Aquatic-Ecosystem

Aquatic or Hydrospheric Ecosystem, Eutrophication

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Aquatic or Hydrospheric Ecosystem

A hydrospheric ecosystem is a “system in the water where living and non-living elements or biotic and abiotic factors exchange materials and transfer of energy also takes place within water“.

Salt-water oceans and seas are the largest ecosystems on the earth forming about 71% of its surface. Freshwater ecosystems, in contrast, covers less than 1%. The distinct properties of water lend some common features to water or Hydrospheric ecosystems are the following:

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1.Temperature:

Water changes its temperature level slower than air, so the temperature in the aquatic ecosystem is more moderate to support life.

2.Absorption of energy:

Although water may appear quite transparent, it takes in a significant quantity of light energy from the sun that sustains life. Even in the clearest water, the intensity of light declines rapidly with depth, so at the depth of 600 feet or more, a little light is left to support photosynthesis.

3.Nutrients

The nutrients in the marine environment tend to be concentrated near the bottom sediments supporting life where light levels frequently are too low to support photosynthesis.

4.Abundant water with appropriate temperature level

Water is an essential requirement for life. It is available generously in the marine ecosystem to support life. The significant aspects that determine the quantity and kind of life in water environments are energy and nutrient. Favorable temperature is present in the marine environment to carry out all metabolic procedures.

5.Productivity of Aquatic Ecosystem

The rate of production of new biomass during the unit time is called productivity.

Identification of productivity: The productivity can be indicated by the usage of CO2 and the release of oxygen in the process of photosynthesis.

Determination of productivity: The productivity of the aquatic community is generally determined by the light and nutrients. Light intensity and quality differ with the water depth, so the primary productivity also varies with the light. The quantity of nutrients also changes with the season. Performance likewise varies from zone to zone.

Zones in a Lake Ecosystem

Ecosystem-lake-zone

Freshwater lakes vary enormously in size, depth, and nutrient content, including unique life zones and temperature stratification i.e. fluctuations.

The distribution of life in lakes relies on:

  1. Access to light
  2. Access to nutrients
  3. Access to place for attachment

The lake ecosystem can be divided into three primary zones.

1.Littoral zone (Near-shore)

The shallow water region near the shore, with light permeating to the bottom, is called the littoral zone.

Plants in this zone

Plants find plentiful light, anchorage, and sufficient nutrients from the bottom sediments. Plants in littoral zone ecosystems are the most varied; water lilies and entirely submerged vascular plants and algae flourish at the inmost area of the littoral zone. The plants of this zone trap sediments carried by stream, increasing the nutrient material in this region. Living among the anchored plants are tiny organisms called plankton. These can be divided into two groups.

Phytoplankton (Greek “drifting plants”): these consist of photosynthetic Protista, bacteria, and algae.

Zooplankton (Greek “drifting animals”): such as protozoa and tiny crustaceans.

Animals in this zone

The greatest variety of animals in the lake is likewise found in this zone. Littoral invertebrate animals consist of small crustaceans, insect larvae, snails flatworms, Hydra and littoral vertebrates include frogs, marine snakes, and turtles.

As the water increases in depth further from the shore, plants are not able to anchor to the bottom and still gather sufficient light for photosynthesis. This open water area is divided into two areas: the upper limnetic zone and the lower profundal zone.

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limnetic-profundal-zone

2.Limnetic zone

The open water zone far from the coast/shore to the depth of reliable light penetration is called the limnetic zone. In this zone, enough light penetrates to support photosynthesis.

Life in the Limnetic zone:

This zone is inhabited by phytoplankton, zooplankton, and fishes.

Phytoplankton: includes cyanobacteria i.e. blue-green algae, dinoflagellates, euglena, and volvox which serve as producers.

Zooplankton: consists of protozoa and small crustaceans.

Fishes: The fishes are found entirely in a totally free-swimming zone which consume protozoa and small crustaceans.

