Fish and shrimp help to determine level of water quality

While some people might think that trying to determine the toxicity of water through the raising of fish or seafood in that water might be an old-fashioned method, it is not.

Using this technique to determine whether bio-organisms are sickened by water is a way to make up for various blind spots in chemical analysis. By simply looking at the symptoms that organisms display in water is enough to determine on a preliminary basis what sort of toxic agent is in the water. Also, just raising fish in the water is not enough to give a well-rounded analysis of the situation. Experts suggest that the best method is to raise both fish and shrimp in the water.

Almost all of the water treatment plants in Taiwan raise fish in their water. Personnel who are responsible for monitoring the water say that if they see that fish have died in the water or are jumping out, this is a warning that plant workers may have missed discovering a toxic agent in the water.

Chen Hung-cheng, a professor at National Taiwan University's Department of Life Sciences, said that by the time an organism dies, the toxicity level in the water is already quite high. In the event of low-level chronic toxicity, organisms will begin displaying a number of symptoms. Yuan Shao-ying, the deputy director of the Environment Protection Administration's Department of Environmental Sanitation and Toxic Substance Management, said that his agency plans to hold a series of lectures in the coming weeks to instruct people on how to alert themselves to the possibility that a toxic agent may have entered the water.

To be sure, reservoirs for potable water undergo water quality inspections on a regular basis. However, Chen said that if the level of toxicity is low and is a chronic toxin, in many instances chemical analysis will not pick up on it. In these circumstances, it is imperative to rely on organisms to help out in the inspection process. He said that organisms living in the water will indicate early on whether there is a toxic agent in the water and their symptoms will also point to what type of toxin it is. After analysts can lock in on the general type of toxin in the water, they can adjust their chemical analysis to look for specific agents.

Toxic agents that could pollute water primarily come from wastewater from heavy metals industries or from agricultural pesticides. Chen said fish are especially sensitive to heavy metals, while shrimp have a high level of sensitivity to agricultural pesticides. If water treatment plants were to raise both organisms in their water, better results could be seen in determining the quality of the water. Chen added that experts in the field are able to determine on a preliminary basis the type of toxic agent hidden in the water just by looking at the symptoms exhibited by the fish or shrimp.

Fish will die when they water they live in is contaminated by a certain level of heavy metals. In a lower concentration of contamination, the fish will not necessarily die. However, at this point the gills of the fish will gradually change color, going first from red to white, and then changing to black. The reason for this is that heavy metals are alkaline matter and will erode the gills of the fish, causing them to turn white. Once the gills are damaged to a certain degree, they will begin to bleed, triggering a change in their color to brown and then black. In the case of shrimp, the gills will simply close up.

The symptoms of contamination by agricultural pesticides are totally different. The two fins on the chest of fish will become straight and upright, facing forward. In the case of shrimp, their body, which is naturally curved, will become rigid and strait. The symptoms of the agricultural pesticides are quite easy to spot.

In addition to being able to make a diagnosis while the organisms are still alive, an examination of the organisms after they have died also yields clues. Chen said that if the mouth of a fish is open when it dies, this means that it died from a lack of oxygen. This would indicate that there is not a sufficient level of oxygen in the water.

In addition, if fish commonly come up to the surface and open and close their mouths to breathe, this indicates that the level of dissolved oxygen in the water is insufficient and could signal the possibility of a contaminant in the water. Meanwhile, if there are white spots, fungus or a white film on the body of the organisms, this would indicate that there are too many organic substances in the water, meaning that the water could be over fertilized. This would also signal that the water has been polluted by a toxic substance.