The oxygen dynamics of the Oyster Ground, North Sea. Impact of eutrophication and environmental conditions

Peeters, J. C. H.; Los, F.J.; Jansen, Robert K.; Haas, Heike; Peperzak, L.; Vries, I. de

doi:10.1080/00785326.1995.10431508

Cited by 28 publications

(21 citation statements)

References 26 publications

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“…In contrast to the DCM new production, the 12 continuous low primary production in the BML will not alleviate low bottom water 13 oxygen concentrations measured, since the production of oxygen due to primary 14 production in the BML will be compensated by oxygen uptake during sedimentary 15 remineralisation (Peeters et al, 1995). stations.…”

Section: Low Bottom Water Dissolved Oxygen and Its Causes 20 21mentioning

confidence: 99%

Sedimentary and water column processes in the Oyster Grounds: A potentially hypoxic region of the North Sea

Weston

Fernand

Nicholls

et al. 2008

Marine Environmental Research

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The purpose of this research was to investigate the potential causes of low oxygen levels in the bottom water of the Oyster Grounds region of the shallow southern North Sea, an area which provides suitable conditions for low oxygen levels to develop. At the end of the summer stratified period, relevant biogeochemical processes were investigated using a combination of sedimentary and water column rate measurements. Phytoplankton nitrate and ammonium uptake was measured throughout the water column using 15N labelled isotopes and showed ammonium uptake dominated in the upper and bottom mixed layer with a maximum 294.4 µmol N m-3 h-1. In the deep chlorophyll maximum at the thermocline, primary production was dominated by nitrate uptake, with an average of 35.0 µmol N m-3 h-1, relative to ammonium uptake, with an average of 24.6 µmol N m-3 h-1. This high relative nitrate uptake will in part result in exportable new production to the isolated bottom mixed layer and sediments, as opposed to regenerated ammonium driven uptake. This biomass export was indicated by significant benthic oxygen consumption rates in the stratified region (782-1275 µmol O2 m-2 h-1 µmol N m-3 h-1) long after the end of the spring bloom. The sediments were also an active net source of nitrate, ammonium, phosphate and silicate into the bottom mixed layer of 4.4, 8.4, 2.3 and 68.8 µmol m-2 h-1, respectively. The export of new production within the thermocline to the bottom mixed layer and the consequent sediment oxygen consumption in the isolated bottom mixed layer in the Oyster Grounds are expected to have contributed to the low bottom water oxygen concentrations of 2.07 mg l-1 (64.7 µmol l-1) measured. The long stratified period associated with this low oxygen is predicted to occur more regularly in the future and continued monitoring of this ecologically important region is therefore essential if the causes of these potentially damaging low oxygen levels are to be fully understood

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Section: Low Bottom Water Dissolved Oxygen and Its Causes 20 21mentioning

confidence: 99%

Sedimentary and water column processes in the Oyster Grounds: A potentially hypoxic region of the North Sea

Weston

Fernand

Nicholls

et al. 2008

Marine Environmental Research

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“…The same applies to the Oyster Grounds site (see Figure 5, region 2) where simulated minimum near-bottom concentrations yield 6-6.5 mg O 2 L −1 . As the Oyster Grounds are well known being susceptible to low O 2 conditions (de Wilde et al, 1984;Peeters et al, 1995;Weston et al, 2008;Greenwood et al, 2010), this region is also used for a detailed analysis. At this site, the comparison with Figure 4 indicates a strong influence of the NL-1 and UK-2 rivers, and the NA (not shown).…”

Section: Spatial Distributions Of Tn From Different Sourcesmentioning

confidence: 99%

“…In the North Sea -a northwestern European shelf sea -hypoxic conditions occurred in the summers of the 1980s (Rachor and Albrecht, 1983;von Westernhagen and Dethlefsen, 1983;Brockmann and Eberlein, 1986;Peeters et al, 1995), causing death of benthic and demersal species (von Westernhagen and Dethlefsen, 1983). Different studies showed that these occurrences of low O 2 conditions evolved during seasonal stratification (von Westernhagen and Dethlefsen, 1983;Peeters et al, 1995), driven by eutrophication due to excess riverine nutrient loads (Brockmann and Eberlein, 1986;Brockmann et al, 1988;Peeters et al, 1995).…”

