scholarly journals The impact of intertidal areas on the carbonate system of the southern North Sea

2020 ◽  
Vol 17 (16) ◽  
pp. 4223-4245
Author(s):  
Fabian Schwichtenberg ◽  
Johannes Pätsch ◽  
Michael Ernst Böttcher ◽  
Helmuth Thomas ◽  
Vera Winde ◽  
...  
Keyword(s):  
Organic Matter ◽  
North Sea ◽  
German Bight ◽  
Anaerobic Degradation ◽  
Wadden Sea ◽  
Total Alkalinity ◽  
Carbonate System ◽  
Southern North Sea ◽  
The North ◽  
The North Sea

Abstract. The coastal ocean is strongly affected by ocean acidification because of its shallow water depths, low volume, and the closeness to terrestrial dynamics. Earlier observations of dissolved inorganic carbon (DIC) and total alkalinity (TA) in the southern part of the North Sea, a northwest European shelf sea, revealed lower acidification effects than expected. It has been assumed that anaerobic degradation and subsequent TA release in the adjacent back-barrier tidal areas (Wadden Sea) in summertime is responsible for this phenomenon. In this study the exchange rates of TA and DIC between the Wadden Sea tidal basins and the North Sea and the consequences for the carbonate system in the German Bight are estimated using a 3D ecosystem model. The aim of this study is to differentiate the various sources contributing to observed high summer TA in the southern North Sea. Measured TA and DIC in the Wadden Sea are considered as model boundary conditions. This procedure acknowledges the dynamic behaviour of the Wadden Sea as an area of effective production and decomposition of organic material. According to the modelling results, 39 Gmol TA yr−1 were exported from the Wadden Sea into the North Sea, which is less than a previous estimate but within a comparable range. The interannual variabilities in TA and DIC, mainly driven by hydrodynamic conditions, were examined for the years 2001–2009. Dynamics in the carbonate system are found to be related to specific weather conditions. The results suggest that the Wadden Sea is an important driver for the carbonate system in the southern North Sea. On average 41 % of TA inventory changes in the German Bight were caused by riverine input, 37 % by net transport from adjacent North Sea sectors, 16 % by Wadden Sea export, and 6 % were caused by internal net production of TA. The dominant role of river input for the TA inventory disappears when focusing on TA concentration changes due to the corresponding freshwater fluxes diluting the marine TA concentrations. The ratio of exported TA versus DIC reflects the dominant underlying biogeochemical processes in the Wadden Sea. Whereas aerobic degradation of organic matter played a key role in the North Frisian Wadden Sea during all seasons of the year, anaerobic degradation of organic matter dominated in the East Frisian Wadden Sea. Despite the scarcity of high-resolution field data, it is shown that anaerobic degradation in the Wadden Sea is one of the main contributors of elevated summer TA values in the southern North Sea.

scholarly journals The impact of intertidal areas on the carbonate system of the southern North Sea

2020 ◽  
Author(s):  
Fabian Schwichtenberg ◽  
Johannes Pätsch ◽  
Michael Ernst Böttcher ◽  
Helmuth Thomas ◽  
Vera Winde ◽  
...  
Keyword(s):  
Organic Matter ◽  
North Sea ◽  
German Bight ◽  
Anaerobic Degradation ◽  
Wadden Sea ◽  
Total Alkalinity ◽  
Carbonate System ◽  
Southern North Sea ◽  
The North ◽  
The North Sea

Abstract. The coastal ocean is strongly affected by ocean acidification because it is shallow and has a low volume. Earlier observations of dissolved inorganic carbon (DIC) and total alkalinity (TA) in the southern part of the North Sea and the German Bight, a Northwest-European shelf sea, have revealed lower acidification effects than expected. It has been assumed that anaerobic degradation and subsequent TA release in the adjacent tidal areas (Wadden Sea) in summer time is responsible for this phenomenon. In this study the exchange rates of TA and DIC between the Wadden Sea and the North Sea and the consequences for the carbonate system in the German Bight are estimated using a 3-D ecosystem model. Observed TA and DIC sources in the Wadden Sea were considered as boundary conditions. This procedure is based on the dynamic behaviour of the Wadden Sea as an area of effective production and decomposition of organic material. In addition, modelled tidal water mass exchange was used to transport material between the open North Sea and the Wadden Sea. In the model, 39 Gmol TA yr−1 were exported from the Wadden Sea into the North Sea, which is lower than a previous estimate, but within a comparable range. Furthermore, the interannual variabilities of TA and DIC concentrations, which were mainly driven by hydrodynamic conditions, were examined for the years 2001–2009. Variability in the carbonate system of the German Bight is related to weather in that the occurrence of weak meteorological blocking situations leads to enhanced accumulation of TA there. The results suggest that the Wadden Sea is an important driver of the carbonate system variability in the southern North Sea. According to the model results, on average 63 % of all TA mass changes in the German Bight were caused by net transport, 25 % by Wadden Sea export, 9 % were caused by the internal production of TA and 3 % caused by effective TA river loads (i.e. river load including freshwater dilution). The ratio of exported TA and DIC reflects the dominant underlying biogeochemical processes in the different Wadden Sea areas. Aerobic degradation of organic matter plays a key role in the North Frisian Wadden Sea during all seasons of the year. In the East Frisian Wadden Sea anaerobic degradation of organic matter dominated.

