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Dynamics of Dissolved and Particulate Polyunsaturated Aldehydes in Mesocosms Inoculated with Different Densities of the Diatom Skeletonema marinoi  [PDF]
Charles Vidoudez,Jens Christian Nejstgaard,Hans Henrik Jakobsen,Georg Pohnert
Marine Drugs , 2011, DOI: 10.3390/md9030345
Abstract: A survey of the production of polyunsaturated aldehydes (PUA) of manipulated plankton communities is presented here. PUA are phytoplankton-derived metabolites that are proposed to play an important role in chemically mediated plankton interactions. Blooms of different intensities of the diatom Skeletonema marinoi were generated in eight mesocosms filled with water from the surrounding fjord by adding different amounts of a starting culture and nutrients. This set-up allowed us to follow PUA production of the plankton community over the entire induced bloom development, and to compare it with the natural levels of PUA. We found that S. marinoi is a major source for the particulate PUA 2,4-heptadienal and 2,4-octadienal (defined as PUA released upon wounding of the diatom cells) during the entire bloom development. Just before, and during, the decline of the induced diatom blooms, these PUA were also detected in up to 1 nM concentrations dissolved in the water. In addition, we detected high levels of the PUA 2,4-decadienal that was not produced by the diatom S. marinoi. Particulate decadienal correlated well with the cell counts of the prymnesiophyte Phaeocystis sp. that also developed in the fertilized mesocosms. Particulate decadienal levels were often even higher than those of diatom-derived PUA, indicating that PUA sources other than diatoms should be considered when it comes to the evaluation of the impact of these metabolites.
Phytoplankton Cell Lysis Associated with Polyunsaturated Aldehyde Release in the Northern Adriatic Sea  [PDF]
Fran?ois Ribalet, Mauro Bastianini, Charles Vidoudez, Francesco Acri, John Berges, Adrianna Ianora, Antonio Miralto, Georg Pohnert, Giovanna Romano, Thomas Wichard, Raffaella Casotti
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0085947
Abstract: Diatoms are able to react to biotic and abiotic stress, such as competition, predation and unfavorable growth conditions, by producing bioactive compounds including polyunsaturated aldehydes (PUAs). PUAs have been shown to act against grazers and either enhance or inhibit the growth of different phytoplankton and bacteria both in culture and in the field. Presence of nanomolar concentrations of dissolved PUAs in seawater has been reported in the North Adriatic Sea (Mediterranean), suggesting that these compounds are released in seawater following diatom cell lysis. However, the origin of the PUAs and their effects on natural phytoplankton assemblages remain unclear. Here we present data from four oceanographic cruises that took place during diatom blooms in the northern Adriatic Sea where concentrations of particulate and dissolved PUAs were monitored along with phytoplankton cell lysis. Cell lysis was positively correlated with both concentrations of particulate and dissolved PUAs (R = 0.69 and R = 0.77, respectively), supporting the hypothesis that these compounds are released by cell lysis. However, the highest concentration of dissolved PUAs (2.53 nM) was measured when cell lysis was high (0.24 d?1) but no known PUA-producing diatoms were detected, suggesting either that other organisms can produce PUAs or that PUA-producing enzymes retain activity extracellularly after diatom cells have lysed. Although in situ concentrations of dissolved PUAs were one to three orders of magnitude lower than those typically used in laboratory culture experiments, we argue that concentrations produced in the field could induce similar effects to those observed in culture and therefore may help shape plankton community composition and function in the oceans.
