scholarly journals Spawning by the European eel across 2000 km of the Sargasso Sea

2019 ◽  
Vol 15 (4) ◽  
pp. 20180835 ◽  
Author(s):  
Michael J. Miller ◽  
Håkan Westerberg ◽  
Henrik Sparholt ◽  
Klaus Wysujack ◽  
Sune R. Sørensen ◽  
...  
Keyword(s):  
North Atlantic Ocean ◽  
European Eel ◽  
Sargasso Sea ◽  
Silver Eel ◽  
Historical Collections ◽  
The North ◽  
Longitudinal Zone ◽  
Dramatic Decline ◽  
German Research

It has been known for about a century that European eels have a unique life history that includes offshore spawning in the Sargasso Sea about 5000–7000 km away from their juvenile and adult habitats in Europe and northern Africa. Recently hatched eel larvae were historically collected during Danish, German and American surveys in specific areas in the southern Sargasso Sea. During a 31 day period of March and April 2014, Danish and German research ships sampled for European eel larvae along 15 alternating transects of stations across the Sargasso Sea. The collection of recently hatched eel larvae (≤12 mm) from 70° W and eastward to 50° W showed that the European eel had been spawning across a 2000 km wide region of the North Atlantic Ocean. Historical collections made from 1921 to 2007 showed that small larvae had also previously been collected in this wide longitudinal zone, showing that the spatial extent of spawning has not diminished in recent decades, irrespective of the dramatic decline in recruitment. The use of such a wide spawning area may be related to variations in the onset of the silver eel spawning migration, individual differences in their long-term swimming ability, or aspects of larval drift.

scholarly journals How the European eel ( Anguilla anguilla ) loses its skeletal framework across lifetime

2016 ◽  
Vol 283 (1841) ◽  
pp. 20161550 ◽  
Author(s):  
Tim Rolvien ◽  
Florian Nagel ◽  
Petar Milovanovic ◽  
Sven Wuertz ◽  
Robert Percy Marshall ◽  
...  
Keyword(s):  
Bone Loss ◽  
Mechanical Stability ◽  
North Atlantic Ocean ◽  
Anguilla Anguilla ◽  
European Eel ◽  
Sargasso Sea ◽  
Morphological Transformation ◽  
The North ◽  
Life Cycle Stages ◽  
Cellular Bone

European eels ( Anguilla anguilla ) undertake an impressive 5 000 km long migration from European fresh waters through the North Atlantic Ocean to the Sargasso Sea. Along with sexual maturation, the eel skeleton undergoes a remarkable morphological transformation during migration, where a hitherto completely obscure bone loss phenomenon occurs. To unravel mechanisms of the maturation-related decay of the skeleton, we performed a multiscale assessment of eels' bones at different life-cycle stages. Accordingly, the skeleton reflects extensive bone loss that is mediated via multinucleated bone-resorbing osteoclasts, while other resorption mechanisms such as osteocytic osteolysis or matrix demineralization were not observed. Preserving mechanical stability and releasing minerals for energy metabolism are two mutually exclusive functions of the skeleton that are orchestrated in eels through the presence of two spatially segregated hard tissues: cellular bone and acellular notochord. The cellular bone serves as a source of mineral release following osteoclastic resorption, whereas the mineralized notochord sheath, which is inaccessible for resorption processes due to an unmineralized cover layer, ensures sufficient mechanical stability as a part of the notochord sheath. Clearly, an eel's skeleton is structurally optimized to meet the metabolic challenge of fasting and simultaneous sexual development during an exhausting journey to spawning areas, while the function of the vertebral column is maintained to achieve this goal.

How does the European eel (Anguilla anguilla) retain its population structure during its larval migration across the North Atlantic Ocean?

