The Puck Bay as an example of deep dredging unfavorably affecting the aquatic environment (original) (raw)
Related papers
The Impact of Dredging Deep Pits on Organic Matter Decomposition in Sediments
Water, Air, & Soil Pollution, 2000
In this study, the results of investigations of organic matter decomposition in natural and dredged areas of the inner Puck Bay (Baltic Sea) are presented. The dredging of relatively deep pits causes environmental problems. Researched post-dredging pits are sediment traps in which 3 times more organic carbon (C org), 3.5 times more total nitrogen (N tot), about 1.5 times more organic phosphorus (P org) and 1.7 times more total phosphorus (P tot) accumulate as compared to the nondredged regions; they are also characterized by very intensive decomposition of organic matter. About 42, 44, 95 and 50% of the annual load of, respectively, C org , N tot , P org and P tot undergo decomposition in the dredged area, whereas the respective values for natural seabed are ca. 11, 44, 41 and 21%. Reduction of nitrogen in the pit occurs mainly through ammonification, while in the natural areas of seabed denitrification prevails. In non-dredged sediments, 84% of the released nitrogen comes from denitrification whereas in the pit, it is only 18%. Organic matter degradation in the pit sediments manifests itself by a 7-fold increase in the phosphate flux into near-bottom water as compared to natural seabed. The observed phosphate flux originated from the organic matter as well as from the decomposition of inorganic phosphorus compounds. Periodically, sulphate reduction in the pit sediments resulted in hydrogen sulfide occurrence.
Benthic re-colonization in post-dredging pits in the Puck Bay (Southern Baltic Sea)
Estuarine, Coastal and Shelf Science, 2006
The stage of benthic re-colonization at a site formed by sand extraction was investigated some 10 years after the cessation of dredging. The examined post-dredging pit is one of five deep (up to 14 m) pits created with a static suction hopper on the sandy, flat and shallow (1e2 m) part of the inner Puck Bay (the southern Baltic Sea). The topography of the dredged area makes a specific trap for different kinds of organic matter. It is created by the small areas of post-dredging pits as compared to their depths. As a result, organic matter accumulation leads to anaerobic conditions and hydrogen sulfide formation. Macrofauna was not found to occur permanently in the deepest part (11 m) of the cup-shaped depression, which was characterized by its small area (0.2 km 2 ) and steep walls. However, permanent occurrence of meiofauna (max. 180 ind. 10 cm ÿ2 , mainly Nematoda) was noted. Undoubtedly, re-colonization of benthic fauna assemblages, typical of shallow and sandy seabed of the Puck Bay, will not follow in a natural way in the area of post-dredging pits. Also, it could not be expected that the re-colonization sequence would result in the formation of a structure similar to that of the natural depression (the Kuźnica Hollow).
Oceanological and Hydrobiological Studies, 2007
In this study psychrophilic, mesophilic and denitrifying bacterial abundances were studied seasonally (summer, autumn, winter and spring) in the water column and surface sediment layer (0-5 cm) in the post dredging pit Kuźnica II and natural areas of Puck Bay. The research was conducted between VI 2001 and III 2003. In the pit area an increase in mesophilic bacteria and a decrease in denitrifying bacteria numbers were observed, when compared to the natural areas. In the case of the mesophilic bacteria, the increase was visible in the near-bottom waters and surficial sediments during the period of well developed vegetation-in summer and autumn. In the case of denitrifying bacteria, the decrease of number concerned the sediments. Numbers of psychrophilic bacteria in both the natural and dredged areas did not differ significantly over the course of the study. These results suggest that deep dredging can cause the self-purification potential of the ecosystem to be diminished and induce strong bacteriological pollution.
2010
Using hydro-acoustic survey techniques (side-scan sonar and multibeam), high-resolution bathymetric and acoustic images (sonographs) of former marine aggregate extractions, from Tromper Wiek (Rügen Island, Baltic German Coast) were obtained. These data, together with ground-truthing (underwater video and seabed sediment samples) are used to describe the present condition of marks generated by mining, in terms of their morphology and superficial grain size distribution. Different features (pits and furrows), generated by different extraction techniques (anchor suction dredging and trailer hopper suction dredging, respectively) were detected at both of the study sites: Tromper Wiek 1 (sandy gravel seabed) and Tromper Wiek East (sandy seabed). Regeneration varies, depending upon the material extracted and the mining technique applied. In general, it is rapid during the first years following the extraction, becoming almost undetectable over a longer period of time. However, the marks are still detectable after more than 10 years, since they were generated.
