The distribution and seasonal variation of alkalinity in the Southern Bight of the North Sea and in the Western Wadden Sea

doi:10.1016/0077-7579(90)90053-J

Netherlands Journal of Sea Research

Volume 26, Issue 1, October 1990, Pages 11-23

https://doi.org/10.1016/0077-7579(90)90053-J Get rights and content

Abstract

Alkalinity distributions were measured seasonally in the western Wadden Sea and in the Southern Bight of the North Sea. Although the distributions varied considerably both spatially and temporally the relationships with salinity in the areas were linear. The large scattering and the sometimes simultaneous discrepancies between extrapolated and measured freshwater alkalinity are predominantly ascribed to short-term variations in freshwater alkalinity. Only in the Wadden Sea in May was apparent non-conservative behaviour of alkalinity concluded. An analysis of the large scattering revealed more contributors, such as additional (high-alkalinity) freshwater sources and alkalinity supply from the sediments. In the North Sea distributions were mainly scattered early in the year, largely caused by strong variations in the Rhine alkalinity. Alkalinity allowed a discrimination of the plumes of the rivers Rhine and Scheldt (the alkalinity of the latter being much higher). Likewise the salinity-alkalinity plots for Wadden Sea and North Sea were sufficiently different. The actual use of alkalinity as a tracer, however, is strongly hampered by freshwater variations and several additional high-alkalinity sources.

References (41)

A.J.van Bennekom et al.
The seasonal cycles of reactive silicate and suspended diatoms in the Dutch Wadden Sea
Neth. J. Sea Res.
(1974)
J.J. Beukema
Biomass and species richness of the macrobenthic animals living on the tidal flats of the Dutch Wadden Sea
Neth. J. Sea Res.
(1976)
R. Dekker
The macrozoobenthos of the subtidal western Dutch Wadden Sea. I. Biomass and species richness
Neth. J. Sea Res.
(1989)
J.C. Duinker et al.
On the behaviour of copper, zinc, iron and manganese, and evidence for mobilization processes in the Dutch Wadden Sea
Neth. J. Sea Res.
(1974)
W. Helder
The cycle of dissolved inorganic nitrogen compounds in the Dutch Wadden Sea
Neth. J. Sea Res.
(1974)
F.J. Millero et al.
International one-atmosphere equation of state of seawater
Deep-Sea Res.
(1981)
E. Pelletier et al.
Hydrochemistry of dissolved inorganic carbon in the St. Lawrence Estuary (Canada)
Est. coast. mar. Sci.
(1979)
H. Postma
The cycle of nitrogen in the Wadden Sea and adjacent areas
Neth. J. Sea Res.
(1966)
H. Postma et al.
Breakdown and production of fluorescent substances in Dutch waters
Neth. J. Sea Res.
(1976)
J.W. Rommets
The carbon dioxide system; its behaviour in decomposition processes in east Indonesian basins
Neth. J. Sea Res.
(1988)

M.M. Rutgers van der Loeff

Nutrients in interstitial waters of the Southern Bight of the North Sea

Neth. J. Sea Res.

(1980)

L.E. Schemel et al.

Response of northern San Francisco Bay to riverine inputs of dissolved inorganic carbon, silicon, nitrogen and phosphorus

M.J.W. Veldhuis et al.

Phytoplankton primary production and biomass in the western Wadden Sea (The Netherlands); a comparison with an ecosystem model

Neth. J. Sea Res.

(1988)

J.T.F. Zimmerman

Mixing and flushing of tidal embayments in the western Dutch Wadden Sea. Part 1: Distribution of salinity and calculation of mixing time scales

Neth. J. Sea Res.

(1976)

Anonymous

Internationales Hydrologisches Programm

J.D. Burton et al.

Estuarine chemistry

(1976)

J.H. Carpenter et al.

