scholarly journals Noctiluca scintillans: Dynamics, Size Measurements and Relationships With Small Soft-Bodied Plankton in the Belgian Part of the North Sea

2021 ◽  
Vol 8 ◽  
Author(s):  
Anouk Ollevier ◽  
Jonas Mortelmans ◽  
Anaïs Aubert ◽  
Klaas Deneudt ◽  
Michiel B. Vandegehuchte
Keyword(s):  
North Sea ◽  
Temporal Dynamics ◽  
Negative Impact ◽  
Large Cell ◽  
Nutrient Inputs ◽  
Anthropogenic Pressures ◽  
Noctiluca Scintillans ◽  
The North ◽  
The North Sea ◽  
The Relationship

Climate driven changes and anthropogenic pressures on the marine environment have been shown to favor the increase in certain potentially harmful species. Among them, Noctiluca scintillans, a common dinoflagellate, often blooms during warm summers and is known to affect plankton communities. In this study, we assessed the dynamics in abundance and cell size of N. scintillans as well as the relationship between N. scintillans and small soft-bodied zooplankton in the Belgian part of the North Sea (BPNS), since negative correlations between these plankton groups have been previously reported for nearby regions. This study is the first to present consistently counted N. scintillans cell numbers and measured cell lengths, through the analysis of ZooScan images from samples taken monthly at stations throughout the coastal zone of the BPNS. The results show that N. scintillans demonstrated clear seasonal dynamics with both high densities and large cell sizes in spring/summer (May-July). The occurrence of N. scintillans in the analyzed plankton samples and the abundance of N. scintillans at the observed peak intensities nearly tripled over a period of 5 years. A zero-inflated model showed a correlation of N. scintillans abundance with temperature as well as with phosphate concentrations, suggesting that anthropogenic influences such as climate change and riverine nutrient inputs could affect the temporal dynamics of the species. The results, on the other hand, did not show any negative impact of N. scintillans on the soft-bodied plankton community.

Spatial and temporal dynamics of European hake (Merluccius merluccius) in the North Sea

2018 ◽  
Vol 75 (6) ◽  
pp. 2033-2044 ◽  
Author(s):  
Arved Staby ◽  
Jon Egil Skjæraasen ◽  
Audrey J Geffen ◽  
Daniel Howell
Keyword(s):  
North Sea ◽  
Temporal Dynamics ◽  
Trawl Survey ◽  
Merluccius Merluccius ◽  
Frequency Distributions ◽  
The North ◽  
The North Sea ◽  
Northern North Sea ◽  
Central North Sea ◽  
European Hake

Abstract Catches of European hake (Merluccius merluccius) in the North Sea have increased substantially during the last decade, even though there is no directed commercial fishery of hake in this area. We analysed the spatial distributions of hake in the northern the parts of its range, (where it is less well-studied), using ICES international bottom trawl survey data from 1997 to 2015. We examine length-frequency distributions for (i) distinct modes enabling the assignment of fish into categories which likely corresponded to the ages 1, 2, and 3+ and (ii) patterns of seasonal spatial distribution for the different groups. Age categories 1 and 2 fish were most abundant in the northern North Sea, and appear to remain in the North Sea until 2 years of age, when they move into deeper waters. Their distribution has expanded into the western-central North Sea in the last decade. Age category 3+ fish were most abundant in the northern and central North Sea during summer, indicating a seasonal influx of large individuals into this area likely associated with spawning activity. The distribution of these older fish has gradually expanded westward in both seasons.

scholarly journals Observations on herring spawning and larval distribution in the Firth of Clyde in 1958

1959 ◽  
Vol 38 (3) ◽  
pp. 445-453 ◽  
Author(s):  
B. B. Parrish ◽  
A. Saville ◽  
R. E. Craig ◽  
I. G. Baxter ◽  
R. Priestley
Keyword(s):  
North Sea ◽  
Predatory Fish ◽  
Hatching Rate ◽  
Atlantic Herring ◽  
The North ◽  
Larval Distribution ◽  
Sea Bed ◽  
The North Sea ◽  
Newly Hatched Larvae ◽  
The Relationship

