Portugal went on high alert as oil slicks from the sunken tanker Prestige closed in on its shores for the first time yesterday, and a second Spanish nature reserve came under threat. Waves of toxic heavy fuel oil have coated 179 Spanish beaches with sludge despite the efforts of underequipped and overwhelmed volunteers to help the official cleanup. Laden with 77'000 tonnes of fuel oil, the Prestige sprang a leak in stormy weather off the Atlantic coast of Spain on November 13, then broke in two and sank six days after being towed out to sea. The wreckage came to rest 3.5 km (two miles) down, about 130 nautical miles (240 km) off the coast of Galicia in northwestern Spain, but not before an estimated 17'000 tonnes of foul-smelling pollutant gushed into the sea. The French-owned deep-sea submarine Nautile, best known for finding the Titanic, was preparing to make its first exhaustive reconnaissance mission of the wreckage to follow up initial investigations. So far there was no sign the wreck was leaking oil. Spanish radio said the black tide had lapped up on the Cies Islands, a haven for migratory sea birds and nudists. On Tuesday, oil washed ashore near the wetlands of the Corrubedon nature reserve and threatened to choke Spain's most prized stock of shellfish at the river inlet known as the Ria de Arousa. In Aguino, at the mouth of the Ria de Arousa, one volunteer worker wearing a flimsy surgical mask passed out because of the pungent fumes from the fuel oil on Wednesday. Further south in Vigo, an army of 1'000 municipal workers stood at the ready to scrub down any beaches that might be hit. Portugal's Secretary of State for Defence Henrique Freitas told a news conference that a number of small slicks from the tanker were 26 km (16 miles) from Portugal's coast. In the northern Portuguese fishing town of Caminha, near the Spanish border, navy sailors erected a huge crane ready to load crates of absorbent material onto vessels with scoops and booms. It's more difficult here in Portugal than in Spain, which has more money. Portugal is in crisis. Without a doubt this would be a disaster, said Ricardo Maciel, who is unemployed. Commander Augusto Ezequiel, technical director of the Portuguese Navy's Hydrographic Institute, appealed for calm and urged any volunteers to work closely with authorities in containing the spill.