18th December

Described by Joyce as ‘snot green', just how green in the sea?

The 70ft classic steel schooner, Spirit of Oysterhaven, is sailing around the island of Ireland throughout the summer (weather permitting) and is participating in the international Citclops Citizen Science Seawater Project.

In late June on sunny day, the crew of three and 10 teenage trainees set sail from Drogheda, Co Louth, bound for Cobh, Co Cork. Discussing the sea beneath the vessel the consensus was that the water was ‘cold, quite clear and bluish, blue green, or greenish’.

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Trainees onboard Spirit of Oysterhaven with iconic Fastnet Lighthouse in the background

A new Citclops app (www.citclops.eu ) and Coastwatch methods were tested to give more precise observations. Jonno lowered a white Secchi disc into the water on a long rope which sank two metres and disappeared from sight.

“This isn’t bad just off the beach here,” remarked Coastwatch/TCD Citclops project partner Karin Dubsky. “It’s often half that due to sediment from land and strong currents which lifts sand off the seafloor.” She also noted that a plankton bloom was possibly building due to the sunshine and would further reduce visibility and change the water colour.

The team compared sea colour with Forel Ule (FU) scale colours on the Citclops app and used a simple paper version. Sea colour shades are numbered on the FU scale from 1 for deep blue — the colour we would see if there is no interference from sand or plankton or other substances – to 21 for cola brown.

Observations logged on the app are automatically uploaded on the Citclops website www.citclops.eu. Coastwatch survey forms can be used as a paper record with more information added, such as near-surface water temperature and sediment load.

Nature observation entry logged: ‘One big seal watching us, one dead gull and no jellyfish.’ Bluish green, cold and quite clear’ at 15 o C, FU colour 8 and 2m transparency was logged off Ballymoney.

Information that is mapped, compared, interpreted and possibly eventually predicted in weather forecasts, may soon be available for divers and bathers, according to Karin Dubsky.

“This information might also lead to understanding where is and where is likely to be, Ireland’s most transparent water; when and how many metres deep is it; where the warmest bathing water is and where are least/most jellyfish right now.

“Another potential use of the Citclops methods is as an early warning harmful algal bloom alert which is critical for shellfish harvesting. In this regard, Coastwatch is cooperating with the Marine Institute.

“Volunteers are needed – even a single reading is useful. It’s time to find out all this information,” said Karin.

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