Research Highlights
This study compares lipid biomarker and bulk constituents (organic carbon and δ13C, nitrogen and carbonate) in suspended particles (30-4400 m depth) collected at the Oceanic Flux Program site in the northern Sargasso Sea (north Atlantic) off Bermuda during three periods of contrasting oceanographic conditions: following the spring bloom (April 2015), during the low productivity period (November 2015), and two weeks after the passage of the Category 3 Hurricane Nicole (October 2016). Lipids biomarkers were used to evaluate the contributions of phytoplankton, zooplankton and bacterial sources to the particulate organic carbon (POC), diagenetic transformations of suspended POC throughout the water column and within the nepheloid layer, and seasonal and non-seasonal temporal variability, including the impact of an extreme weather event.
Carbon cycling in the Sargasso Sea water column: insights from lipid biomarkers in suspended particles
Pedrosa-Pàmies, R., Conte, M. H., Weber, J.C., Johnson, R.
Progress in Oceanography, Accepted, doi: 10.1016/j.pocean.2018.08.005, 2018.
Hurricane Nicole 12 Oct, 216.
Image: NASA
Some highlights of this study:
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This study evidences a rapid transition in particulate organic matter composition accompanies the intense organic carbon remineralization in the upper mesopelagic layer.
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Depth profiles of suspended lipids reveal a depth evolution in deep-sea zooplankton and bacterial communities within the deep ocean as well as heterogeneity in particulate organic composition.
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Extreme weather events, such as the passage of Hurricane Nicole, can have a major influence on particle cycling in the oligotrophic ocean.
Total lipids in suspended in suspended particles collected in the norther Sargasso Sea (OFP site).
Distribution and sources of organic matter in size-fractionated nearshore and inner-shelf sediments
of the NW Mediterranean
Quirós-Collazos, L.*, Pedrosa-Pàmies, R.*, Sanchez-Vidal, A., Guillén, J., Duran, R., Cabello, P.
Estuarine, Coastal and Shelf Science, 189, 267-280, doi: 10.1016/j.ecss.2017.03.004, 2017.
*Both authors contributed equally to this work.
POC versus TN in the different grain-size fraction. Different style lines show the linear fit for each grain size fraction (see legend)
Continental shelves are recognized to play a key role in the biogeochemical cycle of carbon, linking terrestrial and marine carbon reservoirs. In this study we investigated the physical and biogeochemical processes that control the source, transport and fate of organic carbon (OC) in the continental shelf off Barcelona city, in the NW Mediterranean Sea. Surface sediment samples were collected from depths of 10–40 m during late summer and autumn 2012. Grain size and biogeochemical parameters such as OC, its stable isotope δC, total nitrogen (TN) and OC/TN ratios were analysed in size-fractionated sediments. The influence of environmental factors over the study area was determined using hydrological and oceanographic time series, together with video images of the Barcelona coast line and nearshore region.
Some highlights of this study:
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The grain size distribution and OC content of surface sediments across a nearshore environment off Barcelona city is mainly influenced by the terrestrial input of sediments and the sediment redistribution by wave activity.
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Each of the different grain-size fractions is loaded with different amounts of OC, thus hydrodynamic perturbations have an influence on the redistribution of OM in surface sediments.
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Adding the results of this study to those obtained in deeper areas by Pedrosa-Pàmies et al. (2013, see below) suggested that, despite a significant amount of OC is degraded before reaching the continental slope, the shelf acts as a source of fine particles carrying OC for deeper regions.
Enhanced carbon export to the abyssal depths driven by atmosphere dynamics
Pedrosa-Pàmies, R., Sanchez-Vidal, A., Canals, M., Lampadariou, N, Dimitris, V., Gogou, A., Parinos, C., Calafat, A.
Geophysical Research Letters, 43 (16), 8626-86-36, doi: 10.1002/2016GL06978, 2016.
Long‐term biogeochemical observations are critical to understand the natural ability of the oceans to fix CO2 into organic carbon and export it to the deep as sinking particles. Here we present results from a 3 year (2010–2013) sediment trap deployment that allowed detecting interannual variations of carbon fluxes beyond 4000 m depth in the Eastern Mediterranean Sea. Anomalous atmospheric conditions triggering strong heat losses in winter–spring 2012 resulted in convective mixing, nutrient uplifting, and a diatom‐dominated bloom southeast of Crete. Phytoplankton growth, reinforced by the arrival of nutrients from airborne Etna volcano ash, was the highest in the last decade (satellite‐derived Chl a concentrations up to 1.9 mg m−3). This situation caused carbon export to increase by 2 orders of magnitude (12.2 mg m−2 d−1) with respect to typical values, which demonstrates how pulses of sinking fresh phytodetritus linked to rare atmospheric processes can episodically impact one of the most oligotrophic environments in the world ocean.
