Nutrient turnover at the sediment/water interface in shallow eutrophic coastal waters

The nutrient situation in eutrophic shallow coastal water systems is characterized by particular features. In addition to water exchange with the open sea, interactions at the sediment/water interface play a significant role. With the help of investigation on phosphate sorption/desorption balances and on the denitrification capacity of shallow coastal waters, the following general conclusions can be made: The phosphate concentrations in the water are primarily determined by physico-chemical reactions with the sediment, and less by the rhythm of the phytoplankton primary production. Through intensive interactions between sediment and water, a phosphate "equilibrium" concentration which fluctuates very little is maintained over the whole year. High primary production rates are possible at these low equilibrium concentrations of phosphate. The phosphate sorption capacity of sediments is a characteristic parameter of shallow systems. Sediments with a high organic matter content exhibit the highest phosphate sorption capacities. With the development of nearly anearobic conditions, nitrate reduction can occur at a rate, when the appropriate amount of nitrate is made available to the reaction. Under optimal conditions for nitrate reduction, nitrate concentration is also not a parameter characterizing the nature of the water body

Nitrous oxide water column distribution during the transition from anoxic to oxic conditions in the Baltic Sea

International audienceIn January 2003, a major inflow of cold and oxygen-rich North Sea Water in the Baltic Sea terminated an ongoing stagnation period in parts of the central Baltic Sea. In order to investigate the role of North Sea Water inflow to the Baltic Sea with regard to the production of nitrous oxide (N2O), we measured dissolved and atmospheric N2O at 26 stations in the southern and central Baltic Sea in October 2003. At the time of our cruise, water renewal had proceeded to the eastern Gotland Basin, whereas the western Gotland Basin was still unaffected by the inflow. The deep water renewal was detectable in the distributions of temperature, salinity, and oxygen concentrations as well as in the distribution of the N2O concentrations: Shallow stations in the Kiel Bight and Pomeranian Bight were well-ventilated with uniform N2O concentrations near equilibrium throughout the water column. In contrast, stations in the deep basins, such as the Bornholm and the Gotland Deep, showed a clear stratification with deep water affected by North Sea Water. Inflowing North Sea Water led to changed environmental conditions, especially enhanced oxygen (O2) or declining hydrogen sulfide (H2S) concentrations, thus, affecting the conditions for the production of N2O. Pattern of N2O profiles and correlations with parameters like oxygen and nitrate differed between the basins. The dominant production pathway seems to be nitrification rather than denitrification. No indications for advection of N2O by North Sea Water were found. A rough budget revealed a significant surplus of in situ produced N2O after the inflow. However, due to the permanent halocline, it can be assumed that the formed N2O does not reach the atmosphere. Hydrographic aspects therefore are decisive factors determining the final release of produced N2O to the atmosphere

Distribution of N₂O in the Baltic Sea during transition from anoxic to oxic conditions

In January 2003, a major inflow of cold and oxygen-rich North Sea Water terminated an ongoing stagnation period in parts of the central Baltic Sea. In order to investigate the role of North Sea Water inflow in the production of nitrous oxide (N2O), we measured dissolved and atmospheric N<2O at 26 stations in the southern and central Baltic Sea in October 2003. At the time of our cruise, water renewal had proceeded to the eastern Gotland Basin, whereas the western Gotland Basin was still unaffected by the inflow. The deep water renewal was detectable in the distributions of temperature, salinity, and oxygen concentrations as well as in the distribution of the N2O concentrations: Shallow stations in the Kiel Bight and Pomeranian Bight were well-ventilated with uniform N2O concentrations near equilibrium throughout the water column. In contrast, stations in the deep basins, such as the Bornholm and the Gotland Deep, showed a clear stratification with deep water affected by North Sea Water. Inflowing North Sea Water led to changed environmental conditions, especially enhanced oxygen (O2) or declining hydrogen sulphide (H2S) concentrations, thus, affecting the conditions for the production of N2O. Pattern of N2O profiles and correlations with parameters like oxygen and nitrate differed between the basins. Because of the positive correlation between ΔN2O and AOU in oxic waters the dominant production pathway seems to be nitrification rather than denitrification. Advection of N2O by North Sea Water was found to be of minor importance. A rough budget revealed a significant surplus of in situ produced N2O after the inflow. However, due to the permanent halocline, it can be assumed that the N2O produced does not reach the atmosphere. Hydrographic aspects therefore are decisive factors determining the final release of N2O produced to the atmosphere

Differences in the faecal microbiome in Schistosoma haematobium infected children vs. uninfected children

