A summary of potential effects of water-based recreation

Engine emissions

Noise disturbance

Antifouling paint

Sewage discharge and other waste discharges

Disturbance to wildlife

Erosion and turbidity

Engine emissions

Research on the environmental impact of marine engine has tended to concentrate on the potential impact of 2 stroke outboard engines

Available evidence suggests that marine engine exhaust emissions have limited observable impact on the Annex I & II features.

In particular, evidence of hydrocarbon loading in the marine sediment is inconclusive and lead concentration is not thought to be significant. This is not to discount the possibility that accumulation of emissions in the sediment may have the potential to cause longer-term impacts.

Accidental discharge of oil and fuel present can have a potentially significant effect on the marine environment, due to the concentrated nature of the pollutants that may reach the water.

Noise Disturbance

Noise disturbance relates largely to impacts upon other people rather than impacts upon the natural environment. Such issues lie outside the scope of this study.

The potential impacts of noise disturbance on sublittoral and other marine communities are not known and there remains uncertainty about the extent to which dolphins and seals are sensitive to the sound of recreational activities.

Antifouling paints

There remains a large degree of uncertainty regarding the impact of copper on the marine environment.

Experimentally it has been demonstrated that copper ingestion above natural levels can prove toxic to marine organisms. However, in field studies, the effects have been shown to be variable.

The actual contribution of copper based antifouling paints to copper contamination in the marine environment is also uncertain.

Whilst there was a great deal of investigation into the effects of TBT on marine life there has been a lack of subsequent work on the replacement biocides. This information gap needs to be addressed in future research.

It is known than elevated concentrations of copper can occur in the vicinity of marina basins and in those areas where land side boat maintenance activities take place. However, there is no evidence to suggest that this is having a significant impact on the environment in those areas

In many areas, the concentration of copper in the marine environment directly attributable to leisure boats is negligible compared to that originating from land side industrial activities and commercial shipping.

Sewage Discharge and other Waste Discharges

The effect of raw and treated sewage discharge from boats in fast flushing coastal areas and open seas is negligible, particularly in the context of sewage discharge from water companies’ treatment plants.

Boat sewage discharge in poor flushing estuarine and coastal bays and harbours can have a significant impact on human health and the aquatic environment.

In such areas where there are already low levels of dissolved oxygen and high levels of nutrients in the water, an increase in BOD and nutrient levels, resulting from boat sewage discharge, can damage marine fauna and flora.

Chemical toilet additives can have a localised impact on marine fauna and flora.

Disturbance to Wildlife

It is very difficult to assess the impact on species of boating-related disturbance in isolation from other sources of disturbance, both natural and human influenced.

Wildlife may be disturbed not only by the boats themselves but also by the participants, particularly where the boats allow the users access to sensitive habitats.

All types of craft, whether human, wind or engine powered, have the potential to cause disturbance.

Sailing is more widespread and more likely to occur in winter than motor boating and therefore has the potential to cause disturbance in more sites and at more times of the year.

Small craft such as canoes, rowing boats and personal watercraft have the potential to cause disturbance in areas which are inaccessible to larger craft

The effect which disturbance has on waterfowl varies greatly between the different species of bird and also depends upon the size and characteristics of the water body and the availability of alternative sites.

Depending on the magnitude of the disturbance, some birds may take flight temporarily, but return after the disturbance ends. Other birds may modify their feeding habits, whilst more sensitive species may suffer reduced breeding success or, ultimately, desert the site.

Many boating activities such as water-skiing and personal watercrafting take place predominantly at high tide and therefore will not disturb feeding waders, but have the potential to affect roosting birds.

In addition to waterfowl, boating may cause disturbance to wildlife such as dolphins and seals although the impact of such disturbance is of uncertain magnitude

Engine sound and erratic manoeuvres can distract feeding dolphins and may drive them away from an area. Where boating takes place in shallow coastal waters frequented by seals or in the vicinity of haul-out sites it can cause disturbance.

The main environmental impact of diving in off-shore waters is the collection of species for human consumption or as souvenirs, although this has little impact on annex I and II species.

Erosion and Turbidity

Boating may have a direct impact on vegetation through boat contact with banks, scouring and uprooting of submerged vegetation by hull, chains, oars and anchors and cutting of vegetation by propellers.

Indirectly, boats may impact on vegetation by the generation of wash and wake and the consequent effect of erosion and turbidity, although in open coastal areas this is likely to be insignificant in comparison to natural processes.

The impacts of boat-induced turbidity are likely to be insignificant in fast flushing coastal areas, but may be significant in localised areas in low flushing waters.

Sub-aqua may contribute to localised erosion and turbidity through direct contact with features and ‘finning’, the kicking action of the feet. The latter may cause sea bed sediments to rise into the water column, temporarily blocking light penetration.

Water aeration is an area which is often cited as being a beneficial impact of boating. However, in comparison to natural wave generation it is unlikely that motorised craft contribute significantly to aeration in water bodies.

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