pollution

Full-sibling, size-matched ‘all-fish’ growth hormone transgenic (TG; gene construct EO-1α) and non-transgenic (NTG) Atlantic salmon (Salmo salar L.) comprised of conventional diploid (DIP) and reproductively-sterile triploid (TRIP) fish were fed the same experimental grower diet in freshwater until they tripled their weight. The study was conducted to provide baseline data on growth performance, feed efficiency, nutrient digestibility, skeletal disorders, bone ash content and bone mineral composition of NTG/DIP, NTG/TRIP, TG/DIP and TG/TRIP fish and to determine if a practical grower diet for conventional NTG/DIP Atlantic salmon requires modification for TG/TRIP fish. TG fish consumed a significantly higher amount of feed on a daily basis but due to enhanced growth rates, better feed conversion ratios and higher nitrogen retention efficiency they achieved target weight gain in a considerably shorter period (40%) than NTG fish. Total feed required to produce the same fish biomass was reduced by 25%; representative of a significant reduction in overall feed intake. Of TG fish, TRIP had some significant effects on production traits primarily due to lower feed intake relative to DIP fish. Although feed intake was lower in TG/TRIP fish, feed efficiency, digestibility and nutrient retention efficiencies were equal to those of TG/DIP fish and, without exception; TG/TRIP fish out-performed their conventional NTG counterparts, regardless of ploidy. TG/DIP and TG/TRIP fish demonstrated a higher cellular capacity to direct dietary non-protein energy towards satisfying their daily metabolic energy requirements, allowing for a higher proportion of dietary amino acids to be directed towards protein biosynthesis; rather than catabolised as a dietary energy source. Since dietary protein is the largest and most expensive component of salmon feeds and also the major source of nitrogenous pollution from salmon farming, this could represent a highly beneficial alteration of energy metabolism which could result in more economical and ecologically-sustainable Atlantic salmon aquaculture, especially when conducted in closed-containment land-based systems. Although bone ash content of TG fish was slightly lower than NTG fish, no significant differences in key bone mineral composition were observed and the occurrence of skeletal disorders was low (<4%), regardless of transgenics or ploidy.

Author(s): S.M. Tibbetts , C.L. Wall , V. Barbosa-Solomieu , M.D. Bryenton , D.A. Plouffe , J.T. Buchanan , S.P. Lall

Kochi: While the expert committee report on fish dying in large numbers in  the Chalakudy River has not yet  been released,  public protest is mounting against the Nitta Jelatin Company, accusing it of letting untreated effluents from its plant in Kathikkudam into the river and causing the deaths.
The Nitta Gelatin India Limited Action Council, which has been spearheading the agitation against alleged disposal of untreated effluents from the plant  into the river, has intensified its protest since the fish deaths were reported. And people of  the five panchayats  of Puthanve­likara,  Annamanada, Kadukutty, Kuzhoor and Parakkadavu  went on hartal on Tuesday  protesting against the  pollution of the Chalakudy river.
"The legislators, Pollution Control Board officials and Kerala Water Authority (KWA) are being apathetic in dealing with this serious problem. If stringent measures are not taken to prevent further pollution of the river, several panchayats of the two districts will be hit by drinking water scarcity,"said M.P Shajan, member of Puthan­velikara panchayat. But according to initial reports of the state Pollution Control Board, effluents from the plant may not have led to the  fish dying in the river.

