WATER QUALITY in Irish coastal areas and estuaries is showing significant improvement, according to a British scientific journal.
A report for the Marine Pollution Bulletin by three scientists attached to the Environmental Protection Agency (EPA) says that dissolved oxygen conditions in a number of estuaries “continue to improve”.
This is “probably” due to more extensive municipal waste-water treatment, the authors, Shane O’Boyle, Georgina McDermott and Robert Wilkes, say.
They single out Castletown estuary in Dundalk, the Lee estuary and Lough Mahon in Cork city and the Liffey estuary in Dublin as showing the benefits of such treatment.
The survey of 95 areas around the coast from Lough Swilly in Donegal to Dundalk bay represents “the most comprehensive overview to date” of oxygen conditions in Irish estuarine and nearshore coastal waters, the authors say.
Testing at 533 monitoring stations was conducted over four years between 2003 and 2007.
Of the 95 water bodies surveyed, 85 had sufficient level of oxygen to support aquatic life. These 85 corresponded to a surface area of 3,125sq km.
Some 10 areas, representing a surface area of just over 20 sq km, were found to be deficient in oxygen but were still able to support aquatic life. No evidence of hypoxia or anoxia was found by the team.
This contrasts with a global increase in seasonally-persistent hypoxic zones due to declining dissolved oxygen levels associated with coastal pollution.
The authors challenge a report published in the US journal Science last year which claimed that coastal pollution had created 20 “dead zones” or hypoxic areas around the Irish coast.
That assessment, which relied on data from the Ospar Commission, the northeast Atlantic marine environment body, is “in no way supported by the observations presented here”, the Marine Pollution Bulletin contributors state.
Improved waste-water treatment, licensing of industrial emissions and closure of older more polluting industries has had a positive impact, the authors say.
Over 80 per cent of discharges in 2006 received secondary treatment at least, according to the EPA, compared to only 21 per cent of discharges between 2000 and 2001.
However, they also note that another report in 2006 noted that a quarter of discharges to Irish surface waters from agglomerations with a population of 500 people or over received no treatment or only “very basic” treatment.
They predict that the situation is “expected to improve significantly”, and oxygen deficiency may be eliminated altogether from the coast as a result of measures associated with the EU nitrate and urban waste-water treatment directives, and the Water Framework directive.
The study has been welcomed by Dr Brendan O’Connor, director of Aqua-fact, a Galway-based environmental consultancy.
"This is a very comprehensive factual study," he told The Irish Times.
“Ireland could be the envy of many highly-industrialised countries if we continue in this direction, and we just have to be watchful and ensure we continue to implement legislation and support regular monitoring.
“If we can also improve our freshwater quality we should see great benefits with our groundwater supplies – groundwater being our ‘oil’ resource,” Dr O’Connor says.
