Every maritime ecosystem on the planet has marine organisms. They are a diverse collection of species, and their special physical traits enable them to survive in the harsh conditions of the ocean, including its extreme depths, pressure, and darkness. Some examples of common marine organisms include phytoplankton, zooplankton, seaweeds, seagrasses, and more. This article will explain to you about Marine Organisms which will be helpful in preparing the Environment Syllabus for the UPSC Civil Service exam.

Phytoplankton

• 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. Cyanobacteria, silica-encased diatoms, dinoflagellates, green algae, and chalk-coated coccolithophores are a few examples of frequent types.
• More than 60% of the oxygen produced by all plants is produced by 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.

Zooplankton

• Planktons that are heterotrophic and occasionally detritivores are called zooplankton.
• They are heterotrophic, which means they must eat other plants or animals because they are unable to make their own food. This specifically means that they consume phytoplankton.
• Zooplankton play an important role in the food web, nutrient recycling, and the transfer of organic matter from primary producers to secondary consumers such as fish.
• They are more abundant in mangrove waterways than in adjacent coastal waters, and a large proportion of mangrove juvenile fish are zooplanktivorous.
• The quantity of fish stock is determined by zooplankton.
• As a result, zooplankton communities are used to assess the productivity of the ecosystem in relation to its fishery resources, fertility, and health status.
• The zooplankton contains a wide variety of species, including the single-celled Radiolaria as well as the eggs or larvae of herrings, crabs, and lobsters.
• Protozoa and copepods, which are essential sources of food for larger animals, are examples of permanent plankton, or holoplankton.
• Holoplankton, also known as permanent plankton, includes copepods and protozoa, which are crucial sources of food for larger creatures.
• Young starfish, clams, worms, and other bottom-dwelling creatures are examples of temporary plankton, or meroplankton, which live and feed as plankton until they depart to develop into adults in their appropriate environments.

Zooplankton Groups

*To know more about the topic, click this link Zooplankton

Sea-Grass

• These are flowering plants that can be found on the seafloor and in our oceans.
• It belongs to the class of marine angiosperms. They frequently spend their entire lives underwater.
• They have tiny blooms and strap-like or oval leaves, and photosynthesis depends on sunshine.
• Despite the fact that seagrasses may grow on anything from mud to rock, muddy and sandy substrata are where the majority of the rich green seagrass beds are found.
• Important Species: Sea Cow Grass (Cymodocea serrulata), Thready Seagrass (Cymodocea rotundata), Needle Seagrass (Syringodium isoetifolium), Flat-tipped Seagrass (Halodule uninervis), Spoon Seagrass (Halophila ovalis), and Ribbon Grass are a few of the significant seagrass species (Enhalus acoroides).
• These are currently in danger despite once being in great abundance in the Gulf of Mannar region.

Sea-Grass

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Seaweeds

• The term "seaweed" is used to refer to a huge variety of marine plants and algae that can be found in rivers, lakes, and other bodies of water in addition to the ocean.
• The term refers to a few more varieties of macroalgae from the Rhodophyta (red), Phaeophyta (brown), and Chlorophyta (green) families.
• Other species, including planktonic algae, play a crucial role in collecting carbon, creating at least 50% of Earth's oxygen.
• Seaweed species like kelps provide crucial nursery habitats for fisheries and other marine creatures and hence protect food sources.

Seaweeds

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Conclusion

Due to the high salt concentrations, marine organisms that dwell in marine habitats encounter significant challenges. Ions are generally widely distributed in saltwater. As a result, the body's salt levels become excessive. In order to remove the surplus salt ions and preserve an internal equilibrium, marine organisms produce urine that is highly concentrated.

FAQs

MCQs

1. Which of the following is a primary producer in the marine food web?

A) Fish
B) Zooplankton
C) Phytoplankton
D) Sharks

2. What is the main consequence of ocean acidification on marine organisms?

A) Coral reef bleaching
B) Loss of habitat for marine species
C) Damage to calcium carbonate structures
D) Increased marine biodiversity

3. Which of the following is most directly impacted by rising ocean temperatures?

A) Coral reefs
B) Fish populations
C) Coastal cities
D) Sea turtles

4. What is the primary function of zooplankton in the marine food web?

A) Primary production of energy
B) Grazing on phytoplankton
C) Shelter for fish larvae
D) Feeding on marine predators

5. How do marine organisms help mitigate climate change?

A) By absorbing CO2 during photosynthesis
B) By increasing the global temperature
C) By releasing oxygen into the atmosphere
D) By reducing human carbon emissions

GS Mains Questions and Model Answers

Q1: Discuss the importance of marine organisms in regulating the Earth's climate and supporting biodiversity.

Answer: Marine organisms play a critical role in regulating the Earth’s climate and supporting biodiversity. Phytoplankton, as primary producers, are responsible for absorbing significant amounts of carbon dioxide through photosynthesis, which helps in mitigating climate change. Additionally, marine organisms such as fish, corals, and mollusks contribute to the overall biodiversity of the oceans. Coral reefs, for example, provide habitat for a vast number of species, thus maintaining marine biodiversity. The loss of marine organisms, particularly due to human activities such as overfishing, pollution, and climate change, threatens both climate stability and biodiversity, leading to cascading effects on global ecosystems.

Q2: How do human activities impact marine ecosystems and what measures can be taken to protect marine organisms?

Answer: Human activities, including overfishing, pollution, and the emission of greenhouse gases, have a significant negative impact on marine ecosystems. Overfishing depletes fish populations, disrupting the food web. Pollution, including plastic waste and oil spills, harms marine organisms and destroys habitats. Climate change, through ocean warming and acidification, stresses marine life, particularly coral reefs and shell-forming organisms. To protect marine organisms, it is essential to enforce sustainable fishing practices, reduce plastic waste, implement marine protected areas (MPAs), and take immediate action to reduce global carbon emissions.

Q3: Analyze the role of marine organisms in the global carbon cycle and their impact on climate change mitigation.

Answer: Marine organisms, particularly phytoplankton, are crucial in the global carbon cycle. They absorb carbon dioxide during photosynthesis, helping to lower atmospheric CO2 levels. The carbon absorbed by these organisms is transferred through the food web to higher trophic levels, and a portion of it eventually sinks to the ocean floor, thus storing carbon in the deep ocean. This natural carbon sequestration process plays a vital role in regulating global carbon levels and mitigating climate change. However, human-induced changes such as ocean acidification and warming threaten the ability of marine organisms to perform these functions effectively. Protecting marine ecosystems is essential to maintaining this critical role in climate change mitigation.

Previous Year Questions on Marine Ecosystems

1. UPSC CSE Prelims 2020:

Question: Which of the following marine organisms plays a key role in the process of carbon sequestration?

A) Fish
B) Sea turtles
C) Phytoplankton
D) Coral reefs

Answer: (C)

Explanation: Phytoplankton play a vital role in carbon sequestration by absorbing CO2 through photosynthesis, which helps mitigate climate change.

2. UPSC CSE Mains 2019 (GS Paper 3):

Question: Evaluate the effects of climate change on marine organisms and suggest measures to protect marine biodiversity.

Answer: Climate change has profound effects on marine organisms, including ocean warming, acidification, and habitat loss. These changes disrupt marine ecosystems and threaten biodiversity. To protect marine biodiversity, measures such as reducing carbon emissions, establishing marine protected areas (MPAs), and promoting sustainable fishing practices must be implemented. Additionally, global cooperation is essential to address the environmental impacts of climate change on marine life.