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Gerhard J Herndl - One of the best experts on this subject based on the ideXlab platform.
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seasonal dynamics of Marine Snow associated and free living demethylating bacterial communities in the coastal northern adriatic sea
Environmental Microbiology Reports, 2019Co-Authors: Paul Steiner, Gerhard J Herndl, Eva Sintes, Ingrid Ivancic, Mirjana Najdek, Rafel Simo, Daniele De Corte, Daniela Maric PfannkuchenAbstract:The extent of DMSP demethylation has been hypothesized to depend on DMSP availability and bacterial sulfur demand, which might lead to niche differentiation of the demethylating bacterial community. In this study, we determined DMSP concentrations in Marine Snow and the ambient water over a seasonal cycle and linked DMSP concentrations to the abundance of bacteria harbouring the demethylation dmdA gene in the Adriatic Sea. In Marine Snow, DMSP concentrations were up to four times higher than in the ambient water and three times higher in Marine Snow in summer than in winter. The average dmdA:recA gene ratio over the sampling period was 0.40 ± 0.24 in Marine Snow and 0.48 ± 0.21 in the ambient water. However, at the subclade level, differences in the demethylating bacterial community of Marine Snow and the ambient water were apparent. Seasonal patterns of potentially demethylating bacteria were best visible at the oligotype level. In the ambient water, the SAR116 and the OM60/NOR5 clade were composed of oligotypes that correlated to high DMSP concentrations, while oligotypes of the Rhodospirillales correlated to low DMSP concentrations. Our results revealed a pronounced seasonal variability and spatial heterogeneity in DMSP concentrations and the associated demethylating bacterial community.
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Eukaryotic microbes, principally fungi and labyrinthulomycetes, dominate biomass on bathypelagic Marine Snow
The ISME Journal, 2017Co-Authors: Alexander B Bochdansky, Melissa A Clouse, Gerhard J HerndlAbstract:In the bathypelagic realm of the ocean, the role of Marine Snow as a carbon and energy source for the deep-sea biota and as a potential hotspot of microbial diversity and activity has not received adequate attention. Here, we collected bathypelagic Marine Snow by gentle gravity filtration of sea water onto 30 μm filters from ~1000 to 3900 m to investigate the relative distribution of eukaryotic microbes. Compared with sediment traps that select for fast-sinking particles, this method collects particles unbiased by settling velocity. While prokaryotes numerically exceeded eukaryotes on Marine Snow, eukaryotic microbes belonging to two very distant branches of the eukaryote tree, the fungi and the labyrinthulomycetes, dominated overall biomass. Being tolerant to cold temperature and high hydrostatic pressure, these saprotrophic organisms have the potential to significantly contribute to the degradation of organic matter in the deep sea. Our results demonstrate that the community composition on bathypelagic Marine Snow differs greatly from that in the ambient water leading to wide ecological niche separation between the two environments.
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seasonal variation in Marine Snow associated and ambient water prokaryotic communities in the northern adriatic sea
Aquatic Microbial Ecology, 2014Co-Authors: Jana Vojvoda, Dominique Lamy, Eva Sintes, Juan Antonio Garcia, Valentina Turk, Gerhard J HerndlAbstract:The structure and activity of prokaryotic communities were determined in Marine Snow and in the ambient water of the northern Adriatic Sea in different seasons (autumn, spring and summer). The seasonal variation in the composition of Marine-Snow-associated and ambient- water bacterial communities was assessed by T-RFLP (Terminal Restriction Fragment Length Polymorphism) on the 16S rRNA gene (16S rDNA) and 16S rRNA transcript (16S rRNA) level. On the 16S rDNA level, the bacterial community composition of the Marine Snow and ambient water was similar in summer and autumn, but not in spring. In contrast, on the 16S rRNA level, indica- tive of the active bacterial community, the Marine-Snow-associated bacterial community was different from that of the ambient-water, and different from the bacterial community on the 16S rDNA level, except in autumn. To phylogenetically characterize the bacterial and archaeal com- munity composition associated with Marine Snow and the ambient water, clone libraries of 16S rDNA and 16S rRNA were constructed from 2 contrasting seasons. Phylogenetic profiling re vealed a higher similarity among bacterial communities in summer compared to late autumn. Certain bacterial and archaeal groups were exclusively associated with summer or autumn Marine Snow, suggesting that Marine-Snow-associated prokaryotic communities are subjected to successional changes similar to ambient-water communities. Moreover, the presence of bacterial groups enriched in Marine Snow including Vibrionales and sulphate-reducing bacteria is consistent with niche partitioning and metabolic adaptations of the particle-associated microbiota.