The Hindu A Kadar tribal man fishing in the Chalakkudy river. A primitive hunter-gatherer tribal group, the Kadars these days do fishing for their livelihood. A scene from Vazhachal forest range in Thrissur district. Photo: H. Vibhu
Environmentalists and guardians of the Kerala's biodiversity have reasons to worry on this World Environment Day as massive fish kills continue to be reported from various parts of the State.
Incidents of dead fishes washing up on the banks of Chalakudy River on two successive days from May 29 are the latest in the list. It has raised alarm among the public about pollution and its effect on marine wealth.
A hartal in protest against fish kills was held in seven panchayats — four panchayats in Thrissur and three in Ernakulam– that share the banks of the Chalakudy River on Tuesday.
"Pollution of water bodies caused by pollutants, including sewage, has led to the decline of oxygen level. Our district coordinator has reported that this was supposed to be the reason behind fish kills reported from Chalakudy River as well. We will be writing to the agencies concerned besides holding a study into the reasons for fish-kills reported in the State," K.P. Laladas, member-secretary, Kerala State Bio-diversity Board, told The Hindu.
K.G. Padmakumar, former Assistant Director of the Regional Research Centre, Kumarakom, Kerala Agriculture University, said the initial days of the monsoon were crucial for maintaining fish wealth.
"It is the breeding period for fish species and as they come up to the surface of the water they will be exposed to all sorts of pollutants that will be flushed into the river in rain. The monsoon after a severe drought-like condition, as the one experienced by the State this year, when rivers go dry is all the more critical. Besides, unscientific and outright dangerous methods of fishing like passing electric current and poisoning the water also affect the fish wealth," he said.
Repeated pleas to authorities concerned to be extra vigilant during the start of the monsoon to protect fish species have fallen on deaf ears. "What we need is dedicated environmental policing and courts to settle environmental issues.
The NGIL Action Council that had called for the hartal has alleged that discharge of toxic industrial waste by the Nitta Gelatin India Limited (NGIL), an Indo-Japanese industrial venture along the banks of the Chalakudy River in Kadukutty panchayat in Thrissur, was behind fish kills.
"We have been demanding the closure of the company for polluting river. About five tonnes of fishes were dead in recent incidents and many species are likely to become extinct in the river. The company, which has been using up lakhs of litres of water from the river for its production purposes was polluting the same river by discharging industrial effluents," said K.M. Anil Kumar, convener of the Action Council, while warning sustained campaign for the closure of the company.
G. Susheelan, managing director, NGIL, however, refuted this allegation. He said that the company had been discharging treated water to the river for the last 35 years of its operations and cannot be held responsible for the recent isolated incidents.
"Fish kills were reported four-and-a-half kilometre and seven kilometres downstream of the company's discharge point. Fish-kills, however, were concentrated in two points and not all along the stretch of the river from the discharge point, which should have been the case if we were responsible. So something has happened at those two points and there should be a thorough investigation to reveal it," he said.
Meanwhile, the Ernakulam district fisheries department, which had collected water samples from within the limits of the district and got it tested at the fisheries college at Panangad, has found high pH and ammonia content level that could prove toxic to the flora and fauna. "Besides, the nitrate level also was on the higher side. We have submitted reports to Thrissur and Ernakulam district collectors," said M.S. Saju, Deputy Director, Fisheries, Ernakulam.
Interestingly, the Pollution Control Board officials in Thrissur have found the pH and biochemical oxygen demand level in the water samples collected from the district within permissible limits. Neither was the ammonia content alarming.
But a senior official admitted that the sample was collected a considerable period of time after fish-kills were reported. "The findings can vary based on the timings of sample collection, he said.
The trade unions of NGIL have come out in support of the company stating that there was no basis to the allegation that the discharge of effluent was behind fish-kills in Chalakudy River. A release issued jointly by CITU, INTUC, and BMS said this was the first such allegation against the company in its 35 years of existence.