BACKGROUND: Several infectious diseases and therapeutic interventions cause gut microbe dysbiosis and associated pathology. We characterised the gut microbiome of children exposed to the helminth Schistosoma haematobium pre- and post-treatment with the drug praziquantel (PZQ), with the aim to compare the gut microbiome structure (abundance and diversity) in schistosome infected vs. uninfected children. METHODS: Stool DNA from 139 children aged six months to 13 years old; with S. haematobium infection prevalence of 27.34% was extracted at baseline. 12 weeks following antihelminthic treatment with praziqunatel, stool DNA was collected from 62 of the 139 children. The 16S rRNA genes were sequenced from the baseline and post-treatment samples and the sequence data, clustered into operational taxonomic units (OTUs). The OTU data were analysed using multivariate analyses and paired T-test. RESULTS: Pre-treatment, the most abundant phyla were Bacteroidetes, followed by Firmicutes and Proteobacteria respectively. The relative abundance of taxa among bacterial classes showed limited variation by age group or sex and the bacterial communities had similar overall compositions. Although there were no overall differences in the microbiome structure across the whole age range, the abundance of 21 OTUs varied significantly with age (FDR<0.05). Some OTUs including Veillonella, Streptococcus, Bacteroides and Helicobacter were more abundant in children ≤ 1 year old compared to older children. Furthermore, the gut microbiome differed in schistosome infected vs. uninfected children with 27 OTU occurring in infected but not uninfected children, for 5 of these all Prevotella, the difference was statistically significant (p <0.05) with FDR <0.05. PZQ treatment did not alter the microbiome structure in infected or uninfected children from that observed at baseline. CONCLUSIONS: There are significant differences in the gut microbiome structure of infected vs. uninfected children and the differences were refractory to PZQ treatment

Distribution of methane in the water column of the Baltic Sea

The distribution of dissolved methane in the water column of the Baltic Sea was extensively investigated. A strong correlation between the vertical density stratification, the distribution of oxygen, hydrogen sulfide, and methane has been identified. A widespread release of methane from the seafloor is indicated by increasing methane concentrations with water depth. The deep basins in the central Baltic Sea show the strongest methane enrichments in stagnant anoxic water bodies (max. 1086 nM and 504 nM, respectively), with a pronounced decrease towards the pelagic redoxcline and slightly elevated surface water concentrations (saturation values of 206% and 120%, respectively). In general the more limnic basins in the northern part of the Baltic are characterized by lower water column methane concentrations and surface water saturation values close to the atmospheric equilibrium (between 106% and 116%). In contrast, the shallow Western Baltic Sea is characterized by high saturation values up to 746%

Nikola Vranješ, Na pragu vječnosti. Promišljanja o pastoralu umirućih, Glas Koncila, Zagreb, 2015.

Biogeochemical cycles of carbon, nutrients, and oxygen transmit mean states, trends and variations of the physical realm in coastal upwelling systems to their food webs and determine their role in regional budgets of greenhouse gases. This contribution focuses on biogeochemical processes in the northern Benguela Upwelling System (NBUS), where low oxygen levels in upwelling source water are a major influence on carbon and nutrient cycles. Based on measurements during numerous expeditions and results of 3-D regional ecosystem modeling (project GENUS; Geochemistry and Ecology of the Namibian Upwelling System) we here examine source water character, effects of low oxygen conditions on nutrient masses and ratios, and of diazotrophic N2-fixation on productivity of the system and its transition to the adjacent eastern South Atlantic. In available observations, the effects of denitrification in water and sediment and phosphate release from sediments are minor influences on nitrate:phosphate ratios of the system, and excess phosphate in aged upwelling water is inherited from upwelling source water. Contrary to expectation and model results, the low N:P ratios do not trigger diazotrophic N2-fixation in the fringes of the upwelling system, possibly due to a lack of seeding populations of Trichodesmium. We also examine the flux of carbon from the sea surface to either sediment, the adjacent sub-thermocline ocean, or to regenerated nutrients and CO2. Observed fluxes out of the surface mixed layer are significantly below modeled fluxes, and suggest that regeneration of nutrients and CO2 is unusually intense in the mixed layer. This contributes to very high fluxes of CO2 from the ocean to the regional atmosphere, which is not compensated for by N2-fixation. Based on observations, the NBUS thus is a significant net CO2 source (estimated at 14.8 Tg C a− 1), whereas the CO2 balance is closed by N2-fixation in the model. Methane concentrations were low in surface waters in on-line measurements during 1 expedition, and based on these our estimate for the emission of methane for the entire Benguela system is below 0.2 Tg CH4 a− 1

Effect of elevated CO2 on organic matter pools and fluxes in a summer Baltic Sea plankton community