Journal of Coastal Research
Using hydro-acoustic survey techniques (side-scan sonar and multibeam), high-resolution bathymetric and acoustic images (sonographs) of former marine aggregate extractions, from Tromper Wiek (Rügen Island, Baltic German Coast) were obtained. These data, together with ground-truthing (underwater video and seabed sediment samples) are used to describe the present condition of marks generated by mining, in terms of their morphology and superficial grain size distribution. Different features (pits and furrows), generated by different extraction techniques (anchor suction dredging and trailer hopper suction dredging, respectively) were detected at both of the study sites: Tromper Wiek 1 (sandy gravel seabed) and Tromper Wiek East (sandy seabed). Regeneration varies, depending upon the material extracted and the mining technique applied. In general, it is rapid during the first years following the extraction, becoming almost undetectable over a longer period of time. However, the marks are still detectable after more than 10 years, since they were generated.
THE ECOLOGICAL ASPECTS OF DREDGING - INNOVATIVE SOLUTIONS
Hydraulic construction in the basins of ports is very frequently associated with dredging works. The dredging works are necessary for normal functioning of the ports though lead to changes in the environment, which are expressed minimum in a change of the sea bottom profile and consequently in the hydrology in the water area of a port etc. The ecological legislation of different countries of the world is intended for limitation of the negative effect of dredging works on the aqueous environment with the help of regulating measures. Such regulating measures are fixed, in particular, by the Helsinki Convention on the protection of the marine environment in the region of the Baltic sea (HELCOM), by the Bucharest Convention on the protection of the Black sea from pollution, and the London Convention on preventing of pollution of the seas by the discharges of the wastes and other materials (the London convention on damping-LCD). The motives for the fulfilling of strict nature-conservation requirements by dredging companies are both the negative consequences of the non-observance of the standards of environmental legislation and the requirements of the financial-credit organizations (the World Bank, OECD, Atradius), with which the contractors interact, as well as the public opinion on the activity of dredging companies, the political aspects, and the overall concern about preservation of the environment. At the same time the innovative approach of dredging companies to the improvement of their production technologies for the purpose of the decrease of negative impact on the environment increases their competitive ability. For observing the very rigid established norms on the limitation of turbidity of the water area and retaining the safe ecological background at dredging the contractors develop different technologies and equipment of ecological dredging. Dutch based international dredging and marine contractor Van Oord has developed and successfully exploits the auger dredger. It works with highly contaminated sediments where it is required to prevent its penetration to the environment. The Auger dredger has the following advantages as ecological friendly dredger: the soil is accurately removed with an auger by thin layers at an accuracy of up to 5 cm; the soil in the mixture with water is not spreading around the basin in a wide plume because high density of mixture is reached. Fig.1. Auger dredging unit. The measures for the limitation of impact on the environment at dredging are those used both in the zone of dredging itself and in the zone of transportation of the soil. For example, in the zone of dredging we may install the so-called silt screens, which ensure cutting off the area of dredging from the rest of the water area,
A Review of Environmental Implications of Dredging Activities
—Dredging is a global anthropogenic excavation activity of removing sediments from water bodies and depositing it elsewhere. It is a mixed blessing as it has both beneficial and adverse impacts. This paper is on a review of environmental implications of dredging. The objective of the paper is to review previous works by researchers on the environmental consequences of dredging. The method used is a review of academic/journal articles, internet materials, conference / workshop papers, textbooks, bulletins and publicly available materials on dredging activities. The results of the study revealed that previous authors whose works were reviewed have a convergent view that apart from the beneficial impacts of dredging (e.g. keeping waterways navigable, flood and storm protection and provision of materials for road construction and building), it has lots of adverse environmental impacts, including environmental pollution, erosion, widespread hydrological changes, reduction in the population of aquatic lives like destruction of fish spawning grounds and benthic organisms and resuspension of particulate matter column that has elevated levels of lead, copper, zinc and nickel in Phytoplankton. Recommendations of the study include: (1) establishment of environmental legislations and regulations for dredging operation; (2) use of green technology in dredging activities to minimize suspension of sediments and contamination/pollution of dredging environments; and (3) creation of awareness among dredging contractors, regulators and marine communities where dredging take place on the economic and ecological values of the marine ecosystems that are usually very sensitive, fragile and productive.