Apart from the extensive egg surveys carried out by Norwegian workers (Runnstrom, 1941) most of the investigations on the spawning of the Atlantic Herring have depended on studies of the distribution of the spawning fish, on captures of newly hatched larvae, and on records of the occurrence of herring eggs in the stomachs of predatory fish species (principally haddock). With the exception of recent observations by Bolster and Bridger (1957), attempts to sample egg concentrations quantitatively in the North Sea and neighbouring areas have usually proved abortive. In consequence little is known of the distribution and density of eggs on the spawning grounds, their percentage fertilization, mortality during the egg stage, hatching rate, and the relationship between the distribution of eggs and the nature of the sea-bed.

Shetland beached bird surveys: national and European context

1995 ◽  
Vol 103 ◽  
pp. 165-179 ◽  
Author(s):  
M. Heubeck
Keyword(s):  
North Sea ◽  
Annual Variation ◽  
Herring Gull ◽  
British Isles ◽  
European Context ◽  
The North ◽  
Bird Survey ◽  
The North Sea ◽  
The Relationship

SynopsisA Shetland-wide beached bird survey was established in March 1979 and monthly surveys have continued since. This paper presents results from March 1979 to December 1992 during which time a total of 34 320 corpses of seabird and seaduck were found, of which 34023 (99.1%) were specifically identified. Corpses of guillemot (8911), fulmar (8707), kittiwake (4421), herring gull (2264), shag (1843) and great black-backed gull (1785) comprised 82.1% of the identified total, the remainder being made up of 31 other species. The relationship between the numbers of each species found, and their numbers and occurrence in Shetland waters is discussed. A total of 2781 corpses were judged to have been oiled before their deaths, of which 2732 (98.2%) were specifically identified. The six species most frequently found oiled were guillemot (1170 corpses), fulmar (543), kittiwake (184), razorbill (131), puffin (111) and shag (99).Variations in both the percentage of corpses found that were oiled, and the number of oiled corpses found per kilometre of beach surveyed, are examined and discussed. Comparison is made with results from beached bird surveys elsewhere in the British Isles and in other countries bordering the North Sea. In some species, notably the pelagic auks, there was considerable annual variation in the numbers of unoiled corpses found while in other species the number of unoiled corpses found changed more gradually over the 14 years. Reference is made to similar changes observed in other beached bird surveys and possible reasons for these changes are discussed.

scholarly journals Rebound in functional distinctiveness following warming and reduced fishing in the North Sea

2021 ◽  
Vol 288 (1942) ◽  
pp. 20201600
Author(s):  
Juliette Murgier ◽  
Matthew McLean ◽  
Anthony Maire ◽  
David Mouillot ◽  
Nicolas Loiseau ◽  
...  
Keyword(s):  
North Sea ◽  
Temporal Dynamics ◽  
Distinct Species ◽  
Common Species ◽  
Fishing Pressure ◽  
The North ◽  
Spatial And Temporal Dynamics ◽  
Recent Climate ◽  
The North Sea

Functionally distinct species (i.e. species with unique trait combinations in the community) can support important ecological roles and contribute disproportionately to ecosystem functioning. Yet, how functionally distinct species have responded to recent climate change and human exploitation has been widely overlooked. Here, using ecological traits and long-term fish data in the North Sea, we identified functionally distinct and functionally common species, and evaluated their spatial and temporal dynamics in relation to environmental variables and fishing pressure. Functionally distinct species were characterized by late sexual maturity, few, large offspring, and high parental care, many being sharks and skates that play critical roles in structuring food webs. Both functionally distinct and functionally common species increased in abundance as ocean temperatures warmed and fishing pressure decreased over the last three decades; however, functionally distinct species increased throughout the North Sea, but primarily in southern North Sea where fishing was historically most intense, indicating a rebound following fleet decommissioning and reduced harvesting. Yet, some of the most functionally distinct species are currently listed as threatened by the IUCN and considered highly vulnerable to fishing pressure. Alarmingly these species have not rebounded. This work highlights the relevance and potential of integrating functional distinctiveness into ecosystem management and conservation prioritization.

