scholarly journals Life-history strategies of calanoid congeners under two different climate regimes: a comparison

2004 ◽  
Vol 61 (4) ◽  
pp. 709-720 ◽  
Author(s):  
Claudia Halsband-Lenk ◽  
François Carlotti ◽  
Wulf Greve
Keyword(s):  
Life History ◽  
North Sea ◽  
Life History Traits ◽  
Reproductive Period ◽  
Life Cycles ◽  
Life History Strategies ◽  
The North ◽  
Temperature Regimes ◽  
Shelf Sea ◽  
The North Sea

Abstract To evaluate the relationship between different environmental temperature regimes and life-history traits of key planktonic taxa, the life cycles of congener pairs of Temora and Centropages species at two sites, a cold-temperate shelf sea (Helgoland Island, North Sea) and a warm-temperate oceanic site (Bay of Villefranche, Mediterranean) were compared in a multi-annual time-series. In an attempt to assemble a variety of parameters – some detailed, others sporadically measured – a synthesis of the life cycle is presented for each population. Although closely related, congeners showed distinct temperature preferences and specific adaptations of their life cycles to temperature regime. On the other hand, co-existing species such as T. longicornis and C. hamatus in the North Sea showed some analogous life-history traits. C. typicus occupied an intermediate position and was able to tolerate both temperature regimes by shifting its reproductive period between seasons. We point out interannual and inter-site variability in the populations investigated and identify the unsolved questions in regard to the seasonal dynamics of these species that require verification.

scholarly journals Metabarcoding reveals different zooplankton communities in northern and southern areas of the North Sea

2020 ◽  
Author(s):  
Jan Niklas Macher ◽  
Berry B. van der Hoorn ◽  
Katja T. C. A. Peijnenburg ◽  
Lodewijk van Walraven ◽  
Willem Renema
Keyword(s):  
North Sea ◽  
Zooplankton Community ◽  
Taxonomic Diversity ◽  
Molecular Techniques ◽  
Trophic Levels ◽  
List Type ◽  
The North ◽  
Shelf Sea ◽  
The North Sea ◽  
Zooplankton Communities

AbstractZooplankton are key players in marine ecosystems, linking primary production to higher trophic levels. The high abundance and high taxonomic diversity renders zooplankton ideal for biodiversity monitoring. However, taxonomic identification of the zooplankton assemblage is challenging due to its high diversity, subtle morphological differences and the presence of many meroplanktonic species, especially in coastal seas. Molecular techniques such as metabarcoding can help with rapid processing and identification of taxa in complex samples, and are therefore promising tools for identifying zooplankton communities. In this study, we applied metabarcoding of the mitochondrial cytochrome c oxidase I gene to zooplankton samples collected along a latitudinal transect in the North Sea, a shelf sea of the Atlantic Ocean. Northern regions of the North Sea are influenced by inflow of oceanic Atlantic waters, whereas the southern parts are characterised by more coastal waters. Our metabarcoding results indicated strong differences in zooplankton community composition between northern and southern areas of the North Sea, particularly in the classes Copepoda, Actinopterygii (ray-finned fishes) and Polychaeta. We compared these results to the known distributions of species reported in previous studies, and by comparing the abundance of copepods to data obtained from the Continuous Plankton Recorder (CPR). We found that our metabarcoding results are mostly congruent with the reported distribution and abundance patterns of zooplankton species in the North Sea. Our results highlight the power of metabarcoding to rapidly assess complex zooplankton samples, and we suggest that the technique could be used in future monitoring campaigns and biodiversity assessments.HighlightsZooplankton communities are different in northern and southern areas of the North SeaMetabarcoding results are consistent with known species distributions and abundanceMetabarcoding allows for fast identification of meroplanktonic species

scholarly journals Depth-averaged instantaneous currents in a tidally dominated shelf sea from glider observations

2016 ◽  
Author(s):  
Lucas Merckelbach
Keyword(s):  
Real Time ◽  
North Sea ◽  
Current Data ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Real Time Mode ◽  
The North ◽  
Shelf Sea ◽  
The North Sea ◽  
Better Than

