Fishkill and plastic-eating cows

[India] Pollution enters the food chain in multiple ways. If untreated sewage in lakes and river streams contaminates the water that irrigates vegetable farms, poorly managed solid waste could be equally dangerous. Cattle feeding on plastic bags and frequent fishkill in the city lakes are tell-tale signs of an ecosystem gone horribly wrong.

Veterinarians are on record citing operations on cows that revealed upwards of 50kg of plastic bags in their stomachs. The more plastic in their stomach, the less food it consumes. This directly reduces the milk production. Scurrying for food in roadside garbage bins, the cows find it tough to tear the plastic bags. Eventually, the entire bag gets in.

Instances of fishkill, the death of native fish in thousands, are getting more frequent than before in the city lakes. This trend, last seen in Halasuru lake, has serious consequences for the fish-eating public. Dr T V Ramachandra from the Centre for Ecological Sciences, Indian Institute of Science, attributes this to bioaccumulation, accumulation of chemicals in the algae. Fish eats the algae, transferring the toxic substances.

Simply put, bioaccumulation occurs when an organism absorbs a – possibly toxic – substance at a rate faster than that at which the substance is lost by catabolism and excretion. “This happens when the fish feeds on the algae and zooplankton (organisms drifting in the water bodies). The trend is very worrying. It could lead to severe health complications,” points out Dr Ramachandra.

Fish farmers introduced the African cat fish in lakes galore since their survival rate is much better than the native fish. This has, however, complicated matters since the exotic variety even feeds on the native fish.


  • A study by professors from the Department of Environmental Sciences, Bangalore University, R K Somashekhar and Seyed Esmaeil Mahdavian showed that fruits collected from KR Market and Yeshwantpur market had variable concentrations of pesticides.
  • A 2014 study by H L Ramesh and V N Yogananda Murthy found heavy metal contamination in green leafy vegetables, especially palak and coriander.
  • Yogananda Murthy, Research Coordinator, Azyme Biosciences Private Limited, explains: “Green leafy vegetable samples were collected from five sampling stations –  Byramangala, Bellandur, Ramagondanahalli, Jigani and Parappana Agrahara. The lead concentration was exceedingly high in palak (28.43ppm to 149.50ppm) and coriander (54.69ppm to 75.50ppm) in all stations . In coriander leaves, copper, zinc and manganese were found in all stations.”
  • This study also found that farmers were using water from polluted lakes located at the sampling stations. The pollution was due to the direct flow of effluents to lakes from industries and households.


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