THANH HOA (VNS)— Aquaculture farmers in the central province of Thanh Hoa have seen large numbers of their oysters die since the beginning of last month, leaving them tens of billions of dong out of pocket.
The deaths wiped out 60-80 per cent of oysters raised across hundreds of hectares of aqua farms at coastal communes in Quang Xuong, Hau Loc, Nga Son and Hoang Hoa districts.
Tran Thi Hien, a farmer in Quang Xuong District's Quang Nham Commune, said the oysters died due to polluted water being discharged into Quang Nham's waterways and fishing areas.
In addition, workers harvesting jelly fish have seen the animals die after drifting into tidal areas. Polluted water filled with dead jelly fish also exacerbated the oyster deaths, she said.
More than 30 households raised oysters in Quang Nham Commune. Each household has 1-3ha of oysters. For each hectare, local farmers invest VND450-500 million (US$21,400-23,800) to buy baby oysters and run their business.
Le Van Thuan, a farmer in Hau Loc District's Hai Loc Commune, blamed polluted water discharged in the Kenh De River for the oyster deaths. A number of livestock and poultry farms have been set up along the river.
Thuan said he has 7ha of oysters but dozens of tonnes of them died and he suffered a loss of VND700 million ($33,300).
Cao Thanh Tho, head of the Thanh Hoa Department of Agriculture and Rural Development's Aquatic Product Breeding Division, said samples of water, soil and dead oysters were sent to the Ministry of Agriculture and Rural Development's Department of Animal Health for tests.
No parasite causing diseases were discovered on the oysters.
However, the amount of ammonia in the water and soil exceeded regulated levels by ten times.
Tho said oysters were selling slowly this year so oyster farmers had large stocks in their ponds.
The density of oysters in aqua farms was more than 300 per square metres, while the regulated density is only 150-200 per square metre. The high density resulted in a lack of food for the oysters, which may also have led to the deaths.
An additional factor was that oysters were currently in their reproductive season, a time when their immunity is weak. Meanwhile, the weather in the province has been erratic, said Tho.
Do Quoc Canh, chief of the provincial People's Committee secretariat, said that the committee had received reports and proposals on support for farmers in Hau Loc and Hoang Hoa districts. — VNS

The mass mortality of fish reported from the stretch of the Karamana, near the Thiruvallam and Pallathukadavu ghats last week, could have been caused by the unusual rise in water temperature, reduction in flow and a surge in the concentration of sewage pollution.
A preliminary study conducted by the Department of Aquatic Biology and Fisheries, University of Kerala, says the mass fish kill was due to an abrupt dip in the dissolved oxygen in water. Head of the Department A. Biju Kumar says the rise in temperature and reduction in water flow coincided with the summer. The heavy sewage pollution from the Parvathy Puthanar canal could have aggravated the conditions, killing fish in large numbers, he says.
Hundreds of dead fish, including pearl spot, barbs, and a few marine species that fond their way inland through the estuary were found dead in the water, triggering public concern. Despite repeated assurances from the State government, the heavy pollution of the downstream stretches of the Karamana river continues unabated, posing a grave environmental and health hazard for the residents at Thiruvallam and on the Edayar island. Four weeks ago, 20 children who were attending a swimming camp at Thiruvallam contracted leptospirosis, prompting health officials to sound the alarm.
Officials say that cleaning up of the heavily polluted Parvathy Puthanar canal is crucial to the restoration of the river. But the construction of a sewage treatment plant at Muttathara has been dragging on for years.
The Karamana runs through the city, joins the Killi at Pallathukadavu (upstream of Thiruvallam) and flows around the Edayar island on its way to the Poonthura estuary. Both the rivers carry large quantities of raw sewage discharged from city drains. The heavily polluted Parvathy Puthanar canal joins the river at Munnattumukku, near the Poonthura coastal village.
The flow of water on the western side of the island is blocked from heavy silting at Munnattumukku and accretion of sea sand at Kunnumanal. During high tide, seawater from the estuary surges up to Thiruvallam through the eastern side of Edayar. When the tide ebbs, the dirty water from the Parvathy Puthanar rushes in, covering the upstream portions up to Thiruvallam and beyond.
Scientists and environmentalists feel that the pollution of the river water has to be tackled at point sources on a watershed approach with the active involvement of local bodies and the public. They highlight the need for a comprehensive master plan to restore the river.
An environmental monitoring programme on water quality carried out by the Kerala State Council for Science, Technology and Environment (KSCSTE) had revealed heavy pollution in major stretches of the river, with Thiruvallam being the most contaminated reach. KSCSTE is preparing to take up a project to restore an 18-km stretch of the river. “The concept paper has been approved and an action plan is being prepared. The project will be implemented with the help of the Thiruvananthapuram Development Authority and other agencies,” says V.N. Rajasekharan Pillai, executive vice president, KSCSTE.
The Kerala State Biodiversity Board (KSBB) is also embarking on an initiative to create a green belt along the banks of the river. “The project seeks to plant mangroves and bamboo to shore up the banks. It will support the river restoration programme,” KSBB Chairman Oommen V. Oommen says.
Keywords: sewage pollution, Fisheries department, aquatic biology, mass mortality of fish