Sources and Fate of PCBs in the North Sea: A Review of Available Data

1991 ◽  
Vol 24 (10) ◽  
pp. 77-85 ◽  
Author(s):  
J. Klamer ◽  
R. W. P. M. Laane ◽  
J. M. Marquenie
Keyword(s):  
Adverse Effects ◽  
North Sea ◽  
German Bight ◽  
Marine Mammals ◽  
Wadden Sea ◽  
Annual Basis ◽  
The North ◽  
Total Input ◽  
Seal Population ◽  
The North Sea

From literature data it is calculated that on an annual basis, 11 to 17 tonnes of PCBs enter the North Sea. Largest sources are the Atlantic Ocean and the atmosphere: together they account for 60-79% of the total input. Sources with greatest impact are the rivers, sewers and sludge. Highest concentrations are found close to the Dutch shore and in the German Bight. The PCB levels result in adverse effects on the seal population in the Wadden Sea. Of the total world PCB production, at least 57% is still in use and their future dispersal into the oceans cannot easily be controlled. If the increase in ocean PCB concentration continues, it may ultimately result in the extinction of fish-eating marine mammals.

Thalassiosiraspecies (Bacillariophyceae, Thalassiosirales) in the North Sea at Helgoland (German Bight) and Sylt (North Frisian Wadden Sea) – a first approach to assessing diversity

2007 ◽  
Vol 42 (3) ◽  
pp. 271-288 ◽  
Author(s):  
Mona Hoppenrath ◽  
Bank Beszteri ◽  
Gerhard Drebes ◽  
Hannelore Halliger ◽  
Justus E. E. Van Beusekom ◽  
...  
Keyword(s):  
North Sea ◽  
German Bight ◽  
Wadden Sea ◽  
The North ◽  
The North Sea ◽  
North Frisian

scholarly journals Spatial variations in sedimentary N-transformation rates in the North Sea (German Bight)

2020 ◽  
Vol 17 (10) ◽  
pp. 2839-2851 ◽  
Author(s):  
Alexander Bratek ◽  
Justus E. E. van Beusekom ◽  
Andreas Neumann ◽  
Tina Sanders ◽  
Jana Friedrich ◽  
...  
Keyword(s):  
Organic Matter ◽  
North Sea ◽  
German Bight ◽  
Inorganic Nitrogen ◽  
Sediment Cores ◽  
Sampling Site ◽  
Permeable Sediments ◽  
Southern North Sea ◽  
The North ◽  
Sediment Types

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).

A cadmium budget for the German Bight in the North Sea

1997 ◽  
Vol 34 (6) ◽  
pp. 375-381 ◽  
Author(s):  
G. Radach ◽  
K. Heyer
Keyword(s):  
North Sea ◽  
German Bight ◽  
The North ◽  
The North Sea

scholarly journals The Size of Diatoms II. Further Observations on Rhizosolenia styliformis (Brightwell)

1946 ◽  
Vol 26 (3) ◽  
pp. 271-284 ◽  
Author(s):  
R. S. Wimpenny
Keyword(s):  
North Sea ◽  
Indicator Species ◽  
Separate Species ◽  
Southern North Sea ◽  
Auxospore Formation ◽  
The North ◽  
The North Sea ◽  
Set Up ◽  
The Antarctic

1. Diameter measurements of Rhizosolenia styliformis from the Antarctic, the subtropical Atlantic and Pacific Oceans and from the North Sea and neighbouring waters have made it appear necessary to set up two varieties, oceanica and semispina, in addition to the type of the species R. styliformis. The type as I describe it has been called var. longispina by Hustedt, but elsewhere it has often been figured as the var. oceanica of this paper. Var. semispina is synonymous with the form represented by Karsten as R. semispina Hensen. It differs from R. semispina as drawn by Hensen and its synonym R. hebetata forma semispina Gran, but is thought likely to be linked by intermediates. If this is so R. hebetata may have to be extended to include and suppress R. styliformis, as var. semispina is linked to the type by intermediates. Var. oceanica has no intermediate forms and, if R. hebetata is to be extended, this variety should be established as a separate species.2. Var. oceanica is absent from the southern North Sea and appears to be an indicator species related to oceanic inflow.3. Auxospore formation was observed for the type in the southern North Sea in 1935 and biometric observations suggest that a period of 3-4 years elapsed between the production of auxospore generations in that area. Outside the southern North Sea for the type, measurements give no indication of auxospore generations occurring at intervals exceeding a year. While auxospore formation has been seen in var. oceanica from the Shetlands area samples of June 1935 and July 1938, this phenomenon has not been observed for var. semispina.

