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  • 1
    Online Resource
    Online Resource
    Significant shifts in inorganic carbon and ecosystem state in a temperate estuary (1985–2018)
    Wiley ; 2023
    In:  Limnology and Oceanography Vol. 68, No. 8 ( 2023-08), p. 1920-1935
    Details
    In: Limnology and Oceanography, Wiley, Vol. 68, No. 8 ( 2023-08), p. 1920-1935
    Abstract: Estuaries regulate carbon cycling along the land‐ocean continuum and thus influence carbon export to the ocean, and global carbon budgets. The Elbe Estuary in Germany has been altered by large anthropogenic perturbations, such as widespread heavy metal pollution, minimally treated wastewater before the 1980s, establishment of wastewater treatment plants after the 1990s, and an overall nutrient and pollutant load reduction in the last three decades. Based on an extensive evaluation of key ecosystem variables, and an analysis of the available inorganic and organic carbon records, this study has identified three ecosystem states in recent history: the polluted (1985–1990), transitional (1991–1996), and recovery (1997–2018) states. The polluted state was characterized by very high dissolved inorganic carbon (DIC) and ammonium concentrations, toxic heavy metal levels, dissolved oxygen undersaturation, and low pH. During the transitional state, heavy metal pollution decreased by 〉  50%, and primary production re‐established in spring to summer, with weak seasonality in DIC. Since 1997, during the recovery state, DIC seasonality was driven by primary production, and DIC significantly increased by 11  μ mol L −1  yr −1 , and 〉  23  μ mol L −1  yr −1 in the recent decade (2008–2018), in the mid to lower estuary, indicating that, along with the improvement in water quality the ecosystem state is still changing. Large anthropogenic perturbations can therefore alter estuarine ecosystems (on the order of decades), as well as induce large and complex biogeochemical shifts and significant changes to carbon cycling.
    Type of Medium: Online Resource
    ISSN: 0024-3590 , 1939-5590
    URL: Issue
    URL: Article
    DOI: 10.1002/lno.v68.8
    DOI: 10.1002/lno.12395
    Language: English
    Publisher: Wiley
    Publication Date: 2023
    detail.hit.zdb_id: 2033191-5
    detail.hit.zdb_id: 412737-7
    SSG: 12
    SSG: 14
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  • 2
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    Oxygen and Nutrient Trapping in the Southern Benguela Upwelling System
    Frontiers Media SA ; 2021
    In:  Frontiers in Marine Science Vol. 8 ( 2021-9-23)
    Details
    In: Frontiers in Marine Science, Frontiers Media SA, Vol. 8 ( 2021-9-23)
    Abstract: The Benguela Upwelling System in the southeast Atlantic Ocean is of crucial socio-economic importance due to its high productivity. However, predicting its response to global change and understanding past changes are still great challenges. Here, we compile data obtained from a research cruise and an oceanographic mooring to demonstrate that a topographically steered nutrient trapping zone develops in a narrow belt along the coast during the main upwelling season in austral spring and summer in the southern Benguela Upwelling System. High nutrient concentrations within this zone increase the impact of upwelling on the productivity of the southern Benguela Upwelling System, but the efficient nutrient trapping operates at the expense of decreasing oxygen concentrations. This enhances the probability of anoxic events emerging toward the end of the upwelling season. However, at the end of the upwelling season, the front that separates the coastally trapped waters from open shelf waters weakens or even collapses due to upwelling cessation and the reversing current regime. This, in addition to a stronger vertical mixing caused by winter cooling, fosters the ventilation of the nutrient trapping zone, which reestablishes during the following upwelling season. The postulated intensification of upwelling and changes in the ecosystem structure in response to global warming seem to reduce the nutrient trapping efficiency by increasing offshore advection of surface waters and plankton blooms. The intensified upwelling and resulting lower biological oxygen consumption appears to mask the expected impacts of global warming on the oxygen minimum zone (OMZ) in the southern Benguela Upwelling System. In contrast to other OMZs, including those in northern Benguela Upwelling Systems, the OMZ in the southern Benguela Upwelling System reveals so far no detectable long-term decrease in oxygen. Thus, the nutrient trapping efficiency seems to be a critical feature mitigating global change impacts on the southern Benguela Upwelling System. Since it is topographically steered, regional impacts on the nutrient trapping efficiency appear also to explain varying responses of upwelling systems to global change as the comparison between southern and northern Benguela Upwelling System shows. This emphasizes the need for further and more comparable studies in order to better understand the response of Eastern Boundary Upwelling Systems and their ecosystem services to global change.
