The importance of sediments in the transformation and turnover of nutrients and organic matter in the Wadden Sea and German Bight

Beusekom, Justus E. E. van; Brockmann, U. H.; Hesse, Kirsten; Hickel, Wolfgang; Poremba, K.; Tillmann, Urban

doi:10.1007/bf02764176

Cited by 64 publications

(66 citation statements)

References 60 publications

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“…Total annual remineralization in the North Frisian Wadden Sea amounts to about 33 mol C m Ϫ2 (400 g C m Ϫ2 ), with the water column and benthic processes contributing similar amounts (Van Beusekom et al 1999). The difference between total production and remineralization of about 8 mol C m Ϫ2 (100 g C m Ϫ2 ) is in line with the heterotrophic nature of the Wadden Sea (Postma 1954;Van Beusekom et al 1999). The estimates of benthic mineralization were mainly based on core and chamber incubations and therefore might have underestimated the benthic mineralization rates by excluding advective processes.…”

Section: Discussionmentioning

confidence: 99%

Transport and mineralization rates in North Sea sandy intertidal sediments, Sylt-Rømø Basin, Wadden Sea

et al. 2005

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We investigated the rates of the main microbiological processes (primary production, aerobic and anaerobic carbon degradation) and transport phenomena in an intertidal sand plate with a combination of in situ microsensor measurements and incubations. The sand was coarse, organically poor (0.6-1 mg of total organic carbon per gram dry weight of sediment), and highly permeable to water flow (k ϭ 1.5-7 ϫ 10 Ϫ11 m 2 ). Aerobic respiration rates ranged from 105 to 175 mmol m Ϫ2 d Ϫ1, sulfate reduction rates from 0.08 to 13.7 mmol m Ϫ2 d Ϫ1, and net primary production Ͻ35 mmol m Ϫ2 d Ϫ1 . In situ microsensor measurements showed large changes in oxygen and sulfide concentrations in the top 10 cm, depending on tides and waves. The observed dynamics and high aerobic degradation rates imply that pressure gradients drive advective influx of oxygen and organic material from the water column into the sediments. Our results show that intertidal porous sand plates have high aerobic degradation rates, despite having an organic matter content that is one to two orders of magnitude lower than that of fine-grained deposits with similar decomposition rates.

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Section: Discussionmentioning

confidence: 99%

Transport and mineralization rates in North Sea sandy intertidal sediments, Sylt-Rømø Basin, Wadden Sea

et al. 2005

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“…Denitrification is a major sink for N on the continental shelves and in the estuaries (Jickells 1998). It is still under debate how to quantify this loss of river borne N before it enters the coastal sea (Van Beusekom et al 1999). In Tables 4 and 5 the nutrient loads given are not yet reduced by a retention factor.…”

Section: Methodsmentioning

confidence: 99%

Variability of continental riverine freshwater and nutrient inputs into the North Sea for the years 1977–2000 and its consequences for the assessment of eutrophication

Radach¹,

Pätsch²

2007

Estuaries and Coasts

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We determined the monthly and annual riverine freshwater, nitrogen (N) and phosphorus (P) loading into the North Sea from Belgium, The Netherlands, and Germany for the years 1977-2000. An average of 133 km 3 yr 21 of the 309 km 3 yr 21 precipitation into the watershed is carried by the rivers into the sea. Total freshwater discharge fluctuates with a strong 6-7 yr periodicity, is strongly correlated with precipitation, and exhibits a slight long-term decrease. The temporal changes of regional patterns of precipitation lead to changing ratios of annual discharge of the western rivers compared to the eastern rivers, varying between 2.2 and 3.5. The long-term oscillations in discharge were more pronounced as discharge increased. The annual means of total and dissolved inorganic N and P loads were estimated to be 722 and 582 kt N yr 21 and 48 and 26 kt P yr 21 , respectively. The monthly N loads were much more strongly correlated with discharge, compared to the monthly P loads. Total N and P as well as dissolved inorganic N also demonstrated a 6-7 yr periodicity. The annual N loads decreased by about 17 kt N yr 21 from 1977 to 2000. The total phosphorus and phosphate loads decreased from about 80 and 50 kt P yr 21 in the 1980s to 25 and 12 kt P yr 21 , respectively, in the 1990s. The western rivers contributed the major part of the nutrient loads. The long-term oscillations in their nutrient loads were much more pronounced, compared to the eastern rivers. The area-specific loading rates estimated for all rivers are comparable to earlier estimates using shorter data records, smaller sample sizes, and a less complete watershed monitoring program. The monthly and annual average N:P ratios and their variability increased considerably for individual rivers during the study interval. These results confirm that the water quality of European continental rivers is strongly influenced by intense land use. They demonstrate the necessity for using long time series monitoring results to assess change and evaluate the effects of climate change on the North Sea coastal ecosystems, using ecosystem models on decadal time scales.

