What Lies Beneath: The Secret World of Planktons

In 1899, a German biologist and philosopher by the name of Ernst Haeckel (1834-1919) literally drew the world’s attention to a group of extremely small and intricate oceanic microorganisms know as radiolarians. Together with diatoms and dinoflagellates, these tiny organisms (most with diameters of less than 0.2 mm) comprise a group of plankton known as zooplankton (to be distinguished rom phytoplankton or “plant planktons). Haeckel drew and painted hundreds of pages of radiolarians that no one had previously taken serious notice and published his illustrations in Art Forms in Nature (1899), which is arguably the first coffee table book on nature. Below are a sample of his exquisite drawings.

The spectacular exoskeletal lattices of radiolarians are made from the crystallization of a hard mineral at the junctions of vesicles and resemble the roughly hexagonal shapes of soap bubble layers. The ubiquity of the hexagon in nature testifies to its usefulness as a hexagonal shape that best fills a plane with equal size units, thus leaving no wasted space.

Phytoplanktons, a group of free-floating microalgae, are the most common variety of planktons found in the oceans. Despite their tiny size, they play an out-sized role in regulating the earth’s atmosphere, generating about half the atmosphere’s oxygen, which is as much per year as all land plants. They also form the base of virtually every ocean food web. In short, they make most other ocean life possible.

While planktons as a group may transform the ocean, the atmosphere and the terrestrial environment, they inhabit a world that is barely known and which has only recently been understood to be as complex and diverse as anything found in the rainforests. Thanks to new photographic techniques derived from medical imagery, we can now see the astonishing richness of what is known as the “drifting world” in all its glory. Here is proof.

Plankton collected during winter in the bay of Villefranche-sur-Mer, using a 0.2mm mesh net. The longest organism here is the pteropod mollusc, measuring about 7mm.
Diatom and dinoflagellate bloom in Toba Bay. Diatoms are a type of plankton called phytoplankton, the most common of plankton types. A unique feature of diatom anatomy is that they are surrounded by a cell wall made of silica. Dinoflagellates are mostly marine planktons though they also inhabit freshwater habitats.
Diatoms in chains: Thalassionema nitzschioides is a pennate diatom. The cells, each measuring 10 to 20 microns, are joined together in chains by mucilaginous links.
Looking like an exotic glass bottle, this is the paddle of a Lysmata zoea larva. Photo: Ryo Minemizu.
Hyperiidea on Nausithoe jellyfish. Photo: Ryo Minemizu.
Plankton collected in Shimoda bay in autumn with a 0.2mm mesh net. Organisms measure a maximum of 5 to 7mm.
Gripping the inside of its barrel with two front and two hind legs, this phronima moves its tail to swim with the currents.

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