scholarly journals A decline in primary production in the North Sea over 25 years, associated with reductions in zooplankton abundance and fish stock recruitment

2017 ◽  
Vol 24 (1) ◽  
pp. e352-e364 ◽  
Author(s):  
Elisa Capuzzo ◽  
Christopher P. Lynam ◽  
Jon Barry ◽  
David Stephens ◽  
Rodney M. Forster ◽  
...  
Keyword(s):  
Primary Production ◽  
North Sea ◽  
Fish Stock ◽  
Zooplankton Abundance ◽  
The North ◽  
Stock Recruitment ◽  
The North Sea

Combined analyses reveal environmentally driven changes in the North Sea ecosystem and raise questions regarding what makes an ecosystem model’s performance credible?

2014 ◽  
Vol 71 (1) ◽  
pp. 31-46 ◽  
Author(s):  
Steven Mackinson
Keyword(s):  
Primary Production ◽  
North Sea ◽  
Ecosystem Model ◽  
Ecosystem Approach ◽  
Trophic Levels ◽  
Fish Stock ◽  
Supporting Evidence ◽  
Sea Temperature ◽  
The North ◽  
The North Sea

When an ecosystem model of the North Sea is calibrated to data from multiple trophic levels, the model estimated the primary production required to support the food web correlates temporally with observed changes in sea temperature and nutrient levels, supporting evidence from empirical analyses. However, a different result is given from an alternative calibration using fish stock data only. The inference taken from the emergent primary production – temperature relationship and empirical data are that, on balance, there is stronger overall evidence to support the calibration constrained at multiple trophic levels. Two important implications of the findings are (i) that the relative importance of fishing and environmental effects is likely to be interpreted differently depending on the calibration approach and (ii) the contrasting model calibrations would give different responses to fishing policies. It raises questions regarding how to judge the performance (and credibility) of an ecosystem model and the critical importance of conducting empirical and modelling analyses in parallel. Adopting a combined approach to ecosystem modelling is an important step in the pursuit of operational and defensible tools to support the ecosystem approach to management.

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

2013 ◽  
Vol 10 (6) ◽  
pp. 3767-3792 ◽  
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.

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

2012 ◽  
Vol 9 (11) ◽  
pp. 16625-16662 ◽  
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.

The contribution of the deep chlorophyll maximum to primary production in a seasonally stratified shelf sea, the North Sea

2013 ◽  
Vol 113 (1-3) ◽  
pp. 153-166 ◽  
Author(s):  
Liam Fernand ◽  
Keith Weston ◽  
Tom Morris ◽  
Naomi Greenwood ◽  
Juan Brown ◽  
...  
Keyword(s):  
Primary Production ◽  
North Sea ◽  
Deep Chlorophyll Maximum ◽  
Chlorophyll Maximum ◽  
The North ◽  
Shelf Sea ◽  
The North Sea

Decadal changes in the North Sea food web between 1981 and 1991 — implications for fish stock assessment

2006 ◽  
Vol 63 (11) ◽  
pp. 2586-2602 ◽  
Author(s):  
Alexander Kempf ◽  
Jens Floeter ◽  
Axel Temming
Keyword(s):  
Food Web ◽  
North Sea ◽  
Fish Stock ◽  
Fish Diet ◽  
Data Set ◽  
The North ◽  
Stock Biomass ◽  
Spawning Stock ◽  
The North Sea ◽  
The Impact

The North Sea ecosystem of the early 1980s differed substantially from that of the early 1990s. The current North Sea multispecies fisheries assessment models are parameterized by fish diet data sets that reflect both ecosystem states, as the stomachs were sampled in 1981 and 1991. In this study, multispecies virtual population analysis (MSVPA) was parameterized with either diet data set, leading to different model food webs, each representing the predator's diet selection behavior and spatiotemporal overlap with their prey in the two respective ecosystem states. The impact of these changes in predator preferences and spatiotemporal overlap on recruitment success and on stock developments could be demonstrated by using either stomach data set to estimate historic and future spawning stock biomass and recruitment trajectories. The observed changes in the food web mainly impacted the hindcasted recruitment trajectories, whereas spawning stock biomass estimates were quite robust. In the prediction runs, the differences in the survival rate of the recruits decided whether fish stocks of commercially important species (e.g., Gadus morhua, Merlangius merlangus) would recover or collapse in the near future.

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