Dive Heron - Part 1

We left Bargara for Gladstone, three hours north, where we caught the ferry, a 34-m (112-ft) catamaran, for Heron Island on the Great Barrier Reef. We were going to spend a week at the Delaware North resort (link). Heron Island is in the Capricorn-Bunker Group of islands in the southern part of the Great Barrier Reef Marine Park. They form the Capricornia Cay National Park, so named because the 15 islands straddle the Tropic of Capricorn where temperate and tropical waters meet. From a distance, Heron Island is a small (0.29 square kilometers, 0.11 square miles), undistinguished, sand cay (key) covered with vegetation, but it sits on the leeward edge of a thriving 27 square kilometers (10 square miles) coral reef platform.

Approaching Heron Island

Heron Island ferry in Gladstone marina

On our way out of the harbor at Gladstone, we passed the coal terminal where four bulk carriers were being loaded. Farther down the channel we saw bulk carriers being loaded with aluminum ore. I count. There were nine empty bulk carriers anchored offshore pointing north into the wind waiting to get into the port to load. A guy working on the ferry said that he had seen as many as 30 bulk carriers anchored off Gladstone in the past. Mining and mineral export is the primary industry in the area. The Port of Gladstone is the fifth largest multi-commodity port in Australia and the world’s fourth largest coal exporting terminal. Fifty million tons of coal comprising 70% of exports are shipped from Gladstone each year. Other exports are alumina (aluminum oxide), aluminum and cement products (link).

Bulk carrier loading alumina (raw material to manufacture aluminum metal) at Gladstone

Queensland Alumina Ltd. refinery at Gladstone (red pile is bauxite ore)

Offshore we caught the force of the wind blowing about 20 knots from the north – lots of whitecaps and swells and rocking and rolling. The orientation video said the hull of the Heron Islander was designed to provide a stable ride in rough seas, but everyone was hanging on to something when they moved about the boat. I stood behind the glass wall separating the wheelhouse from the salon on the second deck watching the navigation screen next to the skipper. It gave time, course and direction in degrees and depth in meters; every time I looked, we were  in less than 30 m (90 ft) of water. The ferry makes 20 knots and it took us two hours to cross the 75 km (46 mi) to Heron Island.

Masthead Key

Erskine Key

Near Heron Island, we passed two vegetated cays: Masthead and Erskine, classical images of tropical islands – blue sky, white clouds, green vegetation, turquoise water and golden reef flats. People can camp on Masthead Cay with a permit, but they must be self-contained and make arrangements for a boat to drop them off and pick them up. Approaching Heron Island, we followed a narrow channel through the reef past the hull of a wrecked ship.

Wreck of the HMAS Protector

Staff from the resort were waiting for us at the dock. They led us past the park sign to a small auditorium for a 10-minute orientation on Heron Island, which is a “green zone national marine park,” meaning we couldn’t take anything live or dead (one-third of the Great Barrier Reef is green zone). 

Heron Islander at the end of the pier in the harbor at Heron Island

Before I went to our room, I signed up to go diving the following morning at the Marine Center.

Marine Center at Heron Island

Coral keys like Heron Island are “low isles,” rarely more than a few meters above sea level. They are built over thousands of years on the leeward side of coral reefs from the rubble and sand of dead corals and decaying organic matter from plants and animals. Birds visiting the reef bring plant seeds attached to their feathers and feet, and in their droppings. Seeds that float can be washed ashore by wind and waves. Low-growing vines, grasses and herbs, the first plants to colonize the inchoate island, help bind and stabilize the sand above the high tide line. They’re followed by salt-tolerant shrubs and trees that colonize the growing key and further stabilize it. More sand accumulates and decaying plant material and bird droppings enrich the soils. 

Rande walking through the pisonia forest

A lens of freshwater accumulates beneath the growing key allowing larger trees, like Pisonia grandis, to develop into a forest. Most plants on Heron Island are also found on the mainland, but pisonias only grow on the calcareous soils of coral keys. [Unless otherwise noted, information on the island’s history and environment was gleaned from displays and materials in the resort’s visitor center.] Pisonia trees are distributed throughout the coral cays of the Indian and Pacific Oceans. The species often dominates mature coral cay vegetation, growing in dense strands up to 20 m (66 ft) tall (link).

Casurania (she-oak) forest, a salt-tolerant early colonist

Before I could do a boat dive, I had to make a “refresher” dive in the harbor because I hadn’t made a scuba dive in the past year. Angus, Steff and I took the course with Josh, our dive instructor. At the dive center, he talked about rigging our “kit,” the hand signals we’d use underwater and the skills we’d need to demonstrate (flooded mask, lost regulator, out of air buddy breathing). We suited up, stepped off a boat tied to the dock and met up under the pier to practice our skills. It was my first time in scuba gear in several years. The weight of the tank and 20-pound weight belt, plus the bulky buoyancy compensator and octopus rig (extra regulator if your buddy runs out of air) reminded me why I prefer freediving.