Removal of both dissolved and particulate iron from groundwater  [PDF]
K. Teunissen,A. Abrahamse,H. Leijssen,L. Rietveld
Drinking Water Engineering and Science Discussions , 2008,
Abstract: Iron is the primary source for discolouration problems in the drinking water distribution system. The removal of iron from groundwater is a common treatment step in the production of drinking water. Even when clear water meets the drinking water standards, the water quality in the distribution system can deteriorate due to settling of iron (hydroxide) particles or post-treatment flocculation of dissolved iron. Therefore it is important to remove dissolved and particulate iron to a large extent. This paper describes the study towards the current iron removal processes and experimental work towards improving removal of dissolved and particulate iron. The study was carried out at groundwater treatment plant Harderbroek, consisting of aeration, rapid sand filtration and tower aeration. The research contains two parts: 1) a particle fingerprint of the treatment, resulting in a quantification of particles breaking through the rapid sand filtration. 2) Small column experiments on the oxidation and filterability of iron. The fingerprint showed that operational events such as switching on/off of filters and backwashing have a significant impact on the volume concentration of particles breaking through the filter. A frequency plot of the different size ranges of particles indicates that mainly the filterability of the middle size ranges (2–7 μm) of particles was influenced by switching a filter on/off. A backwash event mainly affects the bigger particle size ranges. The column experiments showed that in the cascade effluent the majority of the iron is dissolved iron(II), indicating that the oxidation of iron(II) to iron(III) is the rate determining step at Harderbroek, which is limited by pH. Dosing caustic soda resulted in a significant increase of the oxidation rate and improved the removal of iron(II) in the column. Crushed limestone filtration gave promising results, but the contact time applied was too short to completely oxidize iron(II).
Diatom Derived Polyunsaturated Aldehydes Do Not Structure the Planktonic Microbial Community in a Mesocosm Study  [PDF]
Carsten Paul,Anna Reunamo,Elin Lindehoff,Johanna Bergkvist,Michaela A. Mausz,Henrik Larsson,Hannes Richter,Sten-?ke W?ngberg,Piia Leskinen,Ulf B?mstedt,Georg Pohnert
Marine Drugs , 2012, DOI: 10.3390/md10040775
Abstract: Several marine and freshwater diatoms produce polyunsaturated aldehydes (PUA) in wound-activated processes. These metabolites are also released by intact diatom cells during algal blooms. Due to their activity in laboratory experiments, PUA are considered as potential mediators of diatom-bacteria interactions. Here, we tested the hypothesis that PUA mediate such processes in a close-to-field mesocosm experiment. Natural plankton communities enriched with Skeletonema marinoi strains that differ in their PUA production, a plankton control, and a plankton control supplemented with PUA at natural and elevated concentrations were observed. We monitored bacterial and viral abundance as well as bacterial community composition and did not observe any influence of PUA on these parameters even at elevated concentrations. We rather detected an alternation of the bacterial diversity over time and differences between the two S. marinoi strains, indicating unique dynamic bacterial communities in these algal blooms. These results suggest that factors other than PUA are of significance for interactions between diatoms and bacteria.
Diatom-Derived Polyunsaturated Aldehydes Activate Cell Death in Human Cancer Cell Lines but Not Normal Cells  [PDF]
Clementina Sansone, Alessandra Braca, Elena Ercolesi, Giovanna Romano, Anna Palumbo, Raffaella Casotti, Maria Francone, Adrianna Ianora
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0101220
Abstract: Diatoms are an important class of unicellular algae that produce bioactive polyunsaturated aldehydes (PUAs) that induce abortions or malformations in the offspring of invertebrates exposed to them during gestation. Here we compare the effects of the PUAs 2-trans,4-trans-decadienal (DD), 2-trans,4-trans-octadienal (OD) and 2-trans,4-trans-heptadienal (HD) on the adenocarcinoma cell lines lung A549 and colon COLO 205, and the normal lung/brunch epithelial BEAS-2B cell line. Using the viability MTT/Trypan blue assays, we show that PUAs have a toxic effect on both A549 and COLO 205 tumor cells but not BEAS-2B normal cells. DD was the strongest of the three PUAs tested, at all time-intervals considered, but HD was as strong as DD after 48 h. OD was the least active of the three PUAs. The effect of the three PUAs was somewhat stronger for A549 cells. We therefore studied the death signaling pathway activated in A549 showing that cells treated with DD activated Tumor Necrosis Factor Receptor 1 (TNFR1) and Fas Associated Death Domain (FADD) leading to necroptosis via caspase-3 without activating the survival pathway Receptor-Interacting Protein (RIP). The TNFR1/FADD/caspase pathway was also observed with OD, but only after 48 h. This was the only PUA that activated RIP, consistent with the finding that OD causes less damage to the cell compared to DD and HD. In contrast, cells treated with HD activated the Fas/FADD/caspase pathway. This is the first report that PUAs activate an extrinsic apoptotic machinery in contrast to other anticancer drugs that promote an intrinsic death pathway, without affecting the viability of normal cells from the same tissue type. These findings have interesting implications also from the ecological viewpoint considering that HD is one of the most common PUAs produced by diatoms.