    Type of Medium: Online Resource
    ISSN: 2296-7745
    URL: Article
    DOI: 10.3389/fmars.2021.730591
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2021
    detail.hit.zdb_id: 2757748-X
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  • 3
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    Spatial variations in sedimentary N-transformation rates in the North Sea (German Bight)
    Copernicus GmbH ; 2020
    In:  Biogeosciences Vol. 17, No. 10 ( 2020-05-28), p. 2839-2851
    Details
    In: Biogeosciences, Copernicus GmbH, Vol. 17, No. 10 ( 2020-05-28), p. 2839-2851
    Abstract: Abstract. In this study, we investigate the role of sedimentary N cycling in the southern North Sea. We present a budget of ammonification, nitrification and sedimentary NO3- consumption and denitrification in contrasting sediment types of the German Bight (southern North Sea), including novel net ammonification rates. We incubated sediment cores from four representative locations in the German Bight (permeable, semi-permeable and impermeable sediments) with labeled nitrate and ammonium to calculate benthic fluxes of nitrate and ammonium and gross rates of ammonification and nitrification. Ammonium fluxes generally suggest oxic degradation of organic matter, but elevated fluxes at one sampling site point towards the importance of bioirrigation or short-term accumulation of organic matter. Sedimentary fluxes of dissolved inorganic nitrogen are an important source for primary producers in the water column, supporting ∼7 % to 59 % of the average annual primary production, depending on water depth. We find that ammonification and oxygen penetration depth are the main drivers of sedimentary nitrification, but this nitrification is closely linked to denitrification. One-third of freshly produced nitrate in impermeable sediment and two-thirds in permeable sediment were reduced to N2. The semi-permeable and permeable sediments are responsible for ∼68 % of the total benthic N2 production rates, which, based solely on our data, amounts to ∼1030 t N d−1 in the southern North Sea. Thus, we conclude that semi-permeable and permeable sediments are the main sinks of reactive N, counteracting eutrophication in the southern North Sea (German Bight).
    Type of Medium: Online Resource
    ISSN: 1726-4189
    URL: Article
    URL: Article
    DOI: 10.5194/bg-17-2839-2020
    DOI: 10.5194/bg-17-2839-2020-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2020
    detail.hit.zdb_id: 2158181-2
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  • 4
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    Online Resource
    An evaluation of long-term physical and hydrochemical measurements at the Sylt Roads Marine Observatory (1973–2019), Wadden Sea, North Sea
    Copernicus GmbH ; 2023
    In:  Earth System Science Data Vol. 15, No. 3 ( 2023-03-07), p. 1037-1057
    Details
    In: Earth System Science Data, Copernicus GmbH, Vol. 15, No. 3 ( 2023-03-07), p. 1037-1057
    Abstract: Abstract. The Sylt Roads pelagic time series covers physical and hydrochemical parameters at five neighboring stations in the Sylt–Rømø bight, Wadden Sea, North Sea. Since the beginning of the time series in 1973, sea surface temperature (SST), salinity, ammonium, nitrite, nitrate, and soluble reactive phosphorus (SRP) have been measured twice a week. The other parameters were introduced later (dissolved silicate (Si) since 1974, pH since 1979, dissolved organic nitrogen (DON) since 1996, dissolved organic phosphorus (DOP) since 2001, chlorophyll a since 1979, and suspended particulate matter (SPM) since 1975), and in the case of dissolved oxygen, were already discontinued (1979–1983). In the years 1977, 1978, and 1983, no sampling took place. Since the start of the continuous sampling in 1984, the sea surface temperature in the bight has risen by +1.11 ∘C, with the highest increases during the autumn months, while the pH and salinity decreased by 0.23 and 0.33 units, respectively. Summer and autumn salinities are generally significantly elevated compared to spring and winter conditions. Dissolved nutrients (ammonium, nitrite, nitrate, and SRP) have displayed periods of intense eutrophication (1973–1998) and de-eutrophication since 1999. Silicate has shown significantly higher winter levels since 1999. Interestingly, phytoplankton parameters did not mirror these large changes in nutrient concentrations, as a seasonal comparison of the two eutrophication periods showed no significant differences with regard to chlorophyll a. This phenomenon might be triggered by an important switch in nutrient limitation during the time series. With regard to nutrients, the phytoplankton was probably primarily limited by silicate until 1998, while, since 1999, the SRP limitation has become increasingly important. All data are available in Rick et al. (2017b–e, 2020a–o) from https://doi.org/10.1594/PANGAEA.150032, https://doi.org/10.1594/PANGAEA.873549, https://doi.org/10.1594/PANGAEA.873545, https://doi.org/10.1594/PANGAEA.873547, https://doi.org/10.1594/PANGAEA.918018, https://doi.org/10.1594/PANGAEA.918032, https://doi.org/10.1594/PANGAEA.918027, https://doi.org/10.1594/PANGAEA.918023, https://doi.org/10.1594/PANGAEA.918033, https://doi.org/10.1594/PANGAEA.918028, https://doi.org/10.1594/PANGAEA.918024, https://doi.org/10.1594/PANGAEA.918034, https://doi.org/10.1594/PANGAEA.918029, https://doi.org/10.1594/PANGAEA.918025, https://doi.org/10.1594/PANGAEA.918035, https://doi.org/10.1594/PANGAEA.918030, https://doi.org/10.1594/PANGAEA.918026, https://doi.org/10.1594/PANGAEA.918036, and https://doi.org/10.1594/PANGAEA.918031.
