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\"For 250 years encrusted wonders have been turning up in fishermen's nets: everything imaginable from prehistoric animal bones to priceless Roman statues. Fishing trawlers annually sweep an area equivalent in size to half the world's continental shelves. Everything in the wake of these bulldozers of the deep is battered. A devastating trail of smashed shipwrecks runs from the North Sea to Malaysia.The profound threat of the global fishing industry remains a black hole in marine archaeology, poorly understood and unmanaged. Fishing and Shipwreck Heritage is the first global analysis of the threat of bottom fishing to underwater cultural heritage, examining the diversity, scale and implications on endangered finds and sites. Throughout, the key questions of whether it is too late to save the planet's three million wrecks and how sustainable management is achievable are debated\"-- Provided by publisher.

Please view the correct Fig 8 here. thumbnail Download: * PPT PowerPoint slide * PNG larger image * TIFF original image Fig 8. The PADM chart incorporates stratigraphic data as well as factoring in the dredging level hypothesis and possible ship draughts.

Dredging is a crucial process for the maintenance and management of aquatic ecosystems, involving the removal of sediment that accumulates in bodies of water such as rivers, lakes, and dams. Specialized dredging equipment operates using vacuum mechanisms to efficiently extract and transport sediment, thus ensuring navigational and ecological integrity. In tropical regions, extreme precipitation exacerbates sediment influx, diminishing reservoir capacity and impacting agricultural irrigation and hydroelectric generation. Furthermore, sediment accumulation can lead to nutrient loading and harmful algal blooms. Over time, sedimentation can lead to significant issues, including reduced water depth and impaired water quality, affecting both aquatic life and human activities reliant on these waterways. Effective dredging not only addresses sediment buildup but also repurposes extracted materials for various applications, including beach nourishment and construction fill. Various methods of sediment removal, including mechanical and hydraulic techniques, are employed based on project needs and environmental conditions. Mechanical dredging utilizes equipment like grabs and clamshells, while hydraulic methods leverage suction and cutting technologies. Choosing the appropriate method involves careful consideration of site-specific factors, ensuring operational efficiency and minimal ecological impact. Ultimately, dredging plays a vital role in sustaining healthy aquatic environments while supporting essential economic activities.

Toxic metal pollution is a leading environmental concern for aquatic systems globally, and remedial dredging has been widely employed to mitigate its harmful impacts. In terms of the short-term impacts of remedial dredging, mixed results are reported in several studies. Despite its immediate negative impacts including saturation of water with toxic metals, increased turbidity, and sediment resuspension, positive impacts can be recorded over a stabilization period of 6–24 months after dredging. Nevertheless, the sustainability of these recorded positive effects cannot be ascertained as some studies have reported long-term regression in remediated sites’ conditions. Evaluation of success determinants, site-measure compatibility, and determination of supplementary measures are keys to achieving and sustaining the projected benefits of remedial dredging and justifying its overall cost. This multicomponent study reviewed published literatures that documented the outcomes of short- and long-term dredging projects in toxic metal-polluted systems globally with a broad goal of examining how sediment removal impacts toxic metal dynamics in the aquatic system and understanding why the sustenance of positive impacts is controversial. In the meantime, this study also explored the preventative and remedial management strategies for attaining and sustaining positive dredging outcomes. The purpose of this study is to provide key recommendations for decision-making and policy development in aquatic toxic metal remediation.

Environmental sediment dredging is one of the most common methods for the remediation of contaminated sediments in lakes; however, debate continues as to whether the effectiveness of dredging methods contributes to this phenomenon. To determine sediment resuspension and nutrient release following dredging with a variety of dredging methods, four dredging treatments at wind speeds of 0–5.2 m/s were simulated in this study, namely suction dredging (SD), grab dredging (GD), ideal dredging with no residual sediments (ID), and non-dredging (ND). Field sediments from suction and grab dredging areas (including post-dredged and non-dredged sediments) of Lake Taihu were used to assess the release abilities of soluble reactive phosphorus (SRP) and ammonia nitrogen (NH 4 + -N) from the sediment-water interface. The effects of residual sediments on nutrient concentrations in water were also evaluated. The results reveal that inhibition of resuspension of particulate matter and nutrients released through sediment dredging decreases with increasing levels of residual sediment. Total suspended particulate matter content in the mean water columns of ID, SD, and GD under wind-induced disturbance (1.7–5.2 m/s) decreased by 67.5%, 56.8%, and 44.3%, respectively; total nitrogen and total phosphorus in ID (SD) treatments were 19.8% (12.9%) and 24.5% (11.2%) lower than that in ND treatment. However, there were ~ 1.6 and 1.5 times higher SRP and NH 4 + -N in the GD treatment compared with the ND treatment at the end of the resuspension experiment (0 m/s). A significant increase in the SRP and NH 4 + -N release rates at the sediment-water interface was also observed in field sediments from a grab dredging area, indicating that GD may pose a short-term risk of nutrient release to the water body. Hence, dredging methods with less residual sediments both during and after dredging improves the dredging quality.

