scholarly journals Turbulence measurements suggest high rates of new production over the shelf edge in the north-eastern North Sea during summer

2018 ◽  
Author(s):  
Jørgen Bendtsen ◽  
Katherine Richardson
Keyword(s):  
North Sea ◽  
Vertical Mixing ◽  
Euphotic Zone ◽  
Shelf Edge ◽  
Nutrient Inputs ◽  
New Production ◽  
The North ◽  
North Eastern ◽  
The North Sea ◽  
Using Data

Abstract. New production, i.e., that driven by allochthonous nutrient inputs, is the only form of primary production that can lead to net increases in organic material and is, therefore, important for understanding energy flow in marine ecosystems. The spatial distribution of new production is generally, however, not well known. Here, using data collected in July 2016, we analyse the potential for vertical mixing to support new production in the upper layers of the north eastern portion of the North Sea. Estimated nitrate fluxes due to turbulent vertical mixing into the euphotic zone were up to 0.5–1 mmol N m−2 d−1 over the shelf-edge (f-ratios > 0.1) while values of

scholarly journals Turbulence measurements suggest high rates of new production over the shelf edge in the northeastern North Sea during summer

2018 ◽  
Vol 15 (23) ◽  
pp. 7315-7332 ◽  
Author(s):  
Jørgen Bendtsen ◽  
Katherine Richardson
Keyword(s):  
North Sea ◽  
Vertical Mixing ◽  
Euphotic Zone ◽  
Bottom Layer ◽  
Depth Range ◽  
Shelf Edge ◽  
Nutrient Inputs ◽  
New Production ◽  
Edge Zone ◽  
The North

Abstract. New production, i.e. that driven by allochthonous nutrient inputs, is the only form of primary production that can lead to net increases in organic material and is, therefore, important for understanding energy flow in marine ecosystems. The spatial distribution of new production is generally, however, not well known. Using data collected in July 2016, we analyse the potential for vertical mixing to support new production in the upper layers of the northeastern portion of the North Sea. Relatively large (up to >0.5 mmol N m−2 d−1) nitrate fluxes due to turbulent vertical mixing into the euphotic zone were found at some stations over the shelf edge, while low values (< 0.1 mmol N m−2 d−1) were found in the deeper open area north of the shelf edge. The low vertical mixing rates (dissipation rates of turbulent kinetic energy below 10−8 W kg−1, corresponding to vertical turbulent diffusion coefficients of 10−6–10−5 m2 s−1) implied f ratios of <0.02 in the open waters north of the shelf edge. In the shallow (<50 m) southern and central part of the study area, inorganic nutrients were low and nitrate undetectable, suggesting negligible new production here, despite relatively high concentrations of chlorophyll a being found in the bottom layer. Thus, high rates of new production seem to be concentrated around the shelf-edge zone and in association with localized features exhibiting enhanced vertical mixing. We find that the nutricline depth is significantly deeper at the shelf edge and interference with increased mixing in this deeper depth range can explain the increased diapycnal nitrate fluxes. Overall, this suggests that the shelf-edge zone may be the major nutrient supplier to the euphotic zone in this area during the period of summer stratification.

scholarly journals Turbulence measurements suggest high rates of new production over the shelf edge in the northeastern North Sea during summer

2020 ◽  
Author(s):  
Jørgen Bendtsen ◽  
Katherine Richardson
Keyword(s):  
North Sea ◽  
Vertical Mixing ◽  
Euphotic Zone ◽  
Bottom Layer ◽  
Ecosystem Structure ◽  
Depth Range ◽  
Shelf Edge ◽  
New Production ◽  
Edge Zone ◽  
Turbulence Measurements

&lt;p&gt;The potential for vertical mixing to support new production in the upper layers of the northeastern portion of the North Sea was analysed from observations obtained during the stratified period in July 2016. Five transects across the shelf edge between the relatively shallow central North Sea and the deep Norwegian trench showed a clear frontal structure in hydrography, turbulent mixing, nutrients and chlorophyll a across the shelf edge. Relatively large (up to &gt;0.5&amp;#8201;mmol&amp;#8201;N&amp;#8201;m&lt;sup&gt;&amp;#8722;2&lt;/sup&gt;&amp;#8201;d&lt;sup&gt;&amp;#8722;1&lt;/sup&gt;) nitrate fluxes due to turbulent vertical mixing into the euphotic zone were found at some stations over the shelf edge, while low values (&lt;&amp;#8201;0.1&amp;#8201;mmol&amp;#8201;N&amp;#8201;m&lt;sup&gt;&amp;#8722;2&lt;/sup&gt;&amp;#8201;d&lt;sup&gt;&amp;#8722;1&lt;/sup&gt;) were found in the deeper open area north of the shelf edge. The low vertical mixing rates implied f ratios less than 0.02 in the open waters north of the shelf edge. In the shallow (&lt;50&amp;#8201;m) southern and central part of the study area, inorganic nutrients were low and nitrate undetectable, suggesting negligible new production here, despite relatively high concentrations of chlorophyll&amp;#160;a being found in the bottom layer. Thus, high rates of new production seem to be concentrated around the shelf-edge zone and in association with localized features exhibiting enhanced vertical mixing. We find that the nutricline depth is significantly deeper at the shelf edge and interference with increased mixing in this deeper depth range can explain the increased diapycnal nitrate fluxes. Overall, this suggests that the shelf-edge zone may be the major nutrient supplier to the euphotic zone in this area during the period of summer stratification. Potential impacts on plankton ecosystem structure are discussed.&lt;/p&gt;&lt;p&gt;Reference:&lt;/p&gt;&lt;p&gt;Bendtsen, J. and Richardson, K.: Turbulence measurements suggest high rates of new production over the shelf edge in the northeastern North Sea during summer, Biogeosciences, 15, 7315&amp;#8211;7332, https://doi.org/10.5194/bg-15-7315-2018, 2018.&lt;/p&gt;

