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e is a lot of salt in the sea—enough to bury every bit of land on theplanet to a depth of about five hundred feet。 millions of gallons of fresh water evaporate from the ocean daily； leaving all their salts behind； so logically the seas ought to grow more saltywith the passing years； but they don’t。 something takes an amount of salt out of the waterequivalent to the amount being put in。 for the longest time； no one could figure out whatcould be responsible for this。
alvin’s discovery of the deep…sea vents provided the answer。 geophysicists realized that thevents were acting much like the filters in a fish tank。 as water is taken down into the crust；salts are stripped from it； and eventually clean water is blown out again through the chimneystacks。 the process is not swift—it can take up to ten million years to clean an ocean—but itis marvelously efficient as long as you are not in a hurry。
perhaps nothing speaks more clearly of our psychological remoteness from the oceandepths than that the main expressed goal for oceanographers during international geophysicalyear of 1957–58 was to study “the use of ocean depths for the dumping of radioactivewastes。” this wasn’t a secret assignment； you understand； but a proud public boast。 in fact；though it wasn’t much publicized； by 1957–58 the dumping of radioactive wastes had alreadybeen going on； with a certain appalling vigor； for over a decade。 since 1946； the united stateshad been ferrying fifty…five…gallon drums of radioactive gunk out to the farallon islands；some thirty miles off the california coast near san francisco； where it simply threw themoverboard。
it was all quite extraordinarily sloppy。 most of the drums were exactly the sort you seerusting behind gas stations or standing outside factories； with no protective linings of anytype。 when they failed to sink； which was usually； navy gunners riddled them with bullets tolet water in （and； of course； plutonium； uranium； and strontium out）。 before it was halted inthe 1990s； the united states had dumped many hundreds of thousands of drums into aboutfifty ocean sites—almost fifty thousand of them in the farallons alone。 but the u。s。 was by nomeans alone。 among the other enthusiastic dumpers were russia； china； japan； new zealand；and nearly all the nations of europe。
and what effect might all this have had on life beneath the seas？ well； little； we hope； butwe actually have no idea。 we are astoundingly； sumptuously； radiantly ignorant of lifebeneath the seas。 even the most substantial ocean creatures are often remarkably little knownto us—including the most mighty of them all； the great blue whale； a creature of suchleviathan proportions that （to quote david attenborough） its “tongue weighs as much as anelephant； its heart is the size of a car and some of its blood vessels are so wide that you couldswim down them。” it is the most gargantuan beast that earth has yet produced； bigger eventhan the most cumbrous dinosaurs。 yet the lives of blue whales are largely a mystery to us。
much of the time we have no idea where they are—where they go to breed； for instance； orwhat routes they follow to get there。 what little we know of them es almost entirely fromeavesdropping on their songs； but even these are a mystery。 blue whales will sometimes breakoff a song； then pick it up again at the same spot six months later。 sometimes they strike upwith a new song； which no member can have heard before but which each already knows。
how they do this is not remotely understood。 and these are animals that must routinely eto the surface to breathe。
for animals that need never surface； obscurity can be even more tantalizing。 consider thefabled giant squid。 though nothing on the scale of the blue whale； it is a decidedly substantialanimal； with eyes the size of soccer balls and trailing tentacles that can reach lengths of sixty feet。 it weighs nearly a ton and is earth’s largest invertebrate。 if you dumped one in a normalhousehold swimming pool； there wouldn’t be much room for anything else。 yet no scientist—no person as far as we know—has ever seen a giant squid alive。 zoologists have devotedcareers to trying to capture； or just glimpse； living giant squid and have always failed。 theyare known mostly from being washed up on beaches—particularly； for unknown reasons； thebeaches of the south island of new zealand。 they must exist in large numbers because theyform a central part of the sperm whale’s diet； and sperm whales take a lot of feeding。
1according to one estimate； there could be as many as thirty million species of animalsliving in the sea； most still undiscovered。 the first hint of how abundant life is in the deepseas didn’t e until as recently as the 1960s with the invention of the epibenthic sled； adredging device that captures organisms not just on and near the seafloor but also buried inthe sediments beneath。 in a single one…hour trawl along the continental shelf； at a depth of justunder a mile； woods hole oceanographers howard sandler and robert hessler netted over25；000 creatures—worms； starfish； sea cucumbers； and the like—representing 365 species。
even at a depth of three miles； they found some 3；700 creatures representing almost 200species of organism。 but the dredge could only capture things that were too slow or stupid toget out of the way。 in the late 1960s a marine biologist named john isaacs got the idea tolower a camera with bait attached to it； and found still more； in particular dense swarms ofwrithing hagfish； a primitive eel…like creature； as well as darting shoals of grenadier fish。
where a good food source is suddenly available—for instance； when a whale dies and sinks tothe bottom—as many as 390 species of marine creature have been found dining off it。
interestingly； many of these creatures were found to have e from vents up to a thousandmiles distant。 these included such types as mussels and clams； which are hardly known asgreat travelers。 it is now thought that the larvae of certain organisms may drift through thewater until； by some unknown chemical means； they detect that they have arrived at a foodopportunity and fall onto it。
so why； if the seas are so vast； do we so easily overtax them？ well； to begin with； theworld’s seas are not uniformly bounteous。 altogether less than a tenth of the ocean isconsidered naturally productive。 most aquatic species like to be in shallow waters where thereis warmth and light and an abundance of organic matter to prime the food chain。 coral reefs；for instance； constitute well under 1 percent of the ocean’s space but are home to about 25percent of its fish。
elsewhere； the oceans aren’t nearly so rich。 take australia。 with over 20；000 miles ofcoastline and almost nine million square miles of territorial waters； it has more sea lapping itsshores than any other country； yet； as tim flannery notes； it doesn’t even make it into the topfifty among fishing nations。 indeed； australia is a large net importer of seafood。 this isbecause much of australia’s waters are； like much of australia itself； essentially desert。 （anotable exception is the great barrier reef off queensland； which is sumptuously fecund。）because the soil is poor； it pro