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  • 1
    Electronic Resource
    Electronic Resource
    Sulphate reduction and sulphur cycling in lake sediments: a review (2001)
    Oxford UK : Blackwell Science Ltd
    Freshwater biology 46 (2001), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. The concentration of sulphate is low in lakes and sulphur cycling has often been neglected in studies of organic matter diagenesis in lake sediments. The cycling of sulphur is, however, both spatially and temporally dynamic and strongly influences many biogeochemical reactions in sediments, such as the binding of phosphorus. This review examines the control of sulphate reduction and sulphur cycling in sediments of lakes with different trophic status.2. The factors that control the rate of sulphate reduction have not been identified with certainty in the various environments because many factors are involved, e.g. oxygen and sulphate concentrations, temperature and organic matter availability.3. Sulphate reduction is less significant under oligotrophic conditions, where mineralization is dominated by oxic decomposition. The supply of organic matter may not be sufficient to support sulphate reduction in the anoxic parts of sediments and, also, sulphate availability may control the rate as the concentration is generally low in oligotrophic lakes.4. There is a potential for significant sulphate reduction in eutrophic lakes, as both the availability of organic matter and sulphate concentration are often higher than in oligotrophic lakes. Sulphate is rapidly depleted with sediment depth, however, and methanogenesis is generally the most important process in overall carbon mineralization. Sulphate reduction is generally low in acidic lakes because of low sulphate availability and reduced microbial activity.5. It is still unclear which of the forms of sulphur deposits are the most important and under which conditions burial occurs. Sulphur deposition is controlled by the rate of sulphate reduction and reoxidation. Reoxidation of sulphides occurs rapidly through several pathways, both under oxic and anoxic conditions. Only a few studies have been able to examine the importance of reoxidation, but it is hypothesized that most of the reoxidation takes place under anoxic conditions and that disproportionation is often involved. The presence of sulphide oxidizing bacteria, benthic fauna and rooted macrophytes may substantially enhance oxic reoxidation. Deposition of sulphur is generally higher in eutrophic than in oligotrophic lakes because of a number of factors: a higher rate of sulphate reduction, enhanced sedimentation of organic sulphur and less reoxidation as a result of reduced penetration of oxygen into the sediments, a lack of faunal activity and rooted macrophytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.2001.00687.x
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Organic matter mineralization in an organic-rich sediment: Experimental stimulation of sulfate reduction by fish food pellets (1994)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 14 (1994), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The combined effects of organic matter additions and temperature on short chain fatty acid (SCFA) turnover, sulfate reduction and nutrient accumulation were examined in an organic-rich fish farm sediment. Fish food pellets, which contribute significantly to the organic matter loss from fish farms, were added to surface sediment at three loadings (2.8; 14.0; 28.0 mg ww g−1 ww sediment; equivalent to organic matter loadings measured during fish farming) and incubated for 30 days in anaerobic bags at 5°C and 15°C. SCFA accumulated to high levels (acetate up to 85 mM, propionate up to 17 mM, butyrate up to 25 mM) in sediments amended with food pellets, and sulfate reduction was stimulated up to 30 times relative to unamended sediments. Sulfate reducers appeared saturated with substrates (SCFA) even in the lowest additions. A low C/N ratio (0.4–1.8) of the major mineralization products (TCO2 and NH4+) indicated preferential nitrogen mineralization in amended sediment compared with the total particulate pool (C/N = 8.8–11.9) and added food pellets (C/N = 8.4).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.1994.tb00088.x
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  • 3
    Electronic Resource
    Electronic Resource
    Interferences between root plaque formation and phosphorus availability for isoetids in sediments of oligotrophic lakes (1998)
    Springer
    Biogeochemistry 43 (1998), S. 107-128 
    Details
    ISSN: 1573-515X