    Type of Medium: Online Resource
    ISSN: 1866-3516
    URL: Article
    DOI: 10.5194/essd-15-1037-2023
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2023
    detail.hit.zdb_id: 2475469-9
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  • 5
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    Metabolic alkalinity release from large port facilities (Hamburg, Germany) and impact on coastal carbon storage
    Copernicus GmbH ; 2022
    In:  Biogeosciences Vol. 19, No. 22 ( 2022-11-14), p. 5151-5165
    Details
    In: Biogeosciences, Copernicus GmbH, Vol. 19, No. 22 ( 2022-11-14), p. 5151-5165
    Abstract: Abstract. Metabolic activities in estuaries, especially these of large rivers, profoundly affect the downstream coastal biogeochemistry. Here, we unravel the impacts of large industrial port facilities, showing that elevated metabolic activity in the Hamburg port (Germany) increases total alkalinity (TA) and dissolved inorganic carbon (DIC) runoff to the North Sea. The imports of particulate inorganic carbon, particulate organic carbon, and particulate organic nitrogen (PIC, POC, and PON) from the upstream Elbe River can fuel up to 90 % of the TA generated in the entire estuary via calcium carbonate (CaCO3) dissolution. The remaining at least 10 % of TA generation can be attributed to anaerobic metabolic processes such as denitrification of remineralized PON or other pathways. The Elbe Estuary as a whole adds approximately 15 % to the overall DIC and TA runoff. Both the magnitude and partitioning among these processes appear to be sensitive to climatic and anthropogenic changes. Thus, with increased TA loads, the coastal ocean (in particular) would act as a stronger CO2 sink, resulting in changes to the overall coastal system's capacity to store CO2.
    Type of Medium: Online Resource
    ISSN: 1726-4189
    URL: Article
    DOI: 10.5194/bg-19-5151-2022
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2022
    detail.hit.zdb_id: 2158181-2
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  • 6
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    Suspended particulate matter drives the spatial segregation of nitrogen turnover along the hyper-turbid Ems estuary
    Copernicus GmbH ; 2022
    In:  Biogeosciences Vol. 19, No. 7 ( 2022-04-11), p. 2007-2024
    Details
    In: Biogeosciences, Copernicus GmbH, Vol. 19, No. 7 ( 2022-04-11), p. 2007-2024
    Abstract: Abstract. Estuaries are nutrient filters and change riverine nutrient loads before they reach coastal oceans. Their morphology have been extensively changed by anthropogenic activities like draining, deepening and dredging to meet economic and social demand, causing significant regime changes like tidal amplifications and in some cases to hyper-turbid conditions. Furthermore, increased nutrient loads, especially nitrogen, mainly by agriculture cause coastal eutrophication. Estuaries can either act as a sink or as a source of nitrate, depending on environmental and geomorphological conditions. These factors vary along an estuary, and change nitrogen turnover in the system. Here, we investigate the factors controlling nitrogen turnover in the hyper-turbid Ems estuary (Northern Germany), which has been strongly impacted by human activities. During two research cruises in August 2014 and June 2020, we measured water column properties, dissolved inorganic nitrogen, dual stable isotopes of nitrate and dissolved nitrous oxide concentration along the estuary. We found that three distinct biogeochemical zones exist along the estuary. A strong fractionation (∼26 ‰) of nitrate stable isotopes points towards nitrate removal via water column denitrification in the hyper-turbid tidal river, driven by anoxic conditions in deeper water layers. In the middle reaches of the estuary nitrification gains importance, turning this section into a net nitrate source. The outer reaches are dominated by mixing, with nitrate uptake in 2020. We find that the overarching control on biogeochemical nitrogen cycling, zonation and nitrous oxide production in the Ems estuary is exerted by suspended particulate matter concentrations and the linked oxygen deficits.
