated with coastal and southern mixed regions and also the summer stratified region. Based on the distribution of a suite of diagnostic biomarkers, including phospholipid fatty acids, source-specific sterols, wax esters and C 25 highly branched isoprenoids, diatoms, dinoflagellates and green algae were identified as major contributors of marine organic matter (MOM) in this setting. The distribution of cholesterol, wax esters and C 20 and C 22 polyunsaturated fatty acids indicate that copepod grazing represents an important process for mineralising this primary production. Net tow data from 2010 revealed much greater phytoplankton and zooplankton biomass in well-mixed waters compared to stratified waters. This appears to be largely reflected in MOM input to surface sediments. Terrestrial organic matter (TOM), derived from higher plants, was identified as a major source of OM regionally, but was concentrated in proximity to major riverine input at the Boyne Estuary and Dundalk Bay. Near-bottom residual circulation and the seasonal gyre also likely play a role in the fate of TOM in the western Irish Sea.

Transparent exopolymer particles (TEP) have been reported as a significant fraction of organic microgels in different oceans. No TEP data have been published for the California Current region off Baja California that indicate the potential contribution of this reservoir to the carbon budget. We measured TEP in seawater samples, using the spectrophotometric method with alcian blue stain, and additional environmental and biological variables during 3 seasons at coastal stations between ~1.4 and 12.0 mi offshore, near 31ºN. Concentrations of TEP obtained with 0.45 µm pore size filters showed spatial and temporal distributions with a tendency to increase from offshore to nearshore and from winter to summer, respectively, ranging from undetectable values to 7.18 µg XG eq·mL–1 (median: 0.70). A significant positive correlation was observed between the concentration of TEP and bacterioplankton abundance (P &lt; 0.05), and between total organic carbon and bacterioplankton abundance (P &lt; ...

Marine phytoplankton growth at high latitudes is extensively limited by iron availability. Icebergs are a vector transporting the bioessential micronutrient iron into polar oceans. Therefore, increasing iceberg fluxes due to global warming have the potential to increase marine productivity and carbon export, creating a negative climate feedback. However, the magnitude of the iceberg iron flux, the subsequent fertilization effect and the resultant carbon export have not been quantified. Using a global analysis of iceberg samples, we reveal that iceberg iron concentrations vary over 6 orders of magnitude. Our results demonstrate that, whilst icebergs are the largest source of iron to the polar oceans, the heterogeneous iron distribution within ice moderates iron delivery to offshore waters and likely also affects the subsequent ocean iron enrichment. Future marine productivity may therefore be not only sensitive to increasing total iceberg fluxes, but also to changing iceberg properti...

Monthly hydrographic, primary production, bacterial production, and settling particulate carbon flux observations were collected between November 1995 and December 1997 at 10.5ЊN, 64.67ЊW within the Cariaco Basin, off Venezuela. Upwelling of Subtropical Underwater (SUW) started around October and lasted through approximately May of the following year. Wind speeds Ͼ7 m s Ϫ1 were observed between January and June, with weaker winds (Ͻ5 m s Ϫ1) between July and December. The upwelling cycle was therefore out of phase with that of the trade winds by 2-3 months. A seasonal cycle punctuated by transient extremes associated with subsurface ventilation events was observed in primary production. High bacterial activity and organic carbon recycling rates were observed near the oxic-anoxic interface. Integrated primary production was 690 gC m Ϫ2 yr Ϫ1 in 1996 and 540 gC m Ϫ2 yr Ϫ1 in 1997. Settling carbon flux measured with sediment traps was about 5.6% of integrated primary production at 275 m and about 1.7% at 1225 m, with no seasonality in the proportion of vertical flux to primary production. In total, between 10 and 11 gC m Ϫ2 yr Ϫ1 were delivered to the bottom sediment of Cariaco, which suggests that between 4 ϫ 10 5 and 1 ϫ 10 6 t of C yr Ϫ1 were delivered to sediments within the upwelling area of the Cariaco Basin. This represents permanent sequestration of carbon previously entrained in the North Atlantic gyre in the area of formation of SUW. Results suggests that upwelled inorganic nitrogen, rather than nitrogen fixation, is responsible for the large productivity and particulate carbon settling flux in the Cariaco Basin.

