The Caribbean's Grand Cayman might be twice the size of Manhattan, but the island makes up for its small size with vast biodiversity. The reefs surrounding Grand Cayman play home to over 30 species of coral, and some 350 species of fish, making it one of the top destinations for ocean-loving tourists. 

Divers recently captured this troubling clip of a luxury cruise ship anchoring on one of the island's reefs. The MV Zenith (Royal Caribbean fleet member) didn't break any laws – the reef overlaps a permitted drop zone – but the footage illustrates just how detrimental human activity can be on fragile marine ecosystems. 

"The Department of Environment was contacted but nothing could be done," says Scott Prodahl, who uploaded the video to his YouTube channel. "As part of the marine park, we are not allowed to fish here, not allowed to hunt lobsters, you can't even pick up an empty shell ....but for some reason you can drop an anchor and wipe out a reef that took thousands of years to grow. This video was shot roughly an hour after the anchor was dropped, I can't imagine what it looks like now."

Anchor damage like this can be long-lasting because it not only breaks coral, but also dislodges it from the seabed. In fact, anchor damage on a reef in the Virgin Islands resulted in a loss of coral cover that was still visible ten years later.

Though they look like underwater plants, corals are actually compact colonies of tiny animals in the phylum Cnidaria. Each polyp builds its home upon the skeleton of the one that came before it, eventually forming the large formations we see in the video. With growth rates of just 0.3 to 10 centimetres per year, it can take up to 10,000 years for a coral reef to form from a group of larvae!

But anchor dragging doesn't just effect the coral itself. The reef and its surrounding sea-grass beds provide a nursery for juvenile fish and other animals. As little as a two percent dip in coral can cause a significant change in the total number of fish and number of species seen in subsequent years.

"The chain was draped across that whole entire span of the reef, so the area that it covered was absolutely massive," Prodahl told Cayman News 27.  "It was constantly moving back and forth across the reef and causing a lot of damage as it did that."

The question on everyone's mind is why a cruise ship would be allowed to anchor here in the first place. This event illustrates just how difficult it is to implement a well-managed marine protected area. With tourism accounting for 50 percent of the nation's GDP, policies often aim to minimise damage rather than to eliminate it.

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Coral cover across the Caribbean has plummeted to just 20 percent of its original surface area since the 1980s. Image: Joshua Kinberg, Flickr

"We have reviewed the video footage and while it is not good to look at, the truth is that this site has been previously impacted," DOE deputy director Tim Austin said in a statement. "It hasn’t been subjected to the same amount of damage as the other anchorage sites, which is why you see surviving coral colonies there.” 

Since the early '80s, coral cover across the entire Caribbean has plummeted to just 20 percent of its original surface area – and Austin has personally watched it unfold.

In a recent interview for Mother Jones, the born-and-raised Cayman Islander recalls his childhood, a time when the dense forest of coral around the island made if difficult to navigate boats.

"Anybody who's been diving in Grand Cayman for a long time would agree that it's very different today," he says. "But it's a very slow death. These things are dropping apart and no one is really aware of it."

The situation in the Cayman Islands has garnered concern from scientists for decades, and some positive changes have been made in recent years, like the development of scattered permanent mooring lines and docks.

Local authorities are now investigating to determine just how much coral was actually affected in this latest incident, but as damage like this continues to chip away at the remaining reef systems, we can expect to see cascading effects in the coming years. Stricter regulations are necessary if we hope to protect these fragile ecosystems.


Top header image: Joshua Kinberg, Flickr