We rented an apartment in Yorkeys
Knob, a small community on the beach about 20 km north of Cairns. It was named
for George “Yorkey” Lawson, a fisherman from Yorkshire, England who homesteaded
there. We looked in Cairns, a city of 150,000 on the east
coast of the Cape York Peninsula, but chose a more relaxed town on the beach
north of the city. Cairns spreads out along a mud flat south of the Barron
River. The downtown was crowded with traffic and tourists, and we had to pay to
park everywhere. In the morning, a constant stream of buses dropped off
hundreds of tourists at the marina where they boarded day-boats going to the Great
Barrier Reef. Tourists that didn’t go to the reef wandered the Esplanade eating
in the restaurants and visiting gift shops and boutiques. I stopped at
three dive shops for information on trips to the Great Barrier Reef, and two underwater
camera shops to get parts for my camera. Unlike Airlie Beach, dive shops and
dive-boat operators are thriving in Cairns. I made a reservation for a day trip on the
Tusa 6, which was recommended by one
of the dive shops.
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| Coral bommie (pinnacle) at Hastings Reef |
The Tusa 6 is a 24-m (79-ft) catamaran with two decks each with a salon (link). The boat advertises
that it can seat 120 people, but only carries 60 (to make you think it’s not
crowded?). My trip had about 20 snorkelers and 15 divers and the back deck was
crowded. We left the marina at 8:00 AM. Outside the harbor, the swell was 1 m (3
ft) and the wind was blowing 20 knots (23 mph) from the south creating
whitecaps as far as I could see. It took us an hour and a half to get to the
first dive site. The divers filled out paperwork detailing our experience
and certifications, and signed a liability release acknowledging that diving can
be dangerous.
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| Entrance to Cairns marina |
We met with Stacy in the salon
behind the wheelhouse where she explained the boat’s dive protocols: divers have
to go with a buddy; they can be guided by a crew member (for an extra fee), or go
unguided; bottom time is 45 minutes; and by Queensland regulations, divers have
to return to the boat with 50 bar of air in their tank (a full tank is 200 bar or
2,900 psi).
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| Stacy briefing divers about Hastings Reef |
When I boarded the boat, I told Stacy that I was doing photography, didn’t have a buddy and wanted to go unguided. She paired me with Mark, in his 30s from San Francisco. He didn’t have a camera, but he had a new buoyancy compensation device, regulator and two dive computers that he wanted to test, so he was content to mosey along while I took pictures.
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| Mark, my dive buddy, at Hastings Reef |
Stacy said that our first dive was
at Hastings Reef and a place called the Fish Bowl, a sheltered area inside the
reef reached through an opening in the outer reef wall, which descended to about
18 m (59 ft). She said that if we went deeper, we would need to take a spade
with us. “Why would I want a spade below 18 m?” I asked, thinking she meant a
small garden trowel. “To bury yourself” she said. “It’s a bit of Australian
humor” a woman diver said and everyone laughed. Stacy was trying to scare us,
or at least make us think it was unsafe to go deeper. Eighteen meters is not
very deep; I’ve been beyond that many times and never needed a spade.
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| Darkcap parrotfish (Scaridae) |
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| Threadfin butterflyfish (Chaetodontidae) |
The trip coast $275 AUS ($200 US);
for that you get all your dive gear and three dives – two in the morning and
one in the afternoon – a buffet lunch and snacks between the morning dives and
after the afternoon dive. Getting 35 people suited up, organized and into the
water within 15 minutes of arriving at the dive site created chaos on the back
deck. Another dive boat was anchored at the site and divers were getting into
the water when we arrived. The four unguided divers received a second briefing
from the trip leader who showed us a diagram of the dive site on which he drew
the boat. He told us the plan was to enter the Fish Bowl, swim around and exit
through the reef wall where we would finish our dive.
