scholarly journals Physical Disturbance by Bottom Trawling Suspends Particulate Matter and Alters Biogeochemical Processes on and Near the Seafloor

2021 ◽  
Vol 8 ◽  
Author(s):  
Clare Bradshaw ◽  
Martin Jakobsson ◽  
Volker Brüchert ◽  
Stefano Bonaglia ◽  
Carl-Magnus Mörth ◽  
...  
Keyword(s):  
Thick Layer ◽  
Otter Trawl ◽  
Hydrodynamic Drag ◽  
Biogeochemical Processes ◽  
Bottom Trawling ◽  
Oxygen Penetration ◽  
Sediment Biogeochemistry ◽  
Seabed Topography ◽  
Faunal Communities ◽  
The Baltic

Bottom trawling is known to affect benthic faunal communities but its effects on sediment suspension and seabed biogeochemistry are less well described. In addition, few studies have been carried out in the Baltic Sea, despite decades of trawling in this unique brackish environment and the frequent occurrence of trawling in areas where hypoxia and low and variable salinity already act as ecosystem stressors. We measured the physical and biogeochemical impacts of an otter trawl on a muddy Baltic seabed. Multibeam bathymetry revealed a 36 m-wide trawl track, comprising parallel furrows and sediment piles caused by the trawl doors and shallower grooves from the groundgear, that displaced 1,000 m3 (500 t) sediment and suspended 9.5 t sediment per km of track. The trawl doors had less effect than the rest of the gear in terms of total sediment mass but per m2 the doors had 5× the displacement and 2× the suspension effect, due to their greater penetration and hydrodynamic drag. The suspended sediment spread >1 km away over the following 3–4 days, creating a 5–10 m thick layer of turbid bottom water. Turbidity reached 4.3 NTU (7 mgDW L–1), 550 m from the track, 20 h post-trawling. Particulate Al, Ti, Fe, P, and Mn were correlated with the spatio-temporal pattern of suspension. There was a pulse of dissolved N, P, and Mn to a height of 10 m above the seabed within a few hundred meters of the track, 2 h post-trawling. Dissolved methane concentrations were elevated in the water for at least 20 h. Sediment biogeochemistry in the door track was still perturbed after 48 h, with a decreased oxygen penetration depth and nutrient and oxygen fluxes across the sediment-water interface. These results clearly show the physical effects of bottom trawling, both on seabed topography (on the scale of km and years) and on sediment and particle suspension (on the scale of km and days-weeks). Alterations to biogeochemical processes suggest that, where bottom trawling is frequent, sediment biogeochemistry may not have time to recover between disturbance events and elevated turbidity may persist, even outside the trawled area.

scholarly journals Evaluating impacts of bottom trawling and hypoxia on benthic communities at the local, habitat, and regional scale using a modelling approach

2019 ◽  
Vol 77 (1) ◽  
pp. 278-289 ◽  
Author(s):  
P D van Denderen ◽  
S G Bolam ◽  
R Friedland ◽  
J G Hiddink ◽  
K Norén ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Spatial Scales ◽  
Benthic Communities ◽  
Regional Scale ◽  
The Baltic Sea ◽  
Benthic Habitats ◽  
Bottom Trawling ◽  
Management Actions ◽  
The Baltic ◽  
Local Habitat

Abstract Bottom trawling disturbance and hypoxia are affecting marine benthic habitats worldwide. We present an approach to predict their effects on benthic communities, and use the approach to estimate the state, the biomass relative to carrying capacity, of the Baltic Sea at the local, habitat, and regional scale. Responses to both pressures are expected to depend on the longevity of fauna, which is predicted from benthic data from 1558 locations. We find that communities in low-salinity regions mostly consist of short-lived species, which are, in our model, more resilient than those of the saline areas. The model predicts that in 14% of the Baltic Sea region benthic biomass is reduced by at least 50%, whereas an additional 8% of the region has reductions of 10–50%. The effects of hypoxia occur over larger spatial scales and lead to a low state of especially deep habitats. The approach is based on a simple characterization of the benthic community, which comes with high uncertainty, but allows for the identification of benthic habitats that are at greatest risk and prioritization of management actions at the regional scale. This information supports the development of sustainable approaches to manage impact of human activities on benthic ecosystems.