Processes affecting the composition of estuarine waters (HCO₃, Fe, Mn, Zn, Cu, Ni, Cr, Co, Cd)

L.E. Cronin

D. Dyrssen et al.

Major and minor elements, chemical speciation in estuarine waters

EON

Ecosysteemmodel van de westelijke Wadden-zee (Ecosystem model of the western Wadden Sea)

Cited by (19)

Tidal and spatial variations of DI<sup>13</sup>C and aquatic chemistry in a temperate tidal basin during winter time
2014, Journal of Marine Systems
Citation Excerpt :
The pelagic carbonate system in the southern part of the North Sea may significantly be impacted by the intense biogeochemical processes taking place within the tidal areas of the southern North Sea (e.g., Brasse et al., 1999; Provoost et al., 2010; Thomas et al., 2005, 2009). Only few studies, however, were carried out on the dynamics in the carbonate system in the tidal basins, so far (Hoppema, 1990; Klaasen and Spilmont, 2012; Moore et al., 2011). The tidal areas of the southern North Sea have been identified as an important source of DIC and alkalinity which is exported into the North Sea by tidal action (Brasse et al., 1999; Provoost et al., 2010; Reimer et al., 1999; Thomas et al., 2005, 2009), and it has been suggested that enhanced organic matter mineralization in the tidal systems may be responsible for the alkalinity production and pH modifications (Brasse et al., 1999; Thomas et al., 2005, 2009; Al-Raei et al., 2009; Provoost et al., 2010).
Here, the pelagic carbonate system and the δ¹³C signature of dissolved inorganic carbonate (DIC) were investigated in a tidal basin of the southern North Sea, the Jade Bay, with respect to tidal cycles and a transect towards the North Sea in winter time (January and November, 2010). Physical parameters, major and trace elements, and nutrient concentrations were considered, too. Primary production and pelagic organic matter respiration were negligible during winter time. Both, the compositional variations on the transects as well as during the tidal cycles indicate the mixing of North Sea with fresh water. The combined spatial co-variations of different parameters indicate an introduction of fresh water that was enriched in DI¹²C, metabolites (e.g., ammonia), protons, and dissolved redox-sensitive elements (e.g., Mn^2 +). During the January campaign, the discharge via the flood gates was limited due to ice cover of the hinterland drainage ditches, allowing for an observation of tidal variations without significant mixing contributions from surface water discharges. Considering a binary mixing model with North Sea and fresh water as end-members, the extrapolated fresh water end-member composition for this campaign is estimated to contain about 3.8 mmol/kg DIC (δ¹³C ≈ − 10 ± 1‰ vs. VPDB), and enhanced concentrations of NH₄⁺, Mn^2 +, and protons compared to North Sea water. The fast temporal response of dissolved geochemical tracers on tidal variations in the Jade Bay indicates a continuous supply of a fresh water component. The measured composition of fresh waters entering the Jade Bay via flood gates (end of October, 2010) did not match the values estimated by the binary mixing model. Therefore, the overall fresh water component likely is a mixture between sources originating from flood gates and (in January) dominating submarine groundwater discharge entering the Jade Bay. This model is consistent with the results obtained during the November campaign, when a more important contribution from flood gates is expected and a more variable fresh water end-member is estimated. The co-variations of the concentrations and the stable carbon isotope composition of DIC are applied to evaluate possible superimposed sink-source-transformation processes in the coastal waters and a general co-variation scheme is suggested.
The continental shelf pump for CO <inf>2</inf> in the North Sea - Evidence from summer observation
2005, Marine Chemistry
