Structure of Pelagic Food Chain and Relationship Between Plankton and Fish Production

1977 ◽  
Vol 34 (12) ◽  
pp. 2344-2353 ◽  
Author(s):  
R. W. Sheldon ◽  
W. H. Sutcliffe Jr. ◽  
M. A. Paranjape
Keyword(s):  
North Sea ◽  
Gulf Of Maine ◽  
Standing Stock ◽  
Phytoplankton Production ◽  
Structural Elements ◽  
Pelagic Ecosystem ◽  
Predator Prey ◽  
The North ◽  
Plankton Production ◽  
The North Sea

Further observations on the standing stocks of pelagic organisms confirm the occurrence of approximately equal biomass over logarithmically equal size ranges. A simple theoretical framework is developed that shows that the structural elements of the pelagic ecosystem can be described in terms of the sizes of predator and prey and of the efficiencies of their interactions. In practice this means that if the standing stock at any size range is known, the standing stock at any other size can be estimated, and if the growth rate at this size is known, the production can be estimated. The theory is tested on three fisheries. For the Gulf of Maine and the North Sea, phytoplankton production is estimated from fishery production. For the area off Peru the fishery production is estimated from the plankton production. Key words: pelagic ecosystem, predator–prey relationships, plankton production, marine fisheries, Peru, North Sea, Gulf of Maine

scholarly journals Geological evolution of the Chalk Group in the northern Dutch North Sea: inversion, sedimentation and redeposition

2018 ◽  
Vol 156 (07) ◽  
pp. 1265-1284
Author(s):  
EVA VAN DER VOET ◽  
LEONORA HEIJNEN ◽  
JOHN J. G. REIJMER
Keyword(s):  
North Sea ◽  
Late Cretaceous ◽  
Seismic Survey ◽  
Structural Elements ◽  
The North ◽  
Show Evidence ◽  
New Finding ◽  
The North Sea ◽  
Thickness Variations ◽  
Well Data

AbstractIn contrast to the Norwegian and Danish sectors, where significant hydrocarbon reserves were found in chalk reservoirs, limited studies exist analysing the chalk evolution in the Dutch part of the North Sea. To provide a better understanding of this evolution, a tectono-sedimentary study of the Late Cretaceous to Early Palaeogene Chalk Group in the northern Dutch North Sea was performed, facilitated by a relatively new 3D seismic survey. Integrating seismic and biostratigraphic well data, seven chronostratigraphic units were mapped, allowing a reconstruction of intra-chalk geological events.The southwestward thickening of the Turonian sequence is interpreted to result from tilting, and the absence of Coniacian and Santonian sediments in the western part of the study area is probably the result of non-deposition. Seismic truncations show evidence of a widespread inversion phase, the timing of which differs between the structural elements. It started at the end of the Campanian followed by a second pulse during the Maastrichtian, a new finding not reported before. After subsidence during the Maastrichtian and Danian, renewed inversion and erosion occurred at the end of the Danian. Halokinesis processes resulted in thickness variations of chalk units of different ages.In summary, variations in sedimentation patterns in the northern Dutch North Sea relate to the Sub-Hercynian inversion phase during the Campanian and Maastrichtian, the Laramide inversion phase at the end of the Danian, and halokinesis processes. Additionally, the Late Cretaceous sea floor was characterized by erosion through contour bottom currents at different scales and resedimentation by slope failures.

scholarly journals Running the gauntlet: the predation environment of small fish in the northern Gulf of St Lawrence, Canada

2005 ◽  
Vol 62 (3) ◽  
pp. 412-416 ◽  
Author(s):  
Daniel E. Duplisea
Keyword(s):  
Body Size ◽  
North Sea ◽  
Prey Size ◽  
Small Fish ◽  
Size Spectra ◽  
Predator Prey ◽  
The North ◽  
Prefer Prey ◽  
Seal Population ◽  
The North Sea

Abstract Predation size spectra were constructed for the northern Gulf of St Lawrence, covering prey size ranges that include pre-recruit cod. Predation by fish and harp seals was modelled with a log-normally distributed predator–prey size ratio along with a relationship between predator body size and the energy required. Fish concentrate predation on prey of weight 0.5–2 g, whereas harp seals prefer prey of 60–125 g. It is speculated that predation caused by harp seals on pre-recruits could be a major factor limiting cod recruitment in the system. The northern Gulf of St Lawrence is a cold boreal system with a large predatory seal population, and cod recruit older than elsewhere. Therefore, cod recruitment may be more strongly affected by predation in the northern Gulf of St Lawrence than in warmer systems such as the North Sea, where recruitment is strongly influenced by temperature.

PETROLEUM HYDROCARBONS IN THE NORTH SEA

1979 ◽  
Vol 1979 (1) ◽  
pp. 629-632 ◽  
Author(s):  
Otto Grahl-Nielsen ◽  
Kjell Westrheim ◽  
Svein Wilhelmsen
Keyword(s):  
Gas Chromatography ◽  
North Sea ◽  
Petroleum Hydrocarbons ◽  
Standing Stock ◽  
Selected Ion Monitoring ◽  
Short Residence Time ◽  
The North ◽  
Alkyl Derivatives ◽  
Water Sampler ◽  
The North Sea

ABSTRACT Since May 1976, a number of water samples have been collected from various areas in the North Sea. Most of the samples were taken at 1 m depth, but samples were also obtained from depths down to 100 m by the use of a specially-developed water sampler. The analysis was carried out by capillary gas chromatography with a mass spectrometer as detector. By selected ion monitoring, the petrogenic hydrocarbons naphthalene, phenanthrene, and dibenzothiophene as well as their alkyl derivatives were detected. The results show that the level of non-volatile petroleum hydrocarbons in the waters of the North Sea is very low indeed. A short residence time thus keeps the standing stock of petroleum hydrocarbons below the detection limit.

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