“Biofiltration of Shrimp Pond Effluent by Oysters in a Raceway System” Adrian B. Jones* and Nigel P. Preston C.S.I.R.O. Division of Fisheries Moreton Bay Prawn Farm Research funded by the Fisheries Research and Development Corporation “Biofiltration of Shrimp Pond Effluent by Oysters in a Raceway System” Adrian B. Jones* and Nigel P. Preston C.S.I.R.O. Division of Fisheries Moreton Bay Prawn Farm Research funded by the Fisheries Research and Development Corporation SaccostreacommercialisSaccostreacommercialis

Oyster’s Filter Feeding ä Oysters filter bacteria and phytoplankton and convert them to meat. ä Oysters filter inorganic material and pellet smaller particles into larger pseudofacaes which can settle out of suspension. ä Oysters filter bacteria and phytoplankton and convert them to meat. ä Oysters filter inorganic material and pellet smaller particles into larger pseudofacaes which can settle out of suspension. - Bacteria - Phytoplankton - Inorganic particles - Detritus - Bacteria - Phytoplankton - Inorganic particles - Detritus - Faeces (organic) and Ammonia Ammonia - Psuedofaeces (inorganic) - Faeces (organic) and Ammonia Ammonia - Psuedofaeces (inorganic) AnusAnus HeartHeart IntestineIntestine StomachStomach MantleMantle GillsGills AdductorMuscleAdductorMuscle Style Sac Labial Palps (mouth) (mouth) HingeHinge

Study Area RedcliffeRedcliffe BrisbaneCityBrisbaneCity MoretonIslandMoretonIsland NorthNorth StradbrokeStradbroke IslandIsland MoretonMoreton BayBay BrisbaneBrisbane Moreton Bay Prawn Farm Prawn Farm Moreton Bay Prawn Farm Prawn Farm

Moreton Bay Prawn Farm

Need for Research ä Need to recapture some of the nutrients from the high cost feed pellets which are not converted into prawn biomass. ä Prawn farm effluent contains elevated concentrations of bacteria, phytoplankton, nutrients and suspended solids, which can potentially adversely affect the water quality in the receiving waters. ä Sewage treatment techniques are often ineffective due to the low specific gravity of most of the effluent particles, and the high volume and salt content. They are also prohibitively expensive. ä To develop a system of long term sustainable aquaculture. ä Need to recapture some of the nutrients from the high cost feed pellets which are not converted into prawn biomass. ä Prawn farm effluent contains elevated concentrations of bacteria, phytoplankton, nutrients and suspended solids, which can potentially adversely affect the water quality in the receiving waters. ä Sewage treatment techniques are often ineffective due to the low specific gravity of most of the effluent particles, and the high volume and salt content. They are also prohibitively expensive. ä To develop a system of long term sustainable aquaculture.

Objectives ä Quantitative determination of the changes in the chemical and biological composition of prawn farm effluent water after biofiltration by different sizes of the Sydney Rock Oyster (Saccostrea commercialis). ä Quantitative determination of the changes in the chemical and biological composition of prawn farm effluent water after biofiltration by different sizes of the Sydney Rock Oyster (Saccostrea commercialis). ä Phytoplankton ä Bacteria ä Nutrients (nitrogen & phosphorus) ä Total Suspended Solids ä Organic / Inorganic Ratio ä Determine the most efficient system to facilitate maximum filtration by the oysters, by adjusting flow rates and recirculation. ä Quantitative determination of the changes in the chemical and biological composition of prawn farm effluent water after biofiltration by different sizes of the Sydney Rock Oyster (Saccostrea commercialis). ä Quantitative determination of the changes in the chemical and biological composition of prawn farm effluent water after biofiltration by different sizes of the Sydney Rock Oyster (Saccostrea commercialis). ä Phytoplankton ä Bacteria ä Nutrients (nitrogen & phosphorus) ä Total Suspended Solids ä Organic / Inorganic Ratio ä Determine the most efficient system to facilitate maximum filtration by the oysters, by adjusting flow rates and recirculation.

