Planthouse experiments to determine the effects of oil and dispersed oil treatments on mangrove seedlings

Full description

In early 1996, experimental tidal tank systems were set up in the planthouse at the Australian Institute of Marine Science (AIMS) near Townsville, Queensland, to investigate the effects of a range of oils and dispersants on mangrove seedlings. Four species groupings of mangroves were used: Aegiceras corniculatum; Avicennia marina var. eucalyptifolia; mixed Ceriops species (Ceriops australis, Ceriops decandra and Ceriops tagal); and Rhizophora stylosa. Seedlings in two distinct age classes were used (approximately 18 months old and greater than 24 months old) and were planted in either sand or fine mud sediments. In May-June 1997, seedlings were treated with various combinations of preweathered oil and dispersant. The oils used were Bunker C fuel, Arabian Light crude, Gippsland Light crude, Thevenard crude, and Woodside condensate. The dispersants used were, Corexit 9527, Corexit 9580, BP-AB and Shell VDC. Combinations of these oils and dispersants were selected in consultation with project advisors in the APPEA Research Working Group.Seedling condition and growth were monitored until November 1997. Growth measurements included stem height, stem diameter and leaf production rate. Effects were measured by percent mortality of the seedlings. Leaves were collected from the seedlings and analysed to identify any notable changes in the amounts of key elements such as sodium, potassium or calcium.
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 an assessment of immediate and short term impacts of oil spills, and to rank toxic effects.The objectives of this experiment were:1. to assess the effects on common Australian mangrove species of a range of oils and dispersed oils most likely to be released in Australian waters. 2. to better understand what caused plants to die from oiling.

Lineage

Maintenance and Update Frequency: notPlanned

Statement: Statement: The tank system:A total of 21 independent tidal tank systems were set up. Each tidal system included a large holding tank in which approximately 65 individually potted seedlings were established. Pots were filled with either sand or fine mud sediments. The bulk of seedlings were collected from Hinchinbrook Channel, to the north of Townsville, during the 1995-1996 fruiting season. A further collection of older seedlings was obtained from different sources, including those from earlier planthouse experiments. At the time of application of oil and dispersants, seedlings were around 18 months and > 24 months old, respectively. In total, 1,368 seedlings were established in the tanks. Shading on the roof of the planthouse reduced ambient light by around 30%.The tidal system:The tanks were flooded each day for 1-2 hrs then drained completely to simulate a daily tidal cycle. Water in the tanks was maintained at approximately 50% seawater with standard nutrient additives to sustain plant growth. Both water and nutrients were refreshed approximately each four months until experimental treatments commenced in May 1997. Flooding levels in the tanks were such that seedling pots and a small section of the stem base were immersed completely while foliage and upper stems remained dry for most of the time.Treatments:Before treatments were applied they were mixed with seawater in an open plastic bin and pre-weathered by agitating with a bilge pump for 24 hrs. Both oils and dispersed oils were preweathered. Dispersants were added in 1:20 ratio by volume with the respective oils. Treatments were applied to individual seedling pots in two doses, 2.0 L/m2 and 0.2 L/m2, based on the surface area of exposed sediment in each pot. Treatments were applied onto water as it drained from each pot, simulating (as far as possible) a marine oil spill arriving with the tide. Elements in green leaves of treated seedlings:Leaves were collected fresh from seedlings and gently washed to remove surface salts, then air dried before oven drying and subsequent grinding. Samples were prepared finally in a perchloric/nitric acid digest before being analysed using ICP-AES analytical method by the Laboratory Services Section at AIMS.

Notes

Credit
Burns, Kathryn A, Dr (Co Investigator)