Plankton is one of the most important components of our oceans, lakes, and rivers. If we were to examine a body of water under a microscope, we would discover an incredible variety of planktonic organisms drifting amidst the movement of currents and waves. These tiny organisms are the foundation of all aquatic life, from the smallest creatures to large marine mammals, and their importance is not limited to the marine ecosystem; they also play a crucial role in regulating the climate and maintaining the stability of terrestrial ecosystems. Plankton is divided into two main groups: phytoplankton, composed of photosynthetic organisms that produce oxygen, and zooplankton, which feeds on phytoplankton and serves as food for other aquatic life. Despite its small size, plankton is not only key to the food chain but also plays a vital role in mitigating climate change by absorbing large quantities of carbon dioxide.
What is plankton and where does it come from?
The term plankton The term “plankton” originates from the Greek word “planktos,” meaning “wanderer” or “vagrant.” This name perfectly describes these microscopic organisms, which cannot move on their own and depend on water currents to drift. The German scientist Victor Hensen was the first to use the term in 1887 to refer to this floating community of aquatic organisms that inhabit both oceans and freshwater. Although most plankton is microscopic, some species, like jellyfish, can reach larger sizes. Due to the diversity of species, it is estimated that they number in the trillions in the oceans, and their presence is even greater in cold seas far from the equator.
Classification of plankton
Plankton is classified mainly according to its diet and size. Here are the main types:
- Phytoplankton: Phytoplankton is the plant plankton that produces its own food through photosynthesis. Its most abundant components include unicellular algae, diatoms and cyanobacteria. Phytoplankton is essential as it contributes greatly to the production of more than 50% of the oxygen we breathe.
- zooplankton: This is the group of small animals that drift with the currents. It is composed of organisms such as copepods and jellyfish, as well as fish larvae and crustaceans. This type of plankton feeds on phytoplankton and is the food source for many fish and marine mammals.
- Bacterioplankton: Composed of bacteria, these organisms play a key role in the decomposition of organic matter and the recycling of nutrients, allowing the reuse of elements such as carbon, nitrogen and phosphorus.
- Virioplankton: Aquatic viruses that play a role in the regulation of planktonic diversity and also in biogeochemical cycles.
Biogeochemical cycles and the ‘biological carbon pump’
Plankton plays a fundamental role in the biogeochemical cyclesespecially in the carbon cycle. During photosynthesis, phytoplankton capture carbon dioxide from the atmosphere, converting it into organic matter. When they die, many of these phytoplankton cells sink to the ocean floor, carrying the captured carbon with them—a phenomenon known as the “biological carbon pump.” This mechanism is crucial for mitigating the effects of climate change, as it effectively removes large amounts of CO₂ from the atmosphere. Zooplankton, by feeding on phytoplankton, also contributes to these cycles. Some of the carbon they consume is respired and returns to the water as CO₂, while some is transformed into waste products that eventually sink as well.
Ecological importance of plankton
El plankton Not only is it the cornerstone of the food chain in aquatic ecosystems, but its impact on climate and fisheries resources makes it essential for life on the planet. Through photosynthesis, phytoplankton reduces carbon dioxide levels in the atmosphere and generates oxygen, directly contributing to global climate stability and the health of aquatic ecosystems. Zooplankton also plays a vital role by undertaking vertical migrations in search of food. These movements, which can reach depths of up to 500 meters, allow for the redistribution of nutrients throughout the water column, benefiting deep-sea species.
Impact of microplastics on plankton
One of the biggest challenges facing plankton today is pollution by microplasticsThese tiny fragments, less than five millimetres in size, are ingested by zooplankton and enter the aquatic food chain. In addition, microplastics can interfere with the photosynthetic processes of phytoplankton by blocking sunlight, thereby reducing their ability to produce oxygen.
Plankton as a bioindicator of water quality
Plankton is a bioindicator, meaning that their presence or absence can be used to assess water quality. For example, cladoceran species such as Daphnia are extremely sensitive to pollutants, and their disappearance can be a first warning sign of environmental degradation.
The role of plankton in climate regulation
In addition to its role in the food chain and biogeochemical cycles, plankton plays an essential role in the climate regulationPhytoplankton, during photosynthesis, produces a compound called dimethylsulfoniopropionate (DMSP), which decomposes into dimethyl sulfide (DMS). This gas is key to the formation of aerosols in the atmosphere, which aid in cloud formation. These clouds reflect solar radiation, cooling the Earth’s surface. This cycle is fundamental for regulating global temperatures, especially in coastal areas, and exemplifies the important role these tiny organisms play in global climate balance. Although plankton may seem insignificant individually, their collective action and the sheer volume they contain in the oceans make their impact on our planet immeasurable. From oxygen production to the base of the food chain, their influence is present in every aspect of life as we know it.