Marine Ecosystem

• Marine ecosystems are vast, covering over 70 percent of the Earth's surface.

• These ecosystems contain a vast array of living things, water, and essential nutrients required by both marine and land organisms.

• Marine ecosystems are important in maintaining the Earth's ecological balance, supporting a wide range of species and habitats.

• They also provide crucial resources for human societies, including food, energy, and recreation.

Division of Oceans

Ocean is classified on the basis of water and land part in it.

• Land part comes under Benthic zone and water part under Pelagic zone and these two parts are further subdivided.

Benthic zone 

• Which forms the basin or floor of the ocean, regardless of depth.

The benthic zone is divisible into sub zones horizontally as follows

A. Supra littoral zone-

• It comprises of the beach down to the edge of the ocean. Beyond this is the Littoral zone.

B. Littoral zone -

• The littoral zone refers to the area between the upper and lower tide levels, also known as the intertidal zone.

• This zone represents the shore of the ocean, between the land and the open sea.

• Waves and tides have a significant impact on the littoral zone, making it a dynamic environment.

• This zone is home to a variety of marine organisms, adapted to survive in the constantly changing conditions of the shore.

• Due to its accessibility and ecological importance, the littoral zone is often studied by marine biologists and ecologists.

C. Sublittoral or continental shelf-

• which extends from the littoral zone to the beginning of the continental slope.

• The continental shelf is the underwater extension of the continent and extends to a depth of 125 to 200 metres.

D. Continental slope-

• Between continental shelf and continental rise.

D. Continental rise -

• It is geologically active area.

• This region has canyons and trenches which are subject to underwater eruptions and avalanches.

E. The bathyal zone -

• The region of the continental slope and rise together comprise the bathyal zone.

• The bathyal zone which is 200 metres deep descends rapidly to a depth of 3,000 or 4,000 m.

F. Abyssal plains-

• These are the plain area in bottom of the sea and here temperature is never above 4°C.

Pelagic Zone 

The water contained in the sea basin, constitute the pelagic zone which is divided as follows

A. The neritic zone-

• It is situated above the sublittoral zone or the continental shelf starting from the edge of the littoral sea and extending up to the edge of the continental shelf, to a depth of 200 m. Beyond this is the deep/open sea.

B. Deep/open sea of the oceanic zone-

It is divided on the basis of light penetration as

1. Epipelagic/Euphotic zone-

• The upper illuminated zone of the open ocean is also called epipelagic zone. So, the euphotic pelagic ocean is named a epipelagic one.

2. The aphotic pelagic zone-

• The pelagic region covers about 90% of the total ocean surface and is characterized by a lower diversity of species and a smaller number of organisms compared to other regions of the ocean.

It is further divided into-

• Mesopelagic.
• Bathypelagic.
• Abyssopelagic zone.

Biotic Components of oceans

Producers

• These are autotrophs and are also known Primary producers.

• They are mainly, some microscopic algae (phytoplankton’s phytoplanktons) besides besides them there are mainly, seaweeds, as brown and red algae also contribute to primary production.

• Producers in the marine ecosystem aremainly phytoplankton , large marine plants, mangroves and sea weeds

Consumers

A. Primary Consumer -

• The herbivores, that feed on producers are shrimps, Molluscs, fish, etc.

B. Secondary Consumers-

• These are carnivores fishas Herring, Herring, Shad, Mackerel, Mackerel, feeding feeding on herbivores.

C. Tertiary Consumers-

• These includes, othercarnivores fishes like, Cod, Halibut, Sea Turtle, Sharks, whale etc.

D. Decomposers-

• Decomposers refer to microorganisms that play a vital role in breaking down dead organic matter of producers and animals.

• Bacteria and fungi are the primary types of microbes involved in this process.

Some of the Marine Organisms

1. Marine Viruses

• Marine viruses are found in large quantities in oceans and have a significant impact on the ecology of the oceanic environment.

• Viruses have the ability to infect and use both prokaryotic and eukaryotic organisms as hosts, which is crucial for the virus to replicate and spread.

• Due to their high abundance and ability to infect marine organisms, marine viruses have a major influence on the food web and nutrient cycling in the ocean.

• While viruses were previously considered harmful to marine life, recent studies suggest that viruses also have a positive ecological role, such as controlling bacterial populations and contributing to the cycling of nutrients in the marine environment.

