altwater aquaponics is a novel concept that is increasingly becoming a viable option in aquaculture science. Countries are looking for ways to use brackish water while increasing seafood availability in areas without a local source. The effluent created by these aquaculture systems can create major ecological and biological setbacks, but multi-trophic integrated aquaculture systems (IMTAs) are potential solutions to reduce the impact of nutrient waste. The objective of this study was to see if Ulva rigida had an effect on 2 specific nutrient levels in small aquaculture systems. Nitrogen is a limiting factor in saltwater while phosphorus is limiting in freshwater, and both can be destructive in watersheds and recirculating systems.
The study ran for a total of 11 days for ammonia testing, 7 days for phosphate testing and 20 days for shrimp population counts. The aquariums were cycled in anticipation of the Ulva rigida and Palamonetes shipment from Florida. A salinity range of 1.023-1.025 with a pH of 8.3, was targeted to reflect high end brackish aquaculture systems. Instant Ocean Marine Salt was used to maintain stable salinity. The shrimp were distributed as evenly as possible between six 20 gallon aquariums. All six aquariums had 5lbs of macro marine rock to aid in the beneficial bacteria growth, creating a microbial bed. Three (3) of the aquariums contained Ulva rigida while the other 3 did not. Phosphate and ammonia (ppm) were collected via API Saltwater Test kits from water samples from each aquarium.
Over 11 days ammonia was tested in each aquarium (n=30). The average ammonia was 0.17 ppm with Ulva rigida, but averaged 0.58 ppm in aquariums without it. These ammonia readings were significantly different between treatments.
Phosphate levels were also tested in each aquarium (n=15). The average phosphate was 0.13 ppm with Ulva rigida, but averaged 0.12 ppm in aquariums without it. The phosphate tests showed that there was little difference between the Ulva rigida present and Ulva rigida not present treatments..
In summary, seaweed such as Ulva rigida did have a significant effect on the nitrogen levels in the shrimp aquaculture systems, and has the potential to reduce waste to levels that would promote cleaner effluent water and more sustainable local seafood