Types

Fresh Water
Brackish Water
Marine
Wetland ecosystem

Lake Ecosystem
Estuary ecosystem
Mangroves ecosystem

Type	Salt content
Fresh	< 5 ppt
Brackish	5-35ppt
Marine	> 35 ppt

Introduction

Fresh Water Ecosystem - Lotic(moving water) and Lentic(Still water)

Moving water has more oxygen than stagnant water

Increase in temperature of a water body increases the rate of depletion of oxygen

Oxygen less soluble in Warm water
Also, Warm water increases the decomposition activity and thereby depletes the oxygen

Hypoxia - Oxygen deficiency in a biotic environment.
Anoxia - Absence of oxygen
Hyperoxia - Excessive supply of oxygen
Euphotic/Photic zone is until the depth where the sunlight is of 1% of surface light (depth also depends on transparency of water)
Aphotic zone - where sunlight can't reach - oxygen still be consumed - Profundal zone
Aquatic organisms have narrow temperature tolerance limit since the water temp are less subjected to change
Dissolve oxygen in fresh water is 10ppm [decreases in warm waters] and if it is below 3-5 ppm, many aquatic organisms going to die
Deep ocean water is cold and nutrient rich than surface ocean waters which is warm and less nutrients

Because marine productivity is more in shallow surface waters which consume nutrients and the deep ocean is relatively undisturbed

Harmful algal blooms are in red/brown/green in color
Biodiversity is more in Oligotrophic lakes than Eutrophic Lakes
Removal of Nutrients from a lake

Onsite P elimination by flocculation and flotation with water backflow

Flocculation is the process by which individual particles of clay aggregate into clot like masses or precipitate into small lumps.
Flocculation occurs as a result of a chemical reaction between the clay particles and another substance, usually salt water.

Floating plant NESSIE with adsorbers (solid that attract certain liquid)
Algae removal by P adsorbers and filters

Anthropogenically acidified lakes looks clear because of low primary productivity while naturally acidified lakes looks brown to yellow colour because of humic substance
Invertebrates are the most common animals found in inter-tidal zones

Dead Zone in the oceans

Areas (no t the ocean bed) that contains little or no oxygen and supports microbial processes that remove vast amount of nitrogen from the ocean
Biological desert - cannot support complex life
Dead zones are well known of the western coasts of North and South America, of the coast of Namibia and of the west coast of India in the Arabian Sea and now in Bay of Bengal
Causes

Dead zones can be caused by natural and by anthropogenic factors.
Use of chemical fertilizers is considered the major human-related cause of dead zones around the world. Runoff from sewage, urban land use, and fertilizers can also contribute to eutrophication.
Natural causes include coastal upwelling and changes in wind and water circulation patterns.

Shadow Zone in Oceans

Shadow zone is an area of almost stagnant water which is vertically sitting between rising currents caused by the rough topography, geothermal heat source and shallower wind-driven current closer to the surface
A research paper recently found that the shadow zones are present in Pacific oceans and Indian Ocean
How they found

Carbon-14 dating has proved that there is oldest water in the North Pacific Ocean.

Significance

The trapped water also traps nutrients and carbon which have a direct impact on the capacity of the ocean to modify climate over centennial time scales.

Sea Grass

Distribution

South East coast of Tamilnadu coast, Lakshadweep islands, few around Andaman & Nicobar islands

Conditions:

Shallow coastal waters
Sandy or muddy bottoms
Calm areas
Clear Water
High Salinity

IUCN has accorded high status for conservation of sea grass

Sea weed Culture

Also known as Marine macroscopic algae
They are plant-like organisms that generally live attached to rock or other hard substrata in coastal areas
Brown algae, Red algae, Green algae, blue-green
Distribution in India

Gulf of Mannar, Gulf of Kutch, Calh Bay, Hanshadweep and Bay islands are the important areas for seaweed culture.

