scholarly journals The potential for mobile demersal fishing to reduce carbon storage and sequestration in seabed sediments

2021 ◽  
Author(s):  
Graham Epstein ◽  
Julie P Hawkins ◽  
Catrin R Norris ◽  
Callum M Roberts
Keyword(s):  
Sediment Resuspension ◽  
Order Estimate ◽  
Sediment Type ◽  
Seabed Sediment ◽  
Flocculent Material ◽  
Sediment Carbon ◽  
Carbon Stores ◽  
Seabed Sediments ◽  
Fish And Shellfish ◽  
The Impact

Subtidal marine sediments are one of the planet's primary carbon stores and strongly influence the oceanic sink for atmospheric CO2. By far the most pervasive human activity occurring on the seabed is bottom trawling and dredging for fish and shellfish. A global first-order estimate suggested mobile demersal fishing activities may cause 160-400 Mt of organic carbon (OC) to be remineralised annually from seabed sediment carbon stores. There are, however, many uncertainties in this calculation. Here, we discuss the potential drivers of change in seabed OC stores due to mobile demersal fishing activities and conduct a systematic review, synthesising studies where this interaction has been directly investigated. Mobile demersal fishing would be expected to reduce OC in seabed stores, albeit with site-specific variability. Reductions would occur due to lower production of flora and fauna, the loss of fine flocculent material, increased sediment resuspension, mixing and transport, and increased oxygen exposure. This would be offset to some extent by reduced faunal bioturbation and respiration, increased off-shelf transport and increases in primary production from the resuspension of nutrients. Studies which directly investigated the impact of demersal fishing on OC stocks had mixed results. A finding of no significant effect was reported in 51% of 59 experimental contrasts; 41% reported lower OC due to fishing activities, with 8% reporting higher OC. In relation to remineralisation rates within the seabed, 14 experimental contrasts reported that demersal fishing activities decreased remineralisation, with four reporting higher remineralisation rates. The direction of effects was related to sediment type, impact duration, study design and local hydrography. More evidence is urgently needed to accurately quantify the impact of anthropogenic physical disturbance on seabed carbon in different environmental settings, and incorporate full evidence-based carbon considerations into global seabed management.

scholarly journals Sound Velocity Estimation of Seabed Sediment Based on Parametric Array Sonar

2020 ◽  
Vol 2020 ◽  
pp. 1-6
Author(s):  
Jingxin Ma ◽  
Haisen Li ◽  
Jianjun Zhu ◽  
Baowei Chen
Keyword(s):  
Parameter Estimation ◽  
Acoustic Parameter ◽  
Velocity Estimation ◽  
Parameters Estimation ◽  
Real Field ◽  
Sound Waves ◽  
Sediment Thickness ◽  
Seafloor Topography ◽  
Seabed Sediment ◽  
Seabed Sediments

Backscattered sound waves of seabed sediments are important information carriers in seafloor detection and acoustic characteristic parameters inversion. Most of the existing methods for estimating geoacoustic parameters are based on multiangle seabed backscattered signal processing and suitable for flat seafloor conditions with uniform sediment thickness. This usually deviates from the real field conditions and affects the accuracy of parameter estimation. In this paper, the sound ray propagation theory is studied and analysed under the condition of sloping seabed and uneven sediment thickness. Based on the phased parameter array sonar system, a method of acoustic parameters estimation of the sediment under inclined seabed conditions is proposed. The simulation results show that the new method shows good adaptability to different inclination angles of the seabed and solves the problem of accuracy of acoustic parameter estimation of the inclined seabed sediments. The model will greatly reduce the seafloor topography requirements in the sediment acoustic parameter inversion, such as velocity, layer thickness, and acoustic impedance.

scholarly journals Comprehensive detection device and physical testing for mechanical properties of seabed sediments and shallow gas

2021 ◽  
Vol 2083 (2) ◽  
pp. 022105
Author(s):  
Zhe Yun Li ◽  
Qing Li
Keyword(s):  
Mechanical Properties ◽  
Real Time ◽  
Gas Separation ◽  
Sensor Placement ◽  
Gas Detection ◽  
Shallow Gas ◽  
Seabed Sediment ◽  
Transmission Part ◽  
Seabed Sediments ◽  
Water Gas