Influence of 70 Watt Electric Lights on the Capture of Fish By Otter Trawl Off Plymouth

1986 ◽  
Vol 66 (3) ◽  
pp. 711-720 ◽  
Author(s):  
M. R. Clarke ◽  
P. L. Pascoe ◽  
L. Maddock
Keyword(s):  
Catch Rate ◽  
Otter Trawl ◽  
Trachurus Trachurus ◽  
Merluccius Merluccius ◽  
Bottom Trawling ◽  
Merlangius Merlangus ◽  
Comparative Trials

The effect of two 70 W underwater electric lamps on the catch rate of a commercial bottom otter trawl was determined by comparative trials both at night and in daylight. It was found that, although the overall numbers and weights of fish caught did not differ, most of the species which were caught in large enough numbers for a judgement to be made showed a reaction to light. Three species, Trachurus trachurus, Merlangius merlangus and Trisopterus minutus were attracted and four species, Eutriglagurnardus, Micromesistius poutassou, Merluccius merluccius and Limanda limanda were scared off by light.The possible use of lights to further the development of selective commercial bottom trawling by attracting or scaring particular species is discussed.

Addressing the effects of bottom trawling on benthic processes using experimental and field studies in the Baltic Sea

2020 ◽  
Author(s):  
Claudia Morys ◽  
Martin Jakobsson ◽  
Mattias Sköld ◽  
Pere Masqué ◽  
Volker Brüchert ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Field Experiments ◽  
Biogeochemical Cycling ◽  
Field Studies ◽  
The Baltic Sea ◽  
Bottom Trawling ◽  
Flux Measurements ◽  
The Baltic ◽  
Benthic Ecosystems ◽  
The Impact

<p>Bottom trawling is one of the most important anthropogenic disturbances affecting marine ecosystems and there has been increased attention to its impacts on seabed habitats as well as the structure and functioning of benthic ecosystems. The impact of bottom trawling is well-known with regard to benthic organisms. However, we still have a poor understanding of its effects on bentho-pelagic coupling and biogeochemical cycling in the sediment. In the Baltic Sea, the study area of the present investigation, there is a particular lack of data.<br>Here, we present new results from field experiments to quantify changes in sediment properties, macrofauna and biogeochemical cycling after the passage of a benthic dredge. To put the results in a broader context, a field survey was conducted in six areas of different commercial trawling intensities in the Bornholm Basin. Acoustic geophysical mapping, isotope profiling, functional categorization of macrofauna and sediment-water nutrient and oxygen flux measurements were used to evaluate the physical disturbance of the seabed. Preliminary results suggest a range of ecological, biogeochemical and physical impacts of trawling in the Baltic Sea, with implications for benthic ecosystem functioning.</p>

scholarly journals The Interplay of Macrofauna Functional Groups Shapes Nitrogen Cycling in Oligotrophic Estuarine Sediments

2021 ◽  
Author(s):  
Mindaugas Zilius ◽  
Darius Daunys ◽  
Marco Bartoli ◽  
Ugo Marzocchi ◽  
Stefano Bonaglia ◽  
...  
Keyword(s):  
Functional Groups ◽  
N Cycling ◽  
Interactive Effects ◽  
Estuarine Sediments ◽  
Biogeochemical Processes ◽  
N Transformations ◽  
Benthic Metabolism ◽  
Solute Fluxes ◽  
The Baltic ◽  
Local Dominance