Abstract. Ocean gliders have become ubiquitous observation platforms in the ocean in recent years. They are also increasingly used in coastal environments. The coastal observatory system COSYNA has pioneered the use of gliders in the North Sea, a shallow tidally energetic shelf sea. For operational reasons, the gliders operated in the North Sea are programmed to resurface every 3–5 hours. The glider's deadreckoning algorithm yields depth averaged currents, averaged in time over each subsurface interval. Under operational conditions these averaged currents are a poor approximation of the instantaneous tidal current. In this work an algorithm is developed that estimates the instantaneous current (tidal and residual) from glider observations only. The algorithm uses a second-order Butterworth low-pass filter to estimate the residual current component, and a Kalman filter based on the linear shallow water equations for the tidal component. A comparison of data from a glider experiment with current data from an ADCP deployed nearby shows that the standard deviations for the east and north current components are better than 7 cm s−1 in near-real time mode, and improve to better than 5 cm s−1 in delayed mode, where the filters can be run forward and backward. In the near-real time mode the algorithm provides estimates of the currents that the glider is expected to encounter during its next few dives. Combined with a behavioural and dynamic model of the glider, this yields predicted trajectories, the information of which is incorporated in warning messages issued to ships by the (German) authorities. In delayed mode the algorithm produces useful estimates of the depth averaged currents, which can be used in (process-based) analyses in case no other source of measured current information is available.

scholarly journals Depth-averaged instantaneous currents in a tidally dominated shelf sea from glider observations

2016 ◽  
Vol 13 (24) ◽  
pp. 6637-6649 ◽  
Author(s):  
Lucas Merckelbach
Keyword(s):  
Real Time ◽  
North Sea ◽  
Current Data ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Real Time Mode ◽  
The North ◽  
Shelf Sea ◽  
The North Sea ◽  
Better Than

Abstract. Ocean gliders have become ubiquitous observation platforms in the ocean in recent years. They are also increasingly used in coastal environments. The coastal observatory system COSYNA has pioneered the use of gliders in the North Sea, a shallow tidally energetic shelf sea. For operational reasons, the gliders operated in the North Sea are programmed to resurface every 3–5 h. The glider's dead-reckoning algorithm yields depth-averaged currents, averaged in time over each subsurface interval. Under operational conditions these averaged currents are a poor approximation of the instantaneous tidal current. In this work an algorithm is developed that estimates the instantaneous current (tidal and residual) from glider observations only. The algorithm uses a first-order Butterworth low pass filter to estimate the residual current component, and a Kalman filter based on the linear shallow water equations for the tidal component. A comparison of data from a glider experiment with current data from an acoustic Doppler current profilers deployed nearby shows that the standard deviations for the east and north current components are better than 7 cm s−1 in near-real-time mode and improve to better than 6 cm s−1 in delayed mode, where the filters can be run forward and backward. In the near-real-time mode the algorithm provides estimates of the currents that the glider is expected to encounter during its next few dives. Combined with a behavioural and dynamic model of the glider, this yields predicted trajectories, the information of which is incorporated in warning messages issued to ships by the (German) authorities. In delayed mode the algorithm produces useful estimates of the depth-averaged currents, which can be used in (process-based) analyses in case no other source of measured current information is available.

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

scholarly journals A marginal habitat, but not a sink: Ecological genetics reveal a diversification hotspot for marine invertebrates in the brackish Baltic Sea

2021 ◽  
Author(s):  
Jonas C Geburzi ◽  
Nele Heuer ◽  
Lena Homberger ◽  
Jana Kabus ◽  
Zoe Moesges ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Life History ◽  
Baltic Sea ◽  
North Sea ◽  
Native Species ◽  
The Baltic Sea ◽  
Evolutionary Trajectory ◽  
The North ◽  
The North Sea ◽  
The Baltic

Aim: Environmental gradients have emerged as important barriers structuring populations and species distributions. We set out to test whether a strong salinity gradient from marine to brackish, represented in a marginal northern European sea, should be considered a diversification hotspot or a population sink, and to identify life history traits that correlate with either evolutionary trajectory. Location: The Baltic Sea, the North Sea and their transition zone. Methods: We accumulated mitochondrial cytochrome oxidase subunit 1 sequence data and data on the distribution, salinity tolerance and life history for 28 species belonging to the Cnidaria, Crustacea, Echinodermata, Mollusca, Polychaeta and Gastrotricha, including seven non-native species. We calculated measures of genetic diversity and differentiation across the environmental gradient, coalescent times and migration rates between North and Baltic Sea populations, and analysed correlations between genetic and life history data. Results: The majority of investigated species is either genetically differentiated and/or is adapted to the lower salinity conditions of the Baltic Sea. Moreover, the species exhibiting population structure have a range of patterns of genetic diversity in comparison to the North Sea, from lower in the Baltic Sea to higher in the Baltic Sea, or equally diverse in North and Baltic Sea. Main conclusions: Our results indicate that the Baltic Sea should be considered a diversification hotspot: The diversity of genetic patterns points towards independent trajectories in the Baltic compared to the North Sea. At the same time, we found limited evidence for the traditional scenario of the Baltic Sea as a population sink with lower diversity and strong gene flow. The North Sea - Baltic Sea region provides a unique setting to study evolutionary adaptation during colonization processes at different stages by jointly considering native and non-native species.

