Are Plankton an Animal or a Plant?

Plankton are microscopic organisms that play an important role in the marine ecosystem.

Plankton are microscopic organisms that play an important role in the marine ecosystem. They are food for shelled animals and fish. Plankton refers to both plant- and animal-like beings that float along the sea's tides and currents. Their name is derived from the Greek word, “planktos,” meaning “drifter” or “wanderer.”

There are two main types of plankton: phytoplankton (plant-like beings) and zooplankton (weak swimming animal-like beings). Some of them are babies that may grow into strong-swimming, non-planktonic adults, whereas others remain plankton throughout their lives. Jellyfish and ocean sunfish are also considered plankton because they are feeble swimmers. Most of the plankton in the ocean are plant-like beings. There are also two smaller types of plankton found floating in the sea, namely, bacterioplankton (bacteria) and microplankton (viruses).

Phytoplankton synthesize their own food through a pigment called chlorophyll by using the sun’s energy. This process is called photosynthesis. Phytoplankton are therefore found in the top layers of the ocean because it is the best site to harness the sun’s energy. Phytoplankton can also obtain nutrients from their surroundings to survive, such as phosphate, nitrate, and calcium. Zooplankton that feed on the phytoplankton are also commonly found in the top layers or ocean. Zooplankton then become food for fish and other larger marine species. Plankton have evolved many different ways to stay afloat. They have spikes to help distribute their weight over a large surface area and help stay afloat. Some other organisms in the ocean such as Copepods produce oil to keep them afloat.

Like plants, phytoplankton take in carbon dioxide and release oxygen accounting for about half of the photosynthesis on the planet. This makes phytoplankton the most important producers of oxygen. Plankton is essential for the marine food chain. Climate change and rising sea temperatures can affect plankton populations, killing them. This affects the food source for many other marine creatures. Very clear water typically has less plankton. Green- or brown-colored water has higher plankton content.

Although plankton are essential for marine ecosystems, too much plankton in one area can create a serious environmental problem. When a plankton population suddenly grows, it is called a “bloom”. A plankton bloom can release dangerous toxins, lead to a red tide, or cause a serious algal bloom. These conditions can cause fish contamination and high fish mortality and damage to the marine ecosystem. Contaminated fish may be caught and consumed by humans, causing serious illnesses and death.