My Department and I understand the Welsh Assembly Government (who are responsible for water quality in and around Wales) do not directly carry out such assessments.
The eutrophication status (of which algal blooms are a consideration) of the waters around the UK coastline is reviewed on a regular basis by the Environment Agency (England and Wales) for the purposes of the nitrate and urban waste water treatment directives. It is also reviewed by the Centre for Environment, Fisheries and Aquaculture Science (CEFAS), for the Convention on the Prevention of Pollution of the Environment of the North East Atlantic (OSPAR) Convention. The latest review under the directives was 2005-06 and under OSPAR was 2002, with a further OSPAR review being completed in the spring of 2007.
Algal blooms in coastal waters are a natural phenomenon. They can be exacerbated by nutrient pollution from human activities e.g. agricultural practices and from sewage. The links between nutrient enrichment and the occurrence of marine algal blooms are complex and an area of continuing research.
The Environment Agency inform me that none of the north-west coastal and marine waters in this Sea Fisheries Committee area are identified as at risk from nutrients in water framework directive risk assessments carried out between 2003-05. These will be reviewed as part of ongoing work on the water framework directive.