• Outside their host they are called virions, and consist of a nucleic acid core surrounded by a protein coat.

2. Marine Bacteria

• Most marine bacteria are rod-shaped (bacillus) or spherical (coccus) and are small.

• Cyanobacteria are also known blue-green algae. They are the only photosynthetic prokaryotes.

• While cyanobacteria are the only photosynthetic prokaryotes, many other bacteria are autotrophs through chemosynthesis and some are heterotrophs.

3. Marine fungi

• Marine fungi are eukaryotes that have cell walls composed of chitin, which is the same compound found in crustacean exoskeletons.

• These fungi are heterotrophic, meaning they obtain their nutrition by breaking down organic matter using exoenzymes.

• Lichens are a unique association between fungi and algae, forming a mutualistic relationship where the fungus provides protection and structural support, while the algae produce food through photosynthesis.

4. Diatoms (Stramenopiles)

• Diatoms are important members of both planktonic and benthic communities.

• They are photosynthetic primary producers and have a cell wall made of silicon dioxide.

• Diatoms reproduce both asexually and sexually.

• Diatoms are an especially important class of phytoplankton because they account for as much as 60 percent of primary productivity in the marine ecosystem and perhaps some 20 percent of the total photosynthesis on Earth.

5. Coccolithophores (Haptophytes)

• Coccolithophores are exclusively marine and photosynthetic.

• They have a calcium carbonate shell made of coccolith plates which may account for up to 40% of modern carbonate production in the oceans, and form sediment known as calcareous oozes.

6. Dinoflagellates (Alveolates)-

• Dinoflagellates, unlike diatoms, do not require silica as a nutrient. Moreover, they can be autotrophic , hetetrophic, or mixotrophic (capable of both autotrophy and heterotrophy).

• Dinoflagellates are one of the most important groups responsible for harmful algal blooms, also known as red tides.

• Dinoflagellates, unlike diatoms, do not require silica as a nutrient.

7. PLankton

• Plankton is a term that describes a collection of organisms that float on the surface of rivers, lakes, and oceans.

• Plankton includes both microscopic plants, such as algae (phytoplankton), and animals like crustaceans and protozoans (zooplankton).

• These organisms can be found in all aquatic ecosystems, except in certain fast-flowing waters.

Phytoplankton 

• Phytoplankton are essential components of ocean and freshwater ecosystems, and they are autotrophic, meaning that they can produce their own food.

• The term "phytoplankton" is derived from the Greek words "phyto," meaning plant, and "plankton," meaning to wander or drift.

• Phytoplankton are microscopic organisms that live in aquatic environments, including both saltwater and freshwater.

• Some examples of phytoplankton include bacteria, protists, diatoms with silica shells, dinoflagellates, green algae, and coccolithophores with chalk coatings.

• These micro-algae are present throughout the lighted regions of all the seas and oceans including the Polar Regions.

• Phytoplankton vary widely in physical and chemical requirements for population growth.

• Diatoms and dinoflagellates also differ significantly with respect to motility, cell-wall composition and ornamentation, and nutritional and reproductive strategies.

• Diatoms have cell walls, called frustules, made of silica (the same material in glass and opal). In contrast, dinoflagellates can have a rigid cell wall, called a theca, made of cellulose plates, or they can have a nonrigid cell membrane (no theca)

Importance of Phytoplakton –

• Phytoplankton plays a crucial role in producing oxygen and nutrients for other organisms through the process of photosynthesis, which utilizes sunlight, nutrients, carbon dioxide, and water.

• As the ocean covers 71% of the Earth, phytoplankton is responsible for producing up to 50% of the oxygen that is essential for breathing.

• Additionally, these microscopic organisms are responsible for cycling most of the Earth’s carbon dioxide between the ocean and the atmosphere.

Factors Affecting Phytoplankton's Biodiversity

A. Nutrient-

• Phytoplanktons require Basic Nutrients for their growth.

• For Example-Diatoms and silico flagellates also require silicate (SiO2) in significant amounts.

• Therefore, nutrient rich water is beneficial for them.

B. Light-

• Phytoplankton's are found in Photic region of the ocean therefore light is basic requirement for them.

C. Temperature-

• One commonly observed phenomenon is that as the temperature rises, the rate of photosynthesis tends to increase. However, beyond a certain point, the rate of photosynthesis declines steeply.

