The word plankton means, “that which drifts”. By this token a colossal number of marine creatures, both plants and animals, vertebrates and invertebrates, qualify as members of this extraordinarily important mass of life that glides and wanders, flaps and flips, floats and flies, sinks and swims within the oceans. The very biggest jellyfish weigh more than half a tonne, some deep sea relatives of the Portuguese Man-O-War would cover a football pitch and some of the colonial salps are the size and shape of ballistic missiles.

Much of plankton is small. Diminutive though these forms are in size, their habits, colour, life cycles and relationships are some of the most bizarre in the animal kingdom and many billions directly comprise the staple diet of the ocean’s very largest inhabitants.