GUWAHATI, May 4 – A test conducted by the Pollution Control Board, Assam (PCBA) on the water samples of the Bishnu Puskar pond of Hayagriv Madhav temple at Hajo has revealed high chemical oxygen demand (COD) and bio-chemical oxygen demand (BOD) values indicating organic pollution.A large number of fish died in the pond on April 18, which raised questions over the possibility of serious water pollution in the water-body. The PCBA collected water samples from five different parts of the pond for the test.
“This implies the presence of organic waste contamination from external and internal sources resulting in depletion of dissolved oxygen in the pond water (low value of dissolved oxygen is observed in the analysis report). Low DO level could be one of the main reasons for such fish kill,” KS Chakraborty, Chief Environmental Scientist, Central Laboratory, PCBA, said in the report.
Chloride, phosphate and nitrate concentrations appeared to be on a higher trend, which indicates optimum nutritional value of pond water to have facilitated over growth of phyto-plankton (e.g. algae etc.) which might lead to damage of water quality through eutrophication, the report noted.
According to the report, pH conductivity and alkalinity values were in normal range which eliminates the possibility of acidic and alkaline adversities.
The PCBA made several recommendations for improvement of water quality for securing long-term well-being of the pond’s fish.
The recommendations include immediate cleaning of the bottom benthic sludge in the pond besides arrangement of partial change of the stagnant water; stopping of discharge of waste matters or waste-water, if any, to the pond immediately; and maintenance of optimum level of fish population in consultation with the Fishery Department.
The PCBA also asked the temple authorities either not to dispose flowers, leaves, fruits and other food materials in the pond or to remove those before sun-set everyday.
It further recommended maintenance of a minimum 1.5 to 2.5 meters of water depth in the pond throughout the year. Another important suggestion included a fixed or floating fountain to be provided at the centre of the pond to maintain optimum dissolved oxygen level through aeration of the water.

Pollution Control Board, Assam (PCBA) has detected high Chemical Oxygen Demand (COD) and Biochemical Oxygen Demand (BOD) in the Bishnu Puskar Pukhuri (pond), HayGrib Madhab Mandir, Hajo which resulted in death of large number of fishes in the pond recently.   
In tests conducted by the experts of the PCBA in the central laboratory of the board on the water sample collected from the five different parts of the pond it was found that high COD and BOD values indicate organic pollution in the pond.
Chief environmental scientist of the central laboratory of the PCBA, KS Chakraborty told the media presence of organic waste contamination from external and internal sources resulting in depletion of dissolved oxygen in the pond water (low value of dissolved oxygen was observed in analysis report).
Chakraborty said low dissolved oxygen (DO) level could be one of the main reasons for such fish kill.   
PCBA found pH, conductivity and alkalinity values were in normal range in the pond which eliminates the possibility of acidic and alkaline adversities.
Chloride, phosphate and nitrate concentrations appear to be in higher trend which indicate optimum nutritional value of pond water to facilitate over growth of phyto-plankton (algae and others) may have lead to damage of water quality through eutrophication," Chakraborty said.
PCBA has also suggested measures for improvement of water quality and for survival of fishes of the Pukhuri.
PCBA's expert said bottom benthic sludge in the pond need to be cleaned up immediately and partial change of stagnant water of the pond may be arranged immediately.
PCBA also suggested stopping discharge of waste matters or waste-water if any to the pond immediately.
Flowers, leaves, fruits and other food materials should either not be disposed in the pukhuri or removed before sun-set everyday.
Minimum 1.5 to 2.5 meter of water depth should be maintained in the pond all through the year.
Optimum level of fish population should be maintained in consultation with fishery department.
A fixed or floating fountain may be provided at the centre of the pond to maintain optimum dissolve oxygen level through aeration of the water. This will add to the beauty of the pond and help in the reduction of organic pollution load.