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extracellular enzymatic activity and secondary production in free living and Marine Snow associated bacteria
Marine Biology, 1992Co-Authors: Markus Karner, Gerhard J HerndlAbstract:Abundance, production (measured as thymidine incorporation) and extracellular enzymatic activity in free-living and Marine-Snow-associated bacteria were measured in the northern Adriatic Sea. Although bacterial density and production were similar in both free-living and Marine-Snow-associated bacteria, hydrolytic activity (α- and β-glucosidase and l-aminopeptidase) was significantly higher in Marine-Snow-associated bacteria, in terms of both absolute and per-cell rates. As concentrations of dissolved total and monomeric carbohydrates and free amino acids in Marine Snow were very close to those in the ambient water, we suggest that the observed differences between free-living and Marine-Snow-associated baycteria do not simply reflect catabolic repression of enzyme expression in one of the bacterial components. Whether substrate induction is responsible for the observed higher hydrolase activity in Marine-Snow bacteria and/or whether there are distinct bacterial species obligatorily associated with Marine Snow remains unknown.
Thomas Kiorboe - One of the best experts on this subject based on the ideXlab platform.
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Effect of Type and Concentration of Ballasting Particles on Sinking Rate of Marine Snow Produced by the Appendicularian Oikopleura dioica
PLoS ONE, 2013Co-Authors: F. Lombard, Lionel Guidi, Thomas KiorboeAbstract:Ballast material (organic, opal, calcite, lithogenic) is suggested to affect sinking speed of aggregates in the ocean. Here, we tested this hypothesis by incubating appendicularians in suspensions of different algae or Saharan dust, and observing the sinking speed of the Marine Snow formed by their discarded houses. We show that calcite increases the sinking speeds of aggregates by ~100% and lithogenic material by ~150% while opal only has a minor effect. Furthermore the effect of ballast particle concentration was causing a 33 m d-1 increase in sinking speed for a 5×10 5 µm 3 ml-1 increase in particle concentration, near independent on ballast type. We finally compare our observations to the literature and stress the need to generate aggregates similar to those in nature in order to get realistic estimates of the impact of ballast particles on sinking speeds.
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copepods use chemical trails to find sinking Marine Snow aggregates
Limnology and Oceanography, 2013Co-Authors: M. Koski, F. Lombard, Thomas KiorboeAbstract:Copepods ; are major consumers of sinking Marine particles and hence reduce the efficiency of the biological carbon pump. Their high abundance on Marine Snow suggests that they can detect sinking particles remotely. By means of laboratory observations, we show that the copepod Temora longicornis can detect chemical trails originating from sinking Marine Snow particles (appendicularian houses). The chemical cue was detected by copepods from a distance of .25 particle radii, with the probability of detection decreasing with distance. The behavior of T. longicornis following the trail resembled the behavior of males tracking pheromone trails, although with a lower tracking velocity. Upon finding a house, the copepod would attach for a short period (10–30 s) and feed intensively. Due to short residence times, daily feeding rates were moderate. Our results demonstrate that even T. longicornis, a species usually considered a microparticle feeder, is able to detect and feed on Marine Snow aggregates. If similar behaviors are displayed by the more dedicated aggregate-feeding copepods, a topic that remains unexplored, the effect of copepods on vertical flux attenuation may be significant.
