A couple days after catching a
cold, I felt good enough to go for a hike, so we drove up to Mossman Gorge (link, link) in the southern section of the Daintree National Park, another “must-see”
attraction north of Port Douglas. The Mossman River spills down the Main Coast
Range of mountains winding its way through weathered granite boulders the size
of small cars. It’s hard to comprehend the amount of energy it took to move these
massive boulders down the mountains, and the time it took for the water
to wear them smooth.
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| Mossman River in Mossman Gorge |
We paid our entrance fees ($19
AUS) at the visitor’s center and caught a shuttle-bus to the trailhead. The
2.4-km (1.5-mi) trail starts on a short elevated boardwalk through the lower
canopy of the rainforest, then follows the river upstream and eventually
becomes a dirt loop trail through the rainforest.
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| Mossman River in Mossman Gorge |
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| Stream in Mossman Gorge from the elevated boardwalk |
We passed several tour groups on
the Mossman Gorge trail. We overheard one guide tell his group that the
rainforest “packages” nutrients and carbon for the Great Barrier Reef, which
the rivers transport to the sea. He said that the reef protects the land from
big swells generated by Pacific storms. He didn’t mention that the tropical
rains wash sediments from lands cleared for sugar cane and cattle grazing, and
nutrients from poor agricultural practices, into the rivers and out to sea
where they choke the estuaries, smother seagrass beds and stimulate algal
growth on the reef.
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| Mossman River |
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| Noah Beach near Cape Tribulation |
Just about every place we stopped
along the Queensland coast between Yeppoon and Port Douglas, a distance of 1,000 km (620 mi), I
was warned not to dive from shore because of salties (saltwater crocodiles). I
met a middle-aged spearfisherman in Port Douglas who, over the years, had two incidents
where salties approached him from behind while he was freediving near
the shore. He wasn’t attacked, but it had to be unnerving to see the largest reptile in the world (link) that has a reputation for attacking humans (link).
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| Four Mile Beach at low tide |
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| Corals and algae at Four Mile Beach |
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| Colony of anemones |
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| Large anemone |
While shallow-water habitats like sandy
bays, seagrass beds and low-relief, rocky reefs are not as glamorous as the
Great Barrier Reef, I never know what I’m going to see (link). And diving from shore or
out of a kayak, I’m not dependent on dive boats and their schedules; I
determine when and where I go, and how long I stay in the water. I finally got
a chance to explore these shallow-water habitats off Port Douglas, but not the
way that I thought I would.
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| Tidepools on Four Mile Beach |
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| Decorated sandgoby (Gobiidae) |
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| Horned sea star |
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| Swimmer crab (their last pair of legs is shaped like paddles) |
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| Who dug this 50-cm (20-in) diameter hole? A stingray searching for food? |
Four Mile Beach at Port Douglas
lies along the edge of a wide bay with a slight offshore slope. On a low tide,
you can walk a couple hundred meters offshore through sand-bottom channels,
low-relief rocky reefs, isolated coral heads and patches of algae and
seagrasses. The manager of our condo complex told us about the low tides at
Four Mile Beach, but rarely have I seen a tide recede this far on an open
coast. I followed the tide out and back, and spent half the day wandering
around with my camera.
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| Mount Sorrow sign at the trailhead |
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| Rande in the lowland rainforest |
The trail begins in a lowland
rainforest valley and ascends steeply through an upland tropical rainforest
populated by several species of palms. The forest was dense and surprisingly
quiet. I stepped over a fallen log off the trail to take a picture and a 75-cm (30-in) dark
brown snake long slithered away.
Was it one of the infamous brown snakes, among the most venomous in Australia? Probably not (they prefer drier habitats); but it gave me pause. There are distance markers
nailed to the trees every kilometer. A trail runner in his 30s passed us coming
down. After about 2 km (1.2 mi), the trail climbed steeply up a ridge dominated
by low wattles (acacias). One particularly steep section had two fixed ropes
that we used going up and coming down. The canopy opened up as we approached
the summit. For the rest of the hike, we saw two couples and two women from
Germany, all in their 20s.
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| Palm trees in the rainforest |
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| Trail marker at 3 km (2 mi) |
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Cloud forest below Mount Sorrow
|
Clouds sliding down the mountain
and mists drifting up the valley turning the upper part of the trail into a
cloud forest. Everything was wet; algae growing on the rocks and exposed tree
roots made the steep trail muddy and slippery. Going up was easier than coming
down (it always is). I was getting over a cold and found myself gasping for air
at the top of the steepest sections. The lookout was a 2 m x 2 m (7 ft x 7 ft)
steel grate with guard rails on a narrow ridge. One couple was heading down as
we arrived at the lookout. Clouds obscured the view to the coast
and, after all the work of climbing to the summit, they didn’t see anything.
While we were having lunch on the platform, there was a break in the clouds. We
could see the ocean and beach to the north, and developed areas to the south.
After lunch we headed back down. We were spent by the time we got back to the
car.
