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  • 1
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. Five oligotrophic clear-water lakes on the Faroe Islands were studied during August 2000. Algal and bacterial production rates, community respiration, and CO2 saturation were determined. In addition, we examined the plankton community composition (phytoplankton and heterotrophic nanoflagellates) and measured the grazing pressure exerted by common mixotrophic species on bacteria.2. High respiration to primary production (6.6–33.2) and supersaturation of CO2 (830–2140 μatm) implied that the lakes were net heterotrophic and that the pelagic heterotrophic plankton were subsidised by allochthonous organic carbon. However, in spite of the apparent high level of net heterotrophy, primary production exceeded bacterial production and the food base for higher trophic levels appeared to be mainly autotrophic.3. We suggest that the observed net heterotrophy in these lakes was a result of the oligotrophic conditions and hence low primary production in combination with an input of allochthonous C with a relatively high availability.4. Mixotrophic phytoplankton (Cryptomonas spp., Dinobryon spp. and flagellates cf. Ochromonas spp.) constituted a large percentage of the plankton community (17–83%), possibly as a result of their capacity to exploit bacteria as a means of acquiring nutrients in these nutrient poor systems.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Ecosystems are supported by organic carbon from two distinct sources. Endogenous carbon is produced by photosynthesis within an ecosystem by autotrophic organisms. Exogenous carbon is produced elsewhere and transported into ecosystems. Consumers may use exogenous carbon with consequent ...
    Type of Medium: Electronic Resource
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  • 3
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    ACS (American Chemical Society)
    In:  Environmental Science & Technology, 51 (17). pp. 9747-9755.
    Publication Date: 2021-05-10
    Description: Previous studies report high and increasing iron (Fe) concentrations in boreal river mouths. This Fe has shown relatively high stability to salinity-induced aggregation in estuaries. The aim of this study was to understand how the speciation of Fe affects stability over salinity gradients. For Fe to remain in suspension interactions with organic matter (OM) are fundamental and these interactions can be divided in two dominant phases: organically complexed Fe, and colloidal Fe (oxy)hydroxides, stabilized by surface interactions with OM. The stability of these two Fe phases was tested using mixing experiments with river water and artificial seawater. Fe speciation of river waters and salinity-induced aggregates was determined by synchrotron-based extended X-ray absorption fine structure (EXAFS) spectroscopy. The relative contribution of the two Fe phases varied widely across the sampled rivers. Moreover, we found selective removal of Fe (oxy)hydroxides by aggregation at increasing salinity, while organically complexed Fe was less affected. However, Fe–OM complexes were also found in the aggregates, illustrating that the control of Fe stability is not explained by the prevalence of the respective Fe phases alone. Factors such as colloid size and the chemical composition of the OM may also impact the behavior of Fe species.
    Type: Article , PeerReviewed
    Format: text
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  • 4
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    PANGAEA
    In:  Supplement to: Lenstra, Wytze K; Egger, Matthias; van Helmond, Niels A G M; Kritzberg, Emma; Conley, Daniel J; Slomp, Caroline P (2018): Large variations in iron input to an oligotrophic Baltic Sea estuary: impact on sedimentary phosphorus burial. Biogeosciences, 15(22), 6979-6996, https://doi.org/10.5194/bg-15-6979-2018
    Publication Date: 2023-01-13
    Description: Estuarine sediments are key sites for removal of phosphorus (P) from rivers and the open sea. Vivianite, an Fe(II)-P mineral, can act as a major sink for P in Fe-rich coastal sediments. In this study, we investigate the burial of P in the Öre Estuary in the northern Baltic Sea. We find much higher rates of P burial at our five study sites (up to ∼ 0.145mol m−2 yr−1) when compared to more southern coastal areas in the Baltic Sea with similar rates of sedimentation. Detailed study of the sediment P forms at our site with the highest rate of sedimentation reveals a major role for P associated with Fe and the presence of vivianite crystals below the sulfate methane transition zone. By applying a reactive transport model to sediment and porewater profiles for this site, we show that vivianite may account for up to ∼ 40% of total P burial. With the model, we demonstrate that vivianite formation is promoted in sediments with a low bottom water salinity and high rates of sedimentation and Fe oxide input. While high rates of organic matter input are also required, there is an optimum rate above which vivianite formation declines. Distinct enrichments in sediment Fe and sulfur at depth in the sediment are attributed to short periods of enhanced input of riverine Fe and organic matter. These periods of enhanced input are linked to variations in rainfall on land and follow dry periods. Most of the P associated with the Fe in the sediment is likely imported from the adjacent eutrophic Baltic Proper. Our work demonstrates that variations in land-to-sea transfer of Fe may act as a key control on burial of P in coastal sediments. Ongoing climate change is expected to lead to a decrease in bottom water salinity and contribute to continued high inputs of Fe oxides from land, further promoting P burial as vivianite in the coastal zone of the northern Baltic Sea. This may enhance the role of this oligotrophic area as a sink for P imported from eutrophic parts of the Baltic Sea.