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| Coral pinnacles at Hastings Reef |
From the salon behind the
wheelhouse, we could see the wall and the Fish Bowl, which was rather small and
already crowded with divers from the other boat. Stacy had mentioned two large
bommies in deeper water, which weren’t on the map, and I asked the trip leader
about them. He pointed to the bommies a couple meters below the surface off the
bow and said we could swim around them.
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| Blackspotted puffer (Tetraodontidae) |
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| Two-line monocle-bream (Nemipteridae) |
Mark and I swam around the bommies
and back to the large, concrete blocks that anchored the mooring for the Tusa 6, then under the boat and into the
Fish Bowl. As we entered, we passed four divers with a guide leaving; as we
left, we passed four divers with a guide entering. The boat photographer was
stationed inside the bowl with a metal “CAIRNS” sign; divers could have their
picture taken with the sign or above a large anemone with anemonefish, which the
boat sold for $30 AUS. Mark and I passed the photographer without stopping.
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| Photographer from the Tusa 6 in the Fish Bowl |
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| Barrier Reef anemonefish (Pomacentridae) - the female is larger than the male |
On our second dive at Hastings Reef,
Mark and I swam along the reef wall away from the boat. I found several caves
near the base of the wall and swam into the larger ones. At 100 bar, we turned
around and headed back to the boat. Imagine my surprise when I stumbled on two
shovels, a pick and some construction debris scattered on the sandy bottom near
the base of the wall. I couldn’t fathom how they got there; there’s no island
at Hastings Reef. Maybe they were used during construction of the large
concrete moorings for the dive boats. Later, when I told Stacy what I had found,
she thought I was joking, until I showed her the picture. I didn’t tell her
that we were more than 20 m deep.
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| Pick and shovels on the sand beyond the reef |
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| A school of juvenile striped catfish (Plotosidae) foraging on the sand |
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| Crimson soldierfish (Holocentridae) in a cave in the reef |
Mark and I were the last divers
back on the boat; our air consumption was pretty well matched and our dives
were more than 50 minutes. We took our gear off and got out of our wetsuits –
no wetsuits were allowed the lower salon.
While we were changing, the trip leader came out to tell us that we
needed to get our lunch because they were holding seconds for 30 people in the
salon until we had eaten.
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| Bluespotted coral trout (Serranidae) |
There are 400 species of hard and soft corals on the Great Barrier Reef, from compact brain and massive corals in areas of high wave energy, to large branching and plate corals in deeper water, to compact branching forms in protected lagoons. Coral reef communities are incredibly diverse, with 1,500 species of fishes and 4,000 species of molluscs (link). I was overwhelmed by the unending array of forms and colors on my first dives – where should I point my camera? At the fish? At the corals? What about the invertebrates? Should I ignore the sand flats with their patch reefs and focus on the reef?
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| Hard corals with a variety growth forms |
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| Mostly soft corals |
After
several dives, I developed a plan – when the visibility was good, I put a dome port (wide angle lens) on my camera and focused on seascapes; when the
visibility was less than good, I used a small telephoto lens and focused on individual corals,
fishes and invertebrates. Because I made 2-3 dives each day, I could
do both during one boat trip. But, as a fish biologist, my first love is marine fishes, which is why they feature
prominently in my photos.
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| Blue blanquillo (Malacanthidae) |
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| Slingjaw wrasse (Labridae) with a parasitic isopod (fish louse) on its back |
In November, two French tourists in
their mid-70s died of heart attacks within minutes of each other while
snorkeling together at Michaelmas Cay. They were part of a group of 21 elderly
tourists that had “pre-existing medical conditions” (link).
A cardiologist in Cairns thought it likely that they were stung by Irukandji,
thumb-nail size jellyfish with venom that can cause cardiac arrest in humans (link).
Speaking of invertebrates, here are a few of the thousands of species that live
on the Great Barrier Reef.