Some earthquakes in the Eastern Mediterranean are tsunamigenic and some of their tsunamis affected the coastal area of the Gulf of Fethiye, SW Turkey. Recent trenching surveys on the low-lying coastal areas of Dalaman delta beach across the Rhodes Pass revealed three probable tsunami impacts as a result of the historical earthquakes of 1303, 1481 and 1741. Yet, there have been relatively few studies of the processes associated with tsunami sediment transport, their deposition and nature in geological record. In addition to the interpretation of sedimentary features, accurate paleoenvironmental assessments might be possible by distinctive biogeochemical researches on marine-sourced organic matters, geochemical properties, quantitative amounts of marine-sourced biomarkers and deterministic ratios. The identification of major lipid biomarkers (fatty acids and sterols) in the samples recovered from the sidewalls of the studied trench, for example, indicated biogenic contributions due to the presence of phytoplankton, zooplankton, dinoflagellates and bacteria. Quantitative estimation of biomarkers and deterministic ratios also indicated some evidences for marine-sourced organic matters, implying that biomarkers can be used to answer the open questions in tsunami and paleotsunami researches.

Recent observations in polar marine waters have shown that a large fraction of primary production may be lost to respiration by planktonic bacteria due to very low bacterial growth efficiencies in cold waters. Here we report that sea temperature may be a key factor (but not the only one) influencing the interaction between bacteria and primary production in North Atlantic and Arctic waters, suggesting that low primary production rates could not sustain bacterial carbon demand in the coldest Arctic waters. The use of freshly produced phytoplankton exudate by bacteria in early- and mid-summer was assessed, together with the bacterial uptake of dissolved inorganic nitrogen (DIN = nitrate and ammonium), in surface waters along a latitudinal gradient from the North Sea to the Arctic sea ice. Bacterial production was independent of the low primary production measured in the coldest waters. Under these conditions, heterotrophic bacteria can consume a large fraction of DIN and N-rich organi...

A drifting sediment trap was deployed and 234 Th activity in the water column was measured to calculate export flux of carbon at a time-series station in the northern Arabian Sea (lat. 21130 0 N; long. 64100 0 E) during the winter monsoon, 10-23 February 1997. The sampling period was characterised by an extensive salp swarm, and salp faecal pellets were the dominant contributors to the particulate matter in the sediment traps. Average 234 Th flux out of the photic zone was 2300 dpm m À2 d À1 and average POC/ 234 Th ratio in trap-derived particles was 0.14 mg/dpm. Average 234 Thderived export flux of carbon was about 332 mg m À2 d À1 , representing 36% of the daily primary production (PP) (925 mg C m À2 d À1). Export of about one-third of the daily PP during the end of the winter monsoon could be due to the episodic nature of salp swarms. Salp swarms are frequently observed in the Arabian Sea and may be a significant pathway for rapid export of carbon from the euphotic zone.

by: ____________________________________ Lady Liliana Espinosa Leal Seasonal variation of hyperiid amphipods was described in the oceanic area between Punta Eugenia Punta Abreojos, Baja California in 2011 that was a cold year due to the influence of La Niña. Zooplankton samples were collected in four IMECOCAL oceanographic campaigns of 2011. The temperature at 10 m depth was similar between January and July with an average of 16 to 17 °C and in October it increased 3 °C. Vertical salinity profiles were more similar in the months of January, April and July, showing influence of subarctic water in the upper layer (33.3-33.7) while in October a range of higher values (33.5-33.8) was observed due to the influence of subtropical water. 63 species were found during the study whose presence varied seasonally. The largest number were filed in October (54) and the lowest (17) in January. Throughout the study Eupronoe minuta, Primno brevidens Lestrigonus schizogeneios and Simorhynchotus anten...

We evaluate a recent region-specific model of export production (Kelly et al., 2018) and some similar fits to in situ data for the California Current Ecosystem using satellite data. The model is a simple linear function of net primary productivity (NPP): Export = 0.08 × NPP + 72 where EF is export flux in mg C m −2 d −1. We confirm that contrary to several global algorithms export efficiency (e-ratio = export/primary productivity) is negatively correlated with net primary productivity. We find that linear models with a steeper slope of EF relative to NPP produce better estimates of the variability range. Choice of the EF model parameterization can more than double the estimate of temporal variability (standard deviation) in satellite-derived EF time series. The best estimates of EF were obtained when using average NPP during a preceding period of~7-8 days. This is in contrast with NPP where the best satellite estimates of in situ NPP were obtained using same day satellite data and the coefficient of determination was monotonically decreasing with increasing time lag. We also find that there is substantial unexplained variability in EF that cannot be explained by existing models.