2006 ◽  
Vol 63 (1) ◽  
pp. 90-106 ◽  
Author(s):  
A James Kettle ◽  
Keith Haines
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Anguilla Anguilla ◽  
European Eel ◽  
Sargasso Sea ◽  
Larval Migration ◽  
The North ◽  
The North Atlantic ◽  
And Migration

A Lagrangian model is presented of the current-carried migration of the leptocephali (larvae) of the European eel (Anguilla anguilla) across the North Atlantic Ocean from the spawning area in the Sargasso Sea to the adult range in Europe and North Africa. The success of larvae in crossing the Atlantic Ocean and reaching particular latitude bins on the eastern side depended strongly on starting location in the Sargasso Sea and migration depth. In the model domain, silver eel spawners can develop strategies for spawning location and migration depth to preferentially target particular regions in the adult range. This observation may help to explain the presence of gradients in molecular markers in eel samples collected across Europe. Spawning in the period of late winter – spring maximizes the average food availability along the 2-year larval trajectory. The fastest transatlantic larval migration in the model is about 2 years, and the route to Europe takes most of the larvae past the east coast of North America in the first year. These model results are consistent with the hypothesis that the European and American eel (Anguilla rostrata) could separate themselves on different sides of the Atlantic Ocean on the basis of the different durations of their larval stages.

scholarly journals Past megadroughts in central Europe were longer, more severe and less warm than modern droughts

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
M. Ionita ◽  
M. Dima ◽  
V. Nagavciuc ◽  
P. Scholz ◽  
G. Lohmann
Keyword(s):  
Central Europe ◽  
North Atlantic Ocean ◽  
Explosive Volcanism ◽  
American Southwest ◽  
The North ◽  
European Climate ◽  
Blocking Activity ◽  
Meteorological Observations ◽  
Dalton Minimum

AbstractMegadroughts are notable manifestations of the American Southwest, but not so much of the European climate. By using long-term hydrological and meteorological observations, as well as paleoclimate reconstructions, here we show that central Europe has experienced much longer and severe droughts during the Spörer Minimum (~AD 1400–1480) and Dalton Minimum (~AD 1770–1840), than the ones observed during the 21st century. These two megadroughts appear to be linked with a cold state of the North Atlantic Ocean and enhanced winter atmospheric blocking activity over the British Isles and western part of Europe, concurrent with reduced solar forcing and explosive volcanism. Moreover, we show that the recent drought events (e.g., 2003, 2015, and 2018), are within the range of natural variability and they are not unprecedented over the last millennium.

scholarly journals Seasonal Barotropic Modulation of the Deep-Water Overflow through the Faroe Bank Channel

2006 ◽  
Vol 36 (12) ◽  
pp. 2328-2339 ◽  
Author(s):  
Iréne Lake ◽  
Peter Lundberg
Keyword(s):  
North Atlantic ◽  
Deep Water ◽  
Satellite Altimetry ◽  
North Atlantic Ocean ◽  
Norwegian Sea ◽  
The North ◽  
Flow Through ◽  
The North Atlantic ◽  
Water Overflow

Abstract As a joint Nordic project, an upward-looking ADCP has been maintained at the sill of the Faroe Bank Channel from 1995 onward. Records from a period in 1998 with three current meters deployed across the channel were used to demonstrate that the Faroe Bank Channel deep-water transport from the Norwegian Sea into the North Atlantic Ocean proper can be reasonably well estimated from one centrally located ADCP. The long-term average of this transport over the period 1995–2001 was found to be 2.1 Sv (Sv ≡ 106 m−3 s−1). The transport record demonstrates a pronounced seasonality. Satellite altimetry shows that this is caused by the northbound Atlantic surface water inflow giving rise to a barotropic modulation of the deep-water flow through the Faroe–Shetland Channel and the southern reaches of the Norwegian Sea.

scholarly journals A Surface Wind Extremes (“Wind Lulls” and “Wind Blows”) Climatology for Central North America and Adjoining Oceans (1979–2012)

2015 ◽  
Vol 54 (3) ◽  
pp. 643-657 ◽  
Author(s):  
Jonny W. Malloy ◽  
Daniel S. Krahenbuhl ◽  
Chad E. Bush ◽  
Robert C. Balling ◽  
Michael M. Santoro ◽  
...  
Keyword(s):  
United States ◽  
North America ◽  
North American ◽  
North Atlantic Ocean ◽  
Grid Point ◽  
Surface Wind ◽  
Wind Speeds ◽  
The North ◽  
Anomalous Wind