Long-term changes in the North Sea ecosystem

2001 ◽  
Vol 9 (3) ◽  
pp. 131-187 ◽  
Author(s):  
R A Clark ◽  
C LJ Frid
Keyword(s):  
North Sea ◽  
Primary Productivity ◽  
Trophic Levels ◽  
Benthic Fish ◽  
Nutrient Inputs ◽  
Climatic Fluctuations ◽  
The North ◽  
Long Term Changes ◽  
The North Sea

Long-term data on the North Sea ecosystem are available for phytoplanktonic, zooplanktonic, benthic, fish, and seabird communities. Temporal changes in these have been examined by numerous researchers over the course of the 20th century, their main objective being to determine how the interannual dynamics of these communities are controlled. Ultimately, long-term changes in the North Sea ecosystem appear to be driven by two wide-ranging, but separate processes. In the northern, western and central areas of the North Sea, long-term changes are predominantly influenced by climatic fluctuations. Here, primary productivity during a particular year is related to the effect of weather on the timing of stratification and the resulting spring bloom. In the southern and eastern areas of the North Sea, the lack of stratification and the large inputs of nutrients mean that primary productivity is more strongly influenced by variations in anthropogenic nutrient inputs, and is only weakly related to climatic variation. Long-term changes at higher trophic levels (zooplankton, benthic, fish, and seabirds) are generally affected by fluctuations in their food source (i.e., the lower trophic levels), although because of the high complexity of the North Sea ecosystem there are many exceptions to these general patterns. However, the weight of evidence shows that long-term changes in the ecosystem may ultimately be related to long-term changes in either climate or nutrients, although the long-term dynamics of certain taxa and communities do show evidence of being influenced by both anthropogenic factors and (or) internal factors such as competition and predation. Key words: long-term changes, North Sea, time series, climate change, ecosystem functioning, anthropogenic impacts.

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 Paleoecology of Late Eocene-Oligocene foraminiferal assemblages in a two-well transect across the North-East Newfoundland shelf

1991 ◽  
Vol 10 (1) ◽  
pp. 57-67
Author(s):  
F. C. Thomas
Keyword(s):  
North Sea ◽  
Late Eocene ◽  
Western Boundary ◽  
Late Oligocene ◽  
North East ◽  
The North ◽  
Early Oligocene ◽  
The North Sea ◽  
Relationship Of ◽  
The Relationship

Abstract. Core samples from the Paleogene of the Bonavista C-99 well on the northeast Newfoundland shelf and cuttings from downdip Blue H-28 contain foraminiferal assemblages which enable reconstruction of paleoenvironments along a downslope transect in Eocene through Late Oligocene-Miocene time. Comparison with coeval assemblages in North Sea wells with respect to structure and grain size of agglutinated taxa between the two areas reveal inter-basin differences.Reconstruction of the paleobathymetry derived from foraminiferal analysis, confirms seismic evidence for shallowing at the Bonavista site beginning in the Early Oligocene. The relationship of the Bonavista assemblages to contour currents is explored with reference to modern regional analogues. Species such as Reticulophragmium amplectens, Haplophragmoides walteri, Eponides umbonatus and Uvigerina ex. gr. miozea-nuttalli persist stratigraphically higher in the deeper Blue site.The paleoslope of this two-well transect is determined as approximately 0.48° during the Middle to Late Eocene and 0.68° during the Late Oligocene-Early Miocene. The bottom water hydrography of the transect can be evaluated by reference to these assemblages and a comparison to flysch-type agglutinated assemblages from a transect in the North Sea. The presence of an Upper Eocene-Middle Miocene hiatus at the Blue site contrasting with apparently continuous Tertiary deposition at Bonavista places a theoretical upper limit of 500–1000 m on the depth of the early Cenozoic western boundary undercurrent.