Smallmouth bass that draw hundreds of millions of dollars to the Chesapeake Bay region for sport fishing are sick, and many look too awful to ever mount as a trophy.

A report released Thursday by the Chesapeake Bay Foundation says the fish, particularly those in the lower Susquehanna River, have been struck by a perfect storm of pollution, parasites, disease and endocrine disruptors that are changing the sex of males.

The catch rates of adult bass fell 80 percent between 2001 and 2005 in some areas of the Susquehanna River, the report said, citing a study by the Pennsylvania Fish and Boat Commission.
The director of the commission, John Arway, said Thursday that he caught and released 200 bass on a summer night before 2005 and can now catch only three or four. Arway said that anglers who come up empty-handed are shying away from the smallmouth bass, valued at nearly $650 million in 2011, according to the American Sportfishing Association.
The foundation is calling on the Environmental Protection Agency to designate a 98-mile stretch of the river as "impaired" under the federal Clean Water Act, "and a decision is due any day," said William Baker, the foundation's president. If the EPA makes the designation, Pennsylvania could be forced to require farms and cities to limit nitrogen and phosphorous pollution that runs into the bay more aggressively than the current cleanup plan that is set to run until 2025.
The Pennsylvania Department of Environmental Protection has said an impaired designation is premature. It said that baby smallmouth bass succumb to disease in some of Pennsylvania's most pristine waters, a mystery that requires more study. "We don't make impairment designations based on the health of a species of fish. We make them based on water quality," said Kevin Sunday, a department spokesman.
Baker called smallmouth bass a "canary in the coal mine" because the fish is sensitive to pollution, and what harms that fish could later affect others. "This report and its findings must not be ignored," Baker said.
In a bit of good news from an unrelated study released this week, the U.S. Fish and Wildlife Service said bullhead catfish in the Anacostia River were found to have about half as many cancerous liver tumors and skin lesions than when a similar survey was completed in 2001. It attributes the decline to efforts to decrease pollution in the Anacostia.
"I think it shows the trend is going downward, and with continued actions it will continue to go lower," said Fred Pinkney, a Fish and Wildlife biologist.
Despite the improvement, bullheads from the Anacostia and several Potomac watershed locations still have liver tumor prevalence significantly higher than the bay-wide estimate for cancer, the study said.
Bullhead catfish are one of several species of catfish in the river that runs through the District and Maryland suburbs. Cancer is so prevalent that local health departments strongly discourage eating catfish from the river.
Smallmouth bass are troubled throughout the watershed. In addition to the Susquehanna, fish with lesions were found in the north and south branches of the Shenandoah River, the south branch of the Potomac River, the Monocacy River and the Cowpasture River.
The Maryland General Assembly recently passed a bill that requires farmers to report the exact amounts of insecticides used to treat their fields. Biologists fear that pesticides, mixed with hormones from human pharmaceuticals in urban wastewater that pours into rivers, are causing male bass to develop eggs in their testes, switching sex.
Arway said the evidence is clear. "We've found black spots on adult fish, exotic viruses, parasites and invasive species . . . some of which we've never seen in our waters before," he said. "We can't wait to research when our final bass dies."