scholarly journals The carbonate system in the North Sea: Sensitivity and model validation

2012 ◽  
Vol 102-104 ◽  
pp. 1-13 ◽  
Author(s):  
Yuri Artioli ◽  
Jeremy C. Blackford ◽  
Momme Butenschön ◽  
Jason T. Holt ◽  
Sarah L. Wakelin ◽  
...  
Keyword(s):  
Model Validation ◽  
North Sea ◽  
Carbonate System ◽  
The North ◽  
The North Sea

scholarly journals The impact of sedimentary alkalinity release on the water column CO<sub>2</sub> system in the North Sea

2016 ◽  
Vol 13 (3) ◽  
pp. 841-863 ◽  
Author(s):  
H. Brenner ◽  
U. Braeckman ◽  
M. Le Guitton ◽  
F. J. R. Meysman
Keyword(s):  
Coastal Zone ◽  
North Sea ◽  
Dissolved Inorganic Carbon ◽  
Co2 Uptake ◽  
Overlying Water ◽  
Southern North Sea ◽  
The North ◽  
Alkalinity Generation ◽  
The North Sea ◽  
The Impact

Abstract. It has been previously proposed that alkalinity release from sediments can play an important role in the carbonate dynamics on continental shelves, lowering the pCO2 of seawater and hence increasing the CO2 uptake from the atmosphere. To test this hypothesis, sedimentary alkalinity generation was quantified within cohesive and permeable sediments across the North Sea during two cruises in September 2011 (basin-wide) and June 2012 (Dutch coastal zone). Benthic fluxes of oxygen (O2), alkalinity (AT) and dissolved inorganic carbon (DIC) were determined using shipboard closed sediment incubations. Our results show that sediments can form an important source of alkalinity for the overlying water, particularly in the shallow southern North Sea, where high AT and DIC fluxes were recorded in near-shore sediments of the Belgian, Dutch and German coastal zone. In contrast, fluxes of AT and DIC are substantially lower in the deeper, seasonally stratified, northern part of the North Sea. Based on the data collected, we performed a model analysis to constrain the main pathways of alkalinity generation in the sediment, and to quantify how sedimentary alkalinity drives atmospheric CO2 uptake in the southern North Sea. Overall, our results show that sedimentary alkalinity generation should be regarded as a key component in the CO2 dynamics of shallow coastal systems.

scholarly journals Enhanced ocean carbon storage from anaerobic alkalinity generation in coastal sediments

2009 ◽  
Vol 6 (2) ◽  
pp. 267-274 ◽  
Author(s):  
H. Thomas ◽  
L.-S. Schiettecatte ◽  
K. Suykens ◽  
Y. J. M. Koné ◽  
E. H. Shadwick ◽  
...  
Keyword(s):  
North Sea ◽  
Co2 Storage ◽  
Global Scale ◽  
Coastal Sediments ◽  
Total Alkalinity ◽  
Co2 Uptake ◽  
Marginal Seas ◽  
The North ◽  
The North Sea ◽  
Ocean Carbon

Abstract. The coastal ocean is a crucial link between land, the open ocean and the atmosphere. The shallowness of the water column permits close interactions between the sedimentary, aquatic and atmospheric compartments, which otherwise are decoupled at long time scales (≅ 1000 yr) in the open oceans. Despite the prominent role of the coastal oceans in absorbing atmospheric CO2 and transferring it into the deep oceans via the continental shelf pump, the underlying mechanisms remain only partly understood. Evaluating observations from the North Sea, a NW European shelf sea, we provide evidence that anaerobic degradation of organic matter, fuelled from land and ocean, generates total alkalinity (AT) and increases the CO2 buffer capacity of seawater. At both the basin wide and annual scales anaerobic AT generation in the North Sea's tidal mud flat area irreversibly facilitates 7–10%, or taking into consideration benthic denitrification in the North Sea, 20–25% of the North Sea's overall CO2 uptake. At the global scale, anaerobic AT generation could be accountable for as much as 60% of the uptake of CO2 in shelf and marginal seas, making this process, the anaerobic pump, a key player in the biological carbon pump. Under future high CO2 conditions oceanic CO2 storage via the anaerobic pump may even gain further relevance because of stimulated ocean productivity.

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