Monk seal killer may be misidentified.

Scientists may have missed a major collaborator, or even fingered the wrong suspect, when investigating the deaths of more than 100 endangered Mediterranean monk seals off the Atlantic coast of the Sahara Desert in May and June last year.

Earlier reports blamed the die-off in two caves of seals on a previously unidentified morbillivirus (SN: 8/30/97, p. 134). However, a Spanish research team has looked into the possibility that the seals died from eating fish that had been contaminated with deadly phycotoxins produced by a bloom of dinoflagellate algae.

"We here suggest intoxication by algal toxins is a more likely cause of the deaths," Mauro Hernandez of the Vida Silvestre Forensic Laboratory in Madrid and his colleagues report in the May 7 Nature.

The researchers examined 117 seal carcasses and analyzed tissues from 8 of them in detail. Several phycotoxins turned up in the seals, and water samples contained three toxic dinoflagellates, including high concentrations of Alexandrium minutum. No one knows how much of these toxins healthy seals can sustain, the researchers note.

Questions remain about both the algal and the viral theories, says John Harwood of the University of Saint Andrews in Scotland. He has little doubt that a morbillivirus was circulating at the time, but he notes that the seals' deaths did not resemble those in other virus outbreaks. "[T]he animals died quickly, with few, if any, overt signs of disease," he notes in the same issue of Nature.

Harwood would have expected even higher algal concentrations if there had been a full-scale bloom where the seals died. If the bloom, with its fast-acting toxins, were farther out in the ocean, it is puzzling that the seals died so close to home, he adds.

Both algae and a virus may have been responsible, Harwood says. He adds that the controversy highlights the need for more information about the seals.