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Individual study: Application of salt to control the invasive marine alga Caulerpa taxifolia in Lake Macquarie, New South Wales, Australia

Published source details

Glasby T.M., Creese R.G. & Gibson P.T. (2005) Experimental use of salt to control invasive marine alga Caulerpa taxifolia in New South Wales, Australia. Biological Conservation, 122, 573-580

Summary

The invasive marine green microalga Caulerpa taxifolia was first confirmed in New South Wales, Australia, in April 2000. It subsequently spread to nine waterways, covering approximately 8.1 km² by 2005. An experiment was undertaken at Lake Macquarie (New South Wales) to determine the effectiveness of different salt concentrations in killing C.taxifolia. (See Case 281 for efficacy of control at Narrawallee Inlet).

Study sites: In Lake Macquarie, New South Wales (Australia), salt application experiments to attempt to control an invasive marine alga, Caulerpa taxifolia, were set up at two sites, separated by about 1 km, in March 2002. Each site had twelve 1 m² plots marked out, each 1-3 m deep. Pairs of treatment plots had salt concentrations of 50, 100, 150 and 200 kg/m² applied. A pair of control plots were positioned near to the treatment plots, and a pair were positioned 50 m from the treatment plots.

Plot sampling: Each plot was sampled prior to salt application, and then after one week, one month and six months. In three 30 x 30 cm quadrats, that were randomly placed within the plot, the number of fronds of Caulerpa, as well as of stems of the seagrass Zostera capricorni was recorded. Also, to investigate possible effects of salting on benthic fauna, three cores (65 mm diameter, 100 mm deep) were taken in each plot. Benthic fauna was identified to family level.

After one week Caulerpa taxifolia frond density in salted plots had decreased by 70-95%, and salted plots had a significantly lower density than unsalted control plots. No fronds were present after one and six months. There was also a decrease in C.taxifolia in the control plots across the experiment, possibly due to winter dieback. Salting also reduced Zostera capricorni shoot density after one and six months compared to control plots. However, Z.capricorni was less adversely affected than C.taxifolia and at salt concentrations below 200 kg/m² it began to recover after six months.

The abundance and diversity of benthic fauna decreased in treatment relative to control plots after one week. It then began to recover after one month. After six months there was no difference between treatment and control in diversity, and in the 150 and 200 kg/m² treatments abundance was higher than the control.


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