Abstract In this paper, a comprehensive detection device for the mechanical properties of seabed sediments and shallow gas is designed, which is mainly composed of the seabed sediment mechanical properties detection part, the shallow gas detection part and the ultrasonic wireless transmission part. The mud water gas separation structure of the shallow gas detection part separates the shallow gas from the mud water, and then the methane concentration in the shallow gas is measured by the non-dispersive infrared methane sensor, which realizes the collection of the submarine shallow gas and the automatic real-time monitoring of the concentration. The measurement of the mechanical properties of seabed sediments realizes the real-time measurement of the three parameters of cone resistance, sidewall friction and pore water pressure, which characterize the mechanical properties of seabed sediments, through strain-sensitive elements. The ultrasonic wireless data transmission part is mainly for the data detected by the mechanical properties of the seabed sediments to be wirelessly transmitted to the sensor placement room through the ultrasonic transducer across the mud-water-gas separation structure. Finally, the data measured by the two parts are transmitted to the mother ship through the cable located in the sensor placement room. The experimental results show that it has the ability to comprehensively detect the mechanical properties of seabed sediments and shallow gas, and has strong operability.

scholarly journals Data heterogeneity and oldness, two difficulties to overcome for the world seabed sediment mapping

2021 ◽  
Vol 4 ◽  
pp. 1-7
Author(s):  
Thierry Garlan ◽  
Isabelle Gabelotaud ◽  
Elodie Marchès ◽  
Edith Le Borgne ◽  
Sylvain Lucas
Keyword(s):  
Global Scale ◽  
Single Product ◽  
Seabed Sediment ◽  
Bathymetric Data ◽  
The World ◽  
Data Heterogeneity ◽  
Sediment Data ◽  
The University ◽  
Seabed Sediments

Abstract. A global seabed sediment map has been developed since 1995 to provide a necessary tool for different needs. This project is not completely original since it had already been done in 1912 when the French hydrographic Office and the University of Nancy produced sedimentary maps of the European and North American coasts. Seabed sediments is one of the last geographical domains which can’t benefit of satellite data. Without this contribution, sediment maps need to use very old data mixed with the new ones to be able to reach the goal of a global map. In general, sediment maps are made with the latest available techniques and are replaced after a few decades, thus generating new cartographic works as if all the previous efforts had become useless. Such approach underestimates the quality of past works and prevents to have maps covering large areas. The present work suggests to standardize all kind of sedimentary data from different periods and from very different acquisition systems and integrate them into a single product. This process has already been done for bathymetric data of marine charts, we discuss in this article of the application of this method at a global scale for sediment data.

scholarly journals Experimental Study of Erosion Threshold of Reconstituted Sediments

2011 ◽  
Author(s):  
Zhihui Ye ◽  
Liang Cheng ◽  
Zhipeng Zang
Keyword(s):  
Shear Stress ◽  
Steady Increase ◽  
Initial Increase ◽  
Threshold Condition ◽  
Seabed Sediment ◽  
Erosion Threshold ◽  
Sediment Types ◽  
Weight Content ◽  
Testing Facility ◽  
Seabed Sediments

Understanding of fundamental erosion characteristics of seabed sediments on which pipelines and other structures are founded is critical for the design of these facilities. The erosion threshold condition of cohesive sediments is not well understood because of the complexity and variability of natural sediments. Most of the existing methods for evaluating the erosion behaviours of seabed sediment are often applicable to the certain particular sediment types and test conditions. There appears to be a need for more research efforts in this area. In present research, the threshold of motion of four moderately consolidated mixtures was tested under unidirectional currents using a testing facility. Three threshold shear stress increase modes were observed, including initial increase mode, steady increase mode and equilibrium mode as mass content of mud Pm increases. A dimensionless threshold shear stress τ* is proposed to quantify the shear strength of these reconstituted mixtures, coupled with variation of coarse particle size. Finally, a predicting model is proposed to illustrate the trend of erosion threshold of the four mixtures as a function of mud weight content. Further understanding of erosion threshold can rely on the various consolidation conditions and different coarse and fine materials inputted in the mixture.

scholarly journals Warm CO in evolved stars from the THROES catalogue

2019 ◽  
Vol 622 ◽  
pp. A123 ◽  
Author(s):  
J. M. da Silva Santos ◽  
J. Ramos-Medina ◽  
C. Sánchez Contreras ◽  
P. García-Lario
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Asymptotic Giant Branch ◽  
Strong Line ◽  
Order Estimate ◽  
Evolved Stars ◽  
Flux Variability ◽  
The Impact ◽  
Loss Rates

