Menu
Allianz and Afloat - Supporting Irish Boating

Ireland's sailing, boating & maritime magazine

In association with ISA Logo Irish Sailing

Health of Caribbean Coral Reefs Threatened by "Aggressive Alga"

30th November 2020
Alga gobbling up a live coral in Caribbean reefs Alga gobbling up a live coral in Caribbean reefs Photo: Bryan Wilson

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”.

Published in Marine Wildlife
Lorna Siggins

About The Author

Lorna Siggins

Email The Author

Lorna Siggins is a print and radio reporter, and a former Irish Times western correspondent. She is the author of Everest Callling (1994) on the first Irish Everest expedition; Mayday! Mayday! (2004) on Irish helicopter search and rescue; and Once Upon a Time in the West: the Corrib gas controversy (2010).

We've got a favour to ask

More people are reading Afloat.ie than ever thanks to the power of the internet but we're in stormy seas because advertising revenues across the media are falling fast. Unlike many news sites, we haven’t put up a paywall because we want to keep our marine journalism open.

Afloat.ie is Ireland's only full–time marine journalism team and it takes time, money and hard work to produce our content.

So you can see why we need to ask for your help.

If everyone chipped in, we can enhance our coverage and our future would be more secure. You can help us through a small donation. Thank you.

Direct Donation to Afloat button

Marine Wildlife Around Ireland One of the greatest memories of any day spent boating around the Irish coast is an encounter with marine wildlife.  It's a thrill for young and old to witness seabirds, seals, dolphins and whales right there in their own habitat. As boaters fortunate enough to have experienced it will testify even spotting a distant dorsal fin can be the highlight of any day afloat.  Was that a porpoise? Was it a whale? No matter how brief the glimpse it's a privilege to share the seas with Irish marine wildlife.

Thanks to the location of our beautiful little island, perched in the North Atlantic Ocean there appears to be no shortage of marine life to observe.

From whales to dolphins, seals, sharks and other ocean animals this page documents the most interesting accounts of marine wildlife around our shores. We're keen to receive your observations, your photos, links and youtube clips.

Boaters have a unique perspective and all those who go afloat, from inshore kayaking to offshore yacht racing that what they encounter can be of real value to specialist organisations such as the Irish Whale and Dolphin Group (IWDG) who compile a list of sightings and strandings. The IWDG knowledge base has increased over the past 21 years thanks in part at least to the observations of sailors, anglers, kayakers and boaters.

Thanks to the IWDG work we now know we share the seas with dozens of species who also call Ireland home. Here's the current list: Atlantic white-sided dolphin, beluga whale, blue whale, bottlenose dolphin, common dolphin, Cuvier's beaked whale, false killer whale, fin whale, Gervais' beaked whale, harbour porpoise, humpback whale, killer whale, minke whale, northern bottlenose whale, northern right whale, pilot whale, pygmy sperm whale, Risso's dolphin, sei whale, Sowerby's beaked whale, sperm whale, striped dolphin, True's beaked whale and white-beaked dolphin.

But as impressive as the species list is the IWDG believe there are still gaps in our knowledge. Next time you are out on the ocean waves keep a sharp look out!

Who is Your Sailor of the Year 2020?
Total Votes:
First Vote:
Last Vote:

Featured Sailing School

INSS sidebutton

Featured Clubs

dbsc mainbutton
Howth Yacht Club
Kinsale Yacht Club
National Yacht Club
Royal Cork Yacht Club
Royal Irish Yacht club
Royal Saint George Yacht Club

Featured Brokers

leinster sidebutton

Featured Webcams

Featured Car Brands

subaru sidebutton

Featured Associations

ISA sidebutton dob
ICRA
isora sidebutton

Featured Events 2021

vdlr21 sidebutton

Featured Sailmakers

northsails sidebutton
uksails sidebutton
quantum sidebutton
watson sidebutton

Featured Chandleries

CHMarine Afloat logo
osm sidebutton
https://afloat.ie/resources/marine-industry-news/viking-marine

Featured Marinas

dlmarina sidebutton

Featured Blogs

W M Nixon - Sailing on Saturday
podcast sidebutton
mansfield sidebutton
BSB sidebutton
wavelengths sidebutton
 

Please show your support for Afloat by donating