Choose your beach carefully the next time you go swimming, as there might be more in the water than you bargained for. New research from the University of South Florida indicates that what gets flushed into your septic tank may end up in the sea in as little as 12 hours.
Dr Joan B. Rose described her research on the risk to health posed by our polluted coastlines. Out-falls which discharge sewage some distance off the shore were often assumed to be the source of the bacteria and viruses commonly associated with human waste.
She found, however, that 40 to 60 per cent of the pollution comes from "non-point sources", seepage from septic tanks and from material washed down through storm drains.
Present in the marine environment were emerging microbial agents such as Cryptosporidium and a newly described toxic bacteria, Pfiesteria. There was a whole range of diarrhoea-causing organisms, and more serious ones including hepatitis A.
In tests a tagged and recognisable bacterial virus was discharged into septic tanks, then tested for in nearby coastal waters.
In one test the tagged virus arrived along the coast 12 hours after it was flushed down the lavatory into a septic tank. She said these "tracer studies" had been conducted for eight years.
"It has been very powerful evidence of both the escape from septic tanks and also the speed that the waste moves." Efforts to control these discharges were necessary, she said, for human health and the health of the ecosystem.
Dr James W. Porter, Professor of Ecology and Marine Science at the University of Georgia, presented data on the exponential growth in diseases which are damaging coastal corals in the Florida Keys.
There was a strong correlation between disease incidence and proximity to polluted waters, he said, although he said he did not know if this was part of an unknown natural cycle or if disease was "more common because of what humankind is doing to the planet".
He takes measurements from 160 monitoring stations along the Keys. Since the project began two years ago there has been a 446 per cent increase in the number of stations showing coral disease and a 244 per cent increase in the number of coral species coming down with disease. In the 1970s researchers were looking at two or four coral diseases, while 14 are under study now.
"Most of these diseases are new to science. We know what they do, we just don't know what they are," he said. "The level of ignorance is really quite frightening."
These changes were "suggestive of the dangers that lie ahead" if action on marine pollution was not taken, he warned, and the corals were like the canaries down coal mines that warned of dangers. "We need to take heed," he said.
Dr Gerardo Vasta of the Centre of Marine Biotechnology at the University of Maryland Biotechnology Institute described losses of oyster stocks to emerging new diseases. These were being fostered by the current warming trend and also because of human-related stresses.
Shellfish under pressure because of a disease load caused by an organism that had no effect in humans were also, therefore, more likely to carry the pathogens which did cause illnesses in humans, he said.