A summary of potential effects
of water-based recreation
Sewage discharge and other waste
Disturbance to wildlife
Erosion and turbidity
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
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.
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
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
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
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
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.