Large-scale responses of nematode communities to chronic otter-trawl disturbance

2008 ◽  
Vol 65 (4) ◽  
pp. 723-732 ◽  
Author(s):  
Hilmar Hinz ◽  
Jan G Hiddink ◽  
James Forde ◽  
Michel J Kaiser
Keyword(s):  
Food Web ◽  
North Sea ◽  
Large Scale ◽  
Life Cycles ◽  
Irish Sea ◽  
Otter Trawl ◽  
Food Web Structure ◽  
Nematode Communities ◽  
The North ◽  
The North Sea

Nematodes, because of their small size and short life cycles, are thought to be less affected by direct trawling mortality compared with the larger macrofauna. However, nematodes may still be indirectly affected by the physical disturbance of trawling through changing sediment characteristics and food web structure. We determined whether nematode communities on two muddy fishing grounds located in the North Sea and Irish Sea were affected by chronic otter-trawl disturbance and quantified these effects. Nematode abundance, production, and genus richness declined in response to trawling within both areas. Nematode biomass did not respond to trawling intensity. Genus composition was affected by trawling only in the North Sea. The responses in abundance of individual nematode genera to increasing trawling intensity were negative as well as positive. These results indicate that despite their size and fast life cycle, nematodes are affected by intensive trawling on muddy fishing grounds. The loss in secondary production from nematodes can have far-reaching consequences for the integrity of the benthic food web. As bottom trawl fisheries are expanding into ever deeper muddy habitats, the results presented here are an important step towards understanding the global ecosystem effects of bottom trawling.

Recent FerryBox observations reveal a strong increase in surface seawater pCO2 in the North Sea

2021 ◽  
Author(s):  
Vlad Macovei ◽  
Yoana Voynova ◽  
Holger Brix ◽  
Wilhelm Petersen
Keyword(s):  
North Sea ◽  
Carbon Dioxide Partial Pressure ◽  
Strong Increase ◽  
Surface Seawater ◽  
Annual Cycles ◽  
The North ◽  
Regime Types ◽  
Shelf Sea ◽  
The North Sea ◽  
Spatio Temporal

<p>Surface seawater carbon dioxide partial pressure (pCO<sub>2</sub>) in the North Sea, a large temperate shelf sea, was measured between 2014 and 2018 using FerryBox-integrated membrane sensors on ships of opportunity. The use of commercial vessels ensured a high spatio-temporal resolution, with data available year-round in areas belonging to all the stratification regime types found in the North Sea. Average annual cycles revealed a dominant biological control on pCO<sub>2</sub> variability, with thermal effects modulating its amplitude. In the regions of freshwater influence, the biogeochemical characteristics of the riverine end-member also influenced the pCO<sub>2</sub> measured near shore. Deseasonalized winter trends of seawater pCO<sub>2</sub> were positive (ranging from 4.4 ± 2.0 µatm yr<sup>-1</sup> to 8.4 ± 2.9 µatm yr<sup>-1</sup> depending on the region), while the trends calculated including all deseasonalized monthly averages were even higher (ranging from 9.7 ± 2.8 µatm yr<sup>-1</sup> to 12.2 ± 1.4 µatm yr<sup>-1</sup>). All these trends were stronger than the atmospheric pCO<sub>2</sub> trend. Consequently, during our study period, the southern North Sea became a stronger source and the northern North Sea became a weaker sink for atmospheric carbon with implications for the Northwestern European Shelf carbon uptake capacity.</p>