Data on the distribution of dissolved inorganic carbon (DIC) and partial pressure of CO₂ (pCO₂) were obtained during a cruise in the North Sea during late summer 2001. A 1° by 1° grid of 97 stations was sampled for DIC while the pCO₂ was measured continuously between the stations. The surface distributions of these two parameters show a clear boundary located around 54°N. South of this boundary the DIC and pCO₂ range from 2070 to 2130 μmol kg⁻¹ and 290 to 490 ppm, respectively, whereas in the northern North Sea, values range between 1970 and 2070 μmol kg⁻¹ and 190 to 350 ppm, respectively. The vertical profiles measured in the two different areas show that the mixing regime of the water column is the major factor determining the surface distributions. The entirely mixed water column of the southern North Sea is heterotrophic, whereas the surface layer of the stratified water column in the northern North Sea is autotrophic. The application of different formulations for the calculation of the CO₂ air–sea fluxes shows that the southern North Sea acts as a source of CO₂ for the atmosphere within a range of +0.8 to +1.7 mmol m⁻² day⁻¹, whereas the northern North Sea absorbs CO₂ within a range of −2.4 to −3.8 mmol m⁻² day⁻¹ in late summer. The North Sea as a whole acts as a sink of atmospheric CO₂ of −1.5 to −2.2 mmol m⁻² day⁻¹ during late summer. Compared to the Baltic and the East China Seas at the same period of the year, the North Sea acts a weak sink of atmospheric CO₂. The anticlockwise circulation and the short residence time of the water in the North Sea lead to a rapid transport of the atmospheric CO₂ to the deeper layer of the North Atlantic Ocean. Thus, in late summer, the North Sea exports 2.2×10¹² g C month⁻¹ to the North Atlantic Ocean via the Norwegian trench, and, at the same period, absorbs from the atmosphere a quantity of CO₂ (0.4 10¹² g C month⁻¹) equal to 15% of that export, which makes the North Sea a continental shelf pump of CO₂.
The influence of intertidal mudflats on the dissolved inorganic carbon and total alkalinity distribution in the German Bight, southeastern North Sea
1999, Journal of Sea Research
The distribution of dissolved inorganic carbon (DIC) and total alkalinity (TA) in the German Bight, southeastern North Sea, was investigated during winter (February/March) 1996. Generally, high biological activity and riverine input dominate the carbon chemistry of this area for most of the year and mask impacts of other processes. During the investigation period, the presence of extended ice sheets, low river discharge and minimal primary productivity in the German Bight allowed the recognition of a considerable influence from sediment–water interaction. Water masses in front of the North Frisian Wadden Sea were clearly distinguished from others by considerably higher DIC and TA concentrations and a different DIC : TA ratio. We suggest that remineralisation products of Wadden Sea sediments and the DIC- and TA-enriched porewaters were subsequently released into the water column by enhanced erosion due to ice drift. The DIC : TA ratio of 1 : 1 indicates that either sulphate reduction or a combination of carbonate dissolution and aerobic remineralisation were the main processes generating this DIC. The calculated amount of DIC delivered from the Wadden Sea to the German Bight of about 10,000 t (equivalent to 76 mmol m⁻² d⁻¹) was in the same order of magnitude as the riverine input and about ten times higher than by diffusion alone. Apparently, for the carbon cycling in the coastal waters, sediment–water interaction may be a relevant process.
Daily and seasonal variations of the partial pressure of CO<inf>2</inf> in surface seawater along Belgian and southern Dutch coastal areas
1999, Journal of Marine Systems
The variations of the partial pressure of CO₂ (pCO₂) and related parameters were determined in surface seawater along the Belgian coast, from January 1995 to June 1996, at both daily and seasonal time scales. The distribution of pCO₂ in this area is regulated by river input from the Scheldt, biological activity and hydrodynamics. The contribution of each of these processes varies as a function of the considered time scale: (i) the daily variation of pCO₂ depends on the tide although modulated by the biological diel cycle; (ii) the seasonal variation of pCO₂ depends on the input from the Scheldt and the seasonal variations of phytoplanktonic biomass. During winter, the plume of the river Scheldt is oversaturated in pCO₂ with respect to the atmosphere. During spring and summer, phytoplankton blooms occur both in the lower Scheldt estuary and in the river plume and may lead to undersaturation of pCO₂ in the easternmost area of the river plume. However, the degradation of phytoplankton induces oversaturation of pCO₂, in the westernmost area of the plume. Furthermore, the inter-annual variation of pCO₂ depends partly on the fluctuations of the discharge of the Scheldt. Our preliminary results strongly suggest that, on an annual basis, the Scheldt plume behaves as a net source of CO₂ to the atmosphere.
