Phytoplanktons produce more than 60% of all the oxygen produced by plants on the entire planet. Phytoplanktons are autotrophic (self-feeding) members of the plankton community and a vital component of freshwater and ocean ecosystems. They serve as the foundation of the entire marine food chain. To survive, phytoplankton is dependent on environmental nutrients including calcium, phosphate, and nitrate. Cyanobacteria, silica-encased diatoms, dinoflagellates, green algae, and chalk-coated coccolithophores are common examples of phytoplanktons. The factors that affect the biodiversity of phytoplanktons include Light, Nutrients, Temperature, Salinity, Distribution, Grazing by Zooplankton, and more. This article will explain to you about Factors affecting the Biodiversity of Phytoplanktons which will be helpful in preparing the Environment Syllabus for the UPSC Civil Service exam.

What are Phytoplanktons?

• Phytoplankton, which is derived from the Greek words Phyto (plant) and Plankton (made to wander or drift), refers to microscopic plant organisms that dwell in freshwater and saltwater aquatic habitats.
• Protists, bacteria, and single-celled plants make up some phytoplankton.
• All phytoplankton have chlorophyll, which they use to absorb sunlight and convert it into chemical energy, just like land plants.
• They exhale oxygen while consuming carbon dioxide. All phytoplankton photosynthesize, but some also consume other species to gain additional energy.
• All seas and oceans, including the Polar Regions, have these microalgae in the littoral zones.
• They act as "pasture grounds" in the aquatic environment and have biomass that is several times bigger than the combined biomass of all plants on land.

Phytoplanktons

Factors Affecting Biodiversity of Phytoplanktons

Light

• Only the topmost ocean layers, where there is enough light for photosynthesis to occur, are home to phytoplankton.
• Light intensity affects the rate of photosynthetic activity there.
• Light fluctuation may be regarded as stress alleviation at high light intensities and stress relief at low light intensities.
• Accordingly, depending on where the variation falls in its range, the light variability may be a source of relief or stress.

Nutrients

• For development and reproduction, nitrogen and phosphorus are the two main inorganic nutrients needed by phytoplankton.
• Significant amounts of silicate (SiO2) are also needed by diatoms and silicoflagellates.
• Some phytoplankton has the ability to fix nitrogen and can thrive in environments with low nitrate concentrations.
• Additionally, because iron concentrations are so low, phytoplankton development is restricted in a lot of the ocean because they need trace levels of iron.

Temperature

• The influence of temperature on changes in photosynthetic output occurs in conjunction with other factors.
• In general, when the temperature rises, photosynthetic rates rise as well, but after a certain point, they start to decline sharply.
• In temperate latitudes, temperature and illumination have an impact on the seasonal variation in phytoplankton production.
• In addition, at low temperatures, phytoplankton grows faster than herbivorous grazers do.

Salinity

• Salinity is another factor that is known to affect the primary productivity of phytoplanktons in addition to light and temperature.
• Lower salinity revealed very minor effects, but increasing CO2 levels significantly accelerated the growth of tiny phytoplankton.
• Salinity variations significantly impacted both freshwater and brackish water phytoplankton, respectively.
• Green algae and diatoms reacted to a rise in salinity similarly in the freshwater phytoplankton populations from the river and the freshwater tidal reaches.

Grazing by Zooplankton

• One of the key elements affecting the size of the phytoplankton standing crop and, consequently, the pace of production, is the grazing rate of zooplankton.
• Grazing results in the most significant losses of phytoplankton biomass in the pelagic environment, making it a powerful selection pressure for characteristics that reduce grazing losses.
• It is not surprising that several constitutive or inducible defense mechanisms, such as preventing ingestion, avoiding digestion, discouraging grazers, or even eliminating zooplankton, have evolved in phytoplankton.
• Cells must also compete with competitors while managing to stay suspended.

Distribution of Phytoplankton

• The marine phytoplankton found in the world's oceans is not spread evenly.
• The tropics and subtropics have concentrations that are 10 to 100 times lower than those found at high latitudes, with the exception of upwelling regions on continental shelves.
• The high amounts of exposure to solar UV-B radiation that often occur within the tropics and subtropics may play a role in phytoplankton dispersion in addition to nutrients, temperature, salinity, and light availability.
• The euphotic zone, the upper layer of the water column where there is enough sunshine to support net production, is the only place where phytoplankton productivity is possible.
• The movement of the wind and waves affects where the organisms are located in the euphotic zone.

Importance of Phytoplanktons

Ocean Health

• The position of phytoplankton at the base of the marine food chain is largely responsible for their relevance.
• Phytoplankton is the primary food supply for small fish, some larger species of fish, and whales.
• Later on, in the food chain, these fish become prey for larger fish and marine animals.
• Shellfish and other bottom-dwelling organisms are nourished by dead phytoplankton that sinks to the ocean floor.
• Population decline of phytoplankton can have detrimental effects on the overall marine ecosystem.
• Variations in the phytoplankton population may be a sign of additional ocean issues, like excessive pollution.

Influence on Global Climate

• The health of the phytoplankton population has an impact on the global climate.
• On Earth, phytoplankton is responsible for around half of all photosynthesis.
• As a result, they serve as a significant carbon dioxide sink, removing the gas from the atmosphere and replacing it with oxygen.
• In this way, the phytoplankton population plays a significant role in preventing global warming and maintaining the planet's overall atmospheric health.