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| View to the north from Mount Sorrow lookout |
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| Rande rappelling (abseiling) down a steep section of the Mount Sorrow Trail |
We stopped at Daintree Tea (link) farm on our way to
the ferry. A woman pulled into the small dirt parking lot right after us. She
was the wife of the farmer who owns Daintree Tea and was replenishing a bin
with boxes of tea for sale and an “honesty box” for the money. His parents
started the 80-acre farm in 1978 and “he’s been here since the beginning.” Her
husband designed and built the harvesting machine because there was nothing
available to buy. The tea plants are less than 1 m (3 ft) high and closely
spaced. The machine trims off the top few centimeters and collects the
cuttings, which are processed into tea bags and loose tea. On average, they get
4 m (13 ft) of rain annually, and can get up to 6 m (20 ft). The combination of
rain, sunshine, warm weather and rich soils make it ideal for tea plants. I
told her we had their black tea in the places we rented in Cairns and Port
Douglas. She was glad that they supported a local business and asked if we were
from America. They ship their tea around the world, including the U.S. She thanked us for stopping.
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| Daintree Tea plantation |
I became a tea drinker in Australia.
Every boat I was on had an electric kettle with near-boiling water and a choice
of powdered coffee or tea. The coffee was freeze dried and terrible, so I drank
black tea. My mother was a tea drinker (her father was from England). I tried various
teas over the years, but always went back to coffee. Like the British, Australians
are tea drinkers. Grocery stores have more kinds of teas than coffees. Every
apartment and condo we rented had an electric kettle, powdered coffee and tea
bags, but no coffee pot. In the morning, we drank “real” coffee that we made in our “plunger” (French
press) with water heated in a kettle. One Aussie told me that he was “shocked”
that American hotels didn’t have electric kettles in the rooms, much like we
were shocked that none of our rentals came with a coffee pot.
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| Poseidon at the marina dock in Port Douglas |
After a week, my cold broke and I felt up to diving. I called ABC Scuba on Friday, but they didn’t have any trips
over the weekend, so I called the Poseidon (link),
a 24-m (80-ft) catamaran that carries 15 divers (and more snorkelers) and got on the boat the next day. There were
nine certified divers on my trip, four taking an introductory course and 15
snorkelers. The weather was warm, there was no wind and the sea was flat calm,
the calmest I’d seen on the Great Barrier Reef. During the briefing, Ethan, one
of the guides, asked if there was anything in particular that we wanted to see.
I said cuttlefish and Ethan said he’d see what he could do. We went to
Agincourt Reef on the outer Great Barrier Reef about 1.5 hours northeast of
Port Douglas. We left at 8:30 AM and I was in the water taking my first picture
at 10:14.
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| Divers descending from the Poseidon at Agincourt Reef 3 |
The first dive was on the
southwest side of Agincourt Reef 3 at New Stonehenge. Cyclones had lifted large
blocks of coral and deposited them on the reef crest where they rose out of the
water like truncated pillars at low tide. The certified divers were split into
two groups based on experience; I was in Ethan’s group of six. The visibility
was over 20 m (66 ft). Ethan said that he would swim slowly along the reef at
16-18 m (53-59 ft) until we got to 100 bar and then return to the boat in
shallower water. As long as we could see him, he said we could do our own
thing. Working five days a week on the Poseidon,
Ethan had made over 2,500 dives at 25 sites in three years, so he knew every
meter of Agincourt.
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| Divers among the bommies |
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| Bleaching of a staghorn coral |
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| Snorkelers off the stern of the Poseidon |
The second dive was at Barracuda
Bommie on the northwest end of Agincourt Reef 2a, and, true to its name, dozens
of small barracuda were swimming above the bommie. We dove down to 20 m (66 ft)
and circled the coral pinnacle twice; it dropped off to more than 30 m (100 ft)
on the outside. Schools of fusiliers and larger barracudas were hanging out
around the pinnacle. Strong currents make this a good place to see cruising
pelagic (water column) fishes. I saw pompanos with swept back medial and caudal fins that make them appear to be swimming faster than they are; Aussies
call them darts.
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| Pickhandle barracuda (Sphyraenidae) at Barracuda Bommie |
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| Snubnose dart (Carangidae) |
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| Lunartail bigeye being cleaned by a small wrasse (Labridae) |
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| Spotted sweetlips (Haemulidae) |
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| Clown triggerfish (Balistidae) |
We left the bommie and swam back to the boat through a maze of patch reefs. Ethan found a tasselled wobbegong, a harmless shark, resting in a small coral cave. The place was really fishy – my favorite dive of the day.
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| Tasselled wobbegong (Orectolobidae) |
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| Mixed school of snappers (Lutjanidae), including blackspot, bluestriped and fiveline |
We made a third dive on the south end of Agincourt Reef 4 at a place called The Point. Ethan found a small lionfish hanging under a ledge on the pinnacle; it was a species that I hadn’t seen before.
