FIELD
EXPERIMENT
SET UP I |
In the field experiment, we applied oil and dispersed oil treatments on
replicated mature plots of R. stylosa under strictly controlled
conditions.
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Field sites were monitored for approximately two
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Field sites were monitored for approximately two years. Approvals
were granted to conduct field experiments in mangroves at Fishermans Landing,
Port Curtis, near Gladstone in Queensland. Treatments included Gippsland Light
crude oil on its own and as dispersed oil using Corexit 9527 in a 1:20 mixture.
Both treatments were pre-weathered in a shallow pond of seawater for 24 hours
prior to application in field plots. Weathered oil treatments, totalling ~1,277
L, were successfully applied to, and contained in, field plots of mature
mangrove stands.
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Successful simulation of a large oil spill was based on
concentrations of hydrocarbons in surface sediments averaging ~30,000
ug.g-1, and extensive mortality of trees 2-7 months after oiling. Oil
adhered to above-ground roots and sediments mostly on the first settling and
deposition from tidal waters. Enclosures were removed within two weeks without
loss of oil from plots into adjacent mangroves.
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Plate
5a, b, c, d, e, f. Field trials were used to further investigate short term
effects of spills of Gippsland crude oil and dispersed oil. |
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A. Study
sites were established in and near to mangrove stands, soon to be filled in with
reclamation works associated with the Gladstone Port development, fringing Port
Curtis, Queensland.
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B. Enclosures, around 35 m2 each, were
installed around replicate plots of mature Rhizophora trees,
approximately 5-8 m tall. Enclosures were tested prior to application of oil
treatments to confirm that oil would remain inside while tidal waters could flow
in and out.
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C. Oil and dispersed oil treatments were prepared in a
shallow pond prior to application, and weathered for 24 hours with periodic
mixing using a small pump.
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D. Approximately 200 litres of oil mixtures
were to be applied to each plot. Difficulties in moving through Rhizophora
mangrove forests meant that the drums full of oil had to be deployed by
helicopter.
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E. The final preparations for applying oil included
surrounding each plot with absorbent booms and having bags of absorbent material
in readiness next to each plot should there be any leakage outside the
enclosures.
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F. Once our preparations were complete, we awaited the
arrival of tidal waters within the plots before adding oil treatments.
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