Pion, L.M. and Bernardino, J.C.M., 2024. Integrated methodology for estimating maintenance dredging intervals at port berths: A case study in a Brazilian estuarine environment. In: Phillips, M.R.; Al-Naemi, S., and Duarte, C.M. (eds.), Coastlines under Global Change: Proceedings from the International Coastal Symposium (ICS) 2024 (Doha, Qatar). Journal of Coastal Research, Special Issue No. 113, pp. 382-386. Charlotte (North Carolina), ISSN 0749-0208. Maintenance dredging is a critical aspect of ensuring navigational safety and accessibility in port terminals worldwide. This paper addresses the urgent need for optimized maintenance dredging procedures by proposing an integrated method that combines bathymetric survey analysis and sediment transport modeling. Focusing on two berth areas within a port terminal in northeastern Brazil, referred as Areas I and II, the method aims to predict intervals between maintenance dredging campaigns. Key steps of the proposed method include processing and analyzing bathymetric data to calculate volumes above the dredging level and historical critical bed levels. A correlation curve is established between these volumes and critical levels, facilitating the estimation of bed evolution rates. Computational modeling using the Delft3D platform allows for scenario simulations, aiding in predicting future critical bed levels. Results indicate successful calibration and verification of the hydrodynamic model, with good agreement between modeled and field-measured data. Correlation curves demonstrate adequate agreement between volumes above the dredging level and critical bed levels. The results indicate the need for maintenance dredging in Area I approximately every 26 days and in Area II every 16 days on average. These intervals are consistent with historical practices over time but are shorter than ideal for terminal operation. The findings underscore the importance of the proposed method in accurately predicting maintenance dredging intervals and optimizing operational decision-making in port terminals. Future research should focus on refining correlation methodologies and overcoming practical challenges to further enhance maintenance dredging optimization in port terminals. This study contributes valuable insights into operational decision-making and underscores the importance of continued research efforts in this field.

Bottom trawling is the most widespread human activity affecting seabed habitats. Here, we collate all available data for experimental and comparative studies of trawling impacts on whole communities of seabed macroinvertebrates on sedimentary habitats and develop widely applicable methods to estimate depletion and recovery rates of biota after trawling. Depletion of biota and trawl penetration into the seabed are highly correlated. Otter trawls caused the least depletion, removing 6% of biota per pass and penetrating the seabed on average down to 2.4 cm, whereas hydraulic dredges caused the most depletion, removing 41% of biota and penetrating the seabed on average 16.1 cm. Median recovery times posttrawling (from 50 to 95% of unimpacted biomass) ranged between 1.9 and 6.4 y. By accounting for the effects of penetration depth, environmental variation, and uncertainty, the models explained much of the variability of depletion and recovery estimates from single studies. Coupled with large-scale, high-resolution maps of trawling frequency and habitat, our estimates of depletion and recovery rates enable the assessment of trawling impacts on unprecedented spatial scales.

The dredging pump is the most critical dredging equipment for the cutter suction dredger, and its performance is one of the decisive factors for the cutter suction dredger productivity. Relying on the Xiamen New Airport Phase II Project, a comparative analysis of the dredging pump performance before and after impeller wear was carried out under medium-coarse sand conveying conditions. The results show that impeller wears will cause the dredging pump head to fall and performance degradation. In the range of normal construction process parameters, the larger the impeller rotational speed is or the smaller the concentration of medium-coarse sand conveying is, the more significant the decline in dredging pump performance will be. The research results can provide guidance for the cutter suction dredger pump working point adjustment and process optimization in the dredging pump wear condition.

Lake Manzala is the largest northern lake in Egypt and receives significant quantities of wastewater. This study was conducted in 2015 and 2022 (before and after dredging) to assess changes in physicochemical parameters [transparency, salinity, dissolved oxygen (DO), chemical oxygen demand (COD), biological oxygen demand (BOD), and nutrients] as well as the community composition of zooplankton in relation to the dredging process. Water quality parameters, particularly salinity, classified the different lake sites into three groups (north, middle, and south) in 2015 and two groups (north-middle and south) in 2022. The highest values for transparency, salinity, and DO were recorded in the northern sector, while the highest values for BOD, COD, and nutrients were found in the southern sector. A total of 43 zooplankton species were identified in 2015, compared to 31 species in 2022. Notably, the number of saline species increased in 2022 to 12 species, and their distribution extended into the northern and middle sectors. Additionally, principal component analysis (PCA) revealed that zooplankton species could be divided into saline and freshwater groups. The study concluded that the chemical parameters and zooplankton composition in 2022 differed significantly from those in 2015 due to dredging, which altered the lake’s ecology by increasing salinity and reducing nutrient levels, particularly in the northern and middle regions.