PLYMPTON, N.S. – Massive numbers of dead starfish, clams, lobsters and mussels have washed up on a western Nova Scotia beach, compounding the mysterious deaths of tens of thousands of herring in the area.
Ted Leighton, an adjunct biology professor at Nova Scotia’s University of Sainte-Anne, said social media photos showing bottom-dwellers strewn in the sand near Plympton, N.S., could be an indication that the phenomenon that has killed schools of herring in St. Marys Bay is possibly spreading to new species.
The retired veterinary pathologist has compiled more than 40 sightings of dead herring since late November, to shed light on an ecological puzzle that has stumped the scientific community.
The herring deaths were cause enough for concern, Leighton said, but now that new species have surfaced dead on a beach in Digby County, it’s time to figure out “what’s really going on.”
“We’re kind of in the dark, not from lack of trying, but from the complexity of the case,” he said. “(There’s) no firm data to rule anything in or out.”
In mid-December, federal scientists said they had yet to determine what is causing the herring die-off, despite a battery of tests. Negative results have been reported for physical damage and several types of bacterial infections and viruses.
Fisheries and Oceans Canada said more tests were expected, including a check by the Canadian Food Inspection Agency for toxins caused by algae, and the possible presence of domoic acid — a toxin sometimes found in shellfish.
Until scientists know what’s killing the herring, it’s hard to say whether other marine life could be vulnerable to the same forces, according to Leighton.
“They may or may not be related,” said Leighton. “If they are related, they may be related in sort of an indirect means … (like) different pieces of global warming.”
Leighton said scientists can make some inferences based on the broad swath of species that were swept ashore in the last “pulse” of deaths.
A starfish, a lobster and a herring have very little in common, said Leighton, and it’s unlikely that an infectious disease, which targets a narrow range of organisms, could wipe out such a diverse cross-section of marine life.
Leighton said the only trait the fish share is where they live — the bottom of St. Marys Bay — so the answer may lie near the sea floor. A lethal change in marine habitat, like toxic water contamination or lack of oxygen, has the potential to wipe out all life it touches, he said.
With only one data point, Leighton reserved predictions about whether the herring problem has jumped species. Whatever comes next, he said life above land may not be immune.
“We depend on the environment as much as the clams do,” Leighton said. “If there’s some corrective action that can be taken we can take it, and if there’s not, perhaps we’ll understand the more complex implications of … the global environmental changes in which we’re all caught up.”
— By Adina Bresge in Halifax