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Saliza Mohd Nazri – Doctor of Biotechnology

Analysis of Jacobs SKM’s benchmark study on effluent emissions from shrimp aquaculture and sugarcane farms

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Introduction

Jacobs SKM was contracted by QCA to give independent advice on environmental and technical issues in the investigation on the regulatory reform of aquaculture in Queensland [1].

Table 1. Summary of effluent emissions by Jacobs SKM [1].

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ComparisonTable 1. Summary of effluent emissions by Jacobs SKM [1].

Table 2. The effluent discharge data from prawn aquaculture farms based on CRC Report 2002 [2] (note: units have been converted to the same unit used by Jacobs SKM for ease of comparison).

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Prawn farm effluent data from Jacobs SKM benchmark study

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Investigation of the value stated in the benchmark study

First row of prawn farm discharges

The original study was conducted by Trott and Alongi [4] but was cited in Burford’s [5] review.

The prawn farm pollutant loads did not lead to eutrophication due to physical and biological processes associated.

Examples of the associated processes :1)the fast settlements of the nutrients within the creeks and forests, 2)the efficient flushing and removal process of sediments during high currents and fluxes, 3)the primary production undergo grazing by the zooplankton,4)the consumption of zooplankton by juvenile fish5) the effluent discharges were in an intermittent pattern that permitted the “fallowing” to take place at the estuary [4].

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Investigation of the highest N value stated in the benchmark study (prawn farm discharges)

•Derived from a study done by Jackson [6] which investigated the effluent loads from three intensive shrimp farms in Australia.

•In the study, it was reported that due to the unusual condition of Farm A, only the discharge values obtained from Farm B and Farm C should be used as indicator of the pollutant loads released from intensive shrimp farms [6].

•This is because Farm A used double amount of water (1.36 X 106 L ha-1 day-1) as the management changed its main shrimp production species from P.monodon to M.japonicus in the early of the study and faced difficulties from the switch.

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Jackson [6] proposed in the conclusion of his research, intensive shrimp

farms would typically produce 1 kg ha-1 day-1 (365 kg ha-1 yr-1)of net loads of

total nitrogen.

In conclusion, if a correction was to be made in the benchmark study, the

657 kg ha-1 yr-1 value of nitrogen effluent stated would be replaced with 365

kg ha-1 yr-1.

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Sugarcane farm effluent data from Jacobs SKM benchmark study

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• Jacobs SKM referenced a report done by Dr McPhee [7] in the first row of the

benchmark study of the sugarcane farm effluent data.

• However, a further investigation into this report by McPhee revealed that there

was also data on the nitrogen emission from sugarcane farms of 300 kg/ha/yr

reported in 1990s (on page 7 of the report).

• Hence, there is a big area of improvement needed on the conclusiveness of the

data extracted by Jacobs SKM. If this had been reported in the benchmark study,

the N emission level would be double than the present data and this would lead to

a different conclusion regarding the relative contributions to effluent loads in GBR.

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121 - 365

<1 - 300

Recommended potential correction

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References[1] Erftemeijer, P.L.A., Benchmark Study : Emissions, Productivity and Employment for Aquaculture and other Types of Land Use in Queensland. 2014, QCA: Jacobs SKM.

[2] ACIL, Submission to the Productivity Commission on Industries in the Great Barrier Reef Catchment and Measure To address Declining Water Quality. 2002.

[3] Bartley, R. and W. Speirs, Review and summary of constituent concentration data from Australia for use in catchment water quality models, in eWater Cooperative Research Centre Technical Report. 2010, CSIRO.

[4] Trott, L.A. and D.M. Alongi, Quantifying and predicting the impact of prawn effluent on the assimilative capacity of coastal waterways and Pond and Effluent management, in FDRC Project 97/212. 2001: Aquaculture CRC Ltd Project E1.

[5] Burford, M.A., et al., A synthesis of dominant ecological processes in intensive shrimp ponds and adjacent coastal environments in NE Australia. Mar Pollut Bull, 2003. 46(11): p. 1456-69.

[6] Jackson, C., N. Preston, and P.J. Thompson, Intake and discharge nutrient loads at three intensive shrimp farms. Aquaculture Research, 2004. 35(11): p. 1053-1061.

[7] McPhee, D., A comparison of anthropogenic discharge quality and quantity into Queensland East Coast catchments. 2001, APFA.

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Conclusions

• The benchmark study done by Jacobs SKM that is used by the QCA in reporting to the Queensland Government in their decision to determine the fate of regulatory reform of aquaculture in Queensland warrants further improvements.

• The unilateral approach adopted by Jacobs SKM in evaluating and comparing the environmental impacts of point source pollutants from aquaculture with other diffuse-source effluents from other agricultural activities may not be the best approach.

• As postulated by Burford [5], bioindicators of ecological processes may potentially be a more accurate and reasonable way of evaluating the water quality affected by prawn farm effluents.

• Primary production rates• Phytoplankton responses to nutrients• Community shifts in zooplankton• Nitrogen isotope ratios in plants

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Acknowledgements

• Prof Ross Barnard

• Helen Jenkins