CO<inf>2</inf> fluxes from a coastal transect: A time-series approach
1998, Marine Chemistry
The coastal ocean is a region with highly variable physical processes, and high and variable rates of primary production and organic matter recycling, but very little is known about the effect of these factors on the flux of CO₂ into or out of this environment. To address this question, a time-series of geochemical measurements was initiated along a 32 km transect across the inner continental shelf, off New Jersey. Water column measurements of temperature, salinity, total carbon dioxide, total alkalinity, oxygen and nutrients were made approximately monthly at seven stations along the transect. Fluxes (−0.43 to −0.84 mol m⁻² yr⁻¹) calculated from local wind speed and the air–sea CO₂ difference indicate that this region acts as a small net sink for atmospheric CO₂ on a yearly averaged basis. The inner and outer stations varied on different time-scales, but in general, surface waters were a source of CO₂ to the atmosphere in the summer and fall, offset by large fluxes into the surface waters during the winter to early spring. The calculated fugacity of surface water carbon dioxide (fCO₂) between April 1994 and April 1996 ranged from 211 to 658 μatm. Superimposed on the large spatial and temporal variability typical of the coastal environment, was a clear seasonal trend in fCO₂ which was primarily responsible for the observed trend in the flux. The dominant processes responsible for the observed changes in fCO₂ are examined in detail. An important finding is that the magnitude of the effect of organic matter cycling on changes in fCO₂ generally decreased in the offshore direction.
Dissolved carbon dioxide in Dutch coastal waters
1996, Marine Chemistry
The role of shelf seas in global carbon cycling is poorly understood. The dissolved inorganic carbon system and air-sea exchange of carbon dioxide (CO₂) are described for the Dutch coastal zone in September 1993. The inorganic carbon chemistry was affected by tidal mixing, wind speed, wind direction, freshwater input, stratification and coastal upwelling. Surface water had a variable fugacity of carbon dioxide (f_CO₂) between 300 and 800 μatm with short-term changes partly related to the tidal cycle. High contents of dissolved inorganic carbon (DIC) and CO₂ in relatively saline water probably originated from mineralisation of accumulated organic matter in water and sediments farther out at sea and transport of water enriched in DIC into the coastal zone by upwelling. Air-sea exchange of CO₂ ranged from —20 to 60 mmol m⁻² day⁻¹. These fluxes are critically discussed in the light of potential stratification. It is not possible to assess from this study whether the Dutch coastal zone is a net sink or source for atmospheric CO₂.

View all citing articles on Scopus

View full text

The distribution and seasonal variation of alkalinity in the Southern Bight of the North Sea and in the Western Wadden Sea

Abstract

Neth. J. Sea Res.

Neth. J. Sea Res.

Neth. J. Sea Res.

Neth. J. Sea Res.

Neth. J. Sea Res.

Deep-Sea Res.

Est. coast. mar. Sci.

Neth. J. Sea Res.

Neth. J. Sea Res.

Neth. J. Sea Res.

Neth. J. Sea Res.

Neth. J. Sea Res.

Neth. J. Sea Res.

Internationales Hydrologisches Programm

Estuarine chemistry

Processes affecting the composition of estuarine waters (HCO3, Fe, Mn, Zn, Cu, Ni, Cr, Co, Cd)

Major and minor elements, chemical speciation in estuarine waters

Ecosysteemmodel van de westelijke Wadden-zee (Ecosystem model of the western Wadden Sea)

Processes affecting the composition of estuarine waters (HCO₃, Fe, Mn, Zn, Cu, Ni, Cr, Co, Cd)