Environmental Monitoring and Assessment, 2019
The potential influence of short-period (May-June 2012) dredging activities (for the installation of a submarine gas pipeline) on physical properties of the marine environment of two shallow-water sites in the Aliveri and Varnavas areas of South Euboean Gulf (Greece) has been evaluated. During the dredging operation in Varnavas, the induced dredge plume traveled up to~750 m from the shoreline, featured by light attenuation coefficient (c p) maxima of 4.01-4.61 m −1 and suspended particulate matter (SPM) concentrations up to 6.01 mg L −1. After dredging the previous parameters reduced to the ambient seawater condition,~0.45 m −1 and < 2.8 mg L −1 on average, respectively. Likewise in Aliveri, the dredging-associated sediment plume drifted offshore up to~400 m from the shoreline, characterized by c p maxima of 2.11-4.86 m −1 and SPM concentrations up to 13.07 mg L −1. After the completion of the excavation and trenching activities, the c p and SPM values were restored to the pre-disturbance condition, 0.6 m −1 and < 2.2 mg L −1 on average, respectively. The migration of the dredge plume in both dredging sites was accomplished through the formation of intermediate and benthic nepheloid layers, whose development and evolution were governed by seawater stratification and flow regime. The dredging-derived SPM levels appeared to increase within a distance of no more than 300 m from the shoreline (near-field zone). Based on data from the literature, this SPM enhancement together with the deposition of a post-dredging residual mud veneer in the near-field zone could deteriorate local marine biota, but in a reversible way.
The relationship between sediment-bound contaminants and biological uptake of these contaminants is complex because of the many physical, chemical, and biological factors that can affect the relationship (McElroy and Means 1988). Operational and procedural problems encountered in determining how a sediment- associated contaminant affects aquatic organisms cause additional complications. If sediment quality criteria (SQC) are to be used to regulate dredged material disposal, prediction of biological responses based on changes in sediment geochemistry, i.e., sediment physical and chemical properties, and sediment contaminant levels must be possible. Radioactive tracers can be used to evaluate the effects of changing concentrations of sediment contaminants on aquatic organisms if the assumption can be made that the contaminant does not degrade during the study. Spiking a sediment with contaminants has generally been accomplished by the addition of organic solvent carriers containing th...
Environmental impact and recovery at two dumping sites for dredged material in the North Sea
Environmental Pollution, 2003
The environmental impact and recovery associated with the long and uninterrupted disposal of large volumes of moderately contaminated dredged material from the port of Rotterdam was studied at nearby dumping sites in the North Sea. Observations were made on sediment contamination, ecotoxicity, biomarker responses and benthic community changes shortly after dumping at the ‘North’ site had ceased and at the start of disposal at the new dumping site ‘Northwest’. During the period of dumping, very few benthic invertebrates were found at the North site. Concentrations of cadmium, mercury, polychlorinated biphenyls (PCBs), polyaromatic hydrocarbons (PAHs) and tributyltin (TBT) in the fine sediment fraction (<63 μm) from this site were 2–3 times higher than at the reference site. In four different bioassays with marine invertebrates the sediments showed no acute toxic effects. In tissue (pyloric caeca) of resident starfish Asterias rubens, residual levels of mercury, zinc, PCBs and dioxin-like activity were never more than twice those at the reference site. Four different biomarkers (DNA integrity, cytochrome P450 content, benzo[a]pyrene hydroxylase activity and acetylcholinesterase inhibition) were used on the starfish tissues, but no significant differences were found between North and the reference site. Minor pathological effects were observed in resident dab Limanda limanda. One year after dumping had ceased at the North site, a significant increase in the species richness and abundance of benthic invertebrates and a concomitant decrease in the fine sediment fraction of the seabed were observed. After 8.2 million m3 of moderately contaminated dredged material had been dumped at the new dumping site Northwest, the species richness and abundance of benthic invertebrates declined over an area extending about 1–2 km eastwards. This correlated with a shift in sediment texture from sand to silt. The contamination of the fine sediment fraction at the Northwest location doubled. It is concluded that marine benthic resources at and around the dumping sites have been adversely affected by physical disturbance (burial, smothering). However, no causal link could be established with sediment-associated contaminants from the dredged spoils.