Thursday, September 22, 2011

Beauty at the bottom of the food chain

Secret Lives of Plankton Revealed in Microscopic Glory The diversity of these ocean drifters, crucial to all life on Earth, is revealed in a new book

From WSJ

Look at the very bottom of the food chain and you will find them.
Plankton are organisms with a name derived from the Greek adjective planktos, meaning “errant”, “wanderer” or “drifter”.
Plankton include microscopic plant-like cells (phytoplankton) and the tiny animals that eat them (zooplankton), and they typically flow with ocean currents.
Though diminutive, their impact on ocean health is monumental– they remove carbon dioxide from the sea and provide our atmosphere with oxygen.

The plankton food web extends from photosynthesizing phytoplankton to whales, seabirds, crabs, worms and starfish of the seabed and thus supports the entire marine food chain.
Despite this important role in the ecosystem, plankton remain mysterious to scientists who have not charted the full extent of their adaptations and biodiversity.
As the plankton habitat alters with sea surface temperatures warming due to global climate change, the plankton are changing their locations with ramifications for the marine food chain.

A glossy new photography book, Ocean Drifters, by Richard R. Kirby, from Firefly Books explores this rarely seen world.
Dr. Kirby and his team collected samples from the Northeast Atlantic and examined them once back in the laboratory.
The plankton are collected in a fine net that can be towed vertically through the water column, or towed obliquely just below the surface.
A bottle at the end of the net collects the plankton.
In the lab the samples were photographed, alive, using a Zeiss microscope.
To create these dramatic photographs, Dr. Kirby utilized dark field microscopy, an illumination technique that highlights the specimen and allows the surrounding area to go dark.

All photographs courtesy Dr Richard Kirby, Royal Society Research Fellow at Plymouth University/Firefly Books.

Single-celled Acantharea and their zooxanthellae.

The zooxanthellae live inside the Acantharea and provides the Acantharea with carbon food source from their photosynthesis, and in return the microalgae gain nutrients from their host.
Although Acantharea can be very abundant in the plankton, little is known about their ecology because they are fragile and difficult to sample.

The eye of this young rockling fish will help it find its food and avoid predators during its short life in the plankton, before it swims to the sea bed where it will live its adult life beneath a rock.

The by-the-wind sailor, Velella velella seen in a side view, bird’s eye view, and fish’s-eye view.

The V. velella is a predatory jellyfish that uses it’s stiff vertical vane of chitin as a diminutive sail to catch the wind.
Air filled tubes form an oval float below the vane that provide bouyancy.
In some V. velella the vane, which makes the animal sail at 45 degrees to the wind, is angled to the right, and in others it is angled to the left.
The prevailing winds sort these two forms so that a particular variant dominates on opposite sides of the Atlantic and Pacific Oceans.

The larva of Luidia sarsi (starfish)

When the yellow-orange juvenile starfish detaches from the larval body and sinks to the sea bed, the rest of the larval body may then continue to swim in the plankton for more than a month before it dies.

A dragonet larva, Callionymus lyra.

Plankton is a critical food source for young fish like this one.

Larvae of a sea anemone

Links :
  • YouTube : Weird creatures feed on plankton - Blue Planet - BBC
  • NOAA : COPEPOD, the global plankton database

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