scholarly journals Emergence of a new predator in the North Sea: evaluation of potential trophic impacts focused on hake, saithe, and Norway pout

2016 ◽  
Vol 73 (5) ◽  
pp. 1370-1381 ◽  
Author(s):  
Xochitl Cormon ◽  
Alexander Kempf ◽  
Youen Vermard ◽  
Morten Vinther ◽  
Paul Marchal
Keyword(s):  
North Sea ◽  
Negative Impact ◽  
Stock Assessment ◽  
Single Species ◽  
Bottom Up ◽  
The North ◽  
Spatial Shift ◽  
Spawning Stock ◽  
The North Sea ◽  
Indirect Impacts

Abstract During the last 15 years, northern European hake (Merluccius merluccius) has increased in abundance, and its spatial distribution has expanded in the North Sea region in correlation with temperature. In a context of global warming, this spatial shift could impact local trophic interactions: direct impacts may affect forage fish through modified predator–prey interactions, and indirect impacts may materialize through competition with other resident predators. For instance, North Sea saithe (Pollachius virens) spatial overlap with hake has increased while saithe spawning-stock biomass has decreased recently notwithstanding a sustainable exploitation. In this context, we investigated the range of potential impacts resulting from most recent hake emergence in the North Sea, with a particular focus on saithe. We carried out a multispecies assessment of North Sea saithe, using the Stochastic MultiSpecies (SMS) model. In addition to top-down processes already implemented in SMS, we built in the model bottom-up processes, relating Norway pout (Trisopterus esmarkii) abundance and saithe weight-at-age. We simulated the effects, on all North Sea species being considered but focusing on Norway pout and saithe, of combining different hake abundance trends scenarios with the inclusion of bottom-up processes in SMS. North Sea saithe FMSY was then evaluated in a multispecies context and contrasted with single-species value. The different scenarios tested revealed a negative impact of hake emergence on saithe biomass, resulting from an increase of predation pressure on Norway pout. These results confirm the competition assumption between saithe and hake in the North Sea and might partially explain the most recent decrease of saithe biomass. This study also highlighted that taking into account bottom-up processes in the stock assessment had a limited effect on the estimation of saithe FMSY which was consistent with single-species value.

scholarly journals Indications of a negative impact of herring on recruitment of Norway pout

2008 ◽  
Vol 65 (6) ◽  
pp. 906-911 ◽  
Author(s):  
Geir Huse ◽  
Are Salthaug ◽  
Morten D. Skogen
Keyword(s):  
Linear Regression ◽  
North Sea ◽  
Negative Impact ◽  
Fish Larvae ◽  
Negative Relationship ◽  
Clupea Harengus ◽  
Poor Correlation ◽  
The North ◽  
Spawning Stock ◽  
The North Sea

Abstract Huse, G., Salthaug, A., and Skogen, M. D. 2008. Indications of a negative impact of herring on recruitment of Norway pout. – ICES Journal of Marine Science, 65: 906–911. The Norway pout (Trisopterus esmarkii) stock in the North Sea has experienced poor recruitment recently. Herring (Clupea harengus) has been suggested to be a major predator on fish larvae in the North Sea. We investigated possible interactions between herring and Norway pout using a simple statistical analysis and a modified stock–recruit relationship. There was a significant negative relationship (linear regression, r = −0.44, p < 0.05) between total herring biomass and recruitment of Norway pout. The spawning stock of Norway pout is typically dominated by 2-year-olds, and there was a strong negative relationship (linear regression, r = −0.79, p < 0.01) between herring biomass and Norway pout spawning-stock biomass (SSB) 2 years later. A Beverton–Holt model fitted to stock–recruit data of Norway pout produced a rather poor correlation (r2 = 0.04). However, when only the Norway pout SSB not overlapping with herring is considered, the fit between the model and the stock–recruit data improves (r2 = 0.31). The analyses indicate a negative impact by herring on recruitment of Norway pout, the most plausible cause for this being herring predation on Norway pout larvae, but field studies are needed to verify such predation.

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