Biological production of methyl bromide in the coastal waters of the North Sea and open ocean of the northeast Atlantic

Abstract. A description of the carbonate system has been incorporated in the MIRO biogeochemical model to investigate the contribution of diatom and Phaeocystis blooms to the seasonal dynamics of air-sea CO2 exchanges in the Eastern Channel and Southern Bight of the North Sea, with focus on the eutrophied Belgian coastal waters. For this application, the model was implemented in a simplified three-box representation of the hydrodynamics with the open ocean boundary box ‘Western English Channel’ (WCH) and the ‘French Coastal Zone’ (FCZ) and ‘Belgian Coastal Zone’ (BCZ) boxes receiving carbon and nutrients from the rivers Seine and Scheldt, respectively. Results were obtained by running the model for the 1996–1999 period. The simulated partial pressures of CO2 (pCO2) were successfully compared with data recorded over the same period in the central BCZ at station 330 (51°26.05′ N; 002°48.50′ E). Budget calculations based on model simulations of carbon flow rates indicated for BCZ a low annual sink of atmospheric CO2 (−0.17 mol C m-2 y-1). On the opposite, surface water pCO2 in WCH was estimated to be at annual equilibrium with respect to atmospheric CO2. The relative contribution of biological, chemical and physical processes to the modelled seasonal variability of pCO2 in BCZ was further explored by running model scenarios with separate closures of biological activities and/or river inputs of carbon. The suppression of biological processes reversed direction of the CO2 flux in BCZ that became, on an annual scale, a significant source for atmospheric CO2 (+0.53 mol C m-2 y-1). Overall biological activity had a stronger influence on the modelled seasonal cycle of pCO2 than temperature. Especially Phaeocystis colonies which growth in spring were associated with an important sink of atmospheric CO2 that counteracted the temperature-driven increase of pCO2 at this period of the year. However, river inputs of organic and inorganic carbon were shown to increase the surface water pCO2 and hence the emission of CO2 to the atmosphere. Same calculations conducted in WCH, showed that temperature was the main factor controlling the seasonal pCO2 cycle in these open ocean waters. The effect of interannual variations of fresh water discharge (and related nutrient and carbon inputs), temperature and wind speed was further explored by running scenarios with forcing typical of two contrasted years (1996 and 1999). Based on these simulations, the model predicts significant variations in the intensity and direction of the annual air-sea CO2 flux.

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NW European shelf under climate warming: implications for open ocean – shelf exchange, primary production, and carbon absorption

Biogeosciences ◽

10.5194/bg-10-3767-2013 ◽

2013 ◽

Vol 10 (6) ◽

pp. 3767-3792 ◽

Cited By ~ 43

Author(s):

M. Gröger ◽

E. Maier-Reimer ◽

U. Mikolajewicz ◽

A. Moll ◽

D. Sein

Keyword(s):

Primary Production ◽

North Sea ◽

Open Ocean ◽

Global Ocean ◽

Fish Stock ◽

Co2 Absorption ◽

Biological Production ◽

The North ◽

European Shelf ◽

The North Sea

Abstract. Shelves have been estimated to account for more than one-fifth of the global marine primary production. It has been also conjectured that shelves strongly influence the oceanic absorption of anthropogenic CO2 (carbon shelf pump). Owing to their coarse resolution, currently applied global climate models are inappropriate to investigate the impact of climate change on shelves and regional models do not account for the complex interaction with the adjacent open ocean. In this study, a global ocean general circulation model and biogeochemistry model were set up with a distorted grid providing a maximal resolution for the NW European shelf and the adjacent northeast Atlantic. Using model climate projections we found that already a~moderate warming of about 2.0 K of the sea surface is linked with a reduction by ~ 30% of the biological production on the NW European shelf. If we consider the decline of anthropogenic riverine eutrophication since the 1990s, the reduction of biological production amounts is even larger. The relative decline of NW European shelf productivity is twice as strong as the decline in the open ocean (~ 15%). The underlying mechanism is a spatially well confined stratification feedback along the continental shelf break. This feedback reduces the nutrient supply from the deep Atlantic to about 50%. In turn, the reduced productivity draws down CO2 absorption in the North Sea by ~ 34% at the end of the 21st century compared to the end of the 20th century implying a strong weakening of shelf carbon pumping. Sensitivity experiments with diagnostic tracers indicate that not more than 20% of the carbon absorbed in the North Sea contributes to the long-term carbon uptake of the world ocean. The rest remains within the ocean's mixed layer where it is exposed to the atmosphere. The predicted decline in biological productivity, and decrease of phytoplankton concentration (in the North Sea by averaged 25%) due to reduced nutrient imports from the deeper Atlantic will probably affect the local fish stock negatively and therefore fisheries in the North Sea.

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NW European shelf under climate warming: implications for open ocean – shelf exchange, primary production, and carbon absorption

Biogeosciences Discussions ◽

10.5194/bgd-9-16625-2012 ◽

2012 ◽

Vol 9 (11) ◽

pp. 16625-16662 ◽

Cited By ~ 2

Author(s):

M. Gröger ◽

E. Maier-Reimer ◽

U. Mikolajewicz ◽

A. Moll ◽

D. Sein

Keyword(s):