Dissolved organic carbon (DOC) and select aldehydes in cloud and fog water: the role of the aqueous phase in impacting trace gas budgets
B. Ervens,Y. Wang,J. Eagar,W. R. Leaitch
Atmospheric Chemistry and Physics Discussions , 2012, DOI: 10.5194/acpd-12-33083-2012
Abstract: Cloud and fog droplets efficiently scavenge and process water-soluble compounds and thus modify the chemical composition of the gas and particle phases. The concentrations of dissolved organic carbon (DOC) in the aqueous phase reach concentrations on the order of ~10 mg C L 1 which is typically on the same order of magnitude as the sum of inorganic anions. Aldehydes and carboxylic acids typically comprise a large fraction of DOC because of their high solubility. The dissolution of species in the aqueous phase can lead to (i) the removal of species from the gas phase preventing their processing by gas phase reactions (e.g. photolysis of aldehydes) and (ii) the formation of unique products that do not have any efficient gas phase sources (e.g. dicarboxylic acids). We present measurements of DOC and select aldehydes in fog water at high elevation and intercepted clouds in a biogenically-impacted location (Whistler, Canada) and in fog water in a more polluted area (Davis, CA). Concentrations of formaldehyde, glyoxal and methylglyoxal were in the micromolar range and comprised ≤2% each individually of the DOC. Comparison of the DOC and aldehyde concentrations to those at other locations shows good agreement and reveals highest levels for both in anthropogenically impacted regions. Based on this overview, we conclude that the fraction of organic carbon (dissolved and insoluble inclusions) in the aqueous phase comprises 1–~40% of total organic carbon. Higher values are observed to be associated with aged air masses where organics are expected to be more highly oxidized and thus more soluble. Accordingly, the aqueous/gas partitioning ratio expressed here as an effective Henry's law constant for DOC (KH*DOC) increases by an order of magnitude from 7×103 M atm 1 to 7×104 M atm 1 during the ageing of air masses. The measurements are accompanied by photochemical box model simulations. They suggest that the scavenging of aldehydes by the aqueous phase can reduce HO2 gas phase levels by two orders of magnitude due to a weaker net source of HO2 production from aldehyde photolysis in the gas phase. Despite the high solubility of dialdehydes (glyoxal, methylglyoxal), their impact on the HO2 budget by scavenging is <10% of that of formaldehyde. The overview of DOC and aldehyde measurements presented here reveals that clouds and fogs can be efficient sinks for organics, with increasing importance in aged air masses. Even though aldehydes, specifically formaldehyde, only comprise ~1% of DOC, their scavenging and processing in the aqueous phase might translate into signific
Dissolved and particulate primary production along a longitudinal gradient in the Mediterranean Sea
D. C. López-Sandoval, A. Fernández,E. Mara ón
Biogeosciences (BG) & Discussions (BGD) , 2011,
Abstract: We have determined the photosynthetic production of dissolved (DOCp) and particulate organic carbon (POCp) along a longitudinal transect in the Mediterranean Sea during the summer stratification period. The euphotic layer-integrated rates of DOCp and POCp ranged between approximately 50–130 and 95–210 mgC m 2 d 1, respectively, and showed an east to west increasing trend. For the whole transect, the relative contribution of DOCp to total, euphotic layer-integrated primary production (percentage of extracellular release, PER) averaged ~37% and did not show any clear longitudinal pattern. In spite of the relatively high PER values, the measured DOCp rates were much lower than the estimated bacterial carbon demand, suggesting a small degree of coupling between phytoplankton exudation and bacterial metabolism. Our results, when compared with previous measurements obtained with the same methods in several ecosystems of contrasting productivity, support the view that the relative importance of DOCp increases under strong nutrient limitation.