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Marine Snow originating from appendicularian houses age dependent settling characteristics
Deep Sea Research Part I: Oceanographic Research Papers, 2010Co-Authors: F. Lombard, Thomas KiorboeAbstract:Abstract The evolution of size, sinking velocity, and dry weight of aging discarded appendicularian houses, a component of Marine Snow, were examined in laboratory experiments. The sizes of discarded houses decrease over time, with a rapid deflation during the first hour, followed by a slower rate of compression leading to a total of 60% and 87% decrease in diameter after 1 h and 5 d, respectively. The initial rapid deflation of the houses is accompanied by a massive loss of its particle content and a 10–63% loss in weight. The initial weight loss is left as a trail of elevated particle and solute concentration in the wake of the sinking house. Subsequently the house weight decreases at a much lower rate that is consistent with bacterial degradation. The combined effect of weight losses and deflation–compression process is an increase in the sinking speed of the houses, by a factor of 1.7–6 after 1.5–3 d. These processes can provide a new insight on the sinking dynamic and flux of appendicularian produced Marine Snow from in situ observations. We applied our laboratory derived rates to field data from the East Atlantic Ocean and estimate that large (2000–4000 μm) houses account for about 1/3 of the 300–500 μm particles in the upper 100 m and loose 30% of their mass before leaving the upper 200 m. The observed deflation–compression process may have several consequences on the dynamics of appendicularian-derived Marine Snow particles. First, it may explain field observations that Marine Snow sinking velocities increase with depth. Second, an initial rapid loss of weight and particles will decrease the potential vertical flux of particulate carbon due to appendicularians. And finally, the trail of particles and solutes may guide zooplankton to the sinking house, and further increase its degradation due to grazing by detrivorous organisms.
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interactions between Marine Snow and heterotrophic bacteria aggregate formation and microbial dynamics
Aquatic Microbial Ecology, 2006Co-Authors: Hanspeter Grossart, Thomas Kiorboe, Kw W Tang, Martin Allgaier, Em M Yam, Helle PlougAbstract:Macroscopic aggregates (Marine Snow) contribute to new production and nutrient dynamics in the upper ocean and vertical fluxes of organic matter to the deep ocean. To test whether microorganisms play a significant role in phytoplankton aggregate formation we studied particle abundance and size as well as abundance, colonization behaviour, and community composition of bacteria during the growth of 2 Marine diatoms (Thalassiosira weissflogii and Navicula sp.) under axenic and non-axenic conditions. Community composition of free-living and attached bacteria during phytoplankton growth and aggregation was studied by amplification of 16S rRNA gene frag- ments and denaturing gradient gel electrophoresis (DGGE). Our results show that the presence of bacteria was a prerequisite for aggregation of T. weissflogii but not of Navicula sp. Occurrences of distinct populations of free-living and attached bacteria depended on phytoplankton growth and aggregation dynamics. The community composition of especially attached bacteria significantly differed between the 2 algal cultures. Our study suggests that phytoplankton aggregation and verti- cal fluxes are closely linked to interactions between the Marine phytoplankton and the ambient microbial community.
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dynamics of microbial communities on Marine Snow aggregates colonization growth detachment and grazing mortality of attached bacteria
Applied and Environmental Microbiology, 2003Co-Authors: Thomas Kiorboe, Kam W Tang, Hanspeter Grossart, Helle PlougAbstract:We studied the dynamics of microbial communities attached to model aggregates (4-mm-diameter agar spheres) and the component processes of colonization, detachment, growth, and grazing mortality. Agar spheres incubated in raw seawater were rapidly colonized by bacteria, followed by flagellates and ciliates. Colonization can be described as a diffusion process, and encounter volume rates were estimated at about 0.01 and 0.1 cm 3 h 1 for bacteria and flagellates, respectively. After initial colonization, the abundances of flagellates and ciliates remained approximately constant at 10 3 to 10 4 and 10 2 cells sphere 1 , respectively, whereas bacterial populations increased at a declining rate to >10 7 cells sphere 1 . Attached microorganisms initially detached at high specific rates of 10 2 min 1 , but the bacteria gradually became irreversibly attached to the spheres. Bacterial growth (0 to 2 day 1 ) was density dependent and declined hyperbolically when cell density exceeded a threshold. Bacterivorous flagellates grazed on the sphere surface at an average saturated rate of 15 bacteria flagellate 1 h 1 . At low bacterial densities, the flagellate surface clearance rate was 5 10 7 cm 2 min 1 , but it declined hyperbolically with increasing bacterial density. Using the experimentally estimated process rates and integrating the component processes in a simple model reproduces the main features of the observed microbial population dynamics. Differences between observed and predicted population dynamics suggest, however, that other factors, e.g., antagonistic interactions between bacteria, are of importance in shaping Marine Snow microbial communities.
Jefferson T Turner - One of the best experts on this subject based on the ideXlab platform.