Distribution of Phyto planktons

• Marine phytoplankton are not uniformly distributed throughout the oceans of the world.

• The areas with the highest concentrations of the mentioned substance are typically located at high latitudes, except for the upwelling areas that can be found on the continental shelves.

• On the other hand, the tropics and subtropics usually have concentrations that are 10 to 100 times lower.

Transport of Phyto Planktons-

• Oceanic currents are responsible for transporting all species of phytoplankton to suitable areas for growth and survival.

• As a result, physical processes can heavily influence the distribution and composition of phytoplankton species, making them a crucial factor in bloom development.

Phytoplankton vs algae

• Phytoplankton are microorganisms that can be found in lakes, streams, and oceans.

• They are free-floating and photosynthetic.

• Phytoplankton include algae, cyanobacteria, protists, and diatoms, as well as other microorganisms.

• Therefore, Not all phytoplankton are algae, as the category encompasses a range of microorganisms.

• Phytoplankton can grow in colonies that are sometimes large enough to be seen by the naked eye.

• These microorganisms play a vital role in aquatic ecosystems as a primary food source for many aquatic animals.

 Blooms, Red Tides, and Toxicity

• A phytoplankton bloom is the development of a level of phytoplankton biomass that is uncharacteristically high for a given water body.

• It is also called as algal bloom.

Although the reasons for this apparent increase are unclear, several have been suggested-

(1) increased nutrient input to coastal oceans from human activities.

(2) large-scale climactic changes (for example, global warming).

(3) transport of toxigenic species in ship ballast water.

(4) increased use of coastal resources for shellfish harvesting and aquaculture.

Consequences of Phytoplankton Blooms

• High concentrations of phytoplankton during blooms can color and cloud the water, reducing the transmission of light in the water column.

• Some species of phytoplankton produce toxins, which can pose a direct threat to human health.

• Cyanobacteria and dinoflagellates are the most common groups of toxin-producing phytoplankton in freshwater and marine environments, respectively.

• Phytoplankton blooms can also result in habitat loss as the excess organic matter from the bloom sinks to the seafloor, where it can lead to the depletion of oxygen and harm benthic communities.

• Although phytoplankton photosynthesis produces oxygen, the decomposition of the dead phytoplankton organic matter can deplete dissolved oxygen in the water to levels too low for fish and other animals.

• The excessive discharge of nitrogen and phosphorus from sediments during hypoxic conditions can provide a source of nutrients for phytoplankton blooms, which poses a significant obstacle to the improvement of water quality and preservation of aquatic ecosystems.

Red Tides

• The commonly used term “red tide” is quite misleading because Phyto plankton blooms frequently are other colours (brown, green, even yellow) and are not a tidal phenomenon.

• The dinoflagellates are associated with worldwide occurrences of red tides.

• A unique characteristic of some red tides is the phenomenon of bioluminescence.

• Light produced by some species of dinoflagellates (can illuminate the waves and surface of the ocean under bloom conditions.

Zooplankton

• Zooplankton play vital role in food web of the food chain, nutrient recycling, and in transfer of organic matter from primary producers to secondary consumers like fishes.

Other Marine Species

1. Seaweeds

• Seaweeds do not possess roots, stems, or leaves, in contrast to flowering plants, as they do not have vascular tissue. Additionally, all of their cells are capable of photosynthesis.

• The color of the thallus is due to the wavelengths that are not absorbed by pigments in the seaweed.

• Seaweeds can reproduce sexually and asexually.

• Types- Brown, green, red algae.

• Uses- human foods, cosmetics, fertilizers, and for the extraction of industrial gums and chemicals

2. Seagrasses-

• Seagrasses are hydrophytes, as they live beneath the water.

• They are the group of flowering plants that is best adapted to the marine environment.

• Seagrasses are found in both temperate and tropical waters.

• As seagrasses depend on their roots for nutrient absorption, they don’t benefit from an increase in nutrients in the water column.

• Leaves also control salt balance, and have an aerenchyme, a gas-filled tissue that aids in oxygen transport.

 Uses of Sea Grasses-

• Unlike seaweeds, seagrasses are not fed upon directly by most marine herbivores as they are too tough to digest.

• Therefore seagrasses makes only a small direct contribution (i.e. through herbivory) to higher levels of the food chain.