Growing evidence suggests substantial quantities of particulate organic carbon (POC) produced in surface waters reach abyssal depths within days during episodic flux events. A 29-year record of in situ observations was used to examine episodic peaks in POC fluxes and sediment community oxygen consumption (SCOC) at Station M (NE Pacific, 4,000-m depth). From 1989 to 2017, 19% of POC flux at 3,400 m arrived during high-magnitude episodic events (≥mean + 2 σ), and 43% from 2011 to 2017. From 2011 to 2017, when high-resolution SCOC data were available, time lags between changes in satellite-estimated export flux (EF), POC flux, and SCOC on the sea floor varied between six flux events from 0 to 70 days, suggesting variable remineralization rates and/or particle sinking speeds. Half of POC flux pulse events correlated with prior increases in EF and/or subsequent SCOC increases. Peaks in EF overlying Station M frequently translated to changes in POC flux at abyssal depths. A power-law mode...

A large bloom of Salpa spp. in the northeastern Pacific during the spring of 2012 resulted in a major deposition of tunics and fecal pellets on the seafloor at , 4000 m depth (Sta. M) over a period of 6 months. Continuous monitoring of this food pulse was recorded using autonomous instruments: sequencing sediment traps, a timelapse camera on the seafloor, and a bottom-transiting vehicle measuring sediment community oxygen consumption (SCOC). These deep-sea measurements were complemented by sampling of salps in the epipelagic zone by California Cooperative Ocean Fisheries Investigations. The particulate organic carbon (POC) flux increased sharply beginning in early March, reaching a peak of 38 mg C m 22 d 21 in mid-April at 3400 m depth. Salp detritus started appearing in images of the seafloor taken in March and covered a daily maximum of 98% of the seafloor from late June to early July. Concurrently, the SCOC rose with increased salp deposition, reaching a high of 31 mg C m 22 d 21 in late June. A dominant megafauna species, Peniagone sp. A, increased 7-fold in density beginning 7 weeks after the peak in salp deposition. Estimated food supply from salp detritus was 97-327% of the SCOC demand integrated over the 6-month period starting in March 2012. Such large episodic pulses of food sustain abyssal communities over extended periods of time.

Phaeodaria, which comprise one group of large, single-celled eukaryotic zooplankton, have been largely ignored by past marine biological studies because Phaeodaria and their delicate skeletons are liable to collapse. As a result, collection and quantification of specimens are difficult, and seasonal changes of phaeodarian abundance have not been thoroughly studied. The transport of biogenic elements by sinking phaeodarians has been estimated for only a few representative species. Sinking particles >1 mm in size and swimmers have traditionally been excluded when estimating sinking particle fluxes. The focus of this study is the large number of phaeodarians among the >1-mm sinking particles collected in the western North Pacific from June 2014 to July 2015. Careful sorting by microscopic examination and chemical analyses revealed that phaeodarians accounted for up to about 10% of the organic carbon in all sinking particles and accounted for a mean of 33% of the organic carbon in the >1-mm sinking particles. The high-standing stocks of phaeodarians at depths of 150-1,000 m in the mesopelagic twilight zone suggested that particles sinking from the euphotic zone as aggregates and fecal pellets can be efficiently exported to the deep sea by the ballasting effect of large phaeodarian particles rich in organic carbon.

We examined variations in organic carbon (OC) pools and microplanktonic carbon fluxes at three stations in the Hudson River estuary during 12 cruises between Octobers of 1996 and 1998. Phytoplankton biomass and net primary production varied from 5 to 40 mol C L Ϫ1 and 0.3 to 318.3 mmol C m Ϫ2 d Ϫ1 , respectively. Biomass and production of bacterioplankton in the surface layer commonly exceeded those of phytoplankton, varying from 0.2 to 72 mol C L Ϫ1 and 1.4 to 70 mmol C m Ϫ2 d Ϫ1 , respectively. Median planktonic respiration varied from 275 to 605 mmol CO 2 m Ϫ2 d Ϫ1 between stations along the salinity gradient. Primary production/respiration (P : R) ratios varied temporally and spatially between 0.003 and 6.60, averaging 0.22. Carbon mass balances revealed that under low river discharges (Ͻ250 m 3 s Ϫ1), the estuary processed 2.4-fold more carbon internally and advected 2.7-fold less carbon seaward than under higher flows. Annual OC budgets suggest that ϳ19 ϫ 10 9 mol C yr Ϫ1 of total organic carbon (TOC) entered the estuary, whereas 30 ϫ 10 9 mol TOC yr Ϫ1 was exported seaward, representing a net gain of 11 ϫ 10 9 mol TOC yr Ϫ1 within the estuary. Microplankton processed ϳ32 ϫ 10 9 mol C yr Ϫ1 , of which 5.6 ϫ 10 9 mol C was attributed to photo-and chemoautotrophic (ϳ72%) and heterotrophic (ϳ28%) production; the remainder was respired to CO 2 (26.5 ϫ 10 9 mol CO 2 yr Ϫ1). The persistent imbalance between carbon oxidation and carbon fixation strongly suggests that the Hudson River estuary usually is net heterotrophic and is a significant source of inorganic carbon to the coastal ocean and atmosphere.

