HUMAN waste flushed down the toilet is having a worse effect on the aquatic environment than anyone had thought.
Some corals off the coast of Florida, which form the world鈥檚 third largest barrier reef, are tainted with bacteria and viruses found in human faeces. Researchers also report this week that prescription drugs flushed into waterways can kill or maim the plankton that are a mainstay of freshwater ecosystems.
On average, half of the live coral off Florida has disappeared in the past five years. 快猫短视频s and politicians have argued vigorously over just who or what is to blame, echoing similar debates elsewhere in the world. Pollution, overfishing and global warming, which can kill the coral鈥檚 symbiotic algae, have all been implicated.
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But some politicians in Florida have refused to accept that sewage has a major impact. For while there is some evidence that human waste can reach coral reefs miles offshore, it is hardly ever detected by water quality tests.
So Erin Lipp, a microbiologist at the University of Georgia in Athens, and her team investigated whether any bacteria or viruses in sewage are contaminating the corals. They analysed the layer of mucus that coats the heads of coral polyps on reefs near shore, and found that the mucus on nine of the 15 corals tested at various locations contained faecal bacteria. Viruses contaminated 14 of the 15 corals (Marine Pollution Bulletin, vol 44, p 666).
Although the team did not study the effect of the sewage on the reefs, the results are significant because faecal bacteria have previously been shown to cause at least one disease that can devastate corals in Florida and the Caribbean. Sewage can also provide nutrients to fuel the growth of algae that attack coral.
Lipp will now repeat her study on corals further offshore. But she says it鈥檚 about time Florida faced up to its sewage problem. There are over 24,000 septic tanks and up to 10,000 illegal cesspools in the Florida Keys alone, she says. Both allow sewage to seep into the ocean, but politicians have been reluctant to accept the damage they are causing to coral reefs because setting up a centralised sewage system would cost millions.
Human waste could also be having a dramatic and unexpected impact on freshwater habitats. The rivers and lakes of Europe and the US are being flooded with high concentrations of artificial chemicals, from prescription drugs to bug repellents and narcotics. Most are excreted and then flushed into the water system.
New research reported to the Ecological Society of America鈥檚 national meeting in Tucson, Arizona, this week suggests that these chemicals could be killing zooplankton, the tiny animals that are an integral part of the food chain in ponds and streams.
Postgraduate student Colleen Flaherty and ecotoxicologist Stanley Dodson, both at the University of Wisconsin in Madison, studied water fleas, or Daphnia, which feed on algae and are eaten by fish. They found that, individually, low concentrations of a cholesterol-lowering drug or an antidepressant, both of which are known to pollute rivers, had little effect on Daphnia. But when exposed to both, even for a short time, the animals developed deformities and died in much higher numbers than usual.