 

Profundal zone

The zone of the deep water under the limnetic zone which is beyond the reach of light penetration is called the profundal zone.

The light is insufficient to support photosynthesis. So, the organisms of this zone are mainly nurtured by fragments that fall from the littoral and limnetic zone and by incoming sediment. Decomposers and detritus feeders, such as snails and certain insect larvae, bacteria, fungi, and fishes, populate it.

Profundal-zone

The intervention of Man in Aquatic Ecosystem
Eutrophication

Human activities may considerably speed up the procedure of eutrophication (adequate nutrition) because nutrients are brought into lakes from farm feedlots and sewage.

Even if solid wastes are removed, water released from the sewage treatment plants is typically abundant in phosphate and nitrates dissolved from wastes and cleaning agents. Rainwater washes of fertilizer from fields where the manure of countless cattle is accumulated. The water for that reason becomes extremely enriched.

The added nutrients support the excessive development of phytoplankton. Producers like blue-green algae form a scum on the lake surface, depriving the submerged plants of sunlight; as a result, they die. The dead plant’s bodies are decomposed by bacteria, utilizing the oxygen present in the water, deprived of oxygen, fish, snails, and insect larvae also die.

Eutrophication

Their rotting bodies fuel more bacterial growth thus, causing more depletion of oxygen. Even without oxygen, particular bacteria (anaerobic bacteria) that produce nasty-smelling gases flourish.

Although it is full of life and nutrients, a contaminated lake smells bad. The majority of the trophic levels consisting of the fish are gotten rid of and the bacteria and blue-green algae dominate the ecosystem.

Another really severe reason for contaminated water is the acid produced by the burning of fossil fuels, which presents a different danger to the fresh-water environment. Only a few of organisms can hold up against the low pH of acidified lakes.

acidified-lakes

 

Multiple Choice Questions (MCQs) with Answers:

