Diel vertical migration (DVM) has been hypothesized to actively transport organic material out of the euphotic layer, thus forming a novel part of the "biological pump." However, quantifying DVM is ...made difficult by observational limitations. Conventionally, the difference between night and day biomass from net trawls in the surface has been assumed to be a consequence of species that have migrated up from their deep daytime depths. However, some of this difference might be an artifact of visual net avoidance. Here, we present a method that facilitates quantification of zooplankton that are migrating, those that are not migrating, and those able to avoid net capture. The algorithm is applied to an extensive data set gathered in the Azores Front region. Results indicate that DVM, and thus active carbon transport, calculated in the traditional manner would overestimate the true value by ∼50%.
There are major gaps in our understanding of the distribution and role of lipids in the open ocean especially with regard to sulfur-containing lipids (S-lipids). Here, we employ a powerful analytical ...approach based on high resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to elucidate depth-related S-lipid production and molecular transformations in suspended particulate matter from the Northeast Atlantic Ocean in this depth range. We show that within the open-ocean environment S-lipids contribute up to 4.2% of the particulate organic carbon, and that up to 95% of these compounds have elemental compositions that do not match those found in the Nature Lipidomics Gateway database (termed “novel”). Among the remaining 5% of lipids that match the database, we find that sulphoquinovosyldiacylglycerol (SQDG) are efficiently removed while sinking through the mesopelagic zone. The relative abundance of other assigned lipids (sulphoquinovosylmonoacylglycerol (SQMG), sulfite and sulfate lipids, Vitamin D2 and D3 derivatives, and sphingolipids) did not change substantially with depth. The novel S-lipids, represented by hundreds of distinct elemental compositions (160–300 molecules at any one depth), contribute increasingly to the lipid and particulate organic matter pools with increased depth. Depth-related transformations cause (i) incomplete degradation/transformation of unsaturated S-lipids which leads to the depth-related accumulation of the refractory saturated compounds with reduced molecular weight (average 455 Da) and (ii) formation of highly unsaturated S-lipids (average abyssopelagic molecular double bond equivalents, DBE=7.8) with lower molecular weight (average 567 Da) than surface S-lipids (average 592 Da). A depth-related increase in molecular oxygen content is observed for all novel S-lipids and indicates that oxidation has a significant role in their transformation while (bio)hydrogenation possibly impacts the formation of saturated compounds. The instrumentation approach applied here represents a step change in our comprehension of marine S-lipid diversity and the potential role of these compounds in the oceanic carbon cycle. We describe a very much higher number of compounds than previously reported, albeit at the level of elemental composition and fold-change quantitation with depth, rather than isomeric confirmation and absolute quantitation of individual lipids. We emphasize that saturated S-lipids have the potential to transfer carbon from the upper ocean to depth and hence are significant vectors for carbon sequestration.
•We investigated sulfolipid production and depth-related cycling in the Atlantic.•The power of FT-ICR MS enabled exhaustive investigation of the sulfolipidome.•We identified 1046 sulfolipid molecular formulae.•Majority of sulfolipids is not characterized up to now (95.7%).•Saturated S-lipids may have the potential to transfer carbon to deep ocean.
The contribution of carbonate‐producing benthic organisms to the global marine carbon budget has been overlooked, the prevailing view being that calcium carbonate (CaCO
3
) is predominantly produced ...and exported by marine plankton in the “biological pump.” Here, we provide the first estimation of the global contribution of echinoderms to the marine inorganic and organic carbon cycle, based on organism‐level measurements from species of the five echinoderm classes. Echinoderms' global CaCO
3
contribution amounts to ~0.861 Pg CaCO
3
/yr (0.102 Pg C/yr of inorganic carbon) as a production rate, and ~2.11 Pg CaCO
3
(0.25 Pg C of inorganic carbon) as a standing stock from the shelves, slopes, and abyssal depths. Echinoderm inorganic carbon production (0.102 Pg C/yr) is less than the global pelagic production (0.4–1.8 Pg C/yr) and similar to the estimates for carbonate shelves globally (0.024–0.120 Pg C/yr). Echinoderm CaCO
3
production per unit area is ~27.01 g CaCO
3
·m
−2
·yr
−1
(3.24 g C·m
−2
·yr
−1
as inorganic carbon) on a global scale for all areas, with a standing stock of ~63.34 g CaCO
3
/m
2
(7.60 g C/m
2
as inorganic carbon), and ~7.97 g C/m
2
as organic carbon. The shelf production alone is 77.91 g CaCO
3
·m
−2
·yr
−1
(9.35 g C·m
−2
·yr
−1
as inorganic carbon) in contrast to 2.05 g CaCO
3
·m
−2
·yr
−1
(0.24 g C·m
−2
·yr
−1
as inorganic carbon) for the slope on a global scale. The biogeography of the CaCO
3
standing stocks of echinoderms showed strong latitudinal variability. More than 80% of the global CaCO
3
production from echinoderms occurs between 0 and 800 m, with the highest contribution attributed to the shelf and upper slope. We provide a global distribution of echinoderm populations in the context of global calcite saturation horizons, since undersaturated waters with respect to mineral phases are surfacing. This shallowing is a direct consequence of ocean acidification, and in some places it may reach the shelf and upper slope permanently, where the highest CaCO
3
standing stocks from echinoderms originate. These organism‐level data contribute substantially to the assessment of global carbonate inventories, which at present are poorly estimated. Additionally, it is desirable to include these benthic compartments in coupled global biogeochemical models representing the “biological pump” and its feedbacks, since at present all efforts have focused on pelagic processes, dominated by coccolithophores. The omission of the benthic processes from modeling will only diminish the understanding of elemental fluxes at large scales and any future prediction of climate change scenarios.