Some highlights of this study related with carbon export to the deep ocean:
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This study demonstrate the coupling of atmospheric conditions including dust (ash) fall, sea surface dynamics and the abyssal ecosystem through the stimulation of primary production and an enhanced fast vertical flux of organic carbon.
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This study demonstrate that relatively fresh diatom cells can reach bathypelagic depths down to 4000 m in the eastern Mediterranean Sea.
SEM image of settling particles in April 2012 at 4000 m depth in the Eastern Mediterranean Sea, showing non-degraded diatoms and ash microspherules.
Composition and sources of sedimentary organic matter in the deep Eastern Mediterranean Sea.
Pedrosa-Pàmies, R., Parinos, C., Sanchez-Vidal, A., Gogou, A., Calafat, A., Canals,
M., Bouloubassi, I., Lampadariou, N.
Biogeosciences, 12, 9935-9989, doi: 10.5194/bgd-12-9935-2015, 2015.
Statistical dendrogram of type-averaged grain size profiles and geographical distribution of grain size compositional types for the bulk fraction
Surface sediments collected from deep slopes and basins (1018–4087 m depth) of the oligotrophic eastern Mediterranean Sea were analysed for bulk elemental and isotopic composition of organic carbon, total nitrogen and selected lipid biomarkers, jointly with grain size distribution and other geochemical proxies. The distribution and sources of sedimentary organic matter were assessed and general environmental variables, such as water column depth and physical circulation patterns, were examined as causative factors of deep-sea sediment characteristics.
Some highlights of this study:
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Wide regional variations were observed amongst the studied proxies, which reflect the multiple factors controlling sedimentation in the deep eastern Mediterranean Sea.
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Our findings highlighted the role of deep eastern Mediterranean basins as depocentres of organic-rich fine-grained sediments (mean 5.4 ± 2.4 μm), with organic matter accumulation and burial being attributed to aggregation mechanisms and hydrodynamic sorting.
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The spatial variability in the yields of sedimentary organic carbon and lipid biomarkers presented in this study highlights the heterogeneous nature of the particle load exported to the deep basins of the Eastern Mediterranean Sea. Such variability must be taken into account during the development of quantitative carbon budgets for this area.
Spatial distributions of the OC-normalized concentrations of ∑Mar (marine lipid biomarkers) in surface sediments of the deep eastern Mediterranean Sea. (∑Mar=∑(phytosterols,C30diols&keto-ols+alkenones))
Impact of storm-induced remobilization on grain size distribution and organic carbon content in sediments
from the Blanes Canyon area, NW Mediterranean Sea
Pedrosa-Pàmies, R., Sanchez-Vidal, A., Calafat, A., Canals, M. and Durán, R., 2013.
Progress Oceanography, doi: 10.1016/j.pocean.2013.07.023, 2013.
Interactions between organic carbon and mineral particles are known to play a key role for the preservation of organic carbon in marine sediments. In this study we combined meteorological, hydrological and oceanographic information with grain size and geochemical analyses (organic carbon, OC, its stable isotope δ13C, and the nitrogen to OC ratio) in different grain size fractions of surface sediments to determine the impact of a major storm on organic matter redistribution in a deep continental margin of the NW Mediterranean Sea. Sediment cores were obtained from the continental shelf, along the axis of the Blanes submarine canyon (BC), and in the adjacent southern open slope before (November 2008) and after (February and May 2009) the occurrence of one of the most severe coastal storms recorded in the last century in the study area.
Some highlights of this study:
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The results obtained show that the hydrodynamic processes that controlled the sorting and differential deposition of particles according to their grain size also controlled the redistribution of particles with different loads of OC. Thus, whereas coarse particles transported to the canyon head were poorly loaded with OC, fine particles reaching greater depths were relatively rich in OC, a significant proportion of which was of marine origin (i.e. derived from marine primary production).
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This adds to evidence that the physical action of waves and currents during storms plays a key role in determining the amount of OC stored in surface sediments not only in the shelf but also in the deep margin and possibly deeper.
Conceptual model of the Blanes submarine canyon environment showing the main processes and sediment and organic carbon transport pathways that were activated during the major storm of December 2008.