Section: Introductionmentioning

confidence: 99%

“…Different studies showed that these occurrences of low O 2 conditions evolved during seasonal stratification (von Westernhagen and Dethlefsen, 1983;Peeters et al, 1995), driven by eutrophication due to excess riverine nutrient loads (Brockmann and Eberlein, 1986;Brockmann et al, 1988;Peeters et al, 1995). In consequence, the 2nd International Conference on the Protection of the North Sea declared to "aim to achieve a substantial reduction (of the order of 50%) in inputs of phosphorus (P) and nitrogen (N) to these areas between " (ICNS-2, 1988, in order to mitigate the effects of eutrophication in the North Sea.…”

Section: Introductionmentioning

confidence: 99%

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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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“…Earlier studies have shown the potential for low oxygen events in the central North Sea (Postma and Rommets, 1984;Peeters et al, 1995;Boers, 2005;Weston et al, 2008;De Wilde et al, 1984) but seasonal and temporal coverage was limited. The North Sea, being surrounded by the industrialised nations of northern Europe including the United Kingdom, The Netherlands, Belgium, Denmark and Germany, receives significant anthropogenic nutrient riverine input with the Rhine, for example, resulting in dissolved inorganic nitrogen inputs of ∼300 ktonnes y −1 (De Jonge et al, 1996).…”

Section: Introductionmentioning

confidence: 99%

Detection of low bottom water oxygen concentrations in the North Sea; implications for monitoring and assessment of ecosystem health

et al. 2010

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Abstract. This paper presents new results from high temporal resolution observations over two years (2007 and 2008) from instrumented moorings deployed in the central North Sea, at the Oyster Grounds and on the northern slope of Dogger Bank (North Dogger). The water column was stratified in the summer at both sites, leading to limited exchange of the water in the bottom mixed layer. Data from these moorings revealed the variable nature of summer oxygen depletion at the Oyster Grounds. The combination of in situ and ship-based measurements allowed the physical and biological conditions leading to decreasing dissolved oxygen concentrations in bottom water to be examined. In 2007 and 2008, the concentration of dissolved oxygen in the bottom water at both sites was observed to decrease throughout the summer period after the onset of stratification. Depleted dissolved oxygen concentration (6.5 mg l −1 , 71% saturation) was measured at the North Dogger, a site which is not significantly influenced by anthropogenic nutrient inputs. Lower oxygen saturation (5.2 mg l −1 , 60% saturation) was measured for short durations at the Oyster Grounds. The seasonal increase in bottom water temperature accounted for 55% of the decrease in dissolved oxygen concentration at the Oyster Grounds compared to 10% at North Dogger.Dissolved oxygen concentration in bottom water at the Oyster Grounds was shown to be strongly influenced by short term events including storms and pulses of particulate organic matter input. In contrast, dissolved oxygen concentration in bottom water at the North Dogger reflected longer seaCorrespondence to: N. Greenwood (naomi.greenwood@cefas.co.uk) sonal processes such as a gradual temperature increase over the summer and a more steady supply of particulate organic matter to the bottom mixed layer. The differences between the study sites shows the need for an improved understanding of the mechanisms driving these processes if the use of oxygen in marine management and ensuring ecosystem health is to be meaningful and successful in the future. These high frequency observations provide greater understanding of the nature of the depletion in bottom oxygen concentration in the North Sea.

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The oxygen dynamics of the Oyster Ground, North Sea. Impact of eutrophication and environmental conditions

Cited by 28 publications

References 26 publications

Sedimentary and water column processes in the Oyster Grounds: A potentially hypoxic region of the North Sea

Sedimentary and water column processes in the Oyster Grounds: A potentially hypoxic region of the North Sea

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

Detection of low bottom water oxygen concentrations in the North Sea; implications for monitoring and assessment of ecosystem health

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