A suite of lipid biomarkers were investigated from surface sediments and particulate matter across hydrographically distinct zones associated with the western Irish Sea gyre and the seasonal bloom. The aim was to assess the variation of organic matter (OM) composition, production, distribution and fate associated with coastal and southern mixed regions and also the summer stratified region. Based on the distribution of a suite of diagnostic biomarkers, including phospholipid fatty acids, source-specific sterols, wax esters and C 25 highly branched isoprenoids, diatoms, dinoflagellates and green algae were identified as major contributors of marine organic matter (MOM) in this setting. The distribution of cholesterol, wax esters and C 20 and C 22 polyunsaturated fatty acids indicate that copepod grazing represents an important process for mineralising this primary production. Net tow data from 2010 revealed much greater phytoplankton and zooplankton biomass in well-mixed waters compared to stratified waters. This appears to be largely reflected in MOM input to surface sediments. Terrestrial organic matter (TOM), derived from higher plants, was identified as a major source of OM regionally, but was concentrated in proximity to major riverine input at the Boyne Estuary and Dundalk Bay. Near-bottom residual circulation and the seasonal gyre also likely play a role in the fate of TOM in the western Irish Sea.

Epibenthic megafauna comprise a large fraction of the deep-sea benthic biomass and are considered important in bioturbation and sediment mineralization processes. However, the sparse and often patchy distribution of these animals makes them difficult to study on meaningful spatial and temporal scales. We used a new time-lapse camera system to measure the movements of mobile megafauna over a 3-month period across a 20 m 2 area of the abyssal sea floor in the eastern North Pacific. This free-vehicle camera system consisted of a time-lapse camera mounted in a tripod frame with a field marker, time releases and flotation assembly. Time-lapse photographs of the sea floor were taken hourly from March to June 1991 at a station off the central California coast (34°50'N, 123°00'W) at a depth of 4100 m. Megafaunal density reached a peak in April, immediately preceding increased fluxes of particulate organic carbon (POC) and chlorophyll a measured in sediment traps at 50 m above bottom. Mobile megafauna were numerically dominated by the holothuroids, Abyssocucumis abyssorum, Peniagone vitrea and Elpidia minutissima. The total area traversed by the megafauna each day was estimated by summing the distance traveled between hourly photographs multiplied by the body width of each animal. Area traversed by the megafauna reached a peak in early May following the peak in faunal density and preceding the peak in POC flux in mid-May. The mobile megafauna traversed 88% of the 20 m 2 area of the sea floor over the 3-month period. Estimates of oxygen consumption for the dominant mobile megafauna revealed that these animals would consume only 1.6% of the particulate organic carbon flux entering the benthic boundary layer. However, the extensive area traversed by the mobile megafauna in a 3-month interval suggests that these animals are important as modifiers of the surface sediment, either through mixing or repackaging of material.

Phaeodaria, which comprise one group of large, single-celled eukaryotic zooplankton, have been largely ignored by past marine biological studies because Phaeodaria and their delicate skeletons are liable to collapse. As a result, collection and quantification of specimens are difficult, and seasonal changes of phaeodarian abundance have not been thoroughly studied. The transport of biogenic elements by sinking phaeodarians has been estimated for only a few representative species. Sinking particles >1 mm in size and swimmers have traditionally been excluded when estimating sinking particle fluxes. The focus of this study is the large number of phaeodarians among the >1-mm sinking particles collected in the western North Pacific from June 2014 to July 2015. Careful sorting by microscopic examination and chemical analyses revealed that phaeodarians accounted for up to about 10% of the organic carbon in all sinking particles and accounted for a mean of 33% of the organic carbon in the >1-mm sinking particles. The high-standing stocks of phaeodarians at depths of 150–1,000 m in the mesopelagic twilight zone suggested that particles sinking from the euphotic zone as aggregates and fecal pellets can be efficiently exported to the deep sea by the ballasting effect of large phaeodarian particles rich in organic carbon.