Abstract The effects of single macrofauna species on benthic nitrogen (N) cycling has been extensively studied, whereas the effect of macrofauna communities on N-related processes remains poorly explored. In this study, we characterized benthic N-cycling in bioturbated sediments of an oligotrophic northern Baltic waters (Öre estuary). Solute fluxes and N transformations (N2 fixation, denitrification and DNRA) were measured in sediments and in macrofauna-bacteria holobionts to partition the role of three dominant macrofauna taxa (Limnecola balthica, Marenzelleria sp. and Monoporeia affinis) in shaping N-cycling, and to disentangle the contribution of different functional groups within the community. In the studied area, benthic macrofauna comprised a low diversity community with extremely high local dominance of three macrofauna taxa, which are widespread and dominant in the Baltic. The biomass of these three taxa in the benthic community explained up to 30% of variation in measured biogeochemical processes, confirming their role in ecosystem functioning. The results also show that these taxa significantly contributed to the benthic metabolism and N-cycling (direct effect) as well as reworked sediments with positive feedback to dissimilative nitrate reduction (indirect effect). Taken together, these functions promoted a re-use of nutrient at the benthic level, limiting net losses (e.g. denitrification) and effluxes to bottom water. Finally, the detection of multiple N transformations in dominating macrofauna holobionts suggested a community-associated active and versatile microbiome, which alternatively contributes to the biogeochemical processes. The present study highlights hidden and interactive effects among microbes and macrofauna, which should be considered in analysing benthic functioning.

scholarly journals Impact of bottom trawling on sediment biogeochemistry: a modelling approach

2020 ◽  
Author(s):  
Emil De Borger ◽  
Justin Tiano ◽  
Ulrike Braeckman ◽  
Adriaan D. Rijnsdorp ◽  
Karline Soetaert
Keyword(s):  
Organic Carbon ◽  
Electric Pulse ◽  
Carbon Mineralization ◽  
Sandy Sediment ◽  
Bottom Trawling ◽  
Benthic Metabolism ◽  
Sedimentary Environments ◽  
Sediment Biogeochemistry ◽  
Sediment Types ◽  
Modelling Approach

Abstract. Bottom trawling in shelf seas can occur more than 10 times per year for a given location. This affects the benthic metabolism, through a mortality of the macrofauna, resuspension of organic matter from the sediment, and alterations of the physical sediment structure. However, the trawling impacts on organic carbon mineralization and associated processes are not well known. Using a modelling approach, the effects of increasing trawling frequencies on early diagenesis were studied in five different sedimentary environments, simulating the effects of a deep penetrating gear (e.g. a tickler chain beam trawl) and a shallower, more variable penetrating gear (e.g. an electric pulse trawl). Trawling events strongly increased oxygen and nitrate concentrations in surface sediment layers, and led to significantly lower amounts of ammonium (43–99 % reduction) and organic carbon in the top 10 cm of the sediment (62–96 % reduction). As a result, total mineralization rates in the sediment were decreased by up to 28 %. The effect on different mineralization processes differed both between sediment types, and between trawling frequencies. The shallow penetrating gear had a slightly smaller effect on benthic denitrification than the deep penetrating gear, but there were no statistically different results between gear types for all other parameters. Denitrification was reduced by 69 % in a fine sandy sediment, whereas nitrogen removal nearly doubled in a highly eutrophic mud. This suggests that even relatively low penetration depths from bottom fishing gears generates significant biogeochemical alterations. Physical organic carbon removal through trawl-induced resuspension of sediments, exacerbated by a removal of bioturbating macrofauna, was identified as the main cause of the changes in the mineralization process.

New Design Code for Interference Between Trawl Gear and Pipelines: DNV RP-F111

2006 ◽  
Author(s):  
Dag O̸. Askheim ◽  
Olav Fyrileiv
Keyword(s):  
Otter Trawl ◽  
Hydrodynamic Drag ◽  
Potential Hazard ◽  
Test Results ◽  
Design Code ◽  
Acceptance Criteria ◽  
Drag Forces ◽  
Analysis Methodology ◽  
Concrete Coating ◽  
Pipeline Design

