In an Antarctic ecosystem, phytoplankton are the main producers. A
species of zooplankton, called krill, are the primary consumers. To some
extent, fish, penguins, seals, whales, and other animals of the ecosystem
depend on krill to survive. Which of these is a biotic factor in this
ecosystem?
A. the amount of ice at any given time
B. che amount of salt in the ocean water
C. the temperature of the air and water
D. the size of the krill population