    Keywords: iron ; Isoetes lacustris ; Littorella uniflora ; manganese ; phosphorus pools ; redox potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Freshwater isoetids exchanges a high proportion of the photosynthetically produced oxygen over the extensive root system and, therefore, they influence the redox potential (Eh) and phosphorus (P) availability in their sediments. Because isoetids rely on the sediment for P uptake, P may be a key element in controlling the distribution of isoetids. We investigated biomass and P availability to isoetids (Littorella uniflora and Isoetes lacustris) in a transect of five stations across the littoral zone in oligotrophic Lake Kalgaard, Denmark. At the two shallowest stations (0.6 and 1.0 m depth) the redox potential in the low organic rhizosphere sediment was high (〉300 mV) and low concentrations of reduced exchangeable iron (Fe) and manganese (Mn) compounds in the sediment and of precipitated Fe and Mn oxides on isoetid roots (plaques) were found. The concentration of sediment P pools was low and so was isoetid P content and isoetid biomass. At intermediate water depth (1.8 m) sediment Eh was high (∼300 mV) and isoetids showed low root plaque concentrations. However, higher concentration of P pools in the rhizosphere was found at 1.8 m and isoetids showed the highest P content and biomass. At deeper stations (2.8 and 4.6 m depth) Eh was low (〈100 mV) in the high organic rhizosphere and high concentrations of plaques were found. The P content in the sediment was high, however, isoetids showed low biomass and low P content. We suggest that the low P content in isoetids growing on P rich organic sediments is partly due to inhibition of the P uptake because of adsorption of P to the oxidized Fe and Mn plaques. However, ratios between oxidized Fe and Fe-bound P, 150 for plaques and 40 for sediment, suggest the isoetids are able to access some of the P that is bound in the plaques. The pools of dissolved P in the porewater were 25–1100 times lower than the estimated annual P requirement for net growth of isoetids while solid fraction P pools were 20–260 times higher than the estimated annual P requirement. Clearly, the oxygen release from isoetid roots decreases the availability of P either by keeping the entire rhizosphere oxidized (low organic sediments) or by the formation of root plaques (high organic sediments).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006010502422
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  • 4
    Electronic Resource
    Electronic Resource
    Biogeochemical cycling of sulfur and iron in sediments of a south-east Asian mangrove, Phuket Island, Thailand (1994)
    Springer
    Biogeochemistry 26 (1994), S. 145-161 
    Details
    ISSN: 1573-515X
    Keywords: mangrove sediments ; sulfate reduction ; sulfur and iron dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Benthic sulfate reduction and sediment pools of sulfur and iron were examined during January 1992 at 3 stations in the Ao Nam Bor mangrove, Phuket, Thailand. Patterns of sulfate reduction rates (0–53 cm) reflected differences in physical and biological conditions at the 3 stations, and highest rates were found at the vegetated site within the mangrove (Rhizophora apiculata) forest. Due to extended oxidation of mangrove sediments, a large portion of the added35S-label was recovered in the chromium reducible pools (FeS2 and S0) (41–91% of the reduced sulfur). Pyrite was the most important inorganic sulfur component, attaining pool sizes 50–100 times higher than acid volatile pools (FeS). HCl-extractable (0.5 M HCl) iron pools, including Fe(II)HCl and Fe(III)HCl, were generally low and Fe(III)HCl was only present in the upper surface layers (0–5 cm). Maximum concentrations of dissolved Fe2+ (35–285 μM) occurred just about the depth where dissolved ΣH2S accumulated. Furthermore Fe2+ and ΣH2S coexisted only where concentrations of both were low. There was an accumulation of organic sulfur in the deep sediment at 2 stations in the inner part of the mangrove. The reoxidation of reduced sulfides was rapid, and storage of sulfur was minor in the upper sediment layers, where factors like bioturbation, the presence of roots, or tidal mixing enhance oxidation processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00002904
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  • 5
    Electronic Resource
    Electronic Resource
    Seasonality of sulfate reduction and pore water solutes in a marine fish farm sediment: the importance of temperature and sedimentary organic matter (1996)
    Springer
    Biogeochemistry 32 (1996), S. 15-39 
    Details
    ISSN: 1573-515X
    Keywords: fish farm sediment ; carbon mineralization ; sulfate reduction ; acetate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Sulfate reduction and pore water solutes related to sulfur cycling and anaerobic processes (short chain fatty acids (SCFA), SO4 2−, TCO2, NH4 +, dissolved sulfides (∑H2S) and CH4) were examined during one year at a marine fish farm. Mineralization of fish farm waste products was rapid in this non-bioturbated, organic rich sediment. Stimulation of sulfate reduction rates (SRR) occurred primarily in the surface layers where the organic matter was deposited. Acetate was the most important (〈99%) of the measured SCFA attaining high concentrations during summer months (up to 4.7 mM). The acetate profiles exhibited distinct seasonal cycles, where periods with high concentrations in the pore waters were found coincident with a high pool of particulate organic matter in the surface sediments