Marine construction works often lead to temporary increases in vessel traffic, which, in addition to the construction activity itself, contribute to underwater ambient noise in the affected area and increase the risk of vessel collision for marine mammals. Using a 3 yr data set of cliff-based observations, we investigated whether the presence/absence of minke whales, bottlenose dolphins and grey seals varied with the overall number and type of vessels present during the construction of an underwater gas pipeline through a bay on the northwest coast of Ireland. Results from binary generalised estimation equations showed a positive relationship between the presence of bottlenose dolphins and the overall number of boats, as well as the number of construction vessels. However, the presence of the 2 taxa with higher hearing sensitivity at low frequencies -minke whales and grey seals -was negatively correlated with the total number of boats and the number of utility vessels (as well as the number of fishing boats in the case of minke whales). While bottlenose dolphins may have been attracted to either the vessels per se or high prey concentrations coinciding with construction activities, both minke whales and grey seals appear to have been displaced by high levels of vessel traffic, most likely due to noise disturbance. Careful consideration of mitigation measures, especially for taxa with low-frequency hearing, is therefore essential in the planning phase of offshore construction activities, which should also take local circumstances into account.
Long-term monitoring programmes of a comparatively small area complement larger scale, but temporally limited surveys and can provide extensive datasets on seasonal occurrence and fine-scale habitat use of multiple species. A marine mammal monitoring programme, involving year-round, land-based observations, has been conducted in Broadhaven Bay candidate Special Area of Conservation, north-west Ireland, during 2002, 2005 and 2008–2011. Nine cetacean and two seal species have been recorded, with grey seal, harbour porpoise, common and bottlenose dolphins, and minke whale present throughout the year. Generalized additive models, taking into account observer effort, sighting conditions (sea state) and interannual variation, did not reveal any significant seasonal patterns in the occurrence of grey seals, bottlenose dolphins and minke whales. On the other hand, common dolphin presence in Broadhaven Bay was highest during autumn and winter. Bottlenose dolphins could be separated spatially from both common dolphins and minke whales in a classification tree by their preferential use of the shallower inshore areas of the bay (<30 m depth). However, common dolphins and minke whales, which occurred mainly in the deeper outer section of Broadhaven Bay, could not be spatially distinguished from each other, and grey seals were distributed over the entire bay. Broadhaven Bay represents an important marine mammal habitat with respect to overall species diversity and the regular occurrence of bottlenose dolphin, harbour porpoise, grey and harbour seals (all listed under Annex II of the EU Habitats Directive).
This paper presents and applies an economic model developed for the management of dredged marine sediments. The model predicts direct project costs and direct, indirect and induced economic impacts. The model is applied to analyse the economic aspect of the specific potential beneficial use of dredged sediment for land reclamation in an Irish context. The model results show the potential economic benefits to land reclamation of using dredged sediment including its value as a potential substitute for quarry based material and as an alternative to traditional offshore dredged sediment disposal, where appropriate. Analysis of other sediment management approaches including wetland creation, is also presented with the results for wetland creation indicating its potential, where appropriate, as a valuable alternative to offshore disposal. Indicative economic benefits are predicted by the model for the different dredge sediment management approaches analysed.
Objective: The management of dredged sediments is a major challenge for many ports and harbours who need to maintain navigable access. Sediment volumes produced may be significant and expensive to manage. This paper presents financial modelling and analysis for the management of dredged marine sediment using a financial model developed which has the potential to be used as decision support tool by stakeholders in the Sector including Ports, Engineering Consultancies and Regulators. Data/Methodology: A decision support tool has been developed to assess the financial aspect of a range of management uses for dredged marine sediments for a range of different countries. The model allows financial analysis of the full range of processes from sediment generation to ultimate end use. Required inputs include sediment characteristics, relevant logistical data, financial impact area on a national scale and financial data including direct costings. Results/Findings: Results are presented for a specific beneficial use of dredged sediment (wetland creation). It outlines the potential of the decision support tool to financially assess a range of sediment management options. This will provide potentially valuable information for the optimum management of dredged marine sediments and allow comparison between traditional disposal options and potential beneficial use scenarios. Implications for research/Policy: The financial model developed will assist stakeholders and decision makers, including Port Authorities, in assessing the economic feasibility of a range of beneficial uses of dredged sediments. Such financial analyses may indicate the potential for an expanded range of beneficial use options for dredged marine sediments and help change traditional attitudes towards this type of material, which has often been considered a waste. Ultimately it may influence policy at a National and at an EU level.
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