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| Giant clams have symbiotic algae (zooxanthellae) in their mantle tissues |
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| Leopard sea cucumber |
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| Orange sponge |
Divers can walk on the boat with
just their swimmers (bathing suit) and get kitted out for diving. I brought my
wetsuit, mask, fins and snorkel; the rest of the gear included a weight belt,
tank, buoyancy compensation device (BCD), dive computer, pressure gauge and two
regulators, one for the diver and a yellow “octopus” regulator for your buddy
if he or she runs out of air. The dive computer tracked maximum and average
depths, bottom time, no decompression time and, if you go too deep for too
long, decompression stops on the way back to the surface. After the dive, by
regulation, the trip leader recorded our bottom time, maximum depth and amount
of air remaining in our tanks, and then had us sign it.
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| Christmas tree worms and coral clams in a massive Porites coral |
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| Closeup of a Christmas tree worms (polychaetes) |
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| Thorny oyster |
I talked to the skipper on the way
back to Cairns. She said we made 20-22 knots over the 30 miles back from the
reefs. I asked her about diving the reefs farther offshore; she said that when
the offshore winds drop to 10-15 knots and the swells are less than 2 m, they
run to those reefs. The calmer periods occur between fronts that spin up the
east coast from the Australian Bight. Winter is the windy time; summer is
calmer, with higher air temps, higher humidity and lots of rain.
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| Returning to Cairns |
On one of our walks around Cairns,
we passed a colony of spectacled flying foxes roosting in trees near the Library.
Hundreds of these megabats (1.5 m, 5 ft wingspan) live in this colony. At
night, they fly up to 70 km (43 mi) searching for nectar-producing flowers and
fruit. While they’re lapping up flower nectar with their long tongue, pollen
sticks to the fur on their pointed nose, which they carry to other flowers (cross-pollination).
They also distribute seeds over long distances when they eat fruit and spit out
the seeds. These activities help maintain the diversity of the tropical forest.
Flying foxes are protected, but their numbers are decreasing because of loss of
habitat forcing them to live in closer contact with humans (interpretive sign
under the colony).
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| Colony of spectacled flying foxes in Cairns |
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| Spectacled flying foxes |
I made a couple more trips on the Tusa 6 while we were in Cairns; Rande
came on one of the trips to go snorkeling. I asked the skipper on the way out
where we were going. She was talking on the radio to skippers of other dive
boats to find out where they were going. We ended up back at the same places
and doing the same dives that I did on my first trip. When I checked in, I said
I wanted to go unguided. They paired me with Helene, a young woman from
Switzerland with only 10 open water dives. There were more than 20 divers (four Japanese with a Japanese-speaking guide, eight guided, four unguided and six novices)
and 15 snorkelers. The back deck was chaos with everyone getting into their
gear at the same time. The guides staggered the order of groups entering the
water; the unguided divers went first, which was fine with me – better to see
the reef before the masses scared the larger fishes away.
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| Helene, my dive buddy, at Hastings Reef |
On the first dive at Hastings Reef,
Helene and I swam under the boat past a 1-m (3-ft) great barracuda to the
mooring line at the bow and descended to the concrete anchor. Novice divers
often prefer to descend along the anchor line, which gives them a reference
point in the water column. The water was full of particles – great for planktivores, bad for photographers. We swam around the larger of the two bommies,
turned around at 120 bar, swam under the boat and into the Fish Bowl where we
finished our dive. There was another dive boat moored nearby when we surfaced,
and one more arrived before we departed. Too many divers in too small a space.
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| Great barracuda (Sphyraenidae) |
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| Steephead parrotfish (Scaridae) being cleaned by a wrasse with its head under the gill cover |
Back on the boat, we ate fresh fruit
while the crew filled our tanks for the second dive, which was the wall off the
port side of the boat. We swam through the narrow cut between a tall bommie and
the wall into a large school of blue fusiliers, which Helene filmed with her
GoPro camera. We zig-zagged up and down the wall inspecting the nooks
and crannies. Helene was inexperienced, but she did fine swimming slowly with
me while I took pictures. She used her air more quickly than I did, so our
dives were 10-15 minutes shorter than they would have been with a more
experienced diver. I took her picture and later sent it to her via email.
