In a recent study published by the Purdue Agriculture News, the researchers stated that the risk of E. coli in hydroponic and aquaponic systems may be greater than once thought and that the fish could cause an E. coli contamination of the lettuce. "Since the researches did not perform traceback, there is no evidence to prove this at all", says Marc Laberge with the Aquaponic Association. The association presents more concerns about the study findings and the publication. "We hope to reduce the possibility of studies like this creating unnecessary fear, or unsubstantiated claims that could harm the growth of the aquaponic (and hydroponic) industry."
The debate is all about a research published earlier this month. Purdue Agriculture News informed the public about a study related to the contamination risk of Shiga toxin-producing E. coli (STEC) in Aquaponic and Hydroponic production. "Risk of E. coli in hydroponic and aquaponic systems may be greater than once thought", the publication read.
Researchers conducted the study from December 2017 through February 2018. The study consisted of side-by-side aquaponic and hydroponic systems in a controlled environment lab growing lettuce, basil, and tomatoes with tilapia. The study indicates that both the aquaponic and hydroponic systems contained Shiga toxin-producing E. coli (STEC) at the time of sampling. It did not find the presence of Listeria spp., or Salmonella spp. The authors contend that the aquaponic system and specifically the fish feces were likely the sources of E. coli.
However, according to the Aquaponics Association, there is no evidence to prove that this was the actual source of contamination since the authors admit traceback was not performed, and there were several other possible introductions. "Blaming fish feces as the contaminating source seems incredibly misleading when so
many other options exist, and no traceback proved that as the source. The contents of the fish intestines were tested for the presence of E. coli, and none was found", they point out in a letter to the public.
"The pathogen was present in the water and on the root system of the plants. The researchers did not detect it in the edible portion of the plants. However, if the water is positive for a contaminant, and it accidentally splashes onto the edible portion of the crop throughout its life, or during harvest, this could still result in a food safety concern."
"Our findings conclude that while there is a low chance of the persistence of a pathogen in properly designed aquaponic and hydroponic systems, there is still a potential concern. No agricultural system is immune to this. Compared to soil production, soil-less crops grown in a controlled environment are far less likely to become infected pathogens from mammals, birds and other creatures which are difficult to prevent in field crop production. Human contamination or poor handling practices are of significant concern (Pattillo et al., 2015). The best way to avoid risk is to adhere to food safety guidelines set forth by the USDA, GlobalGAPs, the Aquaponic Association, and other accredited organizations", they continue.
"Overall, this and other research into food safety are ongoing, and new information becomes available continuously to help shape the best practices for proper greenhouse management. As the Aquaponic Association, we hope to provide the most accurate and reliable resources for this purpose. At the same time, we hope to reduce the possibility of studies like this creating unnecessary fear, or unsubstantiated claims that could harm the growth of the aquaponic (and hydroponic) industry. Other research must be performed to validate or negate this study's outcomes. "
Read the full response from the Aquaponics Association here.