AbstractThis study explores long-term deviations from wind averages, specifically near the surface across central North America and adjoining oceans (25°–50°N, 60°–130°W) for 1979–2012 (408 months) by utilizing the North American Regional Reanalysis 10-m wind climate datasets. Regions where periods of anomalous wind speeds were observed (i.e., 1 standard deviation below/above both the long-term mean annual and mean monthly wind speeds at each grid point) were identified. These two climatic extremes were classified as wind lulls (WLs; below) or wind blows (WBs; above). Major findings for the North American study domain indicate that 1) mean annual wind speeds range from 1–3 m s−1 (Intermountain West) to over 7 m s−1 (offshore the East and West Coasts), 2) mean durations for WLs and WBs are high for much of the southeastern United States and for the open waters of the North Atlantic Ocean, respectively, 3) the longest WL/WB episodes for the majority of locations have historically not exceeded 5 months, 4) WLs and WBs are most common during June and October, respectively, for the upper Midwest, 5) WLs are least frequent over the southwestern United States during the North American monsoon, and 6) no significant anomalous wind trends exist over land or sea.

scholarly journals Climate-related variations in the occurrence and distribution of mackerel (Scomber scombrus) in Icelandic waters

2012 ◽  
Vol 69 (7) ◽  
pp. 1289-1297 ◽  
Author(s):  
Olafur S. Astthorsson ◽  
Héðinn Valdimarsson ◽  
Asta Gudmundsdottir ◽  
Guðmundur J. Óskarsson
Keyword(s):  
North Atlantic ◽  
North Atlantic Ocean ◽  
Warm Period ◽  
Cold Period ◽  
Sea Temperature ◽  
Scomber Scombrus ◽  
The North ◽  
Large Numbers ◽  
Icelandic Waters

Abstract Astthorsson, O. S., Valdimarsson, H., Gudmundsdottir, A., and Óskarsson, G. J. 2012. Climate-related variations in the occurrence and distribution of mackerel (Scomber scombrus) in Icelandic waters. – ICES Journal of Marine Science, 69: . Based on long-term investigations on sea temperature in Icelandic waters, five climatic periods are defined from the mid-1880s until today. These are a cold period between 1880 and 1920, a warm period between 1921 and 1964, a cold period between 1965 and 1971, one of intermediate conditions (alternating warm and cold) between 1972 and 1995, and finally a warm period from 1996 until today. Mackerel were first reported from Icelandic waters in 1895, were then found intermittently until 1996, and from then appeared almost every year and since 2007 in large numbers in many areas around Iceland. The occurrence of mackerel appears to be confined mainly to warm periods in the North Atlantic Ocean and around Iceland. The unprecedented occurrence and extended distribution of the species began at the onset of the recent warm period during the mid-1990s and, in recent years, 0-group and age 1 mackerel have also been observed in Icelandic waters. This expansion in distribution resulted initially in a bycatch fishery, which then developed into a direct fishery within the Icelandic Exclusive Economic Zone, increasing from ∼1700 t in 2006 to ∼120 000 t in 2009 and 2010.

scholarly journals Influence of multidecadal hydroclimate variations on hydrological extremes: the case of the Seine basin

2019 ◽  
Author(s):  
Rémy Bonnet ◽  
Julien Boé ◽  
Florence Habets
Keyword(s):  
Soil Moisture ◽  
Large Scale ◽  
North Atlantic Ocean ◽  
North Pacific Ocean ◽  
Seine River ◽  
River Flows ◽  
The North ◽  
Hydroclimate Variability ◽  
Extreme Hydrological Events

Abstract. The multidecadal hydroclimate variations of the Seine basin since the 1850s are investigated. Given the scarcity of long term observations of hydrological variables, a hydrometeorological reconstruction is developed based on an method that combines the results of a downscaled long-term atmospheric reanalysis and local observations of precipitation and temperature. This method improves the representation of daily flows as well as at longer time steps. This reconstruction provide therefore an interesting tool to study the multidecadal hydroclimate variability of the Seine basin, as well as its possible influence on extreme hydrological events. Based on this reconstruction, it is shown that the Seine river flows, groundwater and soil moisture, have been influenced by multidecadal variations from the 1850s. Spring precipitations play a central role by directly influencing the multidecadal variability of spring flows, but also soil moisture and groundwater recharge, which then modulate summer river flows. Groundwater controls a large part of the multidecadal variations in river flows, particularly in summer and fall. These hydroclimate variations seem to influence extreme hydrological events. The positive multidecadal phases indeed appear to be more conducive to flooding, with twice as many flood days as in the negative phases while the negative multidecadal phases seems to influenced the droughts intensity. These hydroclimate variations over the Seine basin are driven by anomalies in large scale atmospheric circulations, which themselves appear to be influenced by sea surface temperature anomalies over of the North Atlantic Ocean and the North Pacific Ocean.