Sampling near Bermuda by trawling and SCUBA diving yielded 16 species of salps in August 1989 and March-April 1990. Several species occurred in the surface waters only at particular times of the day. suggesting diel vertical migrations on different schedules. At the time of sampling, salps were present in low numerical abundances and constituted only a small fraction of the total zooplankton biomass.

Recent observations in polar marine waters have shown that a large fraction of primary production may be lost to respiration by planktonic bacteria due to very low bacterial growth efficiencies in cold waters. Here we report that sea temperature may be a key factor (but not the only one) influencing the interaction between bacteria and primary production in North Atlantic and Arctic waters, suggesting that low primary production rates could not sustain bacterial carbon demand in the coldest Arctic waters. The use of freshly produced phytoplankton exudate by bacteria in early- and mid-summer was assessed, together with the bacterial uptake of dissolved inorganic nitrogen (DIN = nitrate and ammonium), in surface waters along a latitudinal gradient from the North Sea to the Arctic sea ice. Bacterial production was independent of the low primary production measured in the coldest waters. Under these conditions, heterotrophic bacteria can consume a large fraction of DIN and N-rich organi...

Changes in the sinking rates, ash-free dry weights, particulate carbon and nitrogen content, and carbon:nitrogen ratios from the fecal pellets of several species of oceanic salps were examined in ten-day decomposition studies. Although bacteria and protozoa became abundant in the incubation vessels, most of the fecal pellets remained physically intact throughout the study. Bacterial activity in the pellets (measured by the rate of uptake of 3H-thymidine) increased, but microbial degradation had little effect on the sinking speeds of most of the fecal pellets. The average losses of ash-free dry weight and carbon and nitrogen content, along with changes in carbon:nitrogen ratio, were small compared to their initial values. We conclude that microbial degradation of large salp fecal pellets would not prevent the vertical flux to the deep ocean of a significant fraction of the particulate organic material contained in the pellets. The fecal pellets of oceanic salps provide a rapid, and potentially important, mechanism for the consolidation and vertical transport of organic and lithogenic material associated with minute particles in the open ocean.

Marine phytoplankton growth at high latitudes is extensively limited by iron availability. Icebergs are a vector transporting the bioessential micronutrient iron into polar oceans. Therefore, increasing iceberg fluxes due to global warming have the potential to increase marine productivity and carbon export, creating a negative climate feedback. However, the magnitude of the iceberg iron flux, the subsequent fertilization effect and the resultant carbon export have not been quantified. Using a global analysis of iceberg samples, we reveal that iceberg iron concentrations vary over 6 orders of magnitude. Our results demonstrate that, whilst icebergs are the largest source of iron to the polar oceans, the heterogeneous iron distribution within ice moderates iron delivery to offshore waters and likely also affects the subsequent ocean iron enrichment. Future marine productivity may therefore be not only sensitive to increasing total iceberg fluxes, but also to changing iceberg properti...

Investigating Particle Size-Flux Relationships that the particle size-flux relationships may be different within the euphotic zone than in the shallow twilight zone and hypothesize that the changing nature of sinking particles with depth must be considered when investigating the remineralization length scale of sinking particles in the ocean.

A suite of lipid biomarkers were investigated from surface sediments and particulate matter across hydrographically distinct zones associated with the western Irish Sea gyre and the seasonal bloom. The aim was to assess the variation of organic matter (OM) composition, production, distribution and fate associated with coastal and southern mixed regions and also the summer stratified region. Based on the distribution of a suite of diagnostic biomarkers, including phospholipid fatty acids, source-specific sterols, wax esters and C 25 highly branched isoprenoids, diatoms, dinoflagellates and green algae were identified as major contributors of marine organic matter (MOM) in this setting. The distribution of cholesterol, wax esters and C 20 and C 22 polyunsaturated fatty acids indicate that copepod grazing represents an important process for mineralising this primary production. Net tow data from 2010 revealed much greater phytoplankton and zooplankton biomass in well-mixed waters compared to stratified waters. This appears to be largely reflected in MOM input to surface sediments. Terrestrial organic matter (TOM), derived from higher plants, was identified as a major source of OM regionally, but was concentrated in proximity to major riverine input at the Boyne Estuary and Dundalk Bay. Near-bottom residual circulation and the seasonal gyre also likely play a role in the fate of TOM in the western Irish Sea.