Surveys of mangrove habitat impacted by oil spill incidents in Australia between 1970 and 1996

Full description

Field surveys to investigate the status of mangroves impacted by oil spills, were undertaken between December 1996 and April 1997. Nine sites were investigated, based initially on information supplied by the APPEA Research Working Group and the Australian Maritime Safety Authority. The site locations surveyed include: Torres Strait, Queensland; Cape Flattery, Queensland; Yorkeys Knob, near Cairns, Queensland; Botany Bay, Sydney, New South Wales; Parramatta River, Sydney, New South Wales; Spencer Gulf, South Australia; Cape Lambert, Western Australia; Johns Creek, Point Samson, Western Australia; Withnell Bay, Western Australia. These sites included most of the sites around the Australian coastine where mangroves had been affected by oil spills between 1970 and 1996.For each site measurements were made of tree and seedling condition, sediments were sampled for hydrocarbon analyses, an incident report was compiled using a standard format and information was collected on any prior studies conducted at each site (see Data Quality for further details).
This research was a component of the project "Fate and effects of oil and dispersed oil on mangrove ecosystems in Australia" and was undertaken to provide a assessment of the longer term impacts of oil spills on mangrove habitat. The objectives of these surveys were:1) to assess damage to mangrove habitat, particularly deforestation, if any;2) to describe the status, recovery and recruitment of trees following the spill;3) to determine the current status of hydrocarbons in the sediments, and4) to systematically document the findings in standardised case study reports
All sites, but one, were visited by the research team. The site near Port Pirie in Spencer Gulf was inaccessible at the time of the survey, and the team relied on data collected for the South Australian Department of Environment and Land Management.

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Maintenance and Update Frequency: notPlanned

Statement: Statement: 1) Measurements of tree and seedling condition:Sites were assessed for damage to mangroves, to be determined chiefly by the extent of deforestation caused by oiling. Mangrove forest structure was measured in oil-damaged, recovering and undamaged plots for comparison. Parameters of forest structure and composition were used to assess condition, including species, stem height, diameter and density. Plants were classified as living and dead, and as trees or seedlings where appropriate. The number of plots chosen and their locations depended on the particular conditions at each site, including the damage each had suffered and its current status. Where areas of oil-deforestation were distinct and identifiable, plots in these locations were often used also to assess current status of seedling recruitment and growth.2) Sediment sampling and hydrocarbon analyses:Sediment samples were collected from core holes cut with a clean spade or trowel. The depth of the sample varied according to field observations on the presence of oil seen and smelled in the slice, and in oil on pore water filling the core holes. Sediment characteristics of soil type and colour were described from these slices to a depth of approximately 20 cm. Observations from slices included notes on the presence of roots and burrows.Sediment samples were placed in clean sample jars, and frozen within 1-2 hours after collection. Subsamples were sent for analysis to Envirotest, an analytical laboratory in Nathan, Queensland. During collection and sample preparation all equipment was cleaned thoroughly before handling each sample. Analytical extractions and gas chromatography (GC-FID) analyses were done by Envirotest.3) Standard set of parameters recorded for each oil spill incident surveyed:(a) Spill DetailsDate of SpillLocationType of OilVolume of Oil ReleasedWeather ConditionDescription of Spill(b) Spill ResponseDescription of Response ActionVolume of Oil RecoveredType and Quantity of Dispersant Used(c) Sediment ConditionSediment TypeHydrocarbons in Sediments(d) Biotic ConditionArea and Extent of Mangrove OiledExtent of Mangrove DeforestationMangrove Species AffectedOther Mangrove Biota AffectedStatus of Plant Condition, Regrowth, Recruitment(e) Habitat RemediationNatural RestorationAssisted Restoration(f) Contact Person(s)/Organisation(s)Spill Management and Clean-upImpact AssessmentRecovery Monitoring and Current StatusSite Access(g) Documentation4) Prior studies at each site:Researchers and officials conducting studies in their respective sites were interviewed, and asked to share any relevant information and observations on those sites. It was not the objective of this study to conduct detailed surveys at each site, but rather to link, if possible, the specific studies at each location. The aim was to review all incidents and to compile information using the standard set of parameters, outlined above.

Notes

Credit
Burns, Kathryn A, Dr (Co Investigator)