The offshore petroleum and the fishing industries are often operating in the same areas. Fishing, in particular bottom trawling, is of concern to pipeline integrity. Such trawling is mainly conducted with two types of trawl gear: otter or beam trawls. The otter trawl boards are steel, more or less rectangular boards which keep the trawl bag open by hydrodynamic drag forces. While the beam trawls use a 10–20 meters long beam to keep the trawl bag open. These trawl gears are dragged along the seabed and represent a potential hazard to pipelines. This paper gives a brief description of types and dimensions of trawl gear. Further it deals with methods for calculating the pipeline response when interacting with bottom trawl gear and finally adresses acceptance criteria for pipeline design and assessment during operation. The calculation methods and acceptance criteria given in this paper are based on test results and research done during the last decades including results from the Kristin, Sno̸hvit and Ormen Lange projects. The above mentioned trawl data, analysis methodology and acceptance criteria are taken from the new DNV Recommended Practice, DNV RP-F111 (2006). This Recommended Practice is an update of the former design code DNV GL 13 (1997). The update was performed mainly due to new types of trawl gear, updated trawl gear data, various experience from application of GL 13 in projects and a general harmonizing process with the pipeline code, DNV OS-F101, and the Hotpipe project, ref Collberg et al. (2005). Large sums are often spent in pipeline projects to protect against trawl gear interaction in terms of concrete coating, trenching or burial. On the other hand the costs of not providing a sufficient protection could be extremely high, with costs related to leakages, failures, stop in production and repair/replacement. This Recommended Practice provides a rational tool to optimize the costs related to trawl gear interference and still ensure that the integrity of the pipeline becomes acceptable.

scholarly journals Sediment biogeochemistry along an oyster aquaculture chronosequence

2020 ◽  
Vol 646 ◽  
pp. 13-27 ◽  
Author(s):  
NE Ray ◽  
AN Al-Haj ◽  
RW Fulweiler
Keyword(s):  
Biogeochemical Processes ◽  
Bare Sediment ◽  
P Cycling ◽  
Sediment Biogeochemistry ◽  
Oyster Aquaculture ◽  
Oyster Farms ◽  
Annual Scale ◽  
Chronosequence Approach

Oyster aquaculture is expanding globally, and there has been a recent research surge examining how oyster farms alter coastal ecosystems. Yet, until now, the role of time in these studies has largely been missing. Here we used an in situ chronosequence approach to determine how the presence of oyster aquaculture (Crassostrea virginica) altered sediment nitrogen (N), oxygen (O2), and phosphorus (P) cycling. Overall we found that the sum of nitrogen fluxes increased significantly following addition of aquaculture, and switched from net N consumption (i.e. net nitrogen fixation: -14.41 µmol N m-2 h-1) to production (i.e. net denitrification: 553.57 µmol N m-2 h-1). Ammonium (NH4+) fluxes did not differ between bare sediment and oyster aquaculture. Additionally, both the magnitude of N2 and NH4+ fluxes oscillated on an annual scale of aquaculture age, but not predictably so. We observed significantly more variance (σ2) in dinitrogen and NH4+ fluxes in sediments beneath aquaculture, indicating increased non-linearity. O2 fluxes increased from Years 4 to 6, before returning to baseline conditions. There were no differences in sediment P cycling. This study demonstrates that sediment biogeochemical processes can become non-linear under the pressure of oyster aquaculture, and this non-linearity likely has important implications for ecosystem function.

scholarly journals The Baltic Sea scale inventory of benthic faunal communities

2016 ◽  
Vol 73 (4) ◽  
pp. 1196-1213 ◽  
Author(s):  
Mayya Gogina ◽  
Henrik Nygård ◽  
Mats Blomqvist ◽  
Darius Daunys ◽  
Alf B. Josefson ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Benthic Communities ◽  
Macoma Balthica ◽  
Benthic Invertebrate ◽  
The Baltic Sea ◽  
Species Abundances ◽  
Faunal Communities ◽  
Community Data ◽  
Wet Weight ◽  
The Baltic

