Coral reefs are under pressure from hurricanes, pollution, bleaching and global warming, and scientists have now confirmed the extent of the threat from an aggressive alga.

The algae, known as peyssonnelid algal crusts (PAC), are colonising reefs in the Caribbean at such an aggressive rate that they are interfering with the reef’s natural ecosystem, according to new research.

Marine biologists from the University of Oxford, California State University Northridge and the Carnegie Institution for Science who have been studying the issue for four years describe the extent of the threat in the Scientific Reports.

The golden-brown, crust-like alga is rapidly overgrowing shallow reefs, and has been described as an “ecological winner” by Dr Bryan Wilson of the University of Oxford’s department of zoology.

“It aggressively occupies any vacant space on the reefs, rapidly overgrows and kills live corals, prevents free-swimming coral larvae from settling on the benthos and becoming adult colonies, and is unaffected by the regular destructive hurricanes that sweep through the area,”he says.

‘It is also seemingly resistant to grazing by fish, and as far as we know, is only fed upon by a single creature, the black spiny urchin (Diadema antillarum),”he said.

The spiny urchin was once abundant in the Caribbean, but was effectively wiped out in the 1980s by a mysterious disease, he says.

“Our research has initially looked into the microbiology of PAC and compared it with that of close relatives (the crustose coralline algae, or CCA) which are known to stimulate the recruitment of coral larvae to reefs,”Dr Wilson says.

A key finding was that the PAC alga manages to inhibit the growth of beneficial marine bacteria which otherwise produce chemical compounds that attract coral larvae to the seafloor.

This means that reefs colonised by the alga are unlikely to host corals again.

The alga is described as having a “dark brown and dirty orange veneer” which stands out among the white sands and light greens, pinks, yellows and other colours that make up the reef.

The scientists say it is unclear if PAC is made up of one algal species or several, and they don’t know what is causing its rapid spread – but describe it as an “alarming trend”

They say that the next stage of their research will be to unravel the alga's “complex physiological mechanisms for this ecological success”, through studying its genome. Ultimately, they say they “hope to find ways to mitigate against this new threat”.

There'a always a sliver lining around our coast. Whats a problem for some can be turned to advantage for others. A reef that sailors avoid during racing on coastal courses from Royal Cork presented the perfect setting for some Cork Harbour surfers at the weekend writes Brian Carlin.

A local hazard, the reef is situated approximately a mile west of the entrance to Cork Harbour, dangerous at high tide as most of the reef is immersed. SCROLL DOWN FOR IMAGES.

Surfers took advantage of the direct southerly swell, the surfers, Mark Barry, John Powell and Brian Hartnett, explained only in these conditions is the reef surfable. The trio enjoyed the best of the January sunshine and gave the shoreline spectators a show worth watching. Photos by Brian Carlin.

The location of record breaking waves that appear only every few years will remain a secret known only to a handful of brave surfers. An international team - including Irish surfers - rode the giant prowler waves off the west coast of Ireland on Monday.

According to a Press Association report one of the six-man team, Briton Andrew Cotton, first spotted it several years ago while on board an Irish Coast Guard helicopter after being rescued from a surf accident off Mullaghmore, Co Sligo.

Last night some west coast surfers told Afloat.ie the location is most likely off the Sligo coast, up to two kilometres offshore and close to an underwater reef.

The terrifying-looking wave, dubbed 'Prowlers', was reportedly up to 50ft high on Tuesday when the Irish, British, Australian and South African surfers ventured out. Photos of it appeared on the front page of the Irish Times yesterday.

The surf team included Bundoran's Richie Fitzgerald who says he had waited for five years for the type of conditions required to surf it and on Monday the waves were in the 40-50ft range. Conditions were perfect due to the massive swell generated by Hurricane Tomas.

West coast surfers who went out on a huge wave yesterday (SCROLL DOWN FOR VID) are refusing to give away the secret location of the new monster wave that produced a spectacular photograph on the front page of the Irish Times newspaper this morning. The surfers have dubbed the new wave 'The Prowler' and say it lies 2km off the west coast. The wave rises on an underwater reef and occurred in the aftermath of Hurricane Tomas. See the photo online HERE