Marine biologist Declan Quigley has said it is “conceivable” that some of the 67 coconuts recorded in Irish waters over the past half-century could have drifted from tropical areas across the Atlantic.
In a paper published on the recent discovery of a stranded coconut on the Cork coast, Quigley said that the relatively thick (>2 cm) fibrous husk or mesocarp of the coconut provides “natural buoyancy”.
This could facilitate its potential dissemination by surface drift over thousands of kilometres in oceanic currents, Quigley writes.
Coconuts can remain afloat in seawater for at least 34 years and potentially drift many thousands of kilometres before either stranding or sinking, he says.
Annual numbers of Coconuts (Cocos nucifera) recorded from Irish waters (1974-2021)
Monthly frequency distribution of Coconuts recorded from Irish waters (1974-2021)
Their ability to germinate appears to be relatively short (maximum 110 days) in warm seawater which suggests that natural dispersal and successful establishment may be restricted to colonization of nearby tropical islands and/or landmasses, he says.
“ However, it is possible that low water temperatures in the north-east Atlantic may result in dormancy and delay germination which might account for the occasional discovery of germinating coconuts stranded on Irish and other north-west European shores,”he says.
“Considering their long-term flotation properties.... it is conceivable that at least some coconuts could easily drift from tropical areas of Central America, Caribbean and Gulf of Mexico via the Gulf Stream and North Atlantic Drift,”he says.
Coconut discovered by Michael Kearney stranded on Owenahincha Beach, Rosscarbery, Co Cork, October 2021
Quigley says that Michael Kearney’s discovery of a stranded coconut (Cocos nucifera) on Owenahincha Beach, near Rosscarbery, Co Cork (as reported in Afloat, 30 October 2021) represents the second known record of same from this coastal county.
“The first specimen was discovered by Dr Dan Minchin on Long Strand, near Castlefreke on 22 September 1987, ironically very close to where Michael found his recent specimen,” he writes.
Cross-section of Coconut showing exocarp, mesocarp, endocarp, and mesosperm (Wikipedia)
Although coconuts have been recorded from several north-west European countries since 1762, including Norway, Faeroe Islands, Scotland, England, Wales, Netherlands, and Channel Islands, Quigley says it is “strange” that the first specimens were not recorded from Irish waters until 1974.
These first specimens were recorded on the Inishkea Islands, Co Mayo and Barrow Strand, Co Kerry.
“Over the last 48 years at least 67 coconuts have been recorded, albeit intermittently and at intervals of several years,”he says.
“Curiously, almost 70% (46) of the specimens were reported over the last two decades, including 42% (28) during 2019,”he says, but he attributes this to better recording.
“Although stranded coconuts, both with and without husks have been reported from many NW European beaches including Ireland, most of these specimens were generally regarded as having been derived from either local refuse, deliberate local release, or washed overboard from passing or wrecked ships,”he says.
Although most of coconuts imported into north-west Europe are destined for human consumption, at least some are known to be deliberately released, he notes.
Coconut with husk removed and showing three distal pore (purchased from Irish retail outlet) Photo: Declan Quigley
Not every coconut makes landfall. On July 18th 2013, a sunken coconut was retrieved by the MFV Ocean Breeze (D96) (Skipper Ciaran Powell, Inis Mor, Aran Islands, Co Galway) while trawling at a depth of 152m, west of the Aran Islands, Co Galway, Quigley notes.
Coconut husk remains stranded on Keel Beach, Achill, Island, 23.02.2016 Photo: Wendy Judge
“During August 2013, another sunken specimen was taken by the MFV Shauna Ann (G276) (Skipper Thomas Fitzpatrick, Inis Mor, Aran Islands, Co Galway) while trawling at a depth of 450m, on the edge of the Porcupine Seabight, off south-west Ireland,” he says.
“Sunken coconuts have been dredged up from depths of 6780m in the Cayman Trench (Caribbean Sea),” he says.
Sunken Coconut taken by demersal trawl W Aran Islands, Co Galway 18.07.2013 Photo: Siubhan Ni Churraidhin
Sunken Coconut taken by demersal trawl on the edge of the Porcupine August 2013 Photo: Declan Quigley
The co-occurrence of other essentially warm-water species - stranded both at the same time and location as coconuts - may provide circumstantial evidence to support the hypothesis for a trans-Atlantic drift.
“For example, on April 17th 1992, Kevin Flannery (Dingle Oceanworld) discovered a coconut along with a Sea Heart (Entada gigas) and a juvenile Loggerhead Turtle (Caretta caretta) stranded together on Kilcummin Strand, Brandon Bay, Co Kerry,” he says.
“On October 8th 2000, Dr Paul Gainey found a coconut stranded alongside an Antidote Caccoon Vine (Fevillea cordifolia) at Perranporth, on the northern coast of Cornwall in Britain,” he says.
“ On July 20th 2019, Liam MacNamara, discovered 22 coconuts along with a specimen of E. gigas stranded together at Fanore, Co Clare,”Quigley writes.
“It is possible that the above coconuts along with the associated tropical species may have originated from the same area in the western Atlantic,” he says.
“ Tropical sea beans and juvenile turtles are known to share the same epipelagic habitat as many other species of current-borne biota (including coconuts) in the North Atlantic Gyre,” he says.
Quigley’s full paper is downloadable below