  1. What is a hydrospheric ecosystem?
    • A. Terrestrial ecosystem
    • B. System in the air
    • C. System in the water
    • D. Desert ecosystem
    • Answer: C
  2. What percentage of the Earth’s surface do salt-water oceans and seas cover?
    • A. 50%
    • B. 61%
    • C. 71%
    • D. 81%
    • Answer: C
  3. Why does the temperature in the aquatic ecosystem change more slowly than in the air?
    • A. Water has a higher specific heat
    • B. Water is transparent
    • C. Water is less dense
    • D. Water has a lower boiling point
    • Answer: A
  4. What is the primary factor determining the quantity and type of life in aquatic environments?
    • A. Temperature
    • B. Nutrients
    • C. Energy and Nutrients
    • D. Sunlight
    • Answer: C
  5. What is productivity in the context of aquatic ecosystems?
    • A. Rate of photosynthesis
    • B. Rate of respiration
    • C. Rate of biomass consumption
    • D. Rate of nutrient cycling
    • Answer: A
  6. What are the two main groups of plankton found in the littoral zone?
    • A. Phytoplankton and Zooplankton
    • B. Cyanobacteria and Diatoms
    • C. Algae and Fungi
    • D. Bacteria and Viruses
    • Answer: A
  7. Which zone of the lake ecosystem is characterized by sufficient light penetration to support photosynthesis?
    • A. Littoral Zone
    • B. Limnetic Zone
    • C. Profundal Zone
    • D. Benthic Zone
    • Answer: B
  8. What zone is beyond the reach of light penetration in the lake ecosystem?
    • A. Littoral Zone
    • B. Limnetic Zone
    • C. Profundal Zone
    • D. Benthic Zone
    • Answer: C
  9. What is the primary source of nutrients for the organisms in the profundal zone?
    • A. Photosynthesis
    • B. Detritus from littoral and limnetic zones
    • C. Bacterial decomposition
    • D. Fish excretion
    • Answer: B
  10. What human activity can accelerate the process of eutrophication in aquatic ecosystems?
  • A. Deforestation
  • B. Agriculture
  • C. Industrialization
  • D. Sewage discharge
  • Answer: D
  1. What happens during eutrophication in a lake ecosystem?
  • A. Increased oxygen levels
  • B. Excessive growth of phytoplankton
  • C. Decreased nutrient levels
  • D. Expansion of fish population
  • Answer: B
  1. What is the main consequence of excessive nutrient input in eutrophication?
  • A. Increased fish diversity
  • B. Depletion of oxygen levels
  • C. Enhanced photosynthesis
  • D. Reduction in water temperature
  • Answer: B
  1. What is a significant environmental risk associated with acidification of lakes?
  • A. Increased fish diversity
  • B. Growth of phytoplankton
  • C. Reduced pH
  • D. Enhanced nutrient cycling
  • Answer: C
  1. Which trophic levels are most affected by eutrophication in a lake ecosystem?
  • A. Producers
  • B. Primary consumers
  • C. Secondary consumers
  • D. Tertiary consumers
  • Answer: A
  1. What is the primary factor determining the distribution of life in lakes?
  • A. Access to nutrients
  • B. Access to light
  • C. Temperature
  • D. Depth of the lake
  • Answer: B
  1. What is the role of the littoral zone in the lake ecosystem?
  • A. Primary production
  • B. Nutrient cycling
  • C. Oxygen production
  • D. Anchorage for plants
  • Answer: D
  1. What types of organisms are found in the limnetic zone?
  • A. Anchored plants
  • B. Fishes and phytoplankton
  • C. Snails and insect larvae
  • D. Detritus feeders
  • Answer: B
  1. What characterizes the profundal zone in terms of light penetration?
  • A. Abundant light
  • B. Sufficient light for photosynthesis
  • C. No light penetration
  • D. Moderate light levels
  • Answer: C
  1. What does the term “eutrophication” mean in the context of aquatic ecosystems?
  • A. Oxygen depletion
  • B. Nutrient enrichment
  • C. Temperature increase
  • D. Salinity decrease
  • Answer: B
  1. What contributes to the bad smell in a eutrophicated lake?
    • A. Increased oxygen levels
    • B. Decomposition of dead plants by bacteria
    • C. Growth of fish population
    • D. Accumulation of detritus
    • Answer: B
  2. What is the primary source of nutrients for organisms in the littoral zone?
    • A. Sediment from profundal zone
    • B. Rainwater
    • C. Detritus from the limnetic zone
    • D. Sediments carried by streams
    • Answer: D
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Frequently Asked Questions (FAQs) about Aquatic Ecosystems and Eutrophication:

  1. What is a hydrospheric ecosystem, and where does it exist?
    • A hydrospheric ecosystem is a system in the water where living and non-living elements exchange materials and transfer energy. It exists in salt-water oceans, seas, and freshwater environments.
  2. What percentage of the Earth’s surface is covered by salt-water oceans and seas?
    • Salt-water oceans and seas cover about 71% of the Earth’s surface.
  3. How does water temperature change in aquatic ecosystems compared to the air?
    • Water changes its temperature slower than air, resulting in a more moderate temperature in aquatic ecosystems.
  4. What is the significance of nutrient concentration in the marine environment?
    • Nutrients in the marine environment, concentrated near bottom sediments, support life in areas where light levels may be too low for photosynthesis.
  5. What are the primary factors determining life in water environments?
    • Energy and nutrients are the significant factors determining the quantity and types of life in water environments.
  6. Define productivity in the context of aquatic ecosystems.
    • Productivity is the rate of production of new biomass during a unit of time, often indicated by the use of CO2 and the release of oxygen during photosynthesis.
  7. How is productivity in aquatic communities determined?
    • The productivity of aquatic communities is generally determined by light and nutrients. Light intensity and quality vary with water depth, affecting primary productivity.
  8. What are the primary zones in a lake ecosystem?
    • The primary zones in a lake ecosystem are the littoral zone (near-shore), limnetic zone (open water), and profundal zone (deep water).
  9. What organisms are found in the littoral zone of a lake?
    • The littoral zone contains a diverse range of plants such as water lilies and submerged vascular plants, as well as invertebrate and vertebrate animals like plankton, snails, insects, frogs, and turtles.
  10. What characterizes the limnetic zone in a lake?
    • The limnetic zone is the open water zone with sufficient light penetration to support photosynthesis. It is inhabited by phytoplankton, zooplankton, and fishes.
  11. Describe the profundal zone and its inhabitants.
    • The profundal zone is the deep water zone beyond the reach of light penetration. It is mainly populated by decomposers, detritus feeders, bacteria, fungi, and fishes.
  12. How can human activities accelerate the process of eutrophication in lakes?
    • Human activities, such as nutrient input from farm feedlots and sewage, can accelerate eutrophication, leading to the excessive growth of phytoplankton.
  13. What happens during eutrophication in a lake ecosystem?
    • Eutrophication involves the overgrowth of phytoplankton, depletion of oxygen due to bacterial decomposition, and the eventual domination of bacteria and blue-green algae in the ecosystem.
  14. What environmental risks are associated with acidification of lakes?
    • Acidification of lakes poses a risk to organisms as only a few can withstand the low pH. This is often caused by the burning of fossil fuels.
  15. Why does a eutrophicated lake often smell bad?
    • A eutrophicated lake smells bad due to the decomposition of dead plants by bacteria, leading to the production of nasty-smelling gases.
  16. How does eutrophication affect trophic levels in a lake?
    • Eutrophication can lead to the elimination of trophic levels, including fish, as bacteria and blue-green algae dominate the ecosystem.
  17. What are the primary factors determining the distribution of life in lakes?
    • Access to light, nutrients, and places for attachment are the primary factors determining the distribution of life in lakes.
  18. How is productivity in aquatic ecosystems identified and determined?
    • Productivity is identified by the usage of CO2 and the release of oxygen in photosynthesis. It is determined by factors such as light intensity, nutrient quantity, and seasonal variations.

 

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Summarizing Aquatic or Hydrospheric Ecosystem

The tutorial goes into the details of aquatic ecosystems, focusing on the hydrospheric environment and the significant impact of human intervention, particularly through eutrophication. Key aspects explored include temperature dynamics, energy absorption, nutrient concentration, and the vital role of water in sustaining life.

The hydrospheric ecosystem, constituting salt-water oceans and seas, occupies a substantial 71% of the Earth’s surface. In contrast, freshwater ecosystems cover less than 1%. Water’s unique properties, such as slower temperature changes compared to air, light absorption, and nutrient distribution, contribute to a conducive environment for diverse life forms.

The productivity of aquatic ecosystems, measured by biomass production over time, relies on factors like light availability and nutrient quantity. The distribution of life in freshwater lakes is examined in three primary zones: the littoral zone (near-shore), limnetic zone (open water), and profundal zone (deep water). Each zone supports distinct plant and animal communities, adapting to varying light and nutrient conditions.

Human intervention, notably eutrophication, emerges as a significant threat to aquatic ecosystems. Eutrophication, accelerated by nutrient influx from farm feedlots and sewage, triggers excessive phytoplankton growth. This results in the demise of submerged plants and subsequent oxygen depletion as bacteria decompose dead plant matter. The consequences include the elimination of trophic levels, foul-smelling gases, and the dominance of bacteria and blue-green algae in the ecosystem.

Furthermore, the tutorial highlights the additional threat of water contamination from acidification due to fossil fuel burning, posing challenges to organisms adapted to low pH in acidified lakes.

In essence, the tutorial provides a comprehensive understanding of the delicate balance within aquatic ecosystems, emphasizing the critical need for sustainable practices to preserve these vital environments.

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