During the austral summer of 2004–2005, a large multi-disciplinary research cruise investigated the development and fate of a naturally iron-fertilised phytoplankton bloom in the Southern Ocean ...(Crozet Plateau). As part of this extensive process study, a neutrally buoyant sediment trap (PELAGRA) was deployed to constrain the magnitude, composition, and variability of upper-ocean particle export. In the productive regime north of the plateau we observed depth-normalised (100-m) organic carbon fluxes between 11 and 440
mg
C
m
−2
d
−1, and in the HNLC control region to the south similarly normalised fluxes between 28 and 46
mg
C
m
−2
d
−1. Mass balance calculations indicate that the high levels of carbon export north of the plateau would need to be maintained for at least 30 days in order to account for estimated seasonal depletion of dissolved silicic acid in surface waters. This would imply that the flux of organic carbon is ≈15
g
C
m
−2 for the period of the bloom north of the plateau. A range of export ratios (proportion of surface production lost to downward flux) was calculated using both contemporaneous and retrospective estimates of integrated production, and these highlight the temporal decoupling between production and export. Calculated export ratios were at their highest north of the plateau and correlate strongly with the selective export of large, heavily silicified diatoms, particularly
Eucampia antarctica, relative to the surface community structure. By normalising the molar elemental ratios measured in the exported particles to the molar elemental ratios of the upper-ocean particle field we also observed a strong decoupling of Si:C and Si:N. This suggests that the decoupling of the global silica and carbon cycles, which is well known as a defining feature of the Southern Ocean, has its origins in the upper ocean.
The metabolic activities of biological communities living at the abyssal seabed create a strong source of nutrients and a sink for oxygen. If the published estimates of vertical mixing based on ...instantaneous microstructure measurements are correct, near to the abyssal seabed away from rough topographic features there should be enhanced concentrations of nitrate and phosphate and depletion of oxygen. Recent data on the vertical concentration profiles of inorganic nutrients and oxygen over the bottom 1000 m of the water column (World Ocean Circulation Experiment ‐ WOCE) provide no such evidence. It is concluded that the effective vertical mixing rates are much more vigorous than previously indicated and may even be higher than estimates of average basin scale rates based on temperature and salinity distributions. We propose that the enhanced mixing associated with rough topography influences the entire volume of the abyssal ocean on short time scales (e.g., one month ‐ one year).
Acantharian cysts were discovered in sediment trap samples from spring 2007 at 2000 m in the Iceland Basin. Although these single‐celled organisms contribute to particulate organic matter flux in the ...upper mesopelagic, their contribution to bathypelagic particle flux has previously been found negligible. Four time‐series sediment traps were deployed and all collected acantharian cysts, which are reproductive structures. Across all traps, cysts contributed on average 3–22%, and 4–24% of particulate organic carbon and nitrogen (POC and PON) flux, respectively, during three separate collection intervals (the maximum contribution in any one trap was 48% for POC and 59% for PON). Strontium (Sr) flux during these 6 weeks reached 3 mg m−2 d−1. The acantharian celestite (SrSO4) skeleton clearly does not always dissolve in the mesopelagic as often thought, and their cysts can contribute significantly to particle flux at bathypelagic depths during specific flux events. Their large size (~ 1 mm) and mineral ballast result in a sinking rate of ~ 500 m d−1; hence, they reach the bathypelagic before dissolving. Our findings are consistent with a vertical profile of salinity‐normalized Sr concentration in the Iceland Basin, which shows a maximum at 1700 m. Profiles of salinity‐normalized Sr concentration in the subarctic Pacific reach maxima at ≤ 1500 m, suggesting that Acantharia might contribute to the bathypelagic particle flux there as well. We hypothesize that Acantharia at high latitudes use rapid, deep sedimentation of reproductive cysts during phytoplankton blooms so that juveniles can exploit the large quantity of organic matter that sinks rapidly to the deep sea following a bloom.
It is premature to sell carbon offsets from ocean iron fertilization unless research provides the scientific foundation to evaluate risks and benefits.
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