Uses

It is considered as the medicinal food of the 21st century (goitre, intestinal and stomach disorders)

Many seaweeds are rich in vitamins and minerals and are eaten in various parts of the world (Japan, China, Korea)
Used in Cosmetic industry
High fiber content of the seaweed acts as a soil conditioner and assists moisture retention, while the mineral content is a useful fertilizer
Source of trace elements
Seaweeds have the potential for use in wastewater treatment

China produces over half of the world’s seaweed harvest a Indonesia 27% of world production
It gained prominence during 13th century, after the discovery of agar-agar in Japan and Alginic Acid in European continent.
Rotten seaweed is a potent source of hydrogen sulfide which is a highly toxic gas

Aquaponics

a technique that combines horticulture and aquaculture, helps the farmer raise fishes while he also grows plants.
In aquaponics fish and plants are grown together in a tank. The tank has fishes in it and on the sides of the tank there are beds for plants. The water from the fish tank which is rich in nutrients due to the fish waste goes into the plants.

Marine snow

Marine snow often includes fecal matter, sand, soot, skin, and other organic and inorganic particles descending to the seafloor

Trophic State Index

In water bodies, the quantities of nitrogen, phosphorous and other biological useful nutrients are the p rimary determinants of water's trophic (energy) state index
Because, if concentrations are increased, it leads to increased growth of plants and organism and thereby increase in trophic levels
Although the term "trophic index" is commonly applied to lakes, any surface water body may be indexed.

Trophic Classifications

Lakes generally classified into oligotrophic, mesotrophic or eutrophic, hyper oligotrophic/hypereutrophic

Oligotrophic	Low nutrient content	Low Primary productivity	Common in cold regions underlain by resistant igneous rocks
Mesotrophic	Moderate nutrients	Moderate primary productivity
Eutrophic	Excessive nutrients	High productivity
Hypereutrophic	Very nutrient rich	Excessive algal booms	Dead zones beneath the surface

Coastal Erosion in India

India’s long peninsular region and islands consta tly battles erosion.
Ministry of Earth Sciences monitors the shoreline changes along the Indian coast on an annual basis
Most erosion - Andaman and Nicobar Islands
Accretion-gradual deposition by water of mud, sand to form dry land- Tamilnadu
Stable shoreline - Goa

A marina is a

dock or basin with moorings and supplies for yachts and small boats

. A marina differs from a port in that a marina does not handle large passenger ships or cargo from freighters.

Groyne : low wall or sturdy timber barrier built out into the sea from a beach to check erosion and drifting. Built at right angles to sea to prevent longshore drift and absorb energy of sea thereby reducing the impact
Geosynthetic tubes used along Odisha coast also helpful in preventing coastal erosion

Ocean deoxygenation

Ocean deoxygenation refers to loss of oxygen from the oceans
How oceans gains oxygen

In upper layer

Due to photosynthesis by autotrophic organisms
Oxygen from the atmosphere dissolving in the under-saturated waters

How oceans lose oxygen

At the surface

Due to the outgassing of oxygen to the atmosphere in oversaturated waters

From the surface to depths

Due to the respiration of aerobic organisms and oxidation of reduced chemical species

Hence, there is an equilibrium in the levels of oxygen in the ocean as it gains and loses
But, this equilibrium is disturbed and there is deoxygenation in the oceans
Causes

Climate change

Ocean warming

Global warming induces ocean warming which causes deoxygenation in oceans
Warmer ocean water holds less oxygen
Warmer ocean waters also more buoyant and hence less mixing with deep waters

Usually, deep ocean waters has less oxygen levels

Warmer water also raises oxygen demand from living organisms (increases the metabolic rates). As a result, less oxygen is available for marine life

Eutrophication (Nutrient pollution)

It causes oxygen loss in coastal waters as fertiliser, sewage, animal and aquaculture waste cause excessive growth of algae, which in turn deplete oxygen as they decompose.

Impact

Decreased oxygen levels increases GHG emissions, methane and N20
Disturbance in nutrient cycles

Aquatic Ecosystem