Heron Island reef

Brownstripe snapper (Lutjanidae)

After the refresher, we took the boat out to Heron Bommie, reportedly one of Jacques Cousteau’s favorite dive sites (link), and tied off to a mooring. Dive sites around the island have boat moorings marked with a white surface float so boats don’t have to anchor, which can destroy corals. There’s a series of large coral heads that start in 5 m (16 ft) of water and extend down the slope to 18 m (60 ft). The largest is reportedly over 700 years old. We descended to where the steeply-sloped coral reef turns into sand, and swam with the current past coral-covered bommies and patch reefs. At first I was overwhelmed by the diversity of the reef – there was so much to look at. What should I photograph? Which fish should I follow?

Top of the reef

Thicklip wrasse (Labridae)

I was buddied with Josh, but consistently brought up the rear of the group because I was taking pictures. I circled a bommie taking pictures of a bright red coral trout. There were air bubbles rising on the other side of the bommie from someone I assumed was in our group. But he turned out to be one of the dive staff who had tagged along to “do his own thing” as Josh put it. He pointed to the cleaner shrimp he was photographing and I took a couple pictures. He gave me the OK hand sign (which means are you okay?), and I signed OK back, but raised my hands palm up gesturing that I had lost the group. He motioned for me to follow and we swam up the reef into shallow water where I rejoined the group. Josh had inflated his orange “safety sausage” (float) so the boat could find us while we did a 3-minute decompression stop at 5 m (15 ft). On the boat, he didn’t say anything about me being “lost.”

Small green sea turtle

Sixband rockcod (Serranidae)

Unlike Heron Island, which was built over the last 6,000 years, Heron Reef began growing two million years ago and is now 150 m (500 ft) thick. Over time, sea levels rose and fell, and coral reefs grew and stopped growing. By 120,000 years ago when sea levels were comparable to today, many reefs had become major structures. Global cooling 18,000 years ago caused sea levels to fall 120 m (400 ft) exposing Queensland’s continental shelf and turning some reefs into hills and cliffs on land. Global temperatures increased 10,000 years ago and sea levels rose to within 30 m (100 ft) of where they are today. As sea level continued to rise, fringing reefs grew around continental islands and new reefs grew on top of old, isolated reefs. As the new reefs reached sea level, they began to develop keys like Heron Island, reef flats and lagoons.

Black noddy terns flying out to sea at sunrise

Most mornings I walked down to the beach before sunrise. Black noddy terns were already heading out to sea to feed on fish and squid, which they pick off the surface, and return to the island at dusk. They are resident, and the largest nesting population, on Heron Island; in some months, there can be 100,000 individuals on the island (link, link). They’re too fast to photograph individuals with my camera. I could hear the wind whistling through their feathers as they passed close by; they looked like little fighter jets twisting and turning in a dog fight only they could see.

Eastern reef egrets

Eastern reef egrets were standing on rocks and tree limbs along the shore. Heron Island was named in 1843 by a geologist on a ship charting safe passages through the GBR for the great number of reef herons. There is no technical difference between egrets and herons, although heron is usually applied to the larger species. The white and gray individuals are color morphs of the same species. Mating pairs usually consist of white and a gray birds; they were building nests when we were there.

Buff-banded rail

Buff-banded rails are common around the resort. Unlike other rails we’ve encountered, these medium-sized rails are not shy; they’re common along the footpaths and we saw them in the open-air restaurant and in the bar. The restaurant has floor-to-ceiling netting around the outside perimeter, but still the birds manage to slip in and forage among the tables. Staff herd them out through specially created exits in the netting. We saw several pairs of sacred kingfishers foraging from trees close to the water. It’s a medium-sized, colorful kingfisher that was a holy bird to the Polynesians who believed it could control the waves (link).

Sacred kingfisher

During our week at Heron Island, I made tank dives every other day. In the morning, the skipper of the boat and the trip leader discussed the best places to dive given the wind and tides. The trip leaders rotated every day and tried to take us to new places. I also spent about 20 hours freediving, occasionally with Rande, but mostly by myself. Staff at the island said the best times to snorkel were two hours before and after the high tide; at low tide, the reef flat is so shallow that it’s hard to swim over it without scrapping the coral (and your belly).

Channel from the harbor through the coral reef

One of my favorite spots for freediving was the channel around the deteriorating hull of the HMAS (His Majesty’s Australian Ship) Protector. The 55-m (180-ft), 920-ton gunboat was built in England and purchased by Australia in 1884 to protect its coastline. Protector served in the Boxer Rebellion and World War I before being dismantled, its parts sold at auction, and converted into a lighter (vessel that transfers goods between vessels, or to and from terminals ) in 1929. It was requisitioned by the U.S. Army for war service in 1943; while being towed to New Guinea, it collided with a tug near Gladstone and was abandoned. In 1945, the hull was sold to Captain Christian Poulson, leaseholder of the first resort on Heron Island. He had it towed to the island and sunk as a breakwater to protect ships when they launched dinghies carrying passengers over the reef flat to shore (link). 

HMAS Protector c. 1900, Port Adelaide, South Australia. Photo by Allan C. Green (1878-1954).
Available from Collection Database of the Australian War Memorial (ID A04936) (link). U.S. PD-1996.

