Corals at the Point of No Return?

 Dr Anjani Ganase, coral reef ecologist, writes about the devastating bleaching taking place on all reefs around Tobago

 As the boat cruised along the coast, the water is clear enough to see the white glow from the reef below. Reef after reef, from the Buccoo Marine Park to Speyside, the white patches are expansive and jarring, some large enough to surround the boat. Rolling back into water way too warm for Christmas season, I saw that what I was dreading become reality. Reefs that were once vibrant with colour looked like snow-capped mountains. Most were bone white, exposing the skeletons, while a few were sickly and pale.  

Throughout my career, I have seen many thriving and healthy reefs. I have also seen many dead coral reefs, barren and devoid of life, in the aftermath of cyclones, dynamite fishing and other mass mortality events. To see corals dying on the reefs around our home islands is beyond tragic. I wonder if all of the Northern Range burned in a single year, would this be a national emergency? Would it be the wakeup call to protect our watershed? Today, all the coral reefs of our country are burning - out of sight and out of mind - from a marine heat wave in the waters around Tobago for the last three months.

 

The largest brain coral in Speyside has started bleaching but it’s not fully bleached as yet. Upper photo   healthy, lower photo bleaching. Photos courtesy Anjani Ganase

Heart-breaking

I’ve studied the coral reefs of Tobago for the last five years. Despite seeing many degraded reefs, I’ve also discovered many reefs that are among the best in the Caribbean, especially the reefs of north-east Tobago, but also in the most visited marine area on the island.

The Buccoo Reef, despite the lack of protection, housed many rare species of corals treasured by the few who still visited the area for its natural wonder. Patches of incredibly rare branching staghorn and elkhorn corals against the white sand shone like jewels in the shallow lagoon adjacent to the Nylon Pool. They are now dimmed by death, likely the first to go when the heat wave started in June. Twenty-five weeks of heat stress have simply cooked them. The fish are gone and the branches of the dead corals already breaking under the weight of algae growing over their skeletal remains.

Most people don’t realise that corals are found in most bays of Tobago, a coastline over 360 km with the most mature and well-developed reefs occurring at Buccoo, and off northeast Tobago. We know of the largest brain coral off Speyside, but nearly all of Tobago’s reefs are home to large and ancient corals similar in size and stature. These are the plating and bouldering mountainous star coral with diameters of up to five metres, and other brain coral colonies of the same species. These corals are also very old, akin to the old Samaan and silk cotton trees of our forests, providing habitats for hundreds of organisms over hundreds of years. They contribute the most to reef structure and house nearshore marine life in Tobago. These species make up to 75 % of the coral cover and structure on our reefs, and over the past month, nearly all of these corals have completely bleached.

The island’s famous brain coral is bleaching as well. This beloved giant sits on the base of the reef, some 50 feet deep, less impacted by warm surface waters, but this year, the heat penetrated beyond 70 feet in many places. Depth and currents provided no relief from the enormous body of warm water around the Lesser Antilles.

 

Coral colony at St Giles before and after bleaching. Photos courtesy Anjani Ganase/ Maritime Ocean Collection

Not yet dead

Many of the bleached corals around Tobago are still alive. They are white because they have lost their symbiotic micro-algae, which lend bright colours and provide the coral host with food generated by photosynthesis. In return, the coral houses and protects the algae, a relationship that works well under normal conditions. Unfortunately, global warming is breaking this symbiosis down, as heat stress causes expulsion of the algae and bleaching. Under extended periods of heat stress and without their regular food supply, the corals will eventually die. There is a chance that recovery is possible if the temperature cools, so the corals can reincorporate the micro-algae into their tissues.

The last severe marine heat wave for Tobago was in 2010. Then, Tobago’s reefs experienced about 97 days of significant heat stress between June to mid-November. This year, ocean temperatures are higher and sustained for much longer, with about 129 days above the thermal tolerance limit for corals (29.4 C). Many reefs had over 31 C temperatures for months. The heat wave continues, with cooling not expected until January. Tobago lost 50 % of its live corals from the 2010 bleaching event with little recovery at most sites to date. There is no doubt that there will be significant coral mortality from this year’s bleaching event. Survivors depend on the how long the heat wave continues, as well as our actions now and in the aftermath.  