and a low activity of the sulfate reducing bacteria (early spring and late summer). Periods with low acetate pools occurred when sulfate reduction rates were high in early summer and in winter were pools of particulate organic matter were decreasing. Methane production was observed concurrent with sulfate reduction in the microbial active surface layers in late summer. Subsurface peaks of SO4 2−, TCO2, NH4 + and ∑H2S were evident in July and August due to rapid mineralization in these surface layers. With decreasing autumn water temperatures mineralization rates declined and subsurface peaks of these solutes disappeared. A strong relationship was found between pore water TCO2, and NH4 +. Ratios between TCO2, and NH4 + were low compared to a control site, attaining minimum values in mid-summer. This indicated rapid nitrogen mineralization of nitrogen rich labile substrates in the fish farm sediment during the entire season.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00001530
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  • 6
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    Metabolomics and traditional indicators unveil stress of a seagrass (Cymodocea nodosa) meadow at intermediate distance from a fish farm (2020)
    Elsevier
    Details
    Publication Date: 2023-02-08
    Description: Seasonal variation of structural, physiological and growth indicators and the metabolome of the seagrass Cymodocea nodosa, as well as biogeochemical conditions of underlying sediment were studied in two meadows growing at increasing distance downstream from a fish farm in the Aegean Sea in order to assess seagrass performance under stress. Horizontal rhizome production decreased significantly with proximity to the fish farm (0.67 and 1.57 g DW m−2 d−1 close and far from the fish-farm, respectively). This coincided with observed effects on ecophyiological indicators, such as rhizome nitrogen, leaf carbon and leaf δ13C, which were elevated with proximity to the fish-farm. Seasonality was shown by some indicators being elevated in either in the warm (C of all tissues and leaf δ34S) or the cold period (N of all tissues). Growth promoting metabolites (sucrose, fructose, myo-inositol, heptacosane, tetracosane, stigmasterol, catechin and alpha-tocopherol) were lower close to the zone, whereas metabolites involved with stress-response (alanine, serine, proline, putrescine, ornithine, 3,4-dihydroxybenzoic acid and cinnamic acid) were higher. We found that growth-promoting metabolites were positively correlated with horizontal rhizome production, whereas the metabolites related to stress were negatively correlated. Metabolomic fingerprinting of seagrass provides opportunities for early detection of environmental degradation in marine ecological studies.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    A facultative mutualism facilitates European seagrass meadows (2023)
    Wiley
    In:  EPIC3Ecography, Wiley, 2023(5), ISSN: 0906-7590
    Details
    Publication Date: 2023-09-18
    Description: Coastal ecosystem functioning often hinges on habitat-forming foundation species that engage in positive interactions (e.g. facilitation and mutualism) to reduce environmental stress. Seagrasses are important foundation species in coastal zones but are rapidly declining with losses typically linked to intensifying global change-related environmental stress. There is growing evidence that loss or disruption of positive interactions can amplify coastal ecosystem degradation as it compromises its stress mitigating capacity. Multiple recent studies highlight that seagrass can engage in a facultative mutualistic relationship with lucinid bivalves that alleviate sulphide toxicity. So far, however, the generality of this mutualism, and how its strength and relative importance depend on environmental conditions, remains to be investigated. Here we study the importance of the seagrass-lucinid mutualistic interaction on a continental-scale using a field survey across Europe. We found that the lucinid bivalve Loripes orbiculatus is associated with the seagrasses Zostera noltii and Zostera marina across a large latitudinal range. At locations where the average minimum temperature was above 1 °C, L. orbiculatus was present in 79% of the Zostera meadows; whereas, it was absent below this temperature. At locations above this minimum temperature threshold, mud content was the second most important determinant explaining the presence or absence of L. orbiculatus. Further analyses suggest that the presence of the lucinids have a positive effect on seagrass biomass by mitigating sulphide stress. Finally, results of a structural equation model (SEM) support the existence of a mutualistic feedback between L. orbiculatus and Z. noltii. We argue that this seagrass-lucinid mutualism should be more solidly integrated into management practices to improve seagrass ecosystem resilience to global change as well as the success of restoration efforts.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
    Format: application/pdf
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