All 3 Uses

plankton
in
The Old Man and the Sea
(Auto-generated)

As he looked down into it he saw the red sifting of the plankton in the dark water and the strange light the sun made now.†
p. 35.3

plankton = tiny or microscopic plants and animals that float in water
...and he was happy to see so much plankton because it meant fish.
p. 35.4 *
The myriad flecks of the plankton were annulled now by the high sun and it was only the great deep prisms in the blue water that the old man saw now with his lines going straight down into the water that was a mile deep.†
p. 40.7

Definitions:

(1) (plankton)
tiny or microscopic plants and animals that float in water such as oceans or lakes and are eaten by larger animals such as fish
(2) (meaning too rare to warrant focus)