scholarly journals First indications for reduced mortality of non-target invertebrate benthic megafauna after pulse beam trawling

2020 ◽  
Vol 77 (2) ◽  
pp. 846-857 ◽  
Author(s):  
Magda J N Bergman ◽  
Erik H Meesters
Keyword(s):  
North Sea ◽  
Type Ii ◽  
Pulse Beam ◽  
Echinocardium Cordatum ◽  
Southern North Sea ◽  
Sea Power ◽  
The Impact ◽  
Reference Areas

Abstract Two alternative stimulation techniques to reduce mortality in benthic megafauna were tested relative to standard tickler chain beam trawling: longitudinal electrodes (pulse trawl) and longitudinal chains. Longitudinal chains caused higher mortality than pulse trawling in 3 species. Standard trawling gave higher mortality in Echinocardium cordatum than pulse trawling. Between longitudinal chain and standard trawling were no significant differences. This trend in decreasing mortality from longitudinal, to standard and then pulse trawling was confirmed by a similar decline in: i) numbers of significant species mortalities per trawl type, ii) average mortalities, i.e. longitudinal chain caused 41% more mortality than standard trawling and pulse trawling 43% less, iii) pre- and post-trawling community dissimilarities. A significant majority of species showed higher mortalities after longitudinal than after standard trawling and, conversely, lower mortalities after pulse trawling. Trawls with longitudinal chains instead of cross tickler chains increase megafaunal impact. On the contrary, pulse trawling can reduce the impact, although average mortality remains substantial (25%) even in impoverished benthic test assemblages in the southern North Sea. Power, generally was low and reference areas, free of (pulse) trawling, and inhabited by more vulnerable taxa will facilitate higher powered studies on the impact of standard and alternative trawling techniques.

scholarly journals The impact of sedimentary alkalinity release on the water column CO<sub>2</sub> system in the North Sea

2016 ◽  
Vol 13 (3) ◽  
pp. 841-863 ◽  
Author(s):  
H. Brenner ◽  
U. Braeckman ◽  
M. Le Guitton ◽  
F. J. R. Meysman
Keyword(s):  
Coastal Zone ◽  
North Sea ◽  
Dissolved Inorganic Carbon ◽  
Co2 Uptake ◽  
Overlying Water ◽  
Southern North Sea ◽  
The North ◽  
Alkalinity Generation ◽  
The North Sea ◽  
The Impact

Abstract. It has been previously proposed that alkalinity release from sediments can play an important role in the carbonate dynamics on continental shelves, lowering the pCO2 of seawater and hence increasing the CO2 uptake from the atmosphere. To test this hypothesis, sedimentary alkalinity generation was quantified within cohesive and permeable sediments across the North Sea during two cruises in September 2011 (basin-wide) and June 2012 (Dutch coastal zone). Benthic fluxes of oxygen (O2), alkalinity (AT) and dissolved inorganic carbon (DIC) were determined using shipboard closed sediment incubations. Our results show that sediments can form an important source of alkalinity for the overlying water, particularly in the shallow southern North Sea, where high AT and DIC fluxes were recorded in near-shore sediments of the Belgian, Dutch and German coastal zone. In contrast, fluxes of AT and DIC are substantially lower in the deeper, seasonally stratified, northern part of the North Sea. Based on the data collected, we performed a model analysis to constrain the main pathways of alkalinity generation in the sediment, and to quantify how sedimentary alkalinity drives atmospheric CO2 uptake in the southern North Sea. Overall, our results show that sedimentary alkalinity generation should be regarded as a key component in the CO2 dynamics of shallow coastal systems.

scholarly journals Multi-Proxy Characterisation of the Storegga Tsunami and Its Impact on the Early Holocene Landscapes of the Southern North Sea

Geosciences ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 270 ◽  
Author(s):  
Vincent Gaffney ◽  
Simon Fitch ◽  
Martin Bates ◽  
Roselyn L. Ware ◽  
Tim Kinnaird ◽  
...  
Keyword(s):  
North Sea ◽  
River System ◽  
Seismic Survey ◽  
Tsunami Deposit ◽  
Southern North Sea ◽  
The North ◽  
Sediment Deposits ◽  
The North Sea ◽  
Northern North Sea ◽  
The Impact

