Plankton

3. , A rapid increase in the population of planktonic organisms, often causing discoloration of the water.
5. , Organisms that obtain their energy by consuming other organisms.
6. , Pertaining to the bottom of a body of water; organisms living on or in the substrate.
8. , Planktonic organisms that spend only a part of their life cycle as plankton.
9. , Larger-sized plankton, visible under a microscope.
10. , Unicellular algae that can be both phytoplankton and sometimes bioluminescent.
12. , Small animals that feed on phytoplankton or other zooplankton.
15. Tide , A bloom of harmful, often toxic, phytoplankton that can lead to the discoloration of water.
17. , Planktonic organisms that spend their entire life cycle in the planktonic phase.
18. , Microscopic organisms that drift or float in aquatic environments.
19. , Free-swimming aquatic organisms, such as fish and squid, capable of active movement.
20. , Zooplankton that remain in the planktonic phase throughout their entire life cycle.

1. , Organisms that produce their own food through processes like photosynthesis.
2. Depth , The depth in the water column where the rate of photosynthesis equals the rate of respiration.
4. , Small crustaceans that are a common type of zooplankton.
7. , Extremely small-sized plankton, smaller than microplankton.
11. , A close and long-term interaction between different biological species.
13. , Microscopic, photosynthetic organisms that form the base of the aquatic food chain.
14. Level , The position an organism occupies in a food chain, indicating its feeding relationship to other organisms.
16. , A type of phytoplankton with a silica-based cell wall, often shaped like a glass shell.