The effects of sediments contaminated with antifoulant paint on coral larvae, coral recuitment, coral recruits and adult corals from the Great Barrier Reef

Full description

On 2 November 2000, the 184 m cargo ship, Bunga Teratai Satu, ran aground on Sudbury Reef, on the Great Barrier Reef and remained grounded for 12 days. The ship was re-floated only 3 days prior to the November 2000 mass coral spawning. No cargo or fuel was lost but the impact resulted in significant contamination of the reef with antifoulant paint containing tributyltin (TBT), copper (Cu) and zinc (Zn). Sediment was collected from the grounding scar site and a control site 1 km from the grounding site in a similar habitat zone. Sediments were ground and sieved and the 1-4 mm fraction retained. Sediments from the control site were used to dilute contaminated sediment to the concentrations required for experimental treatments.Larvae were raised from gametes released by adult Acropora microphthalma, which had been collected from Pelorus Island and spawned in the outdoor aquaria at the Orpheus Island Research Station on November 17 2000. Live crustose coralline algae (Hydrolithon sp.) was collected from Pelorus Island, ground and extracted with methanol to produce a crude inducer stock, which was used to initiate attachment, settlement and metamorphosis of larvae. The influence of contaminated sediment on larval survival and competency was examined by firstly exposing groups of 200, 7 day old larvae for 24 hours to one of 4 contaminated sediment treatments (0, 5, 25 and 100%). Each 500 ml container contained 0.4 g of experimental sediment in 400 ml of filtered seawater. Larvae were then transferred to well cell culture plates (10-20 per well) containing inducer and filtered sea water. After 24 hours, counts of larvae and newly metamorphosed polyps were made using a dissecting microscope. The effect of contaminated sediment upon larval recruitment was examined by exposing previously unexposed 8 day old larvae to 0, 5, 25 and 100% contaminated sediment treatments. Approximately 660 larvae were placed in each 10 l aquaria containing a pre-conditioned terracotta tile and 6 g of experimental sediment in 6 l of filtered seawater. Tiles were raised 2cm above the sediment to allow larvae to settle on the top and bottom of the tiles. Recruitment was scored on each tile after 40 h using a dissecting microscope.The effect of contaminated sediments on previously unexposed coral recruits was examined by firstly placing 16 pre-conditioned tiles in a 500 l outdoor aquarium holding 8 day old larvae at a density of approximately 100 larvae/l. Tiles were elevated 2 cm from the bottom and left for 3 days after which the tiles were removed and the number of recruits counted. Each tile was then placed into individual 10 l aquaria containing 5 l of filtered seawater and one of four contaminated sediment treatments (0, 0.5, 5 and 25%). The number of coral recruits were counted after 38 and 72 hours.Six colonies of Acropora formosa were collected from Magnetic Island and transferred to the outdoor aquaria at the Orpheus Island Research Station. Branchlets, 4-6 cm long were cut from the colonies, mounted on cylindrical holders and acclimatised for 10 days prior to experiments. Five branchlets were randomly placed in each of twenty five 10 l aquaria. Five aquaria were exposed to each of 4 contaminated sediment treatments (0, 5, 25 and 100%) and 5 were used as controls (no sediment). Branchlets were visually inspected every 24 or 48 hours and categorised according to the degree of bleaching that had occurred. Branchlet mortality was also recorded at each census point.The maximum effective quantum yield (Fv/Fm') of each illuminated branchlet was determined using a DIVING-PAM fluorometer. Fv/Fm' ratios were recorded at 15 random locations over the surface of each coral branchlet at 3 mm distance to the coral surface. Zooxanthellae density counts were undertaken on a random subset of experimental branchlets (eight per treatment).The concentrations of TBT, DBT, MBT, Cu and Zn in sediment and water samples from the larval competency experiments and the coral recruit and branchlet toxicity experiments were measured.
This study was undertaken to test the effects of sediments contaminated with anti-foulant paint on survival, competency and recruitment of coral larvae, coral recruits and adult corals.

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Maintenance and Update Frequency: notPlanned

Statement: Statement: The rearing of larvae is described in: Negri AP and Heyward AJ (2000) Inhibition of fertilisation and larval metamorphosis of the coral Acropora millepora (Ehrenberg, 1834) by petroleum products. Marine Pollution Bulletin 41, 420-427.The preparation of the inducer is described in:Heyward AJ and Negri AP (1999) Natural inducers for coral larval metamorphosis. Coral Reefs 18, 273-279.The analyses of butyltins; TBT, dibutyltin (DBT) and monobutyltin (MBT) were conducted at the CSIRO Centre for Advanced Analytical Chemistry, Lucas Heights, New South Wales.Terracotta tiles (11x11 cm) were pre-conditioned by placing them on a patch reef at 4 m depth for 3 months prior to the experiment.Categories used to define the effects of sediment treatments on coral branchlets: (1) dark brown coral tissue, no evidence of bleaching; (2) noticeably lighter than category 1 but no areas of severe bleaching;(3) corallite tips were bleached white, coensteum lighter than category 1;(4) corallite tips severely bleached, coensteum very pale;(5) all tissue severely bleached.

Notes

Credit
Negri, Andrew P, Dr (Co Investigator)

Credit
Smith, Luke D, Mr (Co Investigator)