Doggerland was a landmass occupying an area currently covered by the North Sea until marine inundation took place during the mid-Holocene, ultimately separating the British landmass from the rest of Europe. The Storegga Event, which triggered a tsunami reflected in sediment deposits in the northern North Sea, northeast coastlines of the British Isles and across the North Atlantic, was a major event during this transgressive phase. The spatial extent of the Storegga tsunami however remains unconfirmed as, to date, no direct evidence for the event has been recovered from the southern North Sea. We present evidence of a tsunami deposit in the southern North Sea at the head of a palaeo-river system that has been identified using seismic survey. The evidence, based on lithostratigraphy, geochemical signatures, macro and microfossils and sedimentary ancient DNA (sedaDNA), supported by optical stimulated luminescence (OSL) and radiocarbon dating, suggests that these deposits were a result of the tsunami. Seismic identification of this stratum and analysis of adjacent cores showed diminished traces of the tsunami which was largely removed by subsequent erosional processes. Our results confirm previous modelling of the impact of the tsunami within this area of the southern North Sea, and also indicate that these effects were temporary, localized, and mitigated by the dense woodland and topography of the area. We conclude that clear physical remnants of the wave in these areas are likely to be restricted to now buried, palaeo-inland basins and incised river valley systems.

Erratum: Assessing the Impact of Underwater Clearance of Unexploded Ordnance on Harbour Porpoises (Phocoena phocoena) in the Southern North Sea

2018 ◽  
Vol 44 (3) ◽  
pp. 340-341
Author(s):  
Alexander M. von Benda-Beckman ◽  
Geert Aarts ◽  
H. Özkan Sertlek ◽  
Klaus Lucke ◽  
Wim C. Verboom ◽  
...  
Keyword(s):  
North Sea ◽  
Unexploded Ordnance ◽  
Phocoena Phocoena ◽  
Southern North Sea ◽  
The Impact

Marine heatwaves and cold-spells, and their impact on fisheries in the southern North Sea

2021 ◽  
Author(s):  
Sarah Wakelin ◽  
Bryony Townhill ◽  
Georg Engelhard ◽  
Jason Holt ◽  
Richard Renshaw
Keyword(s):  
North Sea ◽  
Marine Ecosystem ◽  
Extreme Temperature ◽  
Sea Bass ◽  
Extreme Temperature Events ◽  
Southern North Sea ◽  
Red Mullet ◽  
Variable Surface ◽  
Fish And Shellfish ◽  
The Impact

&lt;p&gt;The marine environment experiences temperature variability both in the short and long term due to a combination of variable surface heating, ocean transport and mixing effects. The impact of temperature anomalies on the marine ecosystem depends on their duration and amplitude compared with timescales of the ecological response and the susceptibility of various components of the ecosystem to the change. Even relatively short events can affect reproduction and growth, and potentially cause mortality when organism tolerance limits are exceeded.&lt;br&gt;We focus on sustained (lasting longer than 5 days) temperature events that are extreme relative to the phase of the seasonal cycle and consider both heatwaves and cold-spells. We used daily-mean near-bed temperatures from the CMEMS (https://marine.copernicus.eu/) northwest European Shelf reanalysis and analysis/forecast simulations to identify heatwaves and cold-spells for the period 1993 to 2019. Monthly fisheries landings data for 1993 to 2016 from the Cefas Fisheries Activity Database for England and Wales (https://www.gov.uk/guidance/fishing-activity-and-landings-data-collection-and-processing) were analysed to identify potential impacts of the extreme temperature events on fish and shellfish.&lt;br&gt;Widespread heatwaves and cold-spells occurred in the southern North Sea throughout the period 1993 to 2019 but with no significant trends in the extent or magnitude of events. Winter cold-spells occurred in 1994, 1996, 1997, 2010, 2011, 2013 and 2018 and there were widespread heatwaves in 1998, 2002, 2003, 2006, 2007 and 2014 to 2019. Statistical analysis of the fisheries landings data identified a link between extreme temperature events and key fish and shellfish stocks in the North Sea. Catches of sole and sea bass increased in years with cold-spells, while catches of red mullet and edible crabs decreased. For heatwaves, the impact on fisheries catch data lagged the temperature events by five years: sole, European lobster and sea bass catches increased whilst red mullet catches reduced.&amp;#160;&lt;/p&gt;

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