If the Census Bureau thinks it has its hands full counting Americans, imagine what scientists are up against in trying to tally every living thing in the ocean, including microbes so small they seem invisible.
And just try to get them to mail back a form.
The worldwide Census of Marine Life has four field projects focusing on hard-to-see sea life such as tiny microbes, zooplankton, larvae and burrowers in the sea bed.
Tiny as individuals, these life forms are massive as groups and provide food that helps underpin better-known living things.
"Scientists are discovering and describing an astonishing new world of marine microbial diversity and abundance, distribution patterns and seasonal changes," said Mitch Sogin of the Marine Biological Laboratory in Woods Hole, Mass., leader of the International Census of Marine Microbes.
The Census of Marine Life, which is scheduled to be reported Oct. 4 in London, has involved more than 2,000 scientists from more than 80 nations.
The decade-long census has discovered more than 5,000 new forms of marine life. Researchers think there may be several times that many yet to be found.
Previous updates have focused on larger creatures, such as a city of brittle stars off the coast of New Zealand, an Antarctic expressway where octopuses ride along in a flow of extra salty water, the deepest comb jellyfish ever found and The White Shark Cafe, a deep Pacific Ocean site where sharks congregate in winter.
Now the researchers have turned to the tiniest of things, some of which burrow in the sea floor.
Remotely operated deep-sea vehicles discovered that roundworms dominate the deepest, darkest abyss. Sometimes, more than 500,000 can exist in just over a square yard of soft clay. Only a few different types have been studied.
There are also 16,000 or more species of seaworms. There are loriciferans, which the scientists call "girdle wearers" because of hind shells resembling a corset. And there are hundreds of types of tiny crustaceans.
"Such findings make us look at the deep sea from a new perspective," says researcher Pedro Martinez Arbizu of the German Center for Marine Biodiversity Research. "Far from being a lifeless desert, the deep sea rivals such highly diverse ecosystems as tropical rainforests and coral reefs."
Consider zooplankton, the tiny, often transparent animals that some call sea bugs. They form a vital link in the food chain.
As of 2004, scientists had identified about 7,000 species of zooplankton. Now they expect that to double when they finish analyzing all the samples collected in the marine census.
Improved techniques such as DNA analysis have helped unravel some errors along the way. DNA, of course, is the genetic code in the cells of each living creature.
Tracey Sutton of the Virginia Institute of Marine Science and colleagues led by the Smithsonian Institution's G. David Johnson used genetics to show that three types of fish thought to be different are really one.
They found that even though they look different, the Mirapinnidae (tapetails), Megalomycteridae (bignose fishes) and Cetomimidae (whalefishes) are really the same species. The tapetails are the larvae and when they grow up they become either the bignoses (girls) or the wehalefish (boys).
After studying samples taken from more than 1,000 sites, scientists concluded there may be as many as 100 times more microbe genera in the sea than they had thought. Indeed, a 2007 study in the English Channel alone yielded 7,000 new genera of microorganisms.
Genus is the category of life ranked between family and species. For example the mammal family has many genera, such as homo (humans), canis (dogs) and equus (horse).
What ocean microbes lack in size they make up for in numbers. Marine census researchers calculate there are a "nonillion" of them.
Never heard of nonillion? Well, it's a lot. It's 1,000 times 1 billion, times 1 billion, times 1 billion.
Of course no one can really envision a number like that, so the researchers turned to the popular comparison measure — the African elephant.
A nonillion microbe cells, they say, is about the same weight as 240 billion African elephants — or the equivalent of 35 elephants for every person on Earth.
And that's just the microbes.