Stand aside African wilder beasts - the
plankton are here; millions and millions of plankton, from underwater
insects to juvenile octopuses, these miniscule munchins make the mass
migration of any other animal look like a suburban stroll to the shops.
Marine biologist, Julia Bowett, is passionate about plankton. As one of
the scientists on board the adventure dive and research vessel Undersea
Explorer, she uses their week-long trips along the Great Barrier Reef to
take regular night dives with these nocturnal drifters.
"Plankton refers to a huge variety of plant and animal species," says
Julia, "from single cell algae to a variety of animals in their larval
stages including crustaceans, jellies and invertebrates. Some forms of
plankton are microscopic but others are visible to the naked eye.
"The best time to see plankton is during the night when the animals swim
up into the surface waters of the ocean to feed under cover of darkness.
This happens every night in every ocean across the globe, not just on
the reef, making it the world's biggest migration of animals."
But as Julia
explains, it isn't only the sheer size of this movement that makes
plankton unique. By shining a torch beam under the water, she says
divers will also discover many unique creatures: "it's sort of an
encounter of the alien kind."
"There are some pretty crazy animals. Most are translucent, almost
invisible; some light up the darkness with glowing rainbow colours and
quite a few can look like something from outer space - I think of them
as creatures from the dark side of the ocean and that's not only because
they come out at night.
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"One tiny animal has jaws
ten times the size of its body and there's a shrimp that looks like a
transparent robot built with mechano pieces. Another tiny fish lives in
a mucous bubble - it floats along on the current but bursts out of its
bubble if a predator attacks, swimming away into the darkness while its
enemy pursues the mucous remains.
"And there's another fish species where the males spend their days
clinging to the side of the larger females who use them only for sex -
the rest of the time they just hang on like some form of vestigial
appendage.
"But one of my favourite kinds of plankton are Dinoflagellates, although
they can only be seen with a microscope. These critters wrap themselves
around their food and eat by absorbing it - sort of hugging their meal
till they're full. I'd like to invite one to dinner at Sizzlers.
"One kind of plankton that most people have seen is the 'blue bottle' or
'Portuguese man of war'. They look like one squiggly blue jellyfish but
they're actually a colony of separate animals clinging together.
Different groups in the colony perform special roles for instance: one
group is responsible for locomotion; another for feeding - those ones
include the stinging cells that a lot of us know too well; and another
group is responsible for reproduction - it's a sexy world out there.
These animals hook up while they're floating in the ocean during their
larval stages."
According to Julia, there's one more unique aspect to a night dive in
search of plankton - "it's a once in a lifetime viewing of the animal.
Most plankton animals have a short lifespan - a few days is a long life
for many species. So chances are that no other human will ever see that
little animal again."
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