Algae Tides Make Adriatic Murkier
By MARLISE SIMONS, Special to The New York Times
Published: August 16, 1989
RIMINI, Italy— Like a symptom of a hidden sickness, a vast plague of algae has spread over much of the Adriatic Sea, sullying some of Europe's finest beaches and killing marine life in this part of the Mediterranean.
On calm days, the algae produce brown and yellow layers of slime on the water until winds break them up into millions of jelly clumps that ride the waves and pile up ashore. At dawn, before the tourists arrive, workers rush to scoop up the gelatinous mass.
Scientists link the algae tides to two gentle winters and decades of almost unbridled pollution from Italy's rivers, factors that have disturbed the Adriatic's ecological balance, destroying clams and mussels and making some people ill.
Describing a boat ride through the algae, Daniele Grossi, the head of the local fishermen's cooperative, said, ''There was scum as far as you could see.''
''It got into our engines,'' he said just after bringing his sloop into Rimini harbor. ''The weight has torn the nets.'' Tourist Season Crippled
Direct contact with the eerie tides is not believed to be harmful to humans, but the tides have crippled the tourist season along Italy's Adriatic coast, where more than 6,000 hotels frame sweeping beaches and brazen discotheques. Officials say tourism is off this year by as many as a million visitors, more than a third of the northern Europeans who normally spend part of the summer here. The loss of revenue is expected to exceed $800 million.
Unusual algae blooms have become a problem throughout the Mediterranean in recent summers, off Spain, France, Greece and Turkey as well as Italy.
But there appear to be no records of an algae explosion matching that of the northern Adriatic, which in recent weeks has stretched for 400 miles from Istria in Yugoslavia, along Italy's coast, past Trieste and Venice and affecting resorts as far south as Ancona, Rimini and Pescara.
''The first front arrived on the night of July 7,'' said Gianfrancesco Donati, an official of the tourism board, reporting it like the sighting of an enemy.
While cyclical algae tides have been recorded here since antiquity, scientists say that several varieties of the one-celled organisms are thriving steadily on the tons of phosphates and fertilizers that end up in the Mediterranean. The algae are most prevalent near the mouths of large rivers and the urban sewage outlets. Resorts Using Booms
Some resorts have put down booms of the type used to contain oil spills, hoping to keep the worst scum at bay. In Rimini and Cesenatico, boat owners have gone out in fleets trailing truck tires behind their vessels to churn the waters and permit more oxygen to enter, breaking up the algae.
Almost every town has had a protest meeting where politicians and businessmen have vented their anger against their northern neighbors who pollute the Po River and thus the Adriatic and are therefore blamed for the algae blooms.
Massimo Conti, the Mayor of Rimini, said he had had some very unpleasant encounters with his colleagues from Milan, Bologna and Turin.
''The Adriatic is the mirror of the Po Valley,'' Mr. Conti said.
The Po, Italy's largest river, drains an area of about 27,000 square miles north of here. Running 400 miles from west to east with 12 tributaries, it receives the raw sewage of more than 15 million people, including the entire city of Milan, and almost as many farm animals. It also carries the waste from the country's most important industries -most of it illegally dumped - as well as the runoff of Italy's most intensely farmed land, which experts say receives up to five times the amount of chemical fertilizers required. Process Not Well Understood
Scientists say the exact mechanism causing algae bloom is not well understood. Giorgio Honsell, an algae specialist at the University of Trieste, said he and others believed that the Po, laced with high levels of nitrates and phosphates from fertilizers and soaps, has provided so many nutrients for algae and other forms of plankton that they have proliferated and disrupted the ecological balance.
''The sea has passed its limits,'' Mr. Honsell said. ''The system cannot sustain such algae production.'' Warm winters may have accelerated the process, he continued. Once the algae secrete slime, he said, ''the slime seems to produce a new ecosystem,'' and ''we have found unknown kinds of algae inside this mass.''
As a source of food for other marine creatures, the algae in turn appear to have stimulated other life. At the fishermen's cooperative, for instance, the men talked of the abundance of their catch in the last two years.
''We don't understand,'' Mr. Grossi said. ''There are more sardines and more anchovies than ever.'' He added that the men had also caught types that they thought had disappeared. Clams and Mussels Killed
But biologists say the excess of algae, while enriching the food chain, also creates a deadly trap. As the algae proliferate and decompose, they deprive the waters of oxygen and choke other water creatures to death.
Tons of dead clams and mussels have already washed ashore. Sales of shellfish have been suspended along the Adriatic coast since more than 60 people became sick from eating mussels in mid-July; officials suspect that the mussels were tainted by the algae.
On board the research vessel Daphne eight miles offshore, Attilo Rinaldo, a biologist, took samples from the frothing water. The Daphne was afloat on a bed of gray and brown scum that made the sea look like a cesspool. The ship's instruments registered an enormous layer of algae at a depth of 20 feet.
''In the past days we found a broad area along the coast that is almost without oxygen,'' Mr. Rinaldo said, describing a belt around 30 miles wide. ''Soon we expect to be seeing large quantities of dead fish.''
The trouble with the Adriatic, Mr. Rinaldo continued, is that ''it is shallow, semi-enclosed, all its rivers are of terrible quality and their water is not diluted sufficiently.'' Warnings of Worse to Come
Experts of the World Health Organization have warned that unless weather conditions change significantly, the algae plague is likely to repeat itself or worsen next summer.
The hotel owners of Rimini are suing for nearly $70 million in damages from the province of Lombardy, which is a major contributor to the pollution of the Po.
In late July the Italian Government approved an emergency fund of more than $1 billion to clean up the Po and other rivers.
Hotel owners are not optimistic. They propose that the Government pay for more barriers in the sea and permit the construction of a chain of more than 100 swimming pools and other attractions on the beaches so their profits no longer depend on far-off rivers that dirty the sea.
This has set off a new round of protests, with environmentalists arguing loudly that it is the sea that must be saved and that it is unacceptable to pave the beaches with cement.