Physical preconditioning of oxygen depletion in shelf seas

2020 ◽  
Author(s):  
Charlotte Williams ◽  
Claire Mahaffey ◽  
Matthew Palmer ◽  
Naomi Greenwood
Keyword(s):  
North Sea ◽  
Late Summer ◽  
Global Ocean ◽  
Physical Conditions ◽  
Annual Variability ◽  
The North ◽  
Biogeochemical Models ◽  
Shelf Seas ◽  
Shelf Sea ◽  
The North Sea

<p>The global ocean dissolved oxygen (DO) inventory is decreasing and the areal extent of DO deficiency is increasing. In the shelf sea BML, net DO removal can occur as a result of restricted ventilation due to seasonal thermal stratification, oxygen consumption via pelagic and benthic respiration of organic matter, and nitrification. DO decline is becoming evident in several shelf seas, with recent model studies estimating that large regions of the Northwest European continental shelf seas (325,000 to 400,000 km<sup>2</sup>) have the potential to become seasonally deficient in DO in late summer. It is therefore of vital importance that DO is monitored accurately and effectively in shelf seas.</p><p>Here we present results from AlterECO project, which aimed to provide an alternative, novel framework for the monitoring of shelf sea ecosystem health indicators, including DO, via the deployment of 20 gliders in the North Sea (NW European shelf). Between November 2017 and May 2019 the gliders provided 18 month continuous measurements of T, S, chlorophyll fluorescence, and DO in the seasonally stratified study area, capturing the onset and breakdown of two spring blooms. In both years the gliders captured a weakly stratified, deep (>60m) thermocline in late autumn which was responsible for oxygen deplete (75%)  ‘pools’ in the North Sea. Our results show that preconditioning of pre-bloom transitional periods as well as episodic mixing events drive inter-annual differences in BML DO concentrations. Large inter-annual variability between pre-bloom physical conditions was observed, with the occurrence of anticyclone Hartmut in February 2018 resulting in a much colder water column (and therefore higher solubility of DO) in spring 2018 than 2019. Additionally we will demonstrate that the erosion of mini-blooms during the onset of stratification results in mixing of supersaturated DO surface water into the BML, helping to prevent DO deficiency in the BML in late summer. Comparisons of our high resolution glider data with the latest state of the art biogeochemical models (AMM15-ERSEM) will also be presented. We postulate that understanding the drivers of inter-annual variability in pre-bloom physical conditions is crucial in terms of understanding and predicting DO depletion in shelf seas.</p><p> </p>

scholarly journals Do Norway pout (Trisopterus esmarkii) die from spawning stress? Mortality of Norway pout in relation to growth, sexual maturity, and density in the North Sea, Skagerrak, and Kattegat

2012 ◽  
Vol 69 (2) ◽  
pp. 197-207 ◽  
Author(s):  
J. Rasmus Nielsen ◽  
Gwladys Lambert ◽  
Francois Bastardie ◽  
Henrik Sparholt ◽  
Morten Vinther
Keyword(s):  
North Sea ◽  
Sexual Maturity ◽  
Life History Traits ◽  
Trawl Survey ◽  
Older Individuals ◽  
Fishing Activity ◽  
The North ◽  
Spawning Areas ◽  
The North Sea ◽  
New Evidence

Abstract Nielsen, J. R., Lambert, G., Bastardie, F., Sparholt, H., and Vinther, M. 2012. Do Norway pout (Trisopterus esmarkii) die from spawning stress? Mortality of Norway pout in relation to growth, sexual maturity, and density in the North Sea, Skagerrak, and Kattegat. – ICES Journal of Marine Science, 69: 197–207. The mortality patterns of Norway pout (NP) are not well understood. It has been suggested that NP undergo heavy spawning mortality, and this paper summarizes and provides new evidence in support of this hypothesis. The very low–absent fishing activity in recent years provides a unique opportunity to analyse the natural life-history traits of cohorts in the NP stock in the North Sea. Based on the ICES trawl survey abundance indices, cohort mortality is found to significantly increase with age. We argue that this cannot be explained by selectiveness in the fishery, potential size-specific migrations out of the area, higher predation pressure on older individuals, or differences in survey catchability by NP age from before to after spawning and that it is higher in the main spawning areas than outside. We found that natural mortality (M) is significantly correlated with sexual maturity, sex, growth, and intraspecific stock density. All of this is consistent with a greater mortality occurring mainly from the first to the second quarter of the year, i.e. spawning mortality, which is discussed as being a major direct and indirect cause of stock mortality.

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