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zooplankton fecal pellets Marine Snow phytodetritus and the ocean s biological pump
Progress in Oceanography, 2015Co-Authors: Jefferson T TurnerAbstract:Abstract The “biological pump” is the process by which photosynthetically-produced organic matter in the ocean descends from the surface layer to depth by a combination of sinking particles, advection or vertical mixing of dissolved organic matter, and transport by animals. Particulate organic matter that is exported downward from the euphotic zone is composed of combinations of fecal pellets from zooplankton and fish, organic aggregates known as “Marine Snow” and phytodetritus from sinking phytoplankton. Previous reviews by Turner and Ferrante (1979) and Turner (2002) focused on publications that appeared through late 2001. Since that time, studies of the biological pump have continued, and there have been >300 papers on vertical export flux using sediment traps, large-volume filtration systems and other techniques from throughout the global ocean. This review will focus primarily on recent studies that have appeared since 2001. Major topics covered in this review are (1) an overview of the biological pump, and its efficiency and variability, and the role of dissolved organic carbon in the biological pump; (2) zooplankton fecal pellets, including the contribution of zooplankton fecal pellets to export flux, epipelagic retention of zooplankton fecal pellets due to zooplankton activities, zooplankton vertical migration and fecal pellet repackaging, microbial ecology of fecal pellets, sinking velocities of fecal pellets and aggregates, ballasting of sinking particles by mineral contents, phytoplankton cysts, intact cells and harmful algae toxins in fecal pellets, importance of fecal pellets from various types of zooplankton, and the role of zooplankton fecal pellets in picoplankton export; (3) Marine Snow, including the origins, abundance, and distributions of Marine Snow, particles and organisms associated with Marine Snow, consumption and fragmentation of Marine Snow by animals, pathogens associated with Marine Snow; (4) phytodetritus, including pulsed export of phytodetritus, phytodetritus from Phaeocystis spp., picoplankton in phytodetritus, the summer export pulse (SEP) of phytodetritus in the subtropical North Pacific, benthic community responses to phytodetritus; (5) other components of the biological pump, including fish fecal pellets and fish-mediated export, sinking carcasses of animals and macrophytes, feces from Marine mammals, transparent exopolymer particles (TEP); (6) the biological pump and climate, including origins of the biological pump, the biological pump and glacial/interglacial cycles, the biological pump and contemporary climate variations, and the biological pump and anthropogenic climate change. The review concludes with potential future modifications in the biological pump due to climate change.
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zooplankton fecal pellets Marine Snow and sinking phytoplankton blooms
Aquatic Microbial Ecology, 2002Co-Authors: Jefferson T TurnerAbstract:Zooplankton fecal pellets have long been thought to be a dominant component of the sedimentary flux in Marine and freshwater ecosystems, but that view is changing. The last 2 decades have seen publication of >500 studies using sediment traps, which reveal that zooplankton fecal pellets often constitute only a minor or variable proportion of the sedimentary flux. Substantial proportions of this flux are from organic aggregates ('Marine Snow') of various origins, including phytoplankton blooms, which sediment directly to the benthos. It now appears that mainly large fecal pellets of macrozooplankton and fish are involved in the sedimentary flux. Smaller fecal pellets of microzooplankton and small mesozooplankton are mostly recycled or repackaged in the water column by microbial decomposition and coprophagy, contributing more to processes in the water column than flux to the benthos. The relative contributions of fecal pellets, Marine Snow and sinking phytoplankton to the vertical flux and recycling of materials in the water column are highly variable, dependent upon multiple interacting factors. These include variations in productivity, biomass, size spectra and composition of communities in the overlying water columns, and trophic interactions between various components of the plankton and nekton communities at various times, locations and depths. Other factors include differences in sinking rates, sizes, composition and pollutant contents of fecal pellets produced by various sizes of zooplankters, and zooplankton feeding-fecal pellet production interactions in relation to upwelling and El Nino periods, seasonal life-history-related zooplankton vertical migrations and long-term oceanographic regime shifts. There are also suggestions from the geological record that zooplankton fecal pellets may have been important in ancient oceans. The ecological roles of Marine Snow and phytoplankton aggregates in sedimentary flux also depend on a variety of interacting factors, including sources of origin, degrees of microbial colonization, depth distributions, sinking rates and ingestibility by consumers. Perhaps the major reversal of the previous paradigm on the role of fecal pellets in the sedimentary flux over the last 2 decades has been the realization that much, if not most, of the organic rain from the epipelagic to the abyss is due to direct sedimentation of aggregated phytoplankton, which does not appear to undergo consumption in the water column, and which may be related to seasonality of surface production cycles. Further, there is emerging evidence for benthic responses to sedimented phytodetritus, including apparent synchrony of reproductive cycles of some deep-sea benthic animals with seasonality of sinking of surface blooms. Such episodic input of surface phytodetritus may help resolve apparent discrepancies between average supply and demand of organic matter required to maintain benthic community metabolism. The sedimentary flux of fecal pellets, Marine Snow and sinking phytoplankton is an important component of the biological pump that not only transports and recycles materials in the sea but also may help scrub greenhouse gases from the atmosphere.