Context. This is the second paper of a series making use of Herschel/PACS spectroscopy of evolved stars in the THROES catalogue to study the inner warm regions of their circumstellar envelopes (CSEs). Aims. We analyse the CO emission spectra, including a large number of high-J CO lines (from J = 14–13 to J = 45–44, ν = 0), as a proxy for the warm molecular gas in the CSEs of a sample of bright carbon-rich stars spanning different evolutionary stages from the asymptotic giant branch to the young planetary nebulae phase. Methods. We used the rotational diagram (RD) technique to derive rotational temperatures (Trot) and masses (MH2) of the envelope layers where the CO transitions observed with PACS arise. Additionally, we obtained a first order estimate of the mass-loss rates and assessed the impact of the opacity correction for a range of envelope characteristic radii. We used multi-epoch spectra for the well-studied C-rich envelope IRC+10216 to investigate the impact of CO flux variability on the values of Trot and MH2. Results. The sensitivity of PACS allowed for the study of higher rotational numbers than before indicating the presence of a significant amount of warmer gas (∼200 − 900 K) that is not traceable with lower J CO observations at submillimetre/millimetre wavelengths. The masses are in the range MH2 ∼ 10−2 − 10−5 M⊙, anticorrelated with temperature. For some strong CO emitters we infer a double temperature (warm T¯rot ∼ 400 K and hot T¯rot ∼ 820 K) component. From the analysis of IRC+10216, we corroborate that the effect of line variability is perceptible on the Trot of the hot component only, and certainly insignificant on MH2 and, hence, the mass-loss rate. The agreement between our mass-loss rates and the literature across the sample is good. Therefore, the parameters derived from the RD are robust even when strong line flux variability occurs, and the major source of uncertainty in the estimate of the mass-loss rate is the size of the CO-emitting volume.

scholarly journals Socio-demographic influences on trends of fish consumption during later adult life in the Whitehall II study

2008 ◽  
Vol 100 (5) ◽  
pp. 1116-1127 ◽  
Author(s):  
Tasnime N. Akbaraly ◽  
Eric J. Brunner
Keyword(s):  
Fish Consumption ◽  
Demographic Factors ◽  
Fish Intake ◽  
Phase 3 ◽  
Mixed Effect ◽  
Age Related ◽  
Total Fish ◽  
Socio Demographic Factors ◽  
Fish And Shellfish ◽  
The Impact

Our aim was to investigate how socio-demographic factors influence trends and age-related trajectories of fish consumption. We examined consumption of total, fried and recommended fish (white and oily fish, and shellfish) in the Whitehall II study over 11 years in participants aged 39–59 years at phase 3. The cohort included 8358 British civil servants who completed a FFQ at phase 3 (1991–3), phase 5 (1997–9, n 5430) and phase 7 (2002–4, n 5692). Occupational grade, ethnicity, marital and retirement status were collected at each phase. To analyse changes in age-related trends of fish intake over time according to socio-demographic characteristics, we applied a random mixed-effect model. Over the follow-up a significant increase in consumption of ‘recommended’ (mean: 1·85 to 2·22 portions/week) and total fish (mean: 2·32 to 2·65 portions/week) and a decreasing trend in fried-fish intake (mean: 0·47 to 0·43 portions/week) was observed. Recommended, fried and total fish consumption differed by occupational status, ethnicity, marital status and sex. The trend of age-related fish intake diverged significantly by ethnicity. In South Asian participants (n 432), slope of recommended-fish consumption was significantly higher compared with white participants (0·077 v. 0·025 portions/week per year). For black participants (n 275) slope of fried-fish intake was significantly higher compared with white participants (0·0052 v. − 0·0025 portions/week per year). In terms of public health, our descriptive and analytical work allows detailed understanding of the impact of socio-demographic factors on fish intake and its age-related trends. Such information is valuable for food policies that seek to promote health equity.

scholarly journals The Impact of Fish and Shellfish Consumption on Age-Related Macular Degeneration

Ophthalmology ◽  
2010 ◽  
Vol 117 (12) ◽  
pp. 2395-2401 ◽  
Author(s):  
Bonnielin K. Swenor ◽  
Susan Bressler ◽  
Laura Caulfield ◽  
Sheila K. West
Keyword(s):  
Macular Degeneration ◽  
Age Related Macular Degeneration ◽  
Age Related ◽  
Fish And Shellfish ◽  
The Impact

scholarly journals Classifying seabed sediment type using simulated tidal-induced bed shear stress