Dissolved and particulate primary production along a longitudinal gradient in the Mediterranean Sea  [PDF]
D. C. López-Sandoval,A. Fernández,E. Mara?ón
Biogeosciences (BG) & Discussions (BGD) , 2011, DOI: 10.5194/bg-8-815-2011
Abstract: We have determined the photosynthetic production of dissolved (DOCp) and particulate organic carbon (POCp) along a longitudinal transect in the Mediterranean Sea during the summer stratification period. The euphotic layer-integrated rates of DOCp and POCp ranged between approximately 50–130 and 95–210 mgC m 2 d 1, respectively, and showed an east to west increasing trend. For the whole transect, the relative contribution of DOCp to total, euphotic layer-integrated primary production (percentage of extracellular release, PER) averaged ~37% and did not show any clear longitudinal pattern. In spite of the relatively high PER values, the measured DOCp rates were much lower than the estimated bacterial carbon demand, suggesting a small degree of coupling between phytoplankton exudation and bacterial metabolism. Our results, when compared with previous measurements obtained with the same methods in several ecosystems of contrasting productivity, support the view that the relative importance of DOCp increases under strong nutrient limitation.
Dissolved and particulate primary production along a longitudinal gradient in the Mediterranean Sea
D. C. López-Sandoval,A. Fernández,E. Mara?ón
Biogeosciences Discussions , 2010, DOI: 10.5194/bgd-7-8591-2010
Abstract: We have determined the photosynthetic production of dissolved (DOCp) and particulate organic carbon (POCp) along a longitudinal transect in the Mediterranean Sea during the summer stratification period. The euphotic layer-integrated rates of DOCp and POCp ranged between approximately 50–130 and 95–210 mgC m 2 d 1, respectively, and showed an east to west increasing trend. For the whole transect, the relative contribution of DOCp to total, euphotic layer-integrated primary production (percentage of extracellular release, PER) averaged ~37% and did not show any clear longitudinal pattern. In spite of the relatively high PER values, the measured DOCp rates were much lower than the estimated bacterial carbon demand, suggesting a small degree of coupling between phytoplankton exudation and bacterial metbolism. Our results, when compared with previous measurements obtained with the same methods in several ecosystems of contrasting productivity, support the view that the relative importance of DOCp increases under strong nutrient limitation.
Rare earth element concentrations in dissolved and acid available particulate forms for eastern UK rivers
C. Neal
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2007,
Abstract: Variations in concentration of yttrium (Y), lanthanum (La), cerium (Ce), neodymium (Nd), samarium (Sm) and gadolinium (Gd) among rivers of eastern England and the border with Scotland are described in relation to the dissolved (<0.45 μM) fraction and acid-available particulate (AAP) fractions. The rivers cover a range of rural, agricultural and urban/industrial environments. Yttrium and the lanthanides show significant levels of both dissolved and acid-available particulate forms (typically about 40% in the dissolved form). For the dissolved phase, Y and the lanthanides are linearly correlated with each other and with iron: most of this dissolved component may be in a micro-particulate/colloidal form. The Y and lanthanide relationships show marked scatter and there are anomalously high La concentrations at times for the rivers Great Ouse, Thames and Wear that are probably linked to pollutant sources. For the Ouse, and especially for one of its tributaries, the Swale, relatively high Sm concentrations are probably associated with mineralisation within the catchment and contamination of the associated flood plain. For the AAP components, there are strong linear relationships with Y and the lanthanides across all the rivers. There is also a strong link between these AAP associated REE and AAP iron, although the scatter is greater and the industrial rivers have a lower lanthanide to iron ratio, probably due to iron-rich contaminants.
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