Uta Passow - One of the best experts on this subject based on the ideXlab platform.
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formation of rapidly sinking oil associated Marine Snow
Deep-sea Research Part Ii-topical Studies in Oceanography, 2016Co-Authors: Uta PassowAbstract:Abstract Significant amounts of oil accumulated at the sea surface and in a subsurface plume during the Deepwater Horizon (DwH) spill in the Gulf of Mexico (GoM) in 2010. A substantial fraction of this oil was removed from the Marine environment by mechanical recovery or burning, or it reached shorelines, whereas another fraction remained within the Marine environment, where it dispersed (chemically or naturally), emulsified or sedimented. After the DwH accident the sedimentation of hydrocarbons to the seafloor via rapidly sinking, oil-associated Marine Snow has become a focus of attention, and it has been hypothesized that Marine Snow formation significantly impacted the distribution of the oil from the DwH spill. Here, roller table experiments are presented that investigated the conditions inducing the formation of oil-associated Marine Snow, focusing especially on the effects of oil type, photochemical aging of oil, and the presence of phytoplankton or dispersant. Large, mucus-rich Marine Snow, termed microbial Marine Snow, formed in treatments incubated with the oil that had accumulated at the sea surface. This bacteria-mediated formation of up to cm-sized Marine Snow in the absence of particles >1 µm, represents a unique formation pathway different from that of the physical coagulation of particles. Microbial Marine Snow, albeit smaller, also formed in the presence of crude oil that had been aged for ≥3 weeks in sunlight, but no particles formed in the presence of unaltered crude. The dispersant Corexit 9500A (Corexit:oil ratio=1:100) impeded the formation of microbial Marine Snow, requiring a re-evaluation of the benefits and detriments of Corexit 9500A as a mediating measure. Phytoplankton aggregates also incorporated fossil carbon, providing an alternate pathway for the formation of oil-associated Marine Snow. The ubiquitous formation and rapid sedimentation of oil-rich Marine Snow can explain the high accumulation rate of flocculent material at the seafloor and on corals observed after the DwH spill. These results may raise awareness that oil spill response and assessment need to include sedimentation of hydrocarbons via Marine Snow as a significant distribution mechanism and may guide future modeling efforts and budget calculations.
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assessing the impacts of oil associated Marine Snow formation and sedimentation during and after the deepwater horizon oil spill
Anthropocene, 2016Co-Authors: Kendra L Daly, Uta Passow, Jeffrey P Chanton, David J HollanderAbstract:Abstract The Deepwater Horizon oil spill was the largest in US history, unprecedented for the depth and volume of oil released, the amount of dispersants applied, and the unexpected, protracted sedimentation of oil-associated Marine Snow (MOS) to the seafloor. Marine Snow formation, incorporation of oil, and subsequent gravitational settling to the seafloor (i.e., MOSSFA: Marine Oil Snow Sedimentation and Flocculent Accumulation) was a significant pathway for the distribution and fate of oil, accounting for as much as 14% of the total oil released. Long residence times of oil on the seafloor will result in prolonged exposure by benthic organisms and economically important fish. Bioaccumulation of hydrocarbons into the food web also has been documented. Major surface processes governing the MOSSFA event included an elevated and extended Mississippi River discharge, which enhanced phytoplankton production and suspended particle concentrations, zooplankton grazing, and enhanced microbial mucus formation. Previous reports indicated that MOS sedimentation also occurred during the Tsesis and Ixtoc-I oil spills; thus, MOSSFA events may occur during future oil spills, particularly since 85% of global deep-water oil exploration sites are adjacent to deltaic systems. We provide a conceptual framework of MOSSFA processes and identify data gaps to help guide current research and to improve our ability to predict MOSSFA events under different environmental conditions. Baseline time-series data and model development are urgently needed for all levels of ecosystems in regions of hydrocarbon extraction to prepare for and respond to future oil spills and to understand the impacts of oil spills on the environment.