Ocean acidification is expected to influence plankton community structure and biogeochemical element cycles. To date, the response of plankton communities to elevated CO2 has been studied primarily during nutrient-stimulated blooms. In this CO2 manipulation study, we used large-volume (similar to 55 m(3)) pelagic in situ mesocosms to enclose a natural summer, post-spring-bloom plankton assemblage in the Baltic Sea to investigate the response of organic matter pools to ocean acidification. The carbonate system in the six mesocosms was manipulated to yield average fCO(2) ranging between 365 and similar to 1230 mu atm with no adjustment of naturally available nutrient concentrations. Plankton community development and key biogeochemical element pools' were subsequently followed in this nitrogen-limited ecosystem over a period of 7 weeks. We observed higher sustained chlorophyll a and particulate matter concentrations (similar to 25% higher) and lower inorganic phosphate concentrations in the water column in the highest fCO(2) treatment (1231 mu atm) during the final 2 weeks of the study period (Phase III), when there was low net change in particulate and dissolved matter pools. Size-fractionated phytoplankton pigment analyses indicated that these differences were driven by picophytoplankton (<2 mu m) and were already established early in the experiment during an initial warm and more productive period with overall elevated chlorophyll a and particulate matter concentrations. However, the influence of picophyto-plankton on bulk organic matter pools was masked by high biomass of larger plankton until Phase III, when the contribution of the small size fraction (<2 mu m) increased to up to 90% of chlorophyll a. In this phase, a CO2-driven increase in water column particulate carbon did not lead to enhanced sinking material flux but was instead reflected in increased dissolved organic carbon concentrations. Hence ocean acidification may induce changes in organic matter partitioning in the upper water column during the low-nitrogen summer period in the Baltic Sea.Peer reviewe

Cytokine responses to the anti-schistosome vaccine candidate antigen glutathione-S-transferase vary with host age and are boosted by praziquantel treatment.

BACKGROUND: Improved helminth control is required to alleviate the global burden of schistosomiasis and schistosome-associated pathologies. Current control efforts rely on the anti-helminthic drug praziquantel (PZQ), which enhances immune responses to crude schistosome antigens but does not prevent re-infection. An anti-schistosome vaccine based on Schistosoma haematobium glutathione-S-transferase (GST) is currently in Phase III clinical trials, but little is known about the immune responses directed against this antigen in humans naturally exposed to schistosomes or how these responses change following PZQ treatment. METHODOLOGY: Blood samples from inhabitants of a Schistosoma haematobium-endemic area were incubated for 48 hours with or without GST before (n = 195) and six weeks after PZQ treatment (n = 107). Concentrations of cytokines associated with innate inflammatory (TNFα, IL-6, IL-8), type 1 (Th1; IFNγ, IL-2, IL-12p70), type 2 (IL-4, IL-5, IL-13), type 17 (IL-17A, IL-21, IL-23p19) and regulatory (IL-10) responses were quantified in culture supernatants via enzyme-linked immunosorbent assay (ELISA). Factor analysis and multidimensional scaling were used to analyse multiple cytokines simultaneously. PRINCIPAL FINDINGS: A combination of GST-specific type 2 (IL-5 and IL-13) and regulatory (IL-10) cytokines was significantly lower in 10-12 year olds, the age group at which S. haematobium infection intensity and prevalence peak, than in 4-9 or 13+ year olds. Following PZQ treatment there was an increase in the number of participants producing detectable levels of GST-specific cytokines (TNFα, IL-6, IL-8, IFNγ, IL-12p70, IL-13 and IL-23p19) and also a shift in the GST-specific cytokine response towards a more pro-inflammatory phenotype than that observed before treatment. Participant age and pre-treatment infection status significantly influenced post-treatment cytokine profiles. CONCLUSIONS/SIGNIFICANCE: In areas where schistosomiasis is endemic host age, schistosome infection status and PZQ treatment affect the cellular cytokine response to GST. Thus the efficacy of a GST-based vaccine may also be shaped by the demographic and epidemiological characteristics of targeted populations

Changes in cGMP Levels Affect the Localization of EGL-4 in AWC in Caenorhabditis elegans

The Protein Kinase G, EGL-4, is required within the C. elegans AWC sensory neurons to promote olfactory adaptation. After prolonged stimulation of these neurons, EGL-4 translocates from the cytosol to the nuclei of the AWC. This nuclear translocation event is both necessary and sufficient for adaptation of the AWC neuron to odor. A cGMP binding motif within EGL-4 and the Gα protein ODR-3 are both required for this translocation event, while loss of the guanylyl cyclase ODR-1 was shown to result in constitutively nuclear localization of EGL-4. However, the molecular changes that are integrated over time to produce a stably adapted response in the AWC are unknown. Here we show that odor-induced fluctuations in cGMP levels in the adult cilia may be responsible in part for sending EGL-4 into the AWC nucleus to produce long-term adaptation. We found that reductions in cGMP that result from mutations in the genes encoding the cilia-localized guanylyl cyclases ODR-1 and DAF-11 result in constitutively nuclear EGL-4 even in naive animals. Conversely, increases in cGMP levels that result from mutations in cGMP phosphodiesterases block EGL-4 nuclear entry even after prolonged odor exposure. Expression of a single phosphodiesterase in adult, naive animals was sufficient to modestly increase the number of animals with nuclear EGL-4. Further, coincident acute treatment of animals with odor and the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX) decreased the number of animals with nuclear EGL-4. These data suggest that reducing cGMP levels in AWC is necessary and even partially sufficient for nuclear translocation of EGL-4 and adaptation as a result of prolonged odor exposure. Our genetic analysis and chemical treatment of C. elegans further indicate that cilia morphology, as defined by fluorescent microscopic observation of the sensory endings, may allow for odor-induced fluctuations in cGMP levels and this fluctuation may be responsible for sending EGL-4 into the AWC nucleus