Dublin Bay – The presence of ‘a nuisance algae’ along our shoreline

Councillor Heney wishes to inform constituents that in response to recent complaints received by Dublin City from members of the public in relation to “a nuisance algae” washing up on our coastal beaches, the City Council advises the following;-
“Dublin Bay biosphere has a various vegetation types growing on its sea bed, much of which is within a Special Area of Conservation. This particular material is currently both floating in the sea water and washing up onto coastal marshes and beaches during high tides. It is a naturally occurring seaweed or macro algae called Ectocarpus. Toward the end of its lifecycle Ectocarpus quickly progresses through various stages of decay and it is at this time of year the decaying ectocarpus presents itself with characteristics not too dissimilar to foul effluent or sewage.
Ectocarpus siliculosis is considered to be a naturally occurring nuisance species. Typically growing on the seabed from early springtime until the end of its lifecycle in the autumn when it dies out. At this time of year the seaweed is decaying and becoming uprooted from the sea bed and washing ashore at various locations along Dublin Bay.

When ectocarpus begins to physically degrade, it can produce a malodour (not dissimilar to sewage), as experienced by the public whom have contacted our Department. Also its colour dissipates from a healthy green colour to light then dark brown as it continues to decay in the water or beaches or marsh, (visually not dissimilar to sewage either). Furthermore, when the weed washes ashore onto the beach after a high tide, the seaweed dries out and may be incorrectly identified as caked sewage. This is a natural process within Dublin bay’s rich bio-diversity and for environmental reasons the algae may not be removed from its environment.

Dollymount Strand is among the beaches and bathing areas inspected by Dublin City Council throughout the year, with water samples taken up to 20 times during the bathing season between June and mid-September and on a fortnightly basis throughout the remainder of the year. For your information, the water sample results are updated on the Dublin City Council website www.dublincity.ie and www.beaches.ie

Furthermore, after recent heavy rainfall, combined with high tides, decaying ectocarpus can be washed up on the various footpaths or promenades adjacent to the coastline. Our Waste Management Department does tend to these incidents so as to make pedestrian footways safe and ensuring minimal relocation of this natural material from its environment.

201910 Pollution Control – Ectocarpus Photos