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Marine Snow formation in the aftermath of the deepwater horizon oil spill in the gulf of mexico
Environmental Research Letters, 2012Co-Authors: Uta Passow, Kai Ziervogel, Vernon L Asper, A R DiercksAbstract:The large Marine Snow formation event observed in oil-contaminated surface waters of the Gulf of Mexico (GoM) after the Deepwater Horizon accident possibly played a key role in the fate of the surface oil. We characterized the unusually large and mucus-rich Marine Snow that formed and conducted roller table experiments to investigate their formation mechanisms. Once Marine Snow lost its buoyancy, its sinking velocity, porosity and excess density were then similar to those of diatom or miscellaneous aggregates. The hydrated density of the component particles of the Marine Snow from the GoM was remarkably variable, suggesting a wide variety of component types. Our experiments suggest that the Marine Snow appearing at the surface after the oil spill was formed through the interaction of three mechanisms: (1) production of mucous webs through the activities of bacterial oil-degraders associated with the floating oil layer; (2) production of oily particulate matter through interactions of oil components with suspended matter and their coagulation; and (3) coagulation of phytoplankton with oil droplets incorporated into aggregates. Marine Snow formed in some, but not all, experiments with water from the subsurface plume of dissolved hydrocarbons, emphasizing the complexity of the conditions leading to the formation of Marine Snow in oil-contaminated seawater at depth.
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neutral aldoses as source indicators for Marine Snow
Marine Chemistry, 2008Co-Authors: Annelie Skoog, Alice L Alldredge, Uta Passow, John P Dunne, James W MurrayAbstract:Abstract The chemical characteristics of aggregating material in the Marine environment are largely unknown. We investigated neutral aldose (NA) abundance and composition in aggregation of Marine Snow and other organic matter (OM) size fractions in the field. Four sample sets were fractionated using membrane filtration and ultrafiltration into the following size fractions: particulate material, high-molecular-weight (HMW) material, and low-molecular-weight (LMW) material. We also collected three sample sets of Marine-Snow aggregates. Each sample set contained small, medium, and large aggregate size fractions and each size fraction consisted of 25–50 aggregates. For 7 Marine-Snow samples and for each water-sample size fraction, we determined monomeric and polymeric NA concentration, NA yield (amount of NA-C normalized to organic carbon), and composition; total organic carbon (TOC) concentration; transparent exopolymer particles (TEP) concentration, and TEP propensity (TEP concentration after inducing TEP formation in filtered samples). This is the first study to include compound-specific NA determinations on these four Marine OM size fractions. The mass balances of organic carbon and NA indicated that there were no serious contamination or loss problems. Concentrations, yields, and NA mol fractions in water samples were similar to results from other studies. Glucose and galactose had the highest relative abundance in all size fractions. The NA yield increased with increasing molecular weight or particle size for all fractions except Marine Snow. The NA yield increased in the order: LMW TEP concentration or TEP propensity was positively correlated with concentrations of all individual NAs as well as the sum NA concentrations, indicating that TEP contains neutral sugars in addition to the acidic polysaccharides stained in the determination of TEP concentrations. Despite the relatively low NA yield in Marine Snow, Marine Snow was enriched in NA when compared with seawater, with enrichment factors of 34–225 (average 125). By combining data from this study with data from other studies, we estimate that There was no clear correlation between Marine-Snow aggregate size and NA yield, that is, there appears to be no general age difference between small and large Marine-Snow aggregates. NA composition was similar among different Marine-Snow size fracions collected during the same day, indicating that aggregation/disaggregation reactions resulted in homogenizing NA composition in Marine-Snow aggregates of all sizes. The NA composition of Marine Snow was different from that of other OM size fractions, indicating either that bacterial degradation has modified the composition of Marine Snow to a larger extent than other OM size fractions or that Marine Snow is formed through the aggregation of selected subcomponents of OM.