    Type of Medium: Online Resource
    ISSN: 1726-4189
    URL: Article
    URL: Article
    DOI: 10.5194/bg-19-2007-2022
    DOI: 10.5194/bg-19-2007-2022-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2022
    detail.hit.zdb_id: 2158181-2
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  • 7
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    Online Resource
    Macrofauna as a major driver of bentho‐pelagic exchange in the southern North Sea
    Wiley ; 2021
    In:  Limnology and Oceanography Vol. 66, No. 6 ( 2021-06), p. 2203-2217
    Details
    In: Limnology and Oceanography, Wiley, Vol. 66, No. 6 ( 2021-06), p. 2203-2217
    Abstract: The contribution of sediments to nutrient cycling of the coastal North Sea is strongly controlled by the intensity of fluxes across the sediment water interface. Pore‐water advection is one major exchange mechanism that is well described by models, as it is determined by physical parameters. In contrast, biotransport (i.e., bioirrigation, bioturbation) as the other major transport mechanism is much more complex. Observational data reflecting biotransport, from the German Bight for example, is scarce. We sampled the major sediment provinces of the German Bight repeatedly over the years from 2013 to 2019. By employing ex situ whole core incubations, we established the seasonal and spatial variability of macrofauna‐sustained benthic fluxes of oxygen and nutrients. A multivariate, partial least squares analysis identified faunal activity, in specifically bioturbation and bioirrigation, alongside temperature, as the most important drivers of oxygen and nutrient fluxes. Their combined effect explained 63% of the observed variability in oxygen fluxes, and 36–48% of variability in nutrient fluxes. Additional 10% of the observed variability of fluxes were explained by sediment type and the availability of plankton biomass. Based on our extrapolation by sediment provinces, we conclude that pore‐water advection and macrofaunal activity contributed equally to the total benthic oxygen uptake in the German Bight.
    Type of Medium: Online Resource
    ISSN: 0024-3590 , 1939-5590
    URL: Issue
    URL: Article
    DOI: 10.1002/lno.v66.6
    DOI: 10.1002/lno.11748
    Language: English
    Publisher: Wiley
    Publication Date: 2021
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    SSG: 14
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  • 8
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    Interactive impacts of meteorological and hydrological conditions on the physical and biogeochemical structure of a coastal system
    Copernicus GmbH ; 2020
    In:  Biogeosciences Vol. 17, No. 20 ( 2020-10-21), p. 5097-5127
    Details
    In: Biogeosciences, Copernicus GmbH, Vol. 17, No. 20 ( 2020-10-21), p. 5097-5127
    Abstract: Abstract. The German Bight was exposed to record high riverine discharges in June 2013, as a result of flooding of the Elbe and Weser rivers. Several anomalous observations suggested that the hydrodynamical and biogeochemical states of the system were impacted by this event. In this study, we developed a biogeochemical model and coupled it with a previously introduced high-resolution hydrodynamical model of the southern North Sea in order to better characterize these impacts and gain insight into the underlying processes. Performance of the model was assessed using an extensive set of in situ measurements for the period 2011–2014. We first improved the realism of the hydrodynamic model with regard to the representation of cross-shore gradients, mainly through inclusion of flow-dependent horizontal mixing. Among other characteristic features of the system, the coupled model system can reproduce the low salinities, high nutrient concentrations and low oxygen concentrations in the bottom layers observed within the German Bight following the flood event. Through a scenario analysis, we examined the sensitivity of the patterns observed during July 2013 to the hydrological and meteorological forcing in isolation. Within the region of freshwater influence (ROFI) of the Elbe–Weser rivers, the flood event clearly dominated the changes in salinity and nutrient concentrations, as expected. However, our findings point to the relevance of the peculiarities in the meteorological conditions in 2013 as well: a combination of low wind speeds, warm air temperatures and cold bottom-water temperatures resulted in a strong thermal stratification in the outer regions and limited vertical nutrient transport to the surface layers. Within the central region, the thermal and haline dynamics interactively resulted in an intense density stratification. This intense stratification, in turn, led to enhanced primary production within the central region enriched by nutrients due to the flood but led to reduction within the nutrient-limited outer region, and it caused a widespread oxygen depletion in bottom waters. Our results further point to the enhancement of the current velocities at the surface as a result of haline stratification and to intensification of the thermohaline estuarine-like circulation in the Wadden Sea, both driven by the flood event.
