a.    Extent of the activity

i.   Within the site

Some historical activities may have left a legacy of problems that need consideration in managing the Cardigan Bay cSAC. Two are considered specifically in this section: metal mining and use of polychlorinated biphenyls (PCBs).

ii.  Adjacent to the site

Past metal mining activity on land adjacent to the cSAC, especially in the catchments of the rivers Rheidol, Ystwyth, Clarach and the upper reaches of the Teifi, has left a legacy of spoil heaps of waste material at some sites. Discharges of metal contaminated water have, in many cases, had detrimental impacts on fish populations and the ecological quality of these watercourses.

PCBs were produced for a number of applications because of their chemical and thermal stability. Their manufacture was ceased in the 1970s and they are now included in the UK Red List of substances identified as priorities for reductions because of their environmental impacts. Sources are most likely to come from way beyond the cSAC boundary.

b.    Mechanism for effect on the feature

With PCBs, existing environmental burdens, dispersed in coastal waters attached to sediments, are undoubtedly being accumulated in the food chain to a level in dolphin prey species which may have health implications for the dolphins themselves. PCBs are dispersed globally in the air, and this source will also contribute to the coastal water burden, both via rivers and directly to the sea. Elevated levels of PCBs have been found in dolphins in Cardigan Bay and in a sample of sediment taken from Aberystwyth harbour (outside of the cSAC boundary). Sediment PCB content from different sites in Cardigan Bay suggests that Aberystwyth has not been a major source of PCB in the Bay, and long distance particulate transport from more polluted areas may be much more important.

A relatively high level of accumulated mercury has been reported in dab (a species of flatfish) from Cardigan Bay, and possible sources will be investigated. Mercury can be bioaccumulated, and so dolphins could be at risk from eating some fish species, but mercury is found in fish species all around the world, and not enough is known about bottlenose dolphin food preferences to know whether Cardigan Bay dolphins are at risk from mercury. See ‘Pollution’.

c.    Management Response

i.   Rationale

Follow up investigations by Environment Agency Wales into the PCB contamination of Aberystwyth Harbour suggest that the elevated levels reported from the 1994 sample were localised and no longer present [127] . Further surveillance has since been undertaken and the results will be used to target any further investigations and to provide advice for any consequences for public health and marine species in Cardigan Bay.

Research work is still under way to identify the route by which dolphins accumulate their clearly elevated PCB burden, but there are no obvious mitigation options open to regulators, even if it is discovered which fish species provide the main proportion of PCBs in their diet. It is essential that analytical data on dolphin (and other cetacean) tissue contamination from Cardigan Bay, and other sites, continues to be collected, so that any change in tissue burden with time can be assessed. Environment Agency Wales already supports the cetacean recovery programme sponsored by the DETR and Countryside Council for Wales and needs to plan, with other partners, to continue to gather appropriate data over a significant time period.

There is legitimate concern regarding the accumulation of organohalogens, such as PCBs, by dolphins. Although these chemicals are now likely to be acquired from diffuse sources, their role, and that of persistent organohalogen compounds, will be reviewed at the same time as the formal review of point source discharges. Opportunities for further regulation will also be considered by Environment Agency Wales.

ii.  Type of Response

F4 : There is a known mechanism for the activity to have an effect, but insufficient evidence at present to determine whether or not it is having a significant adverse effect.

iii.  Actions, including links to other policies/plans/measures

Actions

• Continue to be vigilant over activities and pollutant sources which might threaten the integrity of the cSAC, and will take action based on a realistic assessment of risk.
• Continue to routinely monitor the river systems to determine the inputs and loadings of metals being discharged into coastal waters.
• Promote, in partnership with others, the reclamation of disused metal mines where there is significant environmental benefit.

Further actions for which there are currently inadequate financial support or regulatory powers.

• Undertake a monitoring programme to determine location and levels of PCBs and heavy metals in Cardigan Bay. To include water quality and sediment sampling, as well as food chain sampling, to demonstrate source, pathway and uptake.

[127] CEFAS (1997) Monitoring and surveillance of non-radioactive contaminants in the aquatic environment and activities regulating the disposal of wastes at sea, 1994. Aquatic Environment Monitoring Report No. 47, Lowestoft. pp 59