Marine plankton. Light microscopy footage, using darkfield illumination, of a sample of sea water with marine plankton. The object wriggling at centre in the second half of the clip is a sea squirt larva. Plankton consists of a wide range of microbes and microscopic animals and plants (including algae and protozoa) that drift and float in water, providing a vital source of food for larger animals. This sample was collected off the coast of Wales.