Aquatic Ecosystem

Introduction

More than 70% of the surface of the world is made up of water bodies. These water bodies are known to harbor a complex ecosystem of different creatures that interact with one another and the surrounding water body. An ecosystem that is contained within water is known as an aquatic ecosystem. Both biotic and abiotic components make up these ecosystems. Numerous different types of species, including microbes, plants, invertebrates, fish, etc., are supported by these ecosystems.

Types of Aquatic Ecosystems

Aquatic ecosystems are of two types depending on the salinity of the water.  Two types of Aquatic ecosystems are-

• Freshwater ecosystems: 

• • These ecosystems, which make up only roughly 2% of the earth’s surface. They have a salt concentration of less than 0.1%. Rivers, streams, lakes, etc. are included in this type of ecosystem.

• Marine ecosystems: Marine waterbodies occupy up to 75% of the earth’s surface. These habitats have a salt concentration of 3% and are the most common type of aquatic ecosystem found throughout the globe. The marine ecosystems consist of oceans, seas, and estuaries.

Features of Aquatic Ecosystem

• Zonation in aquatic biomes

• • Aquatic systems frequently exhibit both vertical and horizontal stratifications of both physical and chemical components.
  • The types of biodiversity and dominance of organisms in an ecosystem are determined by these zones.

• Lakes and oceans can be classified into photic and non-photic zones based on the penetration of light:
  • Photic zones are those parts of the surface and subsurface where light- penetration is high. These regions are well-lit and show great biodiversity. The epipelagic zone comes under this category.
  • Aphotic zones are darker regions. Due to higher depth and decreased sunshine penetration, the aphotic zones are dark areas and they include bathypelagic and abyssopelagic zones.
• The lakes are classified into the littoral zone and the limnetic zone based on their distance from the beaches.

• • Since it is closest to the shore, the littoral zone has strong sunlight penetration.Due to this rooted aquatic plant growth is seen and it  also supports a large number of species.
  • The off-shore, open water area of an aquatic body is known as the limnetic zone. In contrast to the littoral zone, light only reaches the surface and subsurface regions.

• The ocean is further classified into three zones: the oceanic zone, the neritic zone, and the intertidal zone depending on the distance from the shore.

 

• Lifeforms

• Based on their position in the food chain, the lifeforms in aquatic ecosystems can be classified as producers (phytoplankton and plants), consumers (zooplankton, invertebrates, and fish), and decomposers (microorganisms).
• Based on their habitat within the environment, they can also be classified as periphyton, plankton, neuston, nekton, and benthic.
• The littoral zone is where rooted and floating plants can be found in freshwater habitats.
• Planktons, bacteria, fish, and other aquatic lifeforms predominate in the limnetic zone whereas invertebrates live in the benthic zone.
• Worms, clams, crabs, echinoderms, and other organisms can be found in the ocean’s intertidal zones, whereas phytoplankton and zooplanktons, as well as krill, jellyfish, fish, squids, turtles, and mammals, can be found in the ocean’s pelagic zones.

 

• Thermal stratification 

According to changes in temperature, aquatic habitats frequently have layers. Thermal stratification refers to this change in temperature with depth in an aquatic body.  During summer, the upper layer of water becomes significantly warm and less dense, while the lower layers remain cooler, leading to stratification.Epilimnion, Metalimnion,  and Hypolimnion are the names of the several strata.

• Seasonal changes in water temperature (Lake turnover)

As a result of shifting temperature profiles, many lakes experience seasonal mixing of their water, which results in a cyclical pattern.

During the spring and fall, this turnover allows oxygen-rich water to reach the lake’s bottom areas while also bringing nutrient-rich water to the surface.

• Available nutrients

Freshwater habitats can be classified as oligotrophic, mesotrophic, or eutrophic lakes depending on the amount of nutrients that are available to them. Oligotrophic lakes have more nutrients,  mesotrophic lakes have comparatively fewer nutrients and eutrophic lakes hthe ave least nutrients.

• Dissolved Oxygen(DO)

The water’s temperature affects the oxygen saturation levels. The higher the oxygen levels, the lower the temperature. Fish and other aquatic life are threatened by low amounts of dissolved oxygen. DO determines the richness of aquatic habitat.

Functions of Aquatic Ecosystem

• The aquatic ecosystem is a vital resource that sustains a wide range of creatures, including mammals, invertebrates, and microbes like bacteria and algae.
• An essential connection between the hydrosphere, lithosphere, and atmosphere is provided by the water bodies.
• A significant amount of the planet’s rainfall is caused by water evaporating from the oceans.
• Photosynthesis is carried out by marine photosynthetic bacteria and algae.
• 50 percent of the annual photosynthesis is produced by the ocean.
• Climate change and regional and planetary wind patterns are known to be influenced by oceans and their winds.
• The microbial decomposers that break down organic materials include bacteria and some types of fungi.
• The microorganisms that live in aquatic ecosystems ensure that nutrients are continuously cycled.
• The aquatic systems’ inhabitants, such as fish and other invertebrates, provide food and boost the economy.
• These aquatic ecosystems serve as water purification systems naturally.
• They aid in controlling floods and pollution
• Aquatic environments are used for recreation and transportation.

Summary 

• An aquatic ecosystem comprises any ecosystem supported by a water body.
• Aquatic environments can be either freshwater or marine, depending on salinity.
• Depending on criteria like sunlight penetration, distance from the shore, depth, etc., aquatic habitats are classified into several zones.
• Additionally, each layer’s biodiversity is determined by zonation.
• There is thermal stratification in aquatic habitats.
• Benthic, neuston, nekton, and planktonic creatures are all supported by aquatic ecosystems.
• Aquatic ecosystems perform a wide range of tasks, such as promoting biodiversity, nutrient cycling, flood attenuation, influencing global climate change, etc.

Frequently Asked Questions

1. What are the types of freshwater ecosystems?
   Ans: There are two types of freshwater ecosystems, they are-

• The lotic ecosystem: Moving waterbodies, such as springs, rivers, and canals, are included in this type of freshwater ecosystem.
• The lentic system: This type of freshwater ecosystem includes stagnant water bodies such as ponds and lakes. These water bodies are home to a variety of organisms.

2. Describe the Pelagic zone and Benthic zones
   Ans: Pelagic zone- The pelagic zone is the off-shore, open-water region of an aquatic ecosystem. Phytoplankton, zooplankton, and nekton live there. Zooplankton is the main consumers of the oceans and lakes, while phytoplankton makes up the photosynthetic producers. The most common producers here are algae.
   Benthic zone-The lowest biological zone is the benthic zone. The organisms that reside on the bottom of lakes or oceans are called Benthos. These benthic animals and microbes gather food that sediments down from the photic layers, ie., they are filter feeders.

3. What is a neritic zone?
   Ans: The area of the ocean that is relatively shallow, measuring around 200 metres (660 feet) deep, is known as the neritic zone (or sublittoral zone). Physical oceanography sees it as the location where the oceanic system interacts with the coast, whereas according to marine biology it is a part of the ocean, which forms a stable and illuminated environment for marine life, from plankton up to giant fish and corals to grow and survive.