The oil that spewed into the Gulf of Mexico during the Deepwater Horizon disaster three years ago killed off millions of amoeba-like creatures that form the basis of the gulf's aquatic food chain, according to scientists at the University of South Florida.
The die-off of tiny foraminifera stretched through the mile-deep DeSoto Canyon and beyond, following the path of an underwater plume of oil that snaked out from the wellhead, said David Hollander, a chemical oceanographer with USF.
"Everywhere the plume went, the die-off went," Hollander said.
Related News/Archive
USF researchers find new underwater plume from gulf oil spill
More than a Year ago
The discovery by USF scientists marks yet another sign that damage from the disaster is still being revealed as its third anniversary looms. Although initially some pundits said the spill wasn't as bad as everyone feared, further scientific research has found that corals in the gulf died. Anglers hauled in fish with tattered fins and strange lesions. And dolphins continue dying.
The full implications of the die-off are yet to be seen. The foraminifera are consumed by clams and other creatures, who then provide food for the next step in the food chain, including the types of fish found with lesions. Because of the size of the spill, the way it was handled and the lack of baseline science in the gulf, there's little previous research to predict long-term effects.
The disaster began with a fiery explosion aboard an offshore drilling rig on April 20, 2010. It held the nation spellbound for months as BP struggled to stop the oil, but the spill has largely faded from national headlines. The oil is still there, though.
Weathered particles of oil from Deepwater Horizon are buried in the sediment in the gulf bottom and could be there for as much as a century.
"These are not going away any time soon," Hollander said.
USF researchers dug up core samples from the gulf bottom in 2010, 2011 and 2012, and they plan to return this year and next to compare what they found. Their examination uncovered the massive die-off, according to researcher Patrick Schwing. They also noted an absence of microscopic worms that are normally seen in those areas. The researchers could not estimate how many square miles the die-off covered.
In the core samples, they could see that most of the grayish sediment on the bottom built up gradually over centuries, said Isabel Romero, a researcher working with Hollander. But on top they found a large, dark clump of sediment from the time of the 2010 disaster. The amount registered as 300 times the normal amount of oil-based particles found on the bottom.
The oil in the sediment samples definitely came from the 2010 disaster, Hollander said. The substance bears the same chemical signature as Deepwater Horizon oil.
Effects on fish
That's also the chemical signature of the substance that has clogged the livers of red snapper and other fish found with lesions. The fish livers were trying to screen out the impurities but could not cope with the quantities, he said.
"We're seeing lots of connections with fish diseases," Hollander said. "We're seeing compromised immune systems."
The diseased fish began turning up a few months after BP was able to shut off the flow of oil in July 2010. The discovery of fish with lesions faded out the following year, said Steve Murawski, a USF fisheries biologist who has overseen a project that examined 7,000 fish caught in the gulf.
Scientists are now looking for more subtle effects in red snapper, such as reductions in the number of large fish and a decline in the total population, Murawski said. They are looking for any genetic mutations, too, he said.
"If they get sick, that's one thing," Murawski said. "But if it changed their genes so that they're less resistant to disease or have lower weights, that's a big deal. That would be a real game-changer if true."
BP spokesman Craig Savage said, "No company has done more, faster to respond to an industrial accident than BP did in response to the Deepwater Horizon accident in 2010. As a result of our $14 billion cleanup effort, BP-funded early restoration projects as well as natural recovery processes, the gulf is returning to its baseline condition — the condition it would be in if the accident had not occurred."
But USF oceanographers and biologists are finding lingering effects of Deepwater Horizon. That's no surprise to the biologists, who recall that eight years passed after the Exxon Valdez oil spill before the herring population crashed from immune system problems.
"I spent a lot of time in the marshes in Louisiana," Murawski said. "You can still find a lot of oil in there."
Why soiled sediment?
One intriguing question is why some oil settled into the sediment on the bottom of the gulf a mile deep and stayed there. Hollander says that may be the work of two factors. One is the dispersant called Corexit that BP used to try to spread the oil out so it wouldn't wash ashore. The other is the Mississippi River.
BP sprayed Corexit directly at the wellhead spewing oil from the bottom of the gulf, even though no one had ever tried spraying it below the water's surface before. BP also used more of the dispersant than had been used in any previous oil spill, 1.8 million gallons, to try to break up the oil.
Meanwhile, the spill coincided with the typical spring flood of the mighty Mississippi, which sent millions of gallons of freshwater cascading in to push the oil away from the coast.
The Corexit broke the oil droplets down into smaller drops, creating the plume, Hollander said. Then the smaller oil droplets bonded with clay and other materials carried into the gulf by the Mississippi, sinking into the sediment where they killed the foraminifera.
In some areas where the die-off occurred, he said, the tiny creatures came back, but in others the bottom remains bare. Meanwhile, some of the burrowing kind are digging down into the contaminated sediment — and stirring it up all over again.
Craig Pittman can be reached at craig@tampabay.com.
Three years after BP oil spill, USF research finds massive die-off 04/04/13
[Last modified: Thursday, April 4, 2013 10:42pm]