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| Blue fusiliers (Caesionidae) |
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| Variegated lizardfish(Synodontidae) |
Back on the boat, I saw Rande in
the water among the snorkelers. The surface was choppy and many of the snorkelers
had their heads out of the water. Its difficult for inexperienced snorkelers to keep water out of their snorkels when the wind is blowing and the surface is like a washing machine.
I knew Rande wasn’t having any fun. I put on my weight belt, mask and fins, quickly
slipped off stern and swam over to her. She wasn’t comfortable enough to
continue and I swam with her back to the boat. One of the crew had seen me go
in with a weight belt and told the trip leader, who met me at the stern and
told me I couldn’t wear it while snorkeling – another boat rule. He said they
regularly have experienced free divers on the boat, but don’t allow them to
wear weight belts. I took the belt off, grabbed my camera, jumped back in and swam
over to the shallowest part of the Fish Bowl to take photos of corals and
fishes. I returned to the boat when the
crew called the snorkelers in.
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| Bigeye seabream (Lethrinidae) |
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| Stars-and-stripes puffer (Tetraodontidae) |
We dove at Michaelmas Cay in the afternoon.
Helene and I descended under the boat, swam across the shallow reef platforms
and dropped down the wall to the sand. At 120 bar we turned back to the boat
and up into shallow water. Our dive computers told us that we needed a 2.5 minute
decompression stop before surfacing. I could see that she was nervous about the
stop; we held hands at 5 m (15 ft) and ascended when her computer went to zero.
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| Saddle butterflyfish (Chaetodontidae) |
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| Intermediate cardinalfish (Apogonidae) |
Tusa Dive runs trips to the
Great Barrier Reef most days (link).
The day trips spend three hours traveling to and from the dive sites, and five
hours on the reef. The guides on my trips had made several thousand dives while
working on the Tusa 6, and they have a
rhythm and routine for organizing 40-60 people. All activities (diving, eating, traveling) are planned to the
quarter hour, and sometimes we were hurried along to keep to the schedule. At
each of the stops, there was at least one other boat with a similar number of
divers and snorkelers. The popular sites probably see 100-200 divers and
snorkelers every day, weather permitting. Even so, the dive sites were in good condition, which is
a tribute to the guides and the divers. But I didn’t see many large fishes. The
healthiest coral reefs are far from human population centers and have most of
the biomass tied up in large predatory fishes.
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| Debris from shallow-water corals, probably killed by storms, in the deeper part of the reef |
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| Crown-of-thorns starfish (note damage to the stony coral on its right) |
Half of the coral cover on the
Great Barrier Reef (GBR) was lost between 1985 and 2012; two-thirds of that
decline has happened since 1998 (1). The major sources of mortality were damage
from cyclones (48%), crown-of-thorns starfish (42%) and coral bleaching (10%);
fishing, pollution, tourism, vessel groundings and anchoring, and oil spills
have had relatively minor effects on the GBR as a whole. Damage from cyclones is
directly related to wind speeds and is expected to increase as the ocean warms
and storms increase in intensity (link).
Coastal flooding and nutrient pollution have been implicated in outbreaks of
the crown-of-thorns starfish. There
have been four outbreaks on the Great Barrier Reef since the 1960s; each
outbreak followed severe floods and high inputs of sediments and nutrients from
coastal rivers, which stimulate plankton blooms that provide food for starfish
larvae (link). Rivers in the central
and southern parts of the GBR carry 5-9 times the sediment and nutrient loads
compared to pre-European settlement resulting in an increase in outbreak
frequency from one in 50-80 years pre- settlement to one in 15 years now (link).
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| Coral bleaching occurs when the polyps loose their symbiotic algae |
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| Deviations of sea-surface temperature (degrees C) from the 1961-1990 mean |
Coral bleaching occurs during extended
periods of increased sea temperature when coral polyps loose their symbiotic algae (zooxanthellae) and their white skeleton becomes visible. The chart above shows the deviation
(anomaly) of sea-surface temperatures from the long-term (1961-1990) mean in
degrees Celsius (1 degree C = 1.8 degrees F) (link).