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the characteristics and transparent exopolymer particle tep content of Marine Snow formed from thecate dinoflagellates
Journal of Plankton Research, 1998Co-Authors: Alice L Alldredge, Uta Passow, H D HaddockAbstract:Abundant Marine Snow containing diatoms and detritus, but dominated by large, bio- luminescent thecate dinoflagellates and their temporary vegetative cysts, especially several species of the genus Gonyaulax, was observed at six stations in the Santa Barbara Channel, California, in 1989 and 1994. These aggregates were unusually cohesive and mucus rich, and contained 2-4 times more mass, paniculate organic carbon (POC), paniculate organic nitrogen (PON) and chlorophyll a per unit aggregate volume than more common types of Marine Snow formed from diatoms, fecal matter, larvacean houses or miscellaneous detritus. However, the relationship between aggregate size and the concentration of TEP (transparent exopolymer particles which form the mucus matrix of most Marine Snow) was similar to that of other types of aggregates, suggesting that much of the copious gel-like material within dinoftagellate aggregates was not TEP. While this is the first report of abundant thecate dinoflagellates occurring within large, rapidly sinking Marine aggregates, the data do not suppon the conclusion that mass aggregation and subsequent sedimentation of blooms is pan of the life history adaptations of thecate dinoflagellates, as it is for some diatoms. The high abundance of free-living dinoflagellate cells and temporary cysts, and the similar proportion of dinoflagellat es relative to other algal and chemical components in both aggregates and the surrounding seawater, indicate that the dinoflagellates were not differentially aggregating. Even so, passive accumulation of dinoflagellates in Marine Snow through aggregation processes may result in more rapid transport of dinoflagellate-generated material to the deep ocean, alter the nature of sinking paniculate matter following dinoflagellate blooms, and increase the nutritional value of Marine Snow as a food source for zooplankton and fish.
F. Lombard - One of the best experts on this subject based on the ideXlab platform.
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Eukaryotic and cyanobacterial communities associated with Marine Snow particles in the oligotrophic Sargasso Sea
Scientific Reports, 2019Co-Authors: Regitze Lundgreen, Hanspeter Grossart, F. Lombard, Cornelia Jaspers, Sachia Traving, Daniel Ayala, Torkel Nielsen, Peter Munk, Lasse RiemannAbstract:Marine Snow aggregates represent heterogeneous agglomerates of dead and living organic matter. Composition is decisive for their sinking rates, and thereby for carbon flux to the deep sea. For oligotrophic oceans, information on aggregate composition is particularly sparse. To address this, the taxonomic composition of aggregates collected from the subtropical and oligotrophic Sargasso Sea (Atlantic Ocean) was characterized by 16S and 18S rRNA gene sequencing. Taxonomy assignment was aided by a collection of the contemporary plankton community consisting of 75 morphologically and genetically identified plankton specimens. The diverse rRNA gene reads of Marine Snow aggregates, not considering Trichodesmium puffs, were dominated by copepods (52%), cnidarians (21%), radiolarians (11%), and alveolates (8%), with sporadic contributions by cyanobacteria, suggesting a different aggregate composition than in eutrophic regions. Composition linked significantly with sampling location but not to any measured environmental parameters or plankton biomass composition. Nevertheless, indicator and network analyses identified key roles of a few rare taxa. This points to complex regulation of aggregate composition, conceivably affected by the environment and plankton characteristics. The extent to which this has implications for particle densities, and consequently for sinking rates and carbon sequestration in oligotrophic waters, needs further interrogation.