Authorities in the eastern city of Nanjing are investigating reports that factories along China's Yangtze River have been dumping toxic effluent into the water there, following action by local residents.
Seven factories near Lianmeng village in Nanjing's Qixia district were pumping out large quantities of pollutants into the river water, the Yangtze Evening News quoted local residents as saying.
Villagers had manipulated local pumps and drainage systems to divert the water away from their commercial fish farms, and directly into the Yangtze River, the paper said.
"To test the level of pollution, they bought two large, healthy Crucian carp and put them in a tank full of the polluted water," the paper said.
"In less than 10 minutes, both fish were floating dead on top of the water."
An official who answered the phone at the Qixia district environmental protection bureau said officials were investigating the allegations.
"The environmental protection bureau is at the scene, dealing with this incident," the official said.
"We aren't all assigned to this one incident; we have a specialist team that monitors illegal polluting incidents, and they are all at the scene right now," he said.
"But if you want to know what's going on, you should contact our propaganda department; their entire purpose is to disseminate information."
Calls to the Lianmeng village committee went unanswered during office hours on Thursday.
Local sources later said that the environmental teams had "found no pollutants" at the scene, however.
Already serious
Nanjing-based environmental activist Liu Guanghua said pollution in the Yangtze was already known to be very serious.
"It's not just the chemical factories emptying waste there," Liu said. "Our tests have shown in the past few years that toxic effluent sometimes pours into the Yangtze from the Qinhuai River sluice-gates."
"As soon as they open the sluice-gate from the Qinhuai River, all the fish in the Yangtze River die off," he said. "Downstream of this, there are two intake pipes for a treatment plant for Nanjing's tap water."
"I have photos as evidence that all the fish die when they release the water."
Liu said he and his fellow activists had repeatedly brought up the issue with the authorities, but to no avail.
More than three decades of breakneck economic growth have taken their toll on the country's natural resources, sparking a huge increase in public unrest linked to environmental degradation and health problems caused by pollution.
Activists who confront the authorities and vested commercial interests over pollution are often subject to revenge attacks and government harassment, however.
Activist sentenced
Authorities in the eastern province of Jiangsu on Wednesday sentenced environmentalist Ji Shulong two two years' imprisonment for "obstructing official duty," and "stirring up trouble and picking quarrels," her relatives said.
"This is simply revenge on the part of the police," Ji's nephew Ji Jianjun told RFA's Cantonese Service, who said the charges against his aunt were trumped up.
Officials have admitted that China is facing a "grave" environmental crisis, with more than half its cities affected by acid rain and one-sixth of its major rivers too polluted even to water crops with.
Tap water supplied to millions of residents in hundreds of Chinese cities routinely fails to pass water quality tests, official figures show.
According to a January report from the State Environmental Protection Agency and the Chinese Academy of Engineering, around 90 percent of the water table under China's major cities is polluted to some extent, with residents of the worst-affected areas forced to buy drinking water.
Reported by Fang Yuan for RFA's Mandarin service and by Lin Jing for the Cantonese service. Translated and written in English by Luisetta Mudie.