|
The event | Effects | Monitoring
On the 11th March 2009, the container ship Pacific Adventurer lost 270 tonnes of oil. The oil impacted significant portions of the south-east Queensland coast, in particular the eastern and northern beaches and headlands of Moreton Island, the eastern beaches of Bribie Island, and the beaches and foreshores of the Sunshine Coast, littering them with sticky oil remnants called tarballs.
|
Mermaid Lagoon, Bribie Island © Ross Smith
|
Consequences
Natural action at work in the aquatic environments of the islands
reduced the severity of the oil spill and accelerated the recovery of
the affected areas.
- Weathering is a series of chemical and physical changes that cause spilled oil to break down and become heavier than water. Wave action may result in natural dispersion, breaking a slick into droplets which are then distributed vertically throughout the water column.
- Evaporation occurs when the lighter or more volatile substances within the oil mixture become vapours and leave the surface of the water.
- Oxidation occurs when oil contacts the water and oxygen combines with the oil hydrocarbons to produce water-soluble compounds. This process affects oil slicks mostly around their edges. Thick slicks may only partially oxidize, forming tar balls. These dense, sticky black spheres may linger in the environment, washing up on shorelines long after a spill.
- Biodegradation occurs when micro-organisms, such as bacteria, feed on oil hydrocarbons.
- Emulsification is the process that forms emulsions, which are mixtures of small droplets of oil and water. Emulsions are formed by wave action, and they greatly hamper weathering and cleanup processes.
Oil spills have a wide variety of impacts on the environment, in particular on marine ecosystems. Impacts can be either short or long term. Immediate effects are widespread and impact significantly on marine ecosystems. A variety of marine life is affected, including benthic invertebrate, plankton, fish, mammals and birds.
Top
Immediate effects on the birds
As birds are very mobile they can easily encounter areas of oil contamination. As a result, the oil spill off Queensland’s southern shores had the potential to affect large numbers of birds. When a bird encounters oil it can also suffer ongoing effects such as feather disruption leading to hypothermia, reduced buoyancy, impaired flying ability and reduced ability to hunt for food and to escape from predators, pneumonia from oil inhalation, anaemia following absorption of toxic chemicals via the skin, impairment of the immune system and disruption of thermal balance. Poisoning of birds can also occur due to oil ingestion by preening.
|
Effects on the environment
Moreton and Bribie Islands have a range of habitats, sandy beaches,
rocky foreshores, tidal mudflats, marshes and swamps. Many of these
habitats were affected by the oil spill.
On the exposed sandy eastern beaches of Moreton and Bribie Island
the oil soaked into the sand. Few organisms live fulltime in this
habitat, so the risk to animal life or the food chain is less than in
the other habitats. The recruitment of organisms into this habitat
should be fairly immediate and the effect on the feeding shorebirds
minimal.
Tidal flats are broad, low-tide zones, usually containing rich
plant, animal, and bird communities. On Moreton Island, Heath Island
represents this habitat. Any deposited oil seeping into the muddy
bottoms of these flats will create potentially harmful effects on the
ecology of the area. The benthic organisms and plant communities
(seagrasses) of these flats will be smothered and poisoned resulting in
a loss for a long period of time. Fortunately, Heath Island experienced
little oil inundation.
Mangrove forests are located on the western side of the islands and
around Heath Island and are home to a diversity of plant and animal
life. Mangrove trees have long roots, called prop roots that stick out
well above the water level and help to hold the mangrove tree in place
and help the tree breath in oxygen. A coating of oil on these prop
roots can be fatal to the mangrove tree, smothering the prop roots, and
because they grow so slowly, replacing a mangrove tree can take
decades. Fortunately, little oil flowed to the western side of the
islands and no effect of mangrove death has been noted at Heath Island.
Marshes and swamps with little water movement are likely to incur
more severe impacts as the oil sticks to the plants in these habitats
and the heavier oil components sink to the bottom and are incorporated
into the sediments beneath the plants. In these affected habitats it
may take years to restore. Moreton Island and Bribie Island have
several of these marshes and swamps that experienced inundation by oil.
Fortunately, the oil was removed quickly from these habitats and little
damage has been noted. |
Spitfire Creek, Moreton Island © Dez Wells
Yellow Patch, marsh, Moreton Island © Dez Wells
Osprey Chicks in nest at North Point, Moreton Island © Dez Wells
| Top
Measuring long term effects
 A grant has been obtained from the Australian Government through SEQ Catchments that will allow BASQ to develop a community based monitoring program on the islands.
Several workshops have been arranged to train and inform the local community in species identification and monitoring techniques. The first occurred in late January 2010, and two more are planned for May/June 2010.
 Sites are monitored using 1 hour 500m radius area searches, where all bird species will be recorded. Site locations are identified by a steel star picket with a yellow identifying tag. Four seasonal set survey periods are planned to obtain data – spring 2009, summer, autumn and winter 2010.
It is hypothesised that if sites have been damaged and food webs significantly disrupted that these sites should show a reduction in the abundance of bird species dependent on the food webs in these habitats and secondly, that as these sites recover the abundance of bird species at these sites should increase.
Sites have been established both in and outside of the oil affected sites for comparison.
Historical data has been researched to provide a background of the species richness of these areas.
Several factors have already been identified that will affect the validity of the analysis of the data collected. These include the significant influence of human recreation within these habitats and the quick and effective response by local councils in the oil spill cleanup.
Preliminary results (spring surveys)
During the spring surveys ninety-eight (98) species have been identified at sites on Bribie Island and seventy-four (74) species have been identified at sites on Moreton Island. The Eastern Yellow Robin, Torresian Crow and the Whistling Kite were identified most during surveys on Bribie Island. The White-cheeked Honeyeater, Willie Wagtail, Pied Oystercatcher, Black-fronted Dotterel and the Leaden Flycatcher were identified most at sites on Moreton Island.
Two sites, Kakadu at Bribie Island and Mirapool at Moreton Island contained the highest concentration of birds, 3883 and 2398 individuals respectively. Both these sites were not affected by the oil spill directly.
In areas affected by the oil spill on Bribie Island, the highest number of individuals was at Ocean Beach campground, with 19 species for 36 individual birds while Welsby Lagoon, contained the highest number of species at 33. Spitfire Creek on Moreton Island contained 17 species for the highest number of individuals at 143, whilst Heath Island, Moreton Island contained the highest number of species at 38. Of note was the importance of Moreton Island for the Beach Stone-curlew with 17 individuals sighted. This species is listed as near-threatened under the IUCN Red List. No Beach Stone -curlew were identified on Bribie Island, although historical records show one to two birds at either Kakadu or Buckley’s Hole.
It was noted at Bribie Island and Moreton Island that little oil spill disturbance was evident, with a healthy presence of macroinveterbrate, benthic and rocky shore organisms. It appears these organisms have already re-established. Comparison of the effects in oil spill affected sites against non-oil spill affected sites is therefore difficult. It is probably more interesting to make a comparison between islands based on the intensity of human disturbance at sites. It was obvious that Moreton Island experienced less human pressure on its beaches as many shorebirds were identified along its length, for example the presence of 17 Beach Stone-curlew and 65 individual Australian Pied Oystercatchers on Moreton Island compared to 6 Australian Pied Oystercatchers and no Beach Stone-curlews on Bribie Island beaches.
By Dezmond Wells
Top
|
