Toxics threaten local orca population’s futureBy lgordon | February 18th, 2009 | Category: Featured story, Science |
By Sound News reporter Lyndsay Gordon
When a dead orca calf washed up on the shores of Henry Island in July of last year it was not reported five days later. The recovered body was of little scientific value, due to the heavy decomposition that had already taken place. However, it represented the fears of many researchers. The orca calf was found beside the placenta and was undersized, leading scientists to believe that it was either aborted or prematurely born.
If the calf was a local orca than it would be in addition to the seven local Puget Sound orcas to already have gone missing in the last year. Three of the seven were calves and all are currently presumed dead. The loss is the first decrease in the local population of orcas since the turn of the century when the pods lost fifteen animals.
Jason Wood, the research curator at the Whales Museum, commented on the recent loss, “The loss of the two reproductive females poses a real threat, because when they die they take their reproductive potential with them. They also represent the healthier part of the population.”
The local Puget Sound Orcas have evolved separately from the transient orcas that occasionally visit the area. The two groups never interbreed. “This is unusual to have evolved, because it means losing a few [from the local orca population] can be really devastating,” stated National Marine Fisheries Service’s Brian Gorman.
A likely cause of the disappearances and a remaining threat to surviving orcas is a contaminant called polychlorinated biphenyls or PCBs that is stored in the whales’ blubber. These long-lasting industrial chemicals were banned in the 1970s for their threat to both the environment and human health. The accumulation of PCBs within orcas, specifically, damages the immune system, development, and reproductive processes.
The local orcas are the most toxic whales in the world. When Everet, a local whale at age 22, washed up on shore in 2000, he hadn’t developed his sexual organs and had no sperm. Orcas become sexually viable around the age of fifteen. The PCB load measured from his blubber was alarmingly high, especially for a younger and smaller orca.
According to Kristin Burgess, who is creating a documentary on the local orcas, “They are missing a whole generation of reproductive males.” The males are unable to unload the toxics in their system the way females do when they give birth. She worries that since, “the next generation is just disappearing [that] once the older ones die the population could disappear over night.”
PCBs have shown recent decline in the samplings of seals and other sampled animals. However, the toxics haven’t cycled out of the system, but instead they have been buried in the mud. This decline is made even less promising by the greatly increasing count of polybrominated diphenyl ethers or PBDEs, which are fire retardants still being widely used in at least one of their three forms.
Both toxics have similar effects on orcas and both accumulate in the blubber. The local orcas feed almost entirely, 78%, on the endangered Chinook salmon. Not only is this food supply less plentiful, but the fish in the system have decreased in size as well as numbers. They are also the source of the toxics building up in the orcas.
Burgess suggested that the orcas would probably survive if they could find enough to eat. When the orcas do not find adequate food their body begins to feed off the blubber. This begins to flush the toxics, PCBs and PBDEs both, through their entire system drastically increasing the damage often resulting in indirect death and a failure to reproduce.
Repairing the local salmon populations would repair part of the issue. Unfortunately, due to the nature of the banned PCBs and in use PBDEs, the only way at present to remove them from the marine system is to physically relocate the toxics. Relocation of the toxics merely results in relocating the problem to a different area and system, not resolving it.
Contact Lyndsay Gordon email@example.com