The
Great Barrier Reef has earned its place as one of the great wonders of the
world. Visible from space, it is 2,300 km long and comprises of 2900 reefs and
900 islands to explore.
The
Great Barrier Reef started to develop approximately 600,000 years ago and a
combination of physical and biological factors made conditions suitable for the
growth of many types of coral species (450 known hard coral and 150 soft coral
species) over geological time.
Heron
Island forms part of the Capricorn Bunker group of reefs located at the
southern end of the Great Barrier Reef. The vegetated cay island was named
after the bird species, the reef heron, recently renamed the eastern reef egret
(Egretta sacra). It has taken 11,000 years to develop.
The
reef around Heron Island is a type of shelf reef. Its location and exposure to
the elements: waves, wind, ocean currents, climate and extreme weather events,
have contributed to the type of coral, plant and animal species that inhabit
the reef. Induced pressure from animal activity, for example, grazing and
colonisation, play a part in its continual growth.
Heron
Island attracts a population of 900 of the 1625 species of fish inhabiting the
Great Barrier Reef, for example, parrotfish, butterfly fish, trevally, wrasse,
triggerfish and sea perch.
Parrotfish
are interesting to observe. Some researchers have made mistakes in the past,
identifying species due to an anomaly not apparent in other fish species. For
instance, the ability of parrotfish to change gender (sequential hermaphrodite)
and colour (polychromatism) throughout their lives. Most species start as plain
coloured, small females (initial phase) and at certain points in their lives,
transform into bright coloured, large males (terminal phase).
The
parrotfish diet consists of algae, scraped off coral by using specialised
teeth. The coral remains are excreted from the fish as sand. Research studies
estimates these fish produce 30% of the sand around reefs and are one of the
marine animals that play an important role in maintaining coral reef health.
At
night some parrotfish species have been observed to envelope themselves in a
cocoon of mucous. Apparently, the cocoon masks their scent from reef predators,
like the moray eel (Family Muraenidae).
Nests
made by wedge-tailed shearwaters (Ardenna pacifica), bridled tern (Onychoprion anaethetus)
and the black noddy (Anous minutus) bird species can be spotted all over
the island. The nesting burrows of shearwaters, shelter chicks waiting for
their parents to return with food. Other species that live and breed on the
island all year round include the buff banded rail (Gallirallus philippensis),
the eastern reef egret (Egretta sacra), bar shouldered dove (Geopelia
humeralis), black-faced cuckoo-shrike (Coracina novaehollandiae),
capricorn silver eye, sacred kingfisher (Todiramphus sanctus),
white-bellied sea eagle (Haliaeetus leucogaster), the silver gull (Chroicocephalus
novaehollandiae), and migratory and visiting bird species. Black noddies
are the pretty black and white birds that nest in the pisonia trees (Pisonia
grandis).
These
forests produce a sticky sap, which can unfortunately, trap black noddies,
supplementing the cycle of nutrients from guano and plant material. You can
also find screw palms, casuarina, she oak and other plant and grass species as
you wander around the island.
If
you’re visiting Heron from November to January, loggerhead turtles (Caretta
caretta) and green turtles (Chelonia mydas) make their way slowly
onto beaches at night to lay their eggs. The turtle’s sensitivity to any
artificial light (torches etc.) can distract or disorientate them. Moving too
close to a nesting turtle might also cause them to panic, so it is recommended
to maintain a safe distance of approximately 10 metres away. Just listening to
them breathing in the darkness while they lay their eggs is an amazing
experience.
Heron
Island is but a small microcosm of the Great Barrier Reef, which forms the
biggest tropical Marine Reserve and the largest protected World Heritage Area.
It may have taken its time to develop into the extraordinary beauty it is
today, but wasn’t it well worth the wait.
Please
take a look at the University of Queensland’s Centre for Marine Studies
link for a bird’s eye view of Heron Island.
Written
by Gabrielle Ahern
Salty
Wave Blue – Into all things ecology.
Follow
@SaltyWaveBlue on @Instagram and @Twitter
Book
Photographic Field Guide: Birds of Australia. An Australian Museum / Reed New
Holland Publication. Text by Jim Flegg. 2006. Second Edition.
These links provide some great views, photographs, videos and
information about Heron Island and the Great Barrier Reef.
Reef
Biosearch
National
Geographic
Onboard
– The Tourism Operators Handbook for the Great Barrier Reef
Heron
Island – Great Barrier Reef
Caitlin
Seaview Survey – An underwater view of the coral reefs around Heron Island
