Returning to Normal
The first question many people apparently had after the oil spill at Bligh Reef was, "How soon will Prince William Sound again be normal?" Most scientists interested in the sound and its complement of living creatures have another question to consider first: "For this body of water, what's normal?"
If it means natural, unaffected by human impact, then Prince William Sound hasn't been normal within living memory. It hasn't been itself, so to speak, for the two centuries since Russian fur traders drove sea otters to the brink of extinction.
Unlike other sea mammals, the otters don't keep warm with a layer of blubber. They have those splendid pelts that caused the species such grief, and they have a prodigious metabolism that they fuel by eating great quantities of food. A furry but lean sea otter must eat the equivalent of about a third of its own body weight each day, while a fat seal can make do with only five per cent.
Because sea urchins are among the things that sea otters eat, and because sea urchins are determined grazers of seaweeds, the sound before 1800 probably had more extensive beds of kelp and other weedy growths than it does now. We can only speculate what that meant to the region's ecosystems. Seaweed beds affect everything from water speed to nutrient availability; their presence means more hiding places for small creatures, including young fish, and perhaps more kinds (and numbers) of some organisms and less of others.
As recently as 1970, sea otters were still very scarce in Prince William Sound. Coincidentally, their numbers boomed just as oil-related development bloomed. And, as if those two changes weren't enough to skew our picture of what the sound normally should be, there's also the matter of millions of extra salmon fry pouring in from the hatcheries. Certainly these hordes of hungry youngsters must affect the system; things that baby salmon like to eat must be under more pressure, and things that eat baby salmon must be thriving to an unnatural extent.
Perhaps, to make it easy on ourselves, we could try saying arbitrarily that the state of Prince William Sound was normal enough on March 1, 1989. That's what we knew and loved, even though it was far from pristine.
Yet again, natural variation complicates understanding. According to Ted Cooney, a member of the Institute of Marine Science faculty at the University of Alaska Fairbanks, this was an exceptionally cold winter on the sound. Because plants and animals living on or near the shore could have been killed off by the cold, researchers finding a bed of dead mussels may be seeing the results of petroleum poisoning, of chill, or of interaction between the two. They'll have to investigate to be sure.
Prince William Sound has seen changes in its normal state connected to changes in its plants, its animals, and its weather. It's even seen changes in its geography. In the sound and much of the rest of Southcentral's coastal waters, every century or two massive earthquakes will lift some shorelines beyond the reach of any waves while sinking others below the reach of tides. (In 1964, parts of Montague Island rose by 30 feet.) The intertidal area of the sound has had only 25 years to recover from its last major shift, and no one is sure whether that process is truly complete.
All this complexity doesn't mean that the research teams assessing spill effects can't determine what a healthy, normal Prince William Sound would be. It does mean that they have to make some assumptions, and must allow for a range of variables. That is, if they were drawing a graph of what's normal for Prince William Sound, it couldn't be a single steady blip. It would have to be a kind of moving wave, with peaks and lows dictated unpredictably by earthquakes and glacier retreats, booms and busts of different species, cold winters and hot summers. Normalcy makes a moving target.