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“…Postma (1981) describe the Wadden Sea as a relevant sink for organic and source of inorganic matter. Other studies reported the Wadden Sea constitutes an important sink of N due to benthic denitrification (e.g., Kieskamp et al, 1991;van Beusekom and de Jonge, 1998;van Beusekom et al, 1999). Both would affect N availability in the open North Sea, especially, upstream of the ODZ site.…”

Section: Limitations Of the Model Forcing And Setupmentioning

confidence: 97%

A Novel Modeling Approach to Quantify the Influence of Nitrogen Inputs on the Oxygen Dynamics of the North Sea

et al. 2017

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Oxygen (O 2 ) deficiency, i.e., dissolved O 2 concentrations below 6 mg O 2 L −1 , is a common feature in the southern North Sea. Its evolution is governed mainly by the presence of seasonal stratification and production of organic matter, which is subsequently degraded under O 2 consumption. The latter is strongly influenced by riverine nutrient loads, i.e., nitrogen (N) and phosphorus (P). As riverine P loads have been reduced significantly over the past decades, this study aims for the quantification of the influence of riverine and non-riverine N inputs on the O 2 dynamics in the southern North Sea. For this purpose, we present an approach to expand a nutrient-tagging technique for physical-biogeochemical models -often referred to as 'trans-boundary nutrient transports' (TBNT) -by introducing a direct link to the O 2 dynamics. We apply the expanded TBNT to the physical-biogeochemical model system HAMSOM-ECOHAM and focus our analysis on N-related O 2 consumption in the southern North Sea during 2000-2014. The analysis reveals that near-bottom O 2 consumption in the southern North Sea is strongly influenced by the N supply from the North Atlantic across the northern shelf edge. However, riverine N sources -especially the Dutch, German and British rivers -as well as the atmosphere also play an important role. In the region with lowest simulated O 2 concentrations (around 56 • N, 6.5 • E), riverine N on average contributes 39% to overall near-bottom O 2 consumption during seasonal stratification. Here, the German and the large Dutch rivers constitute the highest riverine contributions (11% and 10%, respectively). At a site in the Oyster Grounds (around 54.5 • N, 4 • E), the average riverine contribution adds up to 41%, even exceeding that of the North Atlantic. Here, highest riverine contributions can be attributed to the Dutch and British rivers adding up to almost 28% on average. The atmospheric contribution results in 13%. Our results emphasize the importance of anthropogenic N inputs and seasonal stratification for the O 2 conditions in the southern North Sea. They further suggest that reductions in the riverine and atmospheric N inputs may have a relevant positive effect on the O 2 levels in this region.

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The importance of sediments in the transformation and turnover of nutrients and organic matter in the Wadden Sea and German Bight

Cited by 64 publications

References 60 publications

Transport and mineralization rates in North Sea sandy intertidal sediments, Sylt-Rømø Basin, Wadden Sea

Transport and mineralization rates in North Sea sandy intertidal sediments, Sylt-Rømø Basin, Wadden Sea

Variability of continental riverine freshwater and nutrient inputs into the North Sea for the years 1977–2000 and its consequences for the assessment of eutrophication

A Novel Modeling Approach to Quantify the Influence of Nitrogen Inputs on the Oxygen Dynamics of the North Sea

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