• Seagrasses play an important role in aiding deposition and stabilizing sediments.

• Seagrasses are also an important habitat for many species.

Mangroves

• Mangroves are a collection of plants that grow in the intertidal zones of the subtropics and tropics.

• These plants thrive in areas where their roots are partially or completely submerged by tides.

• Mangroves are typically found in tropical regions with gentle slopes, high sedimentation rates, and low wave action.

• These coastal ecosystems are similar to salt marshes but are adapted to thrive in warmer climates.

• Mangroves play a crucial role in coastal protection and support a diverse array of wildlife.

• Most important species are red and black mangroves. Both have specialized roots that rise out of the sediment.

Structure of Mangroves

• Mangroves are trees with simple leaves and complex root systems.

• Their roots grow in loose, anoxic sediment and many species have aerial roots (above water) that have an aerenchyme.

• The aerenchyme is linked to the atmosphere through the lenticels, and supplies oxygen to the root system.

Stilt root -

• Stilt roots are a type of adventitious roots that grow from the base of stem nodes.

• These roots grow downward and anchor the tree, preventing it from being uprooted.

• Stilt roots are particularly important for trees that grow in areas with loose or unstable soil, such as mangroves.

• Even individual branches can develop stilt roots to provide additional support.

• In addition to anchoring the tree, stilt roots also provide nutrients and oxygen to the tree.

Basic requirements for Mangroves

A. Temperature-

• Mangroves prefer tropical or subtropical regions.

B. Moisture-

• Mangroves have adapted to keep freshwater in their system.

• They close the pores in their leaves and turn their leaves away from the sun to keep the moisture in.

C. Salt

• Mangroves do not need fresh water.

• They have evolved to be capable of growing in salty water.

 D. Reproduction

• Mangroves propagate through seedlings or propagules which are dispersed by tides into the water.

• The seedlings or propagules require suitable water conditions with moderate salinity to grow.

• Only after finding an optimal environment with the right amount of salinity do the seedlings take root and grow into mature mangrove trees.

Distribution of Mangroves

World

• Mangroves are the dominant vegetation type on around 75% of the world's tropical coastlines between 25° N and 25° S latitude.

• The limited distribution of mangroves is primarily due to their vulnerability to frost and cold temperatures.

• The northernmost locations where mangroves can be found are in the Gulf of Aqaba at the top of the Red Sea and in southern Japan.

• while the most southerly sites for mangrove distribution are Australia and Chathan Island east of New Zealand.

• The highest concentration of mangrove species is, however found in the Indo-Malaysian region.

Region-

South and Southeast Asia > Australia > Americas > West Africa > East Africa and the Middle East

India

• In India, the mangrove vegetation can be observed all along its 5,700 km coastline.

• According to estimates, mangroves cover approximately 700,000 hectares, equivalent to around 6% of the world's mangroves.

• The extent of mangrove cover along the east coast of India is comparatively larger (90%) than the west coast (10%).

• The East coast has 91% of mangrove species and the West coast has 53%.

 Sundarbans (east coast)

• The Sundarbans, located on India's east coast, consists of approximately 9,600 sq. km of mangrove forests and water.

• It is made up of several islands formed by sediment deposits from three major rivers - the Ganga, Brahmaputra, and Meghna - as well as numerous smaller rivers, channels, and creeks.

• The Sundarbans is dominated by mangroves, which make up the most significant flora in the area.

• They can be seen along the Banks of Major Eastern flowing rivers.

• Andhra Pradesh possesses about 582 2 km of mangrove area.

• Tami Nadu is one of the nine maritime states of India endowed with the second longest coastline of 1.076 km.

• The primary mangrove wetlands located in Tamil Nadu consist of the Pichavaram mangroves and Muthupet mangroves.

• These wetlands rely mainly on the Cauvery river for the supply of freshwater.

• They are also found in western coastal areas of Gujrat,Goa and Ratnagiri.

Importance of Mangroves

• Provide a physical habitat and nursery grounds for marine organisms.

• Serve as buffers for storms.

• Protect shorelines from erosion.

• Provide roosting and nesting sites for many birds.

• Provide food for many marine organisms.

• Trap and cycle organic materials, chemicals, and nutrients that sustain ecosystems.