Influence on Human Health

• The significance of plankton extends beyond the water since it affects both the health of the oceans and the climate.
• This in turn affects how well people are able to live. Sardines are one example of a fish that consumes phytoplankton and provides food for both humans and larger fish.
• Commercial fishing provides food and works for numerous communities across the world.
• The fish population and therefore commercial fishing would vanish without phytoplankton.
• Global warming will have a significant influence on us as well, and phytoplankton plays a crucial part in this process, which makes them essential to our survival.

Population Variance

• Scientists are worried that the ozone hole could affect the phytoplankton population by exposing it to the sun's harmful rays, which could lead to their death.
• Additionally damaged by ocean contaminants, such as runoff from industries and agriculture, phytoplankton is frequently missing from areas with high pollution concentrations.
• Phytoplankton is at risk from changes in the climate and wind patterns because they are nourished by nutrients that well up from the ocean floor and iron that the wind deposits on the ocean's surface.
• The current upwellings that feed the phytoplankton and transport necessary minerals to the ocean are driven by winds.
• The sunlight can be reduced by the dust from drier climate conditions, which makes it harder for phytoplankton to perform photosynthesis and live.

Conclusion

Scientists from all over the world are conducting research to learn more about the phytoplankton populations and the further factors affecting them. For decades, scientists have observed how the colour of seawater shifts from blue to green as the phytoplankton population advances. Using NASA satellite photos, scientists are now able to assess the well-being and growth rates of the organisms. The aim is to understand this tiny organism, which is essential to earthly existence, better.

FAQs

Question. What are phytoplanktons?

Question. Why is biodiversity important for phytoplanktons?

Question. What are the main factors that affect the biodiversity of phytoplanktons?

Question. How does nutrient availability affect phytoplankton biodiversity?

Question. How does climate change impact phytoplankton biodiversity?

MCQs

1. Which of the following is a primary factor affecting phytoplankton biodiversity?

A) Ocean depth

B) Availability of sunlight

C) Ocean currents

D) Wind speed

2. What role do nutrients play in the biodiversity of phytoplankton?

A) They increase competition among species

B) They enhance phytoplankton growth and diversity

C) They inhibit photosynthesis

D) They decrease primary production

3. How does water salinity influence phytoplankton biodiversity?

A) Salinity has no effect on phytoplankton

B) Phytoplankton thrive in freshwater only

C) Different phytoplankton species are adapted to varying salinity levels

D) Salinity makes water too toxic for any phytoplankton species

4. Which of the following is a consequence of excess nutrient input in aquatic ecosystems?

A) Decreased phytoplankton diversity

B) Reduced water temperature

C) Increased oxygen levels

D) Algal blooms

5. How does climate change affect phytoplankton diversity?

A) It has no effect on phytoplankton

B) It can alter temperature, nutrient availability, and species competition

C) It increases the growth of all phytoplankton species equally

D) It only affects marine ecosystems

GS Mains Questions and Model Answers

Q1: Discuss the factors affecting the biodiversity of phytoplankton in freshwater and marine ecosystems.

Answer: Phytoplankton biodiversity in both freshwater and marine ecosystems is influenced by factors like nutrient availability, light, temperature, salinity, and pH. Excess nutrients from agricultural runoff can cause eutrophication, leading to harmful algal blooms that reduce diversity. Changes in water temperature due to climate change also affect phytoplankton distribution by favoring certain species over others. Phytoplankton are also sensitive to ocean acidification, which can disrupt their ability to photosynthesize.

Q2: Explain the ecological importance of phytoplankton in maintaining aquatic biodiversity.

Answer: Phytoplankton form the base of the aquatic food web, providing energy to a wide range of organisms from small zooplankton to large marine mammals. Their ability to fix carbon through photosynthesis also plays a significant role in regulating the Earth's carbon cycle. Healthy phytoplankton populations are crucial for maintaining ecosystem functions like oxygen production, nutrient cycling, and supporting aquatic food chains.

Q3: How does pollution affect phytoplankton biodiversity in aquatic ecosystems?

Answer: Pollution, particularly from agricultural runoff (nutrient pollution), industrial waste, and plastic debris, can significantly affect phytoplankton biodiversity. Excessive nutrients can lead to eutrophication, which promotes the growth of a few fast-growing species, often at the expense of others. This can reduce overall biodiversity and disrupt the balance of aquatic ecosystems. Pollution can also introduce toxins that harm phytoplankton directly, further reducing diversity.

Previous Year Questions on Phytoplankton

1. UPSC CSE 2017

Question: "Explain the factors influencing the primary productivity of aquatic ecosystems and its relevance to biodiversity."

Answer: Primary productivity in aquatic ecosystems is influenced by factors like light, temperature, nutrients, and the presence of phytoplankton. Phytoplankton contribute significantly to primary productivity by converting solar energy into chemical energy. This, in turn, supports the entire food chain, making phytoplankton biodiversity crucial for maintaining ecosystem health and species diversity.

2. UPSC CSE 2020

Question: "Discuss the impact of climate change on aquatic ecosystems and their biodiversity."

Answer: Climate change affects aquatic ecosystems by altering temperature, salinity, nutrient levels, and the frequency of extreme weather events. Warmer waters can lead to the dominance of certain phytoplankton species, reducing overall biodiversity. Additionally, ocean acidification impacts the growth and survival of many species, affecting the health of ecosystems that depend on phytoplankton and other marine organisms.