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| Common lionfish (Scorpaenidae) |
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| Doublebar goatfish (Mullidae) |
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| Male Bleeker's parrotfish (Scaridae) grazing on corals |
Fifteen minutes into the dive, Ethan swam over to me and motioned for me to follow him. We swam about 10 m (33 ft) and he pointed to a cuttlefish the size of an American football. It was hovering about a meter (3 ft) above the sand and began swimming slowly as I approached changing colors and texture several times to match its background. Its color patterns ranged from a smooth, homogeneous tan matching sand, to dark, blotchy and spiky matching coral rubble. Cuttlefish are the masters of camouflage; here's how they do it.
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| Cuttlefish over sand |
Unlike bony fishes, cuttlefish do not have swim bladders and have developed a unique mechanism to maintain buoyancy. The cuttlebone of the cuttlefish is a rigid, calcium carbonate structure that functions as a skeletal element and in regulating buoyancy. It's chambered, foam-like structure contains gas at nearly constant pressure. The cuttlefish adjusts its buoyancy by varying the amount water in the cuttlebone (link).
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| Cuttlefish changes the texture of its skin and its outline on coral rubble |
Chromatophores in the skin contain sacs of pigments ringed with tiny muscles that pull the sac open expanding the pigmented area; the elastic membrane around the pigment granules pull them closed. The cuttlefish's brain controls opening and closing of the chromatophores, so cuttlefish (along with squids and octopi) can change color and pattern in milliseconds. Cuttlefish also have specialized reflective cells (iridophores and leucophores) that can reflect light back at different frequencies (iridophores) or "scatter full spectrum light [leucophores] so that they appear white in a similar way that a polar bear's fur appears white." Further, cuttlefish can change the texture of their skin by deforming through pressure areas known as papillae, which can change the outline of the body. And if that's not enough, cuttlefish are believed to be colorblind (link).
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| Cuttlefish |
There are over 30 species of cuttlefish (all in the genus Sepia) in Australian waters; most are small (less than 10 cm, 4 in). The giant cuttlefish occurs in South Australian waters; it grows to about 50 cm and is the largest cuttlefish in the world (link). Swimming with the cuttlefish was the highlight of my day.
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| Cuttlefish |
The ride back to Port Douglas was
flat calm. I took my last picture at 2:46 and we were back at the dock at 4:45.
On the ride back, I sat on the stern by myself watching the Great Barrier Reef
disappear in the distance and thinking about the places that we’d been for the
last three months. We covered 2,000 km (1,200 mi) of Queensland’s coast and I’d
driven over 5,000 km (3,100 mi). A young woman, one of the dive crew, walked
over and asked me if I was “happy where I was.” I said that I was, but didn’t
try to explain why I was sitting alone staring out to sea. These would be my
last dives on the Great Barrier Reef for some time.
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| Leaving the Great Barrier Reef |
Australia doesn’t end at Port
Douglas. There’s a four-wheel drive track from the end of the paved road to
Cooktown, a town of about 2,400 people in the far north of Queensland. That will have to wait for another trip because in three days we’re
leaving for New Zealand.
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| Port Douglas estuary |
Postscript
In the last two decades, the Great
Barrier Reef (GBR) suffered three major coral bleaching events (1998, 2002 and
2016) that, when combined, span the entire 2,300 km (1,426 mi) of the GBR. Corals
provide shelter for algae, which, through photosynthesis, provide food for the
corals. Rising water temperatures disrupt the association between corals and
their algae, which they expel, leading to bleaching. Prolonged bleaching results
in increased coral mortalities. In 2016, the proportion of reefs with extreme
bleaching (>60% of corals) was four times higher, and the proportion of
reefs with no bleaching was five times lower, than in 1998 or 2002. The
severity of the 2016 bleaching was greater in the northern half of the GBR. Of
the 171 reefs surveyed during each of the major bleaching events, only 9% had
never bleached, and most of those were offshore at the southern end of the GBR
where waters are generally cooler (link).
Estimates of coral mortality ranged from 22% over the entire GBR to 35% in the
central and northern sections (link, see also link).
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| Goldband fusiliers (Caesionidae) |
The number of days with elevated
water temperatures explained the recurrence of bleaching at local reefs and
across the GBR. Water quality, prior bleaching (acclimation/adaptation) and management
zoning (e.g., protected reefs) were not correlated with lower bleaching
severity. At lightly affected (<10% of corals affected) and moderately affected
(10-30% affected), many of the more robust coral species escaped with little or
no bleaching. These reefs occurred primarily at the southern end of the GBR. At
extremely affected (60->80%) reefs, there were few lightly bleached species.
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| Bigscale soldierfish (Holocentridae) |
Corals that are good colonizers
and fast growers take 10-15 years to recover from bleaching events, so when
corals die, the recovery of severely affected coral reefs takes decades. The
recovery of long-lived species requires decades without additional severe
bleaching events. The key concern is the return time of severe bleaching events
– will there be enough time for mature coral assemblages to develop between
events? “The chances of the northern Great Barrier Reef returning to its
pre-bleaching assemblage structure are slim given the scale of damage that
occurred in 2016 and the likelihood of a fourth bleaching event occurring
within the next decade or two as global temperatures continue to rise” (link).
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| Shadowfin soldierfish (Holocentridae) |
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