Methods 6 raceways stocked with oysters (3 controls and 3 treatment replicates) 6 raceways stocked with oysters (3 controls and 3 treatment replicates) Collect 3 replicate samples from each raceway (before and after biofiltration) for analysis of Chlorophyll a, bacterial numbers, total suspended solids, & nutrients Collect 3 replicate samples from each raceway (before and after biofiltration) for analysis of Chlorophyll a, bacterial numbers, total suspended solids, & nutrients Effluent from shrimp pond Shrimp pond waste water pumped at constant flow rate Shrimp pond waste water pumped at constant flow rate Biofiltered water released into the environment Biofiltered water released into the environment Moreton Bay Biofiltered water recirculated back through the oysters for further filtering Biofiltered water recirculated back through the oysters for further filtering

Raceways

Raceway Setup

Effluent Water Flow Effluent Channel RacewaysRaceways Recirculating Tank Moreton Bay PrawnPondsPrawnPonds

Reduction in bacterial numbers after oyster biofiltration Continual Flow Recirculating No. of Bacteria per ml x 10 6

Reduction in chlorophyll a concentration after oyster biofiltration Continual Flow Recirculating Chl a concentration (µg.l -1 )

Reduction in Total Suspended Solids after oyster biofiltration Continual Flow Recirculating Control Oysters Total Suspended Solids (g. l -1 ) Treatment Inflow Outflow 92% 76% 54% 09:00 11:00 13:00 15: Total Suspended Solids (g. l -1 ) Sampling Time Inflow Outflow 118% 63% 32% 19%

Reduction in Total Nutrient Concentrations after oyster biofiltration Nitrogen Phosphorus Control Oysters Total Nitrogen (mg. l -1 ) Treatment Inflow Outflow 89% 66% 54% Control Oysters Total Phosphorus (mg. l -1 ) Treatment Inflow Outflow 85% 56%

Summary of Results Water quality% Reduced after once % Reduced after three Parameter through the oysters times through oysters TSS35%84% Bacteria65%88% Chlorophyll a61%80% Nitrogen39%nd Phosphorus44%nd Water quality% Reduced after once % Reduced after three Parameter through the oysters times through oysters TSS35%84% Bacteria65%88% Chlorophyll a61%80% Nitrogen39%nd Phosphorus44%nd

Conclusions ä Oysters can remove from suspension large quantities of phytoplankton, bacteria, nutrients and total suspended solids. ä By employing recirculating within the raceway system, the effects of the oysters are enhanced significantly. ä The use of oysters as natural filters of aquaculture effluent has the potential to provide: ä improved water quality of pond effluent and hence reduced environmental impact. ä reduced pond water exchange through recirculation of biotreated water back into the ponds. ä recapturing of nutrients. ä increased profits. ä increased productivity. ä more productive method of growing and fattening oysters. ä Oysters can remove from suspension large quantities of phytoplankton, bacteria, nutrients and total suspended solids. ä By employing recirculating within the raceway system, the effects of the oysters are enhanced significantly. ä The use of oysters as natural filters of aquaculture effluent has the potential to provide: ä improved water quality of pond effluent and hence reduced environmental impact. ä reduced pond water exchange through recirculation of biotreated water back into the ponds. ä recapturing of nutrients. ä increased profits. ä increased productivity. ä more productive method of growing and fattening oysters.

Continued Research ä Filtration efficiency of oysters at different densities. ä Test effects of flow rate, versus recirculation of water through the oysters. ä Test the efficiency of different sized oysters and determine their growth rate versus those in control oceanic waters. ä Test the ability of macroalgae (Gracilaria edulis) to remove dissolved nitrogen and phosphorus. ä Undertake commercial scale system at Rocky Point Prawn Farm. ä Filtration efficiency of oysters at different densities. ä Test effects of flow rate, versus recirculation of water through the oysters. ä Test the efficiency of different sized oysters and determine their growth rate versus those in control oceanic waters. ä Test the ability of macroalgae (Gracilaria edulis) to remove dissolved nitrogen and phosphorus. ä Undertake commercial scale system at Rocky Point Prawn Farm.

Study Area RedcliffeRedcliffe BrisbaneCityBrisbaneCity MoretonIslandMoretonIsland NorthNorth StradbrokeStradbroke IslandIsland MoretonMoreton BayBay BrisbaneBrisbane Moreton Bay Prawn Farm Prawn Farm Moreton Bay Prawn Farm Prawn Farm

Pond Design Layout InflowInflow OutflowOutflow SettlingAreaSettlingArea Baffles to force water up into oyster trays Baffles Baffle to slow water water MacroalgalAreaMacroalgalArea Oyster Rafts

Integrated Aquaculture Farm HarvestedHarvestedHarvestedHarvestedHarvestedHarvested HarvestedHarvested - Faeces (organic) and Ammonia - Psuedofaeces (inorganic) - Faeces (organic) and Ammonia - Psuedofaeces (inorganic) - Bacteria - Phytoplankton - Inorganic particles - Detritus - Bacteria - Phytoplankton - Inorganic particles - Detritus - Faeces (organic) and Ammonia - Psuedofaeces (inorganic) - Faeces (organic) and Ammonia - Psuedofaeces (inorganic) HarvestedHarvested Nutrient rich food source - high in amino acids Nutrient rich food source - high in amino acids ShrimpShrimp OysterOyster ClamClam AbaloneAbalone MacroalgaeMacroalgae