scholarly journals Two decades of flask observations of atmospheric δO<sub>2</sub>/N<sub>2</sub>, CO<sub>2</sub>, and APO at stations Lutjewad (the Netherlands) and Mace Head (Ireland) plus 3 years from Halley station (Antarctica)

2021 ◽  
Author(s):  
Linh N. T. Nguyen ◽  
Harro A. J. Meijer ◽  
Charlotte van Leeuwen ◽  
Bert A. M. Kers ◽  
Bert A. Scheeren ◽  
...  
Keyword(s):  
The Netherlands ◽  
North Atlantic Ocean ◽  
Calibration Procedure ◽  
Global Ocean ◽  
East Anglia ◽  
The North ◽  
Long Term Trends ◽  
The University ◽  
Gas Cylinders

Abstract. We present 20-year flask sample records of atmospheric CO2, δO2/N2 and APO from the stations Lutjewad (the Netherlands) and Mace Head (Ireland) and a 3-year record from Halley station (Antarctica), including details of the extensive calibration procedure and its stability over time. The results of our inter-comparison involving gas cylinders from various research laboratories worldwide also show that our calibration is of high quality and compatible with the internationally recognised Scripps scale. The measurement records from Lutjewad and Mace Head show similar long-term trends during the period 2002–2018 of 2.31 ± 0.07 ppm yr−1 for CO2 and −21.2 ± 0.8 per meg yr−1 for δO2/N2 at Lutjewad, and 2.22 ± 0.04 ppm yr−1 for CO2 and −21.3 ± 0.9 per meg yr−1 for δO2/N2 at Mace Head. They also show a similar δO2/N2 seasonal cycle with an amplitude of 54 ± 4 per meg at Lutjewad and 61 ± 5 per meg at Mace Head, while CO2 seasonal amplitude at Lutjewad (16.8 ± 0.5 ppm) is slightly higher than that at Mace Head (14.8 ± 0.3 ppm). We show that the observed trends and seasonal cycles are compatible with the measurements from various stations, especially the measurements from Weybourne Atmospheric Observatory (United Kingdom). However, there are remarkable differences in the progression of annual trends between the Mace Head and Lutjewad records for δO2/N2 and APO, which might in part be caused by sampling differences, but also by environmental effects, such as the North Atlantic Ocean oxygen ventilation changes to which Mace Head is more sensitive. The Halley record shows clear trends and seasonality in δO2/N2 and APO, where especially APO agrees well with the continuous measurements at Halley by the University of East Anglia, while CO2 and δO2/N2 present slight disagreements, most likely caused by small leakages during sampling. From our 2002–2018 records, we find good agreement for the global ocean sink: 2.0 ± 0.8 PgC yr−1 and 2.2 ± 0.9 PgC yr−1, based on Lutjewad and Mace Head, respectively. The data presented in this work are available at https://doi.org/10.18160/qq7d-t060 (Nguyen et al., 2021).

scholarly journals Long-term SST Prediction Based on RSST-ARGM

2021 ◽  
Author(s):  
Linqian Zhu ◽  
Qi Liu ◽  
Xiaodong Liu ◽  
Yonghong Zhang
Keyword(s):  
North Atlantic ◽  
Greenhouse Gas Emission ◽  
North Atlantic Ocean ◽  
Seawater Temperature ◽  
Test Method ◽  
Emission Pattern ◽  
The North ◽  
Term Variation ◽  
Long Time

Abstract For the purpose of exploring the long-term variation of regional SST, this paper studies the historical SST in local sea areas and the emission pattern of greenhouse gases and proposes a gray model of regional SST based on atmospheric reflection which can be used to predict SST variation in a long time span. By studying the grey systematic relationship between historical SST data, the model obtains the development law of temperature change, and furtherintroduces different future greenhouse gas emission scenarios as the index coefficient to determine the corresponding changing results of seawater temperature in the next 50 years. Taking the North Atlantic Ocean as an example, the cosine similarity test method is used to verify the model proposed in this paper, and its accuracy is as high as 0.99984. The model predicts that the local SST could reach a maximum of 15.3°C by 2070. This model is easy to calculate, with advantages of the high accuracy and good robustness.

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