Bow of HMAS Protector underwater

Detail of the outside of the hull underwater 

Because of boat traffic, the channel was closed to snorkelers from 8:00 AM to 5:00 PM. I swam out to the wreck along the concrete retaining wall that separates the reef from the channel about 4:00 PM. On one particularly low tide, I walked to the shipwreck on the wall that was built in 1993 to reduce sediment erosion on the ebbing tide. Even with the wall, sediments suspended by boat traffic was transported down the channel past the shipwreck on an ebbing tide and reduced the visibility (and caused a lot of light backscatter in my pictures). The poor visibility allowed me to get closer to some of the larger fish I saw during my week at Heron Island, including rockcod, sweetlips, emperors and coral trout. As I approached a large goldspotted rockcod at the base of the hull, it opened its mouth, flared its gills, rotated its pectoral fins forward and raised its dorsal fin all to make itself look bigger and more threatening. The closer I got, the wider it opened its mouth. Pretty cheeky behavior for a fish one-tenth my size.

Stripey snappers (Lutjanidae) and spangled emperors (Lethrinidae) off the stern of the wreck

Common coral trout (Serranidae), a fish prized by sportfishermen

Goldsoitted rockcod (Serranidae) at the base of the shipwreck

After the sun set, I swam back in the channel where I always saw blacktip reef sharks. They were only 1.5 m (5 ft), but they were nervous and flighty, and in the fading light they would pass close by at speed. Their behavior freaked out some of the snorkelers swimming in the channel. Under the pier I saw painted sweetlips, chubs and trevallies. Some of the fish hovered above the stairs we used to get into the dive boats.

Painted sweetlips (Haemulidae) and goldlined spinefoot (Siganidae) under the pier

Painted sweetlips under the pier

Bigeye trevallies (Carangidae) under the pier

When the tide was high enough, large cowtail stingrays congregated on the shallow sandflat near the beach. Some were buried and only their eyes and tails visible. Several had remoras attached to the upper side of their tails. Cowtail stingrays grow to about 1.8 m (6 ft) disc diameter and are known to have dangerous spines. I avoided swimming over them remembering what happened to Steve Irwin on a reef in northern Queensland: swimming on the surface, he approached a large ray in shallow water from behind when it rose up on the edges of its disc driving its spine into his chest fatally piercing his heart (link).

Cowtail stingray (Dasyatidae) with sharksucker

Sharksucker (Echeneidae) on the tail of a cowtail ray (the ray's spine is visible under the sharksucker)

Cowtail stingray about 1.3 m (4 ft) across

I searched online, but could not find an expert identification of the stingray that killed Steve Irwin and the videos of the attack were destroyed after the inquest into his death. Irwin’s underwater cameraman said the ray was 2.5 m (8 ft) wide with a 30-cm (12-in) barb (link). Another news article described the stingray as a 2-m, 200-kg bull ray with a 30 cm barb (link). Peter West, who was working on an underwater cinematography project with Irwin at Batt Reef and owner of a boat that Irwin chartered, watched the video of attack and said it was a 1-m wide ray, but didn’t identify it, although bull rays were mentioned in the article (link). The southern eagle ray is also known as a bull ray, but it’s less than 1.5 m (4 ft) across, and occurs in temperate waters south of Brisbane in southern Queensland (link); Irwin was killed in tropical waters at Batt Reef off Port Douglas in northern Queensland. While we were in Port Douglas, I met one of the crew on West’s boat at Batt Reef and asked him if he knew what kind of the stingray it was. He told me without hesitation that it was a cowtail stingray. There's also a grainy still frame from the purported "death video" on YouTube that shows Irwin swimming in his trademark khaki uniform above a cowtail stingray in shallow water (link). 

Great Barrier Reef World Heritage Site plaque at Heron Island

The Great Barrier Reef (GBR) was listed as a World Heritage Marine Site in 1981. At 348,000 sq km (134,000 sq mi), it is the most extensive coral reef ecosystem in the world stretching from southern Queensland north for 2,000 km (1,250 mi), and from the low tide level out 250 km (150 mi) offshore to 2,000 m (6,500 ft) deep. The GBR contains 2,500 individual reefs and more than 900 islands ranging from small, sandy keys (about 240) to larger vegetated keys (about 60) to continental islands (600). It contains 400 types of coral, 1,500 species of fish, 4,000 types of molluscs and 240 species of birds. It is the habitat of the dugong (manatee) and the green sea turtle, both of which are threatened with extinction. Ninety-nine percent of the GBR is contained within Australia’s Great Barrier Reef Marine Park, but coral reefs compose just five percent of the park. Queensland has jurisdiction over 900 islands, the area between high and low tide levels and waters within the state. The GBR Marine Park was established in 1975 and is managed by GBR Marine Park Authority, an independent federal agency (link).

to be continued...

Fish identifications based on: Allen, G.R. 2009. Field Guide to Marine Fishes of Tropical Australia and South-east Asia. Western Australia Museum, 4th ed. 287 pp.