    Type of Medium: Online Resource
    ISSN: 1726-4189
    URL: Article
    DOI: 10.5194/bg-17-5097-2020
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2020
    detail.hit.zdb_id: 2158181-2
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  • 9
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    Quantifying Importance of Macrobenthos for Benthic‐Pelagic Coupling in a Temperate Coastal Shelf Sea
    American Geophysical Union (AGU) ; 2021
    In:  Journal of Geophysical Research: Oceans Vol. 126, No. 10 ( 2021-10)
    Details
    In: Journal of Geophysical Research: Oceans, American Geophysical Union (AGU), Vol. 126, No. 10 ( 2021-10)
    Abstract: A novel 3D numerical model resolves interactions among macrobenthos, bioturbation, oxygen consumption, and carbon early diagenesis The role of bioturbation in benthic oxygen consumption is twofold and dependent on sediment properties and hydrodynamics Bioturbation‐induced oxygen transport contributes to more than half of the total benthic oxygen fluxes in the German Bight
    Type of Medium: Online Resource
    ISSN: 2169-9275 , 2169-9291
    URL: Article
    DOI: 10.1029/2020JC016995
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2021
    detail.hit.zdb_id: 2016804-4
    detail.hit.zdb_id: 161667-5
    detail.hit.zdb_id: 3094219-6
    SSG: 16,13
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  • 10
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    Image_9.JPEG
    Frontiers Media SA ; 2021
    In:  Frontiers in Marine Science Vol. 8 ( 2021-6-4)
    Details
    In: Frontiers in Marine Science, Frontiers Media SA, Vol. 8 ( 2021-6-4)
    Abstract: The Elbe estuary is a substantially engineered tidal water body that receives high loads of organic matter from the eutrophied Elbe river. The organic matter entering the estuary at the tidal weir is dominated by diatom populations that collapse in the deepened freshwater reach. Although the estuary’s freshwater reach is considered to manifest vertically homogenous density distribution (i.e., to be well-mixed), several indicators like trapping of particulate organic matter, near-bottom oxygen depletion and ammonium accumulation suggest that the vertical exchange of organic particles and dissolved oxygen is weakened at least temporarily. To better understand the causal links between the hydrodynamics and the oxygen and nutrient cycling in the deepened freshwater reach of the Elbe estuary, we establish a three-dimensional coupled hydrodynamical-biogeochemical model. The model demonstrates good skill in simulating the variability of the physical and biogeochemical parameters in the focal area. Coupled simulations reveal that this region is a hotspot of the degradation of diatoms and organic matter transported from the shallow productive upper estuary and the tidal weir. In summer, the water column weakly stratifies when at the bathymetric jump warmer water from the shallow upper estuary spreads over the colder water of the deepened mid reaches. Enhanced thermal stratification also occurs also in the narrow port basins and channels. Model results show intensification of the particle trapping due to the thermal gradients. The stratification also reduces the oxygenation of the near-bottom region and sedimentary layer inducing oxygen depletion and accumulation of ammonium. The study highlights that the vertical resolution is important for the understanding and simulation of estuarine ecological processes, because even weak stratification impacts the cycling of nutrients via modulation of the vertical mixing of oxygen, particularly in deepened navigation channels and port areas.
    Type of Medium: Online Resource
    ISSN: 2296-7745
    URL: Article
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    DOI: 10.3389/fmars.2021.623714
    DOI: 10.3389/fmars.2021.623714.s001
    DOI: 10.3389/fmars.2021.623714.s002
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    DOI: 10.3389/fmars.2021.623714.s009
    DOI: 10.3389/fmars.2021.623714.s010
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2021
    detail.hit.zdb_id: 2757748-X
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