 

Coral Gardens, the most visited coral reef of Tobago in the Buccoo Reef Marine Park has suffered  bleaching. Photos show healthy and  bleached. Photos courtesy Anjani Ganase

We are all responsible

Climate change is not the problem. Humans are. Our poor history of fisheries management and pollution control among other chronic issues over the last 50 years have weakened our reefs’ resilience and ability to recover in the event of a disturbance. The science is clear that large and old marine protected areas support thriving fisheries, tourism and overall island resilience. Since the 1970s, when we first learned about the issues, we have failed to act. Today, parrotfish are becoming more common on the dinner plate as large predators like sharks, groupers and tunas are no longer present. Parrotfish are important allies for coral recovery. They graze the algae and keep the reefs clean for new corals to settle and grow.

Why do we continue to promote development adjacent to sensitive coral reefs, clearing land and discharging waste directly on to the reefs? When the reefs erode and the forests are cleared, we simply build higher walls and deeper drains to keep the flood waters out. If we continue to be 99 % dependent on fossil fuels, and have the unrealistic expectation that the rest of the world should change but not us, then we are responsible for climate change and the degradation of our islands. Tobago was recently listed among the most desirable islands to visit in the world; how long will this reputation last?

We must change our attitudes and behaviour.

 

Rare staghorn and elkhorn coral in the Buccoo Back Reef suffered 100 % mortality from the marine heat wave. Photos courtesy Anjani Ganase

Time is running out

Our coral reefs are in crisis. Recovery can happen with active management, enforced protection and the support of knowledgeable and aware citizens. It will take time. Here’s what we must commit to, as individuals, communities, and a country.

Corals are extremely sick. If you go snorkelling, diving, fishing, or boating, avoid any activities that would further damage bleached corals. Avoid hunting, especially parrotfish and other herbivores such as sea urchins. These are allies in keeping the coral reefs clean and controlling the algae blooms which are common after corals die. Corals are prone to disease when they are bleached or under heat stress. Do not touch the corals or damage them with spearguns, nets, anchors, not even with gloves. If you bruise the coral tissue, you make them prone to disease. Do not visit coral reefs where corals are bleached or diseased. Diseases are easily spread by boats and underwater or diving equipment. If you dive or fish for a living, please disinfect your gear with a diluted bleach solution, and allow your gear to dry fully in the sun.

As communities, dive associations, village councils, and fisherfolk, we should act together to protect sick reef areas, and to speak out on the importance of the reefs to your community, especially when it comes to proper waste management and infrastructure. Living reefs are major assets to local tourism, so it is important that visitors to the reefs are informed about the precautions that are necessary.

The annual value of our coral reefs is estimated at $164 million USD based on the reef related tourism product, fisheries and coastal protection for Tobago (Burke et al 2008). It is also estimated that severe mass bleaching events will reduce that value by 50 % (Cesar et al 2003).

 

Be the Leader in your Ocean Backyard

Local investment into marine management and protection, in order to build climate resilience of our ocean ecosystems, is long overdue. Trinidad and Tobago has had many opportunities to develop policies for the protection of sensitive land and marine areas; many management and protection plans are shelved. Such systems of biodiversity protection and restoration are critical to our future as a small island state.

 Our government needs to urgently protect our marine resources, regulate pollution and invest in active mechanisms for restoration. As citizens, we need to hold our administrations accountable for the environment which secures our future. Small islands will be most severely affected by the negative impacts of climate change. Let us not hide behind producing relatively small emissions against the larger nations.  Safeguarding the future of humankind is a collective responsibility. An ocean full of fish and healthy coral reefs is essential to the security and well-being of our children and their children.

 

Mt Irvine before and after bleaching. Photos courtesy Anjani Ganase