    Type: Dataset
    Format: application/zip, 4 datasets
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  • 5
    Publication Date: 2023-02-07
    Keywords: Acid volatile sulfur; Chromium reducible sulfur; DEPTH, sediment/rock; Iron; Iron oxides; MULT; Multiple investigations; Ore_estuary_20150425_NB8; Ore Estuary; Phosphorus, authigenic; Phosphorus, detrital; Phosphorus, exchangeable; Phosphorus, iron-bound; Phosphorus, organic; Sulfur
    Type: Dataset
    Format: text/tab-separated-values, 414 data points
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  • 6
    Publication Date: 2023-02-07
    Keywords: Aluminium; Date/Time of event; DEPTH, sediment/rock; Event label; Iron, total; Latitude of event; Longitude of event; Manganese, total; MULT; Multiple investigations; Ore_estuary_20150421_NB1; Ore_estuary_20150422_N6_1; Ore_estuary_20150423_N10; Ore_estuary_20150424_N7; Ore_estuary_20150425_NB8; Ore Estuary; Phosphorus, total; Porosity; Sulfur, total
    Type: Dataset
    Format: text/tab-separated-values, 848 data points
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  • 7
    Publication Date: 2023-02-08
    Keywords: Date/Time of event; DEPTH, sediment/rock; Event label; Latitude of event; Longitude of event; Methane; MULT; Multiple investigations; Ore_estuary_20150421_NB1; Ore_estuary_20150422_N6_1; Ore_estuary_20150423_N10; Ore_estuary_20150424_N7; Ore_estuary_20150425_NB8; Ore_estuary_20150804_NB1; Ore_estuary_20150805_N6_1; Ore_estuary_20150806_N10; Ore_estuary_20150807_NB8_1; Ore_estuary_20150808_N7; Ore Estuary
    Type: Dataset
    Format: text/tab-separated-values, 141 data points
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  • 8
    Publication Date: 2023-02-12
    Keywords: Ammonium; Carbon, inorganic, dissolved; Date/Time of event; DEPTH, sediment/rock; Event label; Hydrogen phosphate; Hydrogen sulfide; Iron 2+; Latitude of event; Longitude of event; Manganese 2+; MULT; Multiple investigations; Ore_estuary_20150421_NB1; Ore_estuary_20150422_N6_1; Ore_estuary_20150423_N10; Ore_estuary_20150424_N7; Ore_estuary_20150425_NB8; Ore_estuary_20150804_NB1; Ore_estuary_20150805_N6_1; Ore_estuary_20150806_N10; Ore_estuary_20150807_NB8_1; Ore_estuary_20150808_N7; Ore Estuary; Sulfate
    Type: Dataset
    Format: text/tab-separated-values, 2000 data points
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  • 9
    Publication Date: 2024-03-15
    Description: Coastal ecosystems are subjected to both large natural variability and increasing anthropogenic impact on environmental parameters such as changes in salinity, temperature, and pH. This study documents the distribution of living benthic foraminifera under the influence of multiple environmental stressors in the Skagerrak-Baltic Sea region. Sediment core tops were studied at five sites along a transect from the Skagerrak to the Baltic Sea, with strong environmental gradients, especially in terms of salinity, pH, calcium carbonate saturation and dissolved oxygen concentration in the bottom water and pore water. We found that living foraminiferal densities and species richness were higher at the Skagerrak station, where the general living conditions were relatively beneficial for Foraminifera, with higher salinity and Ωcalc in the water column and higher pH and oxygen concentration in the bottom and pore water. The most common species reported at each station reflect the differences in the environmental conditions between the stations. The dominant species were Cassidulina laevigata and Hyalinea balthica in the Skagerrak, Stainforthia fusiformis, Nonionella aff. stella and Nonionoides turgida in the Kattegat and N. aff. stella and Nonionellina labradorica in the Öresund. The most adverse conditions, such as low salinity, low Ωcalc, low dissolved oxygen concentrations and low pH, were noted at the Baltic Sea stations, where the calcareous tests of the dominant living taxa Ammonia spp. and Elphidium spp. were partially to completely dissolved, probably due to a combination of different stressors affecting the required energy for biomineralization. Even though Foraminifera are able to live in extremely varying environmental conditions, the present results suggest that the benthic coastal ecosystems in the studied region, which are apparently affected by an increase in the range of environmental variability, will probably be even more influenced by a future increase in anthropogenic impacts, including coastal ocean acidification and deoxygenation.
    Keywords: Abundance; Alkalinity, total; Aragonite saturation state; Baltic Sea; Benthos; Bicarbonate ion; Calcite saturation state; Calculated using CO2SYS; Calculated using seacarb after Nisumaa et al. (2010); Carbon, inorganic, dissolved; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Coast and continental shelf; Community composition and diversity; DEPTH, water; Entire community; Field observation; Foraminifera, benthic; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); LATITUDE; LONGITUDE; OA-ICC; Ocean Acidification International Coordination Centre; Oxygen; Oxygen penetration depth; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); pH; Potentiometric titration; Salinity; Shannon Diversity Index; Soft-bottom community; Species; Species richness; Spectrophotometric; Station label; Temperate; Temperature, water; Type of study
    Type: Dataset
    Format: text/tab-separated-values, 4016 data points
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