2015 ◽  
Vol 367 ◽  
pp. 94-104 ◽  
Author(s):  
Sophie L. Ward ◽  
Simon P. Neill ◽  
Katrien J.J. Van Landeghem ◽  
James D. Scourse
Keyword(s):  
Shear Stress ◽  
Sediment Type ◽  
Bed Shear Stress ◽  
Seabed Sediment

scholarly journals Towards a framework for the quantitative assessment of trawling impact on the seabed and benthic ecosystem

2015 ◽  
Vol 73 (suppl_1) ◽  
pp. i127-i138 ◽  
Author(s):  
A. D. Rijnsdorp ◽  
F. Bastardie ◽  
S. G. Bolam ◽  
L. Buhl-Mortensen ◽  
O. R. Eigaard ◽  
...  
Keyword(s):  
Benthic Community ◽  
Ecological Impact ◽  
Biological Traits ◽  
Fishing Gear ◽  
Ecological Role ◽  
Seabed Sediment ◽  
The North ◽  
Biological Trait ◽  
The Individual ◽  
The Impact

Abstract A framework to assess the impact of mobile fishing gear on the seabed and benthic ecosystem is presented. The framework that can be used at regional and local scales provides indicators for both trawling pressure and ecological impact. It builds on high-resolution maps of trawling intensity and considers the physical effects of trawl gears on the seabed, on marine taxa, and on the functioning of the benthic ecosystem. Within the framework, a reductionist approach is applied that breaks down a fishing gear into its components, and a number of biological traits are chosen to determine either the vulnerability of the benthos to the impact of that gear component, or to provide a proxy for their ecological role. The approach considers gear elements, such as otter boards, twin trawl clump, and groundrope, and sweeps that herd the fish. The physical impact of these elements on the seabed, comprising scraping of the seabed, sediment mobilization, and penetration, is a function of the mass, size, and speed of the individual component. The impact of the elements on the benthic community is quantified using a biological-trait approach that considers the vulnerability of the benthic community to trawl impact (e.g. sediment position, morphology), the recovery rate (e.g. longevity, maturation age, reproductive characteristics, dispersal), and their ecological role. The framework is explored to compare the indicators for pressure and ecological impact of bottom trawling in three main seabed habitat types in the North Sea. Preliminary results show that the Sublittoral mud (EUNIS A5.3) is affected the most due to the combined effect of intensive fishing and large proportions of long-lived taxa.

scholarly journals Seagrass Recovery Following Marine Heat Wave Influences Sediment Carbon Stocks

2021 ◽  
Vol 7 ◽  
Author(s):  
Lillian R. Aoki ◽  
Karen J. McGlathery ◽  
Patricia L. Wiberg ◽  
Matthew P. J. Oreska ◽  
Amelie C. Berger ◽  
...  
Keyword(s):  
Heat Wave ◽  
Heat Waves ◽  
Central Area ◽  
Shoot Density ◽  
Seagrass Meadows ◽  
C Stocks ◽  
Sediment Carbon ◽  
The Impact ◽  
Marine Heat Wave

Worldwide, seagrass meadows accumulate significant stocks of organic carbon (C), known as “blue” carbon, which can remain buried for decades to centuries. However, when seagrass meadows are disturbed, these C stocks may be remineralized, leading to significant CO2 emissions. Increasing ocean temperatures, and increasing frequency and severity of heat waves, threaten seagrass meadows and their sediment blue C. To date, no study has directly measured the impact of seagrass declines from high temperatures on sediment C stocks. Here, we use a long-term record of sediment C stocks from a 7-km2, restored eelgrass (Zostera marina) meadow to show that seagrass dieback following a single marine heat wave (MHW) led to significant losses of sediment C. Patterns of sediment C loss and re-accumulation lagged patterns of seagrass recovery. Sediment C losses were concentrated within the central area of the meadow, where sites experienced extreme shoot density declines of 90% during the MHW and net losses of 20% of sediment C over the following 3 years. However, this effect was not uniform; outer meadow sites showed little evidence of shoot declines during the MHW and had net increases of 60% of sediment C over the following 3 years. Overall, sites with higher seagrass recovery maintained 1.7x as much C compared to sites with lower recovery. Our study demonstrates that while seagrass blue C is vulnerable to MHWs, localization of seagrass loss can prevent meadow-wide C losses. Long-term (decadal and beyond) stability of seagrass blue C depends on seagrass resilience to short-term disturbance events.

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