Primary Production ◽

North Sea ◽

Open Ocean ◽

Global Ocean ◽

Fish Stock ◽

Co2 Absorption ◽

Biological Production ◽

The North ◽

European Shelf ◽

The North Sea

Abstract. Shelves have been estimated to account for more than one fifth of the global marine primary production. It has been also conjectured that shelves strongly influence the oceanic absorption of atmospheric CO2 (carbon shelf pump). Owing to their coarse resolution, currently applied global climate models are inappropriate to investigate the impact of climate change on shelfs and regional models do not account for the complex interaction with the adjacent open ocean. In this study, a global ocean general circulation model and biogeochemistry model were set up with a distorted grid providing a maximal resolution for the NW European shelf and the adjacent North Atlantic. Using model climate projections we found that already a moderate warming of about 2.0 K of the sea surface is linked with a reduction by ~ 30% of biological production on the NW European shelf. If we consider the decline of anthropogenic riverine eutrophication since the 90's the reduction of biological production amounts to 39%. The decline of NW European shelf productivity is twice as strong as the decline in the open ocean (~ 15%). The underlying mechanism is a spatially well confined stratification feedback along the continental shelf break. This feedback reduces the nutrient supply from the deep Atlantic to about 50%. In turn, the reduced productivity draws down CO2 absorption on the NW European shelf by ~ 34% at the end of the 21st century compared to the end of the 20th century implying a strong weakening of shelf carbon pumping. Sensitivity experiments with diagnostic tracers indicate that not more than 20% of the carbon absorbed in the North Sea contributes to the long term carbon uptake of the world ocean. The rest remains within the ocean mixed layer where it is exposed to the atmosphere. The predicted decline in biological productivity and decrease of phytoplankton concentration (by averaged 25%) due to reduced nutrient imports from the deeper Atlantic will probably negatively affect the local fish stock and therefore fisheries in the North Sea.

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Temperature, Salinity and Plankton in the Eastern North Atlantic and Coastal Waters of Britain, 1957.: I. The Characterisation and Distribution of Surface Waters

Journal of the Fisheries Research Board of Canada ◽

10.1139/f63-052 ◽

1963 ◽

Vol 20 (3) ◽

pp. 789-826 ◽

Cited By ~ 11

Author(s):

B. McK. Bary

Keyword(s):

North Sea ◽

North Atlantic ◽

Coastal Waters ◽

Water Bodies ◽

English Channel ◽

Oceanic Water ◽

Climatic Fluctuations ◽

The North ◽

The North Sea ◽

Eastern North Atlantic

Monthly temperature-salinity diagrams for 1957 have demonstrated that three surface oceanic "water bodies" were consistently present in the eastern North Atlantic; two are regarded as modified North Atlantic Central water which give rise to the third by mixing. As well in the oceanic areas, large and small, high or low salinity patches of water were common. Effects of seasonal climatic fluctuations differed in the several oceanic water bodies. In coastal waters, differences in properties and in seasonal and annual cycles of the properties distinguish the waters from the North Sea, English Channel and the western entrance to the Channel.The geographic distributions of the oceanic waters are consistent with "northern" and "southern" water bodies mixing to form a "transitional" water. Within this distribution there are short-term changes in boundaries and long-term (seasonal) changes in size of the water bodies.Water in the western approaches to the English Channel appeared to be influenced chiefly by the mixed, oceanic transitional water; oceanic influences in the North Sea appear to have been from northern and transitional waters.

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Possible resting cysts ofDissodinium pseudolunulaSwift ex Elbrächter et Drebes in the Northeast Atlantic and the North Sea

British Phycological Journal ◽

10.1080/00071618300650071 ◽

1983 ◽

Vol 18 (1) ◽

pp. 61-67 ◽

Cited By ~ 7

Author(s):

A.W.G. John ◽

P.C. Reid

Keyword(s):

North Sea ◽

Northeast Atlantic ◽

The North ◽

The North Sea ◽

Resting Cysts

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Opportunistically recorded acoustic data support Northeast Atlantic mackerel expansion theory

ICES Journal of Marine Science ◽

10.1093/icesjms/fsv243 ◽

2015 ◽

Vol 73 (4) ◽

pp. 1115-1126 ◽

Cited By ~ 11

Author(s):

Jeroen van der Kooij ◽

Sascha M.M. Fässler ◽

David Stephens ◽

Lisa Readdy ◽

Beth E. Scott ◽

...

Keyword(s):

North Sea ◽

Stock Assessment ◽

Detection Algorithm ◽

Trawl Survey ◽

Northeast Atlantic ◽

Acoustic Data ◽

The North ◽

The North Sea ◽

Northern North Sea ◽

Feeding Grounds

Abstract Fisheries independent monitoring of widely distributed pelagic fish species which conduct large seasonal migrations is logistically complex and expensive. One of the commercially most important examples of such a species in the Northeast Atlantic Ocean is mackerel for which up to recently only an international triennial egg survey contributed to the stock assessment. In this study, we explore whether fisheries acoustic data, recorded opportunistically during the English component of the North Sea International Bottom Trawl Survey, can contribute to an improved understanding of mackerel distribution and provide supplementary data to existing dedicated monitoring surveys. Using a previously published multifrequency acoustic mackerel detection algorithm, we extracted the distribution and abundance of schooling mackerel for the whole of the North Sea during August and September between 2007 and 2013. The spatio-temporal coverage of this unique dataset is of particular interest because it includes part of the unsurveyed summer mackerel feeding grounds in the northern North Sea. Recent increases in landings in Icelandic waters during this season suggested that changes have occurred in the mackerel feeding distribution. Thus far it is poorly understood whether these changes are due to a shift, i.e. mackerel moving away from their traditional feeding grounds in the northern North Sea and southern Norwegian Sea, or whether the species' distribution has expanded. We therefore explored whether acoustically derived biomass of schooling mackerel declined in the northern North Sea during the study period, which would suggest a shift in mackerel distribution rather than an expansion. The results of this study show that in the North Sea, schooling mackerel abundance has increased and that its distribution in this area has not changed over this period. Both of these findings provide, to our knowledge, the first evidence in support of the hypothesis that mackerel have expanded their distribution rather than moved away.

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