Abstract This study provides an inventory of the recent benthic macrofaunal communities in the entire Baltic Sea. The analyses of soft-bottom benthic invertebrate community data based on over 7000 locations in the Baltic Sea suggested the existence of 10 major communities based on species abundances and 17 communities based on species biomasses, respectively. The low-saline northern Baltic, characterized by silty sediments, is dominated by Monoporeia affinis, Marenzelleria spp., and Macoma balthica. Hydrobiidae, Pygospio elegans, and Cerastoderma glaucum dominate the community in sandy habitats off the Estonian west coast and in the southeastern and southern Baltic Sea. Deep parts of the Gulf of Finland and central Baltic Sea often experience hypoxia, and when oxygen levels in these regions recover, Bylgides sarsi was the first species to colonize. The southwestern Baltic Sea, with high salinity, has higher macrofaunal diversity compared with the northern parts. To spatially interpolate the distribution of the major communities, we used the Random Forest method. Substrate data, bathymetric maps, and modelled hydrographical fields were used as predictors. Model predictions were in good agreement with observations, quantified by Cohen's κ of 0.90 for the abundance and 0.89 in the wet weight-based model. Misclassifications were mainly associated with uncommon classes in regions with high spatial variability. Our analysis provides a detailed baseline map of the distribution of benthic communities in the Baltic Sea to be used both in science and management.

scholarly journals Impact of bottom trawling on sediment biogeochemistry: a modelling approach

2021 ◽  
Vol 18 (8) ◽  
pp. 2539-2557
Author(s):  
Emil De Borger ◽  
Justin Tiano ◽  
Ulrike Braeckman ◽  
Adriaan D. Rijnsdorp ◽  
Karline Soetaert
Keyword(s):  
Organic Carbon ◽  
Electric Pulse ◽  
Carbon Mineralization ◽  
Sandy Sediment ◽  
Bottom Trawling ◽  
Benthic Metabolism ◽  
Sedimentary Environments ◽  
Sediment Biogeochemistry ◽  
Sediment Types ◽  
Modelling Approach

Abstract. Bottom trawling in shelf seas can occur more than 10 times per year for a given location. This affects the benthic metabolism, through a mortality of the macrofauna, resuspension of organic matter from the sediment, and alterations of the physical sediment structure. However, the trawling impacts on organic carbon mineralization and associated processes are not well known. Using a modelling approach, the effects of increasing trawling frequencies on early diagenesis were studied in five different sedimentary environments, simulating the effects of a deeper-penetrating gear (e.g. a tickler chain beam trawl) versus a shallower, more variable penetrating gear (e.g. an electric pulse trawl). Trawling events strongly increased oxygen and nitrate concentrations in surface sediment layers and led to significantly lower amounts of ammonium (43 %–99 % reduction) and organic carbon in the top 10 cm of the sediment (62 %–96 % reduction). As a result, total mineralization rates in the sediment were decreased by up to 28 %. The effect on different mineralization processes differed both between sediment types and between trawling frequencies. The shallow-penetrating gear had a slightly smaller effect on benthic denitrification than the deeper-penetrating gear, but there were no statistically different results between gear types for all other parameters. Denitrification was reduced by 69 % in a fine sandy sediment, whereas nitrogen removal nearly doubled in a highly eutrophic mud. This suggests that even relatively low penetration depths from bottom fishing gears generate significant biogeochemical alterations. Physical organic carbon removal through trawl-induced resuspension of sediments, exacerbated by a removal of bioturbating macrofauna, was identified as the main cause of the changes in the mineralization process.

scholarly journals Supplementary material to "Impact of bottom trawling on sediment biogeochemistry: a modelling approach"

2020 ◽  
Author(s):  
Emil De Borger ◽  
Justin Tiano ◽  
Ulrike Braeckman ◽  
Adriaan D. Rijnsdorp ◽  
Karline Soetaert
Keyword(s):  
Bottom Trawling ◽  
Sediment Biogeochemistry ◽  
Supplementary Material ◽  
Modelling Approach
Sign in / Sign up

Export Citation Format

Share Document