Coral bleaching will increase with increased ocean warming.
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| Closeup of polyps of a colonial coral [polyps are less than 10 mm (0.4 in) across] |
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| Mushroom corals are single polyps up to 25 cm (10 in) across |
We were getting ready to leave and
I was packing the car next to a guy in his early 50s with tattooed arms and
black wavy hair unloading boxes from the trunk of his car. He asked if we were
heading out for the day; I said no, we were heading north to Port Douglas.
“Good on you mate; most people think that Australia ends at Cairns.” He asked if
we were from the States (our “soft” American accent gives us away). He was from
the state of South Australia about 4,000 km (2,500 mi) away; it took him four
days to drive to Cairns. He was on business and said he managed the pilots that
guided large commercial ships through the Great Barrier Reef.
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| Branching corals above columnar corals |
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| Delicate sea whips are soft corals |
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| Laminar coral in the shape of a vase |
About 6,000 vessels longer than 50
m (164 ft) transit the Great Barrier Reef each year, seventy-five percent of them
take a route between the coast and the reef; most of those are bulk carriers. Their
cargoes include bauxite and alumina, manganese, iron ore, coal, sugar, silica
sand, container freight and petroleum products (link).
At Australia’s request, the International Maritime Organisation designated the
Great Barrier Reef a Particularly Sensitive Area, the first of its kind in the
world. Vessel navigation and pollution prevention controls include: electronic
navigation charts and aids to navigation; requirements for pilotage; designated
shipping routes and ship routing measures; vessel traffic monitoring 24 hours a
day and intervention if ships stray beyond limits; and emergency response
assets, including towing and oil spill response (link).
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| Soft corals lack a stony skeleton and often resemble plants |
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| Feather stars (crinoids) collect food from the water with the sticky side branches on their arms |
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| Polycarpa, an ascidian or sea squirt, feeds by passing water through its body |
The pilots are master mariners;
some are retired military, others spent their lives at sea. None were young – “it’s
a job for the most experienced mariners.” The route inside the reef is shallow with
lots of reefs, and the pilots, who are well paid, know every kilometer. He said
it was the fastest way around eastern Australia, but that the large oil
companies do not send their tankers inside the GBR – “too risky if something goes
wrong.” He had worked on oil and gas drilling rigs in the Middle East and off
Australia, but had never been a pilot. I asked him how he “managed” the pilots;
he said he stroked their egos. He said we’d love Port Douglas and wished us
safe travels.
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| Turtle weed, a common seaweed (macroalga), has a toxin that defends against herbivores |
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(1) From 1985 to 2012, the
Australian Institute of Marine Science conducted 2,258 visual surveys of 214 of
the approximately 3,000 coral reefs on the Great Barrier Reef (GBR). Average
coral cover declined 0.53% per year from 28% in 1985 to 13.8% in 2012, and
1.45% per year from 2006 to 2012. The decline in coral cover probably began before
1985, so the 27-year estimate is conservative. Coral cover and mortality were
not uniform across the GBR; cover was higher (>35%) and mortality was
lower (-0.19% per year, which means coral cover was increasing) in the far
north away from human population centers, compared to the southern GBR (>30 %
cover, 0.47% per year mortality) and central inshore reefs (<25% cover, 1.12%
per year mortality), which are closer to coastal cities. Compared to coral reefs in other parts of the
world, like the Caribbean where coral cover is also decreasing about 1.4% per
year, the GBR has not experienced significant mortalities from diseases, or a
“phase shift” from coral-dominated to algal-dominated reefs (due to
overexploitation of herbivorous fishes). The scientists predicted that “[w]ithout
significant changes to the rates of disturbance and coral growth, coral cover
in the central and southern regions of the GBR is likely to decline to 5–10% by
2022” (link).
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