Problems with fish feces contaminating produce

[jillswindoll]

Hello Everyone!

I was wondering what you all know about the produce being grown in the grow beds becoming contaminated by the very waste water we use to feed our plants. If lower leaves of a lettuce plant are laying on the media or they get fish water splashed on them will they be contaminated? I am assuming actual fish feces could cause human health problems. Is this an issue in traditional farming and the use of cow manure?

Thanks!

[jillswindoll]

I found this on the web about thirty seconds after posting my question! The information comes from "...Dr. James Rakocy, who answers questions concerning aquaponics in this column, is the Director of the University of the Virgin Islands Agricultural Experiment Station and has been doing research in aquaponics for over 20 years."



What steps are taken in aquaponics to ensure that bacteria associated with fish solid waste (E. coli, etc.) do not contaminate crops to be consumed by humans?
Cary Mitchell, Purdue University
West Lafayette, Indiana

Answer
Pathogenic organisms that enter water through fecal contamination are very difficult to isolate and identify. However, coliform bacteria, which are present in large quantities in the intestinal tracts of humans and warm-blooded animals are easily tested and commonly used to indicate fecal contamination. Each person discharges from 100 to 400 billion coliform bacteria per day. They aid digestion through the breakdown of food. The presence of coliforms does not always mean contamination with human or animal waste as some species can grow in soil but Escherichia coli (E. coli) are entirely of fecal origin. Drinking water is considered safe when less than 5% of water samples test positive for total coliform bacteria. However, those samples testing positive must be tested for fecal coliforms. No fecal coliforms are allowed in drinking water but the standard for recreational water is 235 organisms/100 ml in a single sample. There are hundreds of strains of E. coli that are harmless. However, one strain, identified as O157:H7 and associated with cattle feces, creates powerful toxins and has caused many illnesses and deaths.

Aquaponic systems could be exposed to fecal contamination from warm-blooded animals. In an outdoor system contamination could come from birds for example. In an indoor system contamination could come from rodents. However, the dose would be quite small and it would not occur regularly. Any coliform bacteria that get into the system would be highly diluted. I doubt that there would be any contamination from cattle feces. In the 20 years we have been growing plants aquaponically at the University of the Virgin Islands, no one has ever gotten ill. In the past we raised mainly lettuce, which was washed but not cooked to kill bacteria. Normally the leaves do not contact with the culture water, but some water gets on the leaves from splashing or during packaging operations. Look at the alternative, which is field production of lettuce. Manures are often used as a soil amendment, including cattle manure. During rainstorms, soil splashes on the leaves. A field is a more natural habitat for birds, mice, rats, rabbits, squirrels, etc. The issue should be studied. In the meantime, I would not be overly concerned about microbial health risks in aquaponic systems.

[Outbackozzie]

Thats what I was going to say :)

I am eating root crops out of the AP system, and to be honest, with the worms in the growbeds, there is pretty much nothing on the roots of the plants - no gunk or solids at all.

[Jason Palenske]

I wouldn't worry too much Jill, even in traditional soil farming which my uncle does the risk is negligible. The only times you really see outbreaks of E. Coli, such as what happened stateside this year was caused by a large scale contamination. Mother Nature does a great job of giving things a way to clean themselves and stay healthy, it's only when humanity throws things out balance, large scale cattle yard draining into a nearby pepper field, that you have to worry. Aquaponics work with balance and nature and would be far safer.

[anniefish]

Hi all,
I would prefer to have produce with fish poo on it than something drenched with poisons. As you say Jason, mother nature has a way of keeping the balance, it's when people do something out of the norm, that problems arise.
Ann

[anniefish]

Hi all,
I would prefer to have produce with fish poo on it than something drenched with poisons. As you say Jason, mother nature has a way of keeping the balance, it's when people do something out of the norm, that problems arise.
Look at the crisis in China, adding melamine to baby food, what are we coming to? I wouldn't want to be in the shoes of those responsible.
Ann