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Copepods use chemical trails to find sinking Marine Snow aggregates
2016Co-Authors: F. Lombard, M. Koski, Kiørboe T. AAbstract:Copepods; are major consumers of sinking Marine particles and hence reduce the efficiency of the biological carbon pump. Their high abundance on Marine Snow suggests that they can detect sinking particles remotely. By means of laboratory observations, we show that the copepod Temora longicornis can detect chemical trails originating from sinking Marine Snow particles (appendicularian houses). The chemical cue was detected by copepods from a distance of.25 particle radii, with the probability of detection decreasing with distance. The behavior of T. longicornis following the trail resembled the behavior of males tracking pheromone trails, although with a lower tracking velocity. Upon finding a house, the copepod would attach for a short period (10–30 s) and feed intensively. Due to short residence times, daily feeding rates were moderate. Our results demonstrate that even T. longicornis, a species usually considered a microparticle feeder, is able to detect and feed on Marine Snow aggregates. If similar behaviors are displayed by the more dedicated aggregate-feeding copepods, a topic that remains unexplored, the effect of copepods on vertical flux attenuation may be significant. Sinking particles are the main vehicles for the vertical transport of biogenic carbon from the sea surface to the ocean interior and the seafloor (Fowler and Knauer 1986)
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copepods use chemical trails to find sinking Marine Snow aggregates
Limnology and Oceanography, 2013Co-Authors: M. Koski, F. Lombard, Thomas KiorboeAbstract:Copepods ; are major consumers of sinking Marine particles and hence reduce the efficiency of the biological carbon pump. Their high abundance on Marine Snow suggests that they can detect sinking particles remotely. By means of laboratory observations, we show that the copepod Temora longicornis can detect chemical trails originating from sinking Marine Snow particles (appendicularian houses). The chemical cue was detected by copepods from a distance of .25 particle radii, with the probability of detection decreasing with distance. The behavior of T. longicornis following the trail resembled the behavior of males tracking pheromone trails, although with a lower tracking velocity. Upon finding a house, the copepod would attach for a short period (10–30 s) and feed intensively. Due to short residence times, daily feeding rates were moderate. Our results demonstrate that even T. longicornis, a species usually considered a microparticle feeder, is able to detect and feed on Marine Snow aggregates. If similar behaviors are displayed by the more dedicated aggregate-feeding copepods, a topic that remains unexplored, the effect of copepods on vertical flux attenuation may be significant.
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Effect of Type and Concentration of Ballasting Particles on Sinking Rate of Marine Snow Produced by the Appendicularian Oikopleura dioica
PLoS ONE, 2013Co-Authors: F. Lombard, Lionel Guidi, Thomas KiorboeAbstract:Ballast material (organic, opal, calcite, lithogenic) is suggested to affect sinking speed of aggregates in the ocean. Here, we tested this hypothesis by incubating appendicularians in suspensions of different algae or Saharan dust, and observing the sinking speed of the Marine Snow formed by their discarded houses. We show that calcite increases the sinking speeds of aggregates by ~100% and lithogenic material by ~150% while opal only has a minor effect. Furthermore the effect of ballast particle concentration was causing a 33 m d-1 increase in sinking speed for a 5×10 5 µm 3 ml-1 increase in particle concentration, near independent on ballast type. We finally compare our observations to the literature and stress the need to generate aggregates similar to those in nature in order to get realistic estimates of the impact of ballast particles on sinking speeds.
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Marine Snow originating from appendicularian houses age dependent settling characteristics
Deep Sea Research Part I: Oceanographic Research Papers, 2010Co-Authors: F. Lombard, Thomas KiorboeAbstract:Abstract The evolution of size, sinking velocity, and dry weight of aging discarded appendicularian houses, a component of Marine Snow, were examined in laboratory experiments. The sizes of discarded houses decrease over time, with a rapid deflation during the first hour, followed by a slower rate of compression leading to a total of 60% and 87% decrease in diameter after 1 h and 5 d, respectively. The initial rapid deflation of the houses is accompanied by a massive loss of its particle content and a 10–63% loss in weight. The initial weight loss is left as a trail of elevated particle and solute concentration in the wake of the sinking house. Subsequently the house weight decreases at a much lower rate that is consistent with bacterial degradation. The combined effect of weight losses and deflation–compression process is an increase in the sinking speed of the houses, by a factor of 1.7–6 after 1.5–3 d. These processes can provide a new insight on the sinking dynamic and flux of appendicularian produced Marine Snow from in situ observations. We applied our laboratory derived rates to field data from the East Atlantic Ocean and estimate that large (2000–4000 μm) houses account for about 1/3 of the 300–500 μm particles in the upper 100 m and loose 30% of their mass before leaving the upper 200 m. The observed deflation–compression process may have several consequences on the dynamics of appendicularian-derived Marine Snow particles. First, it may explain field observations that Marine Snow sinking velocities increase with depth. Second, an initial rapid loss of weight and particles will decrease the potential vertical flux of particulate carbon due to appendicularians. And finally, the trail of particles and solutes may guide zooplankton to the sinking house, and further increase its degradation due to grazing by detrivorous organisms.