Age and Growth of North Sea Echinoids

1985 ◽  
Vol 65 (3) ◽  
pp. 583-588 ◽  
Author(s):  
A. A. T. Sime ◽  
G. J. Cranmer
Keyword(s):  
Shallow Water ◽  
North Sea ◽  
Age And Growth ◽  
Eastern Area ◽  
The North ◽  
Small Variety ◽  
North Eastern ◽  
The North Sea ◽  
Northern North Sea

The genus Echinus is common throughout the entire northern North Sea. Echinus esculentus L. predominates in the shallow water off the eastern Scottish coast down to 100 m, while the small variety of Echinus acutus var. norvegicus (Düben and Koren) is rarely found in depths of less than 100 m and is most commonly located in the north-eastern area of the North Sea (Cranmer, 1985).

scholarly journals Evidence of a relationship between weight and total length of marine fish in the North-eastern Atlantic Ocean: physiological, spatial and temporal variations

2016 ◽  
Vol 98 (3) ◽  
pp. 617-625 ◽  
Author(s):  
Kélig Mahé ◽  
Elise Bellamy ◽  
Jean Paul Delpech ◽  
Coline Lazard ◽  
Michèle Salaun ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
North Sea ◽  
Temporal Variations ◽  
Bay Of Biscay ◽  
English Channel ◽  
Total Length ◽  
The North ◽  
Eastern Atlantic Ocean ◽  
North Eastern ◽  
The North Sea

Weight–Body Length relationships (WLR) of 45 fish species (37 Actinopterygii and eight Elasmobranchii) were investigated. A total of 31,167 individuals were caught and their biological parameters measured during the four quarters from 2013 to 2015, on five scientific surveys sampling the North-eastern Atlantic Ocean from the North Sea to the Bay of Biscay (ICES Divisions IVb, IVc, VIId, VIIe, VIIg, VIIh, VIIj, VIIIa and VIIIb). Among 45 tested species, all showed a significant correlation between total length (L) and total weight (W). The influence of sex on WLR was estimated for 39 species and presented a significant sexual dimorphism for 18 species. Condition factor (K) of females was always higher than for males. Moreover, a spatial effect on the WLR according to five ecoregions (the Bay of Biscay, the Celtic Sea, the Western English Channel, the Eastern English Channel and the North Sea), was significant for 18 species among 38 tested species. The temporal effect was tested according to components (year and quarter/season). The seasonality effect on WLR is more frequently significant than the year especially for the Elasmobranchii species, and can be related to the spawning season. Finally, depressiform species (skates, sharks and flatfish) are characterized by positive allometric growth, whereas there is no such clear pattern regarding roundfishes growth, whatever their body shape is.

Rapid turnover of dissolved DMS and DMSP by defined bacterioplankton communities in the stratified euphotic zone of the North Sea

2002 ◽  
Vol 49 (15) ◽  
pp. 3017-3038 ◽  
Author(s):  
Mikhail V. Zubkov ◽  
Bernhard M. Fuchs ◽  
Stephen D. Archer ◽  
Ronald P. Kiene ◽  
Rudolf Amann ◽  
...  
Keyword(s):  
North Sea ◽  
Euphotic Zone ◽  
Rapid Turnover ◽  
The North ◽  
The North Sea ◽  
Bacterioplankton Communities

Discarding practices for commercial gadoids in the North Sea

1998 ◽  
Vol 55 (7) ◽  
pp. 1632-1644 ◽  
Author(s):  
Yorgos Stratoudakis ◽  
Robert J Fryer ◽  
Robin M Cook
Keyword(s):  
North Sea ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Melanogrammus Aeglefinus ◽  
The North ◽  
The North Sea ◽  
Merlangius Merlangus ◽  
Using Data ◽  
Species Specific ◽  
Catch Composition

Understanding fishers' discarding behaviour, and anticipating their reactions to changes in the biological or regulatory characteristics of a fishery, are important for dealing with the problem of discarding. In this paper, we investigate the discarding of haddock (Melanogrammus aeglefinus), whiting (Merlangius merlangus), and Atlantic cod (Gadus morhua) in the North Sea, using data collected by scientific observers onboard Scottish demersal vessels. We describe discarding on each trip by species-specific discard curves and explore how these curves depend on biological and regulatory variables. There are large differences in the size of discarded fish between inshore and offshore areas, with offshore-operating vessels discarding larger fish (high-grading). Increases in legal landing size correspond to immediate increases in the size of discarded fish, particularly for haddock and cod in inshore areas. In general, discarding practices for haddock and cod are similar over time and consistent across gears, whereas decisions for the lesser valued whiting are more variable and can be affected by the catch composition.

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