Uses and Threats of Mangroves

Summary of uses

• Ecological uses- Erosion control, Protection from damage, Indicator of climate change, Habitat provision, Water quality management, Carbon Sequestration.

• Economical uses- Fishing, Shrimp and crab industries, Charcoal production, Timber production, Firewood.

• Social uses- Education, Ecotourism, Food, Local employment, Agriculture, Traditional medicine.

Threats to Mangroves

• Climate change.

• Floods and Hurricanes.

• Wildlife, pests, and weeds.

• Coastal development.

• Agriculture.

• Lumber industries etc.

One Liner Question and answers on Marine ecosystem.

Marine ecosystems cover what percentage of the Earth's surface?

They cover over 70 percent of the Earth's surface.

What do marine ecosystems contain?

They contain a vast array of living things, water, and essential nutrients required by both marine and land organisms.

What is the importance of marine ecosystems?

They are important in maintaining the Earth's ecological balance, supporting a wide range of species and habitats, and provide crucial resources for human societies, including food, energy, and recreation.

How are oceans classified?

Oceans are classified based on the water and land parts in them.

What is the Benthic zone?

The Benthic zone is the part of the ocean floor, regardless of depth.

What is the Supra littoral zone?

It comprises of the beach down to the edge of the ocean.

What is the Littoral zone?

The Littoral zone refers to the area between the upper and lower tide levels, also known as the intertidal zone.

What is the Sublittoral or continental shelf?

It extends from the littoral zone to the beginning of the continental slope.

What is the Continental slope?

It is the region between the continental shelf and the continental rise.

What is the Continental rise?

It is a geologically active area with canyons and trenches that are subject to underwater eruptions and avalanches.

What is the Bathyal zone?

It is the region of the continental slope and rise together and extends to a depth of 200 metres.

What are Abyssal plains?

These are the plain areas at the bottom of the sea and the temperature is never above 4°C.

What is the Pelagic zone?

The Pelagic zone is the water contained in the sea basin.

What is the Neritic zone?

It is situated above the sublittoral zone or the continental shelf starting from the edge of the littoral sea and extending up to the edge of the continental shelf, to a depth of 200 m.

What is the Epipelagic/Euphotic zone?

It is the upper illuminated zone of the open ocean.

What is the Aphotic pelagic zone?

It is the zone where light penetration is very low and covers about 90% of the total ocean surface.

What are producers in the marine ecosystem?

Producers in the marine ecosystem are mainly phytoplankton, large marine plants, mangroves, and sea weeds.

What are primary consumers in the marine ecosystem?

Primary consumers in the marine ecosystem are herbivores that feed on producers, such as shrimps, molluscs, and fish.

What are decomposers in the marine ecosystem?

Decomposers refer to microorganisms that play a vital role in breaking down dead organic matter of producers and animals, such as bacteria and fungi.

What are mangroves and where do they grow?

Mangroves are a collection of plants that grow in the intertidal zones of the subtropics and tropics.

What type of areas do mangroves thrive in?

Mangroves are typically found in tropical regions with gentle slopes, high sedimentation rates, and low wave action.

How are mangroves similar to salt marshes?

These coastal ecosystems are similar to salt marshes but are adapted to thrive in warmer climates.

What role do mangroves play in coastal protection?

Mangroves play a crucial role in coastal protection and support a diverse array of wildlife.

What are the most important species of mangroves?

The most important species are red and black mangroves. Both have specialized roots that rise out of the sediment.

What is the structure of mangroves?

Mangroves are trees with simple leaves and complex root systems.

What are stilt roots and why are they important for mangroves?

Stilt roots are a type of adventitious roots that grow from the base of stem nodes. They are particularly important for trees that grow in areas with loose or unstable soil, such as mangroves.

What are the basic requirements for mangroves to grow?

Mangroves prefer tropical or subtropical regions, have adapted to keep freshwater in their system, and do not need fresh water as they have evolved to be capable of growing in salty water.

How do mangroves reproduce?

Mangroves propagate through seedlings or propagules which are dispersed by tides into the water.

Where are mangroves found around the world and in India?

Mangroves are the dominant vegetation type on around 75% of the world's tropical coastlines between 25° N and 25° S latitude. In India, mangrove vegetation can be observed all along its 5,700 km coastline, with the Sundarbans on the east coast consisting of approximately 9,600 sq. km of mangrove forests and water.