Water Pollution

 

Addition of certain substances to the water such as organic, inorganic,

biological, radiological, heat, which degrades the quality of water so that it

becomes unfit for use.

Putrescibility is the process of decomposition of organic matter present in water by microorganisms using oxygen.

Water having DO (dissolved oxygen)  content below 8.0 mg/L may be

considered as contaminated.  Water having DO content below. 4.0 mg/L is

considered to be highly polluted.

Water pollution by organic wastes is measured in terms of Biochemical Oxygen Demand-(BOD). BOD is the amount of dissolved oxygen needed by bacteria in decomposing the organic wastes present in water.

Chemical oxygen demand (COD) is a slightly better mode used to measure pollution load in water. It is the measure of oxygen equivalent of the requirement of oxidation of total organic matter (i.e. biodegradable and non- biodegradable) present in water.

A cripling deformity called Minamata disease due to consumption of fish captured from mercury contaminated Minamata Bay.

Water contaminated with cadmium can cause itai itai disease also called ouch-ouch disease (a painful disease of bones and joints) and cancer of lungs and liver.

The compounds of lead cause anaemia, headache, loss of muscle power and bluish line around the gum

Excess nitrate in drinking water reacts with hemoglobin to form non -functional met haemoglobin, and impairs oxygen transport.  This condition  is  called methaemoglobinemia or blue baby syndrome.

Over exploitation of ground water may lead to leaching of arsenic from soil and rock sources and contaminate ground water.  Chronic exposure to arsenic causes black foot disease. It also causes diarrhoea,-peripheral neuritis, hyperkerotosis and also   lung and skin cancer.

GRASSLAND ECOSYTEM

 

found where rainfall is about 25-75 cm per year, not enough to support a forest, but more than that of a true desert.

vegetation formations that are generally found in temperate climates.

In India, they are found mainly in the high Himalayas. The rest of India’s grasslands aremainly composed of steppes and savannas.

Steppe formations occupy large areas of sandy and saline https://exam.pscnotes.com/soil”>Soil; in western Rajasthan, where the Climate is semi-arid,

The major difference between steppes and savannas is that all the forage in the steppe is  provided only during the brief wet season whereas in the savannas forage is largely from Grasses that not only grow during the wet season but also from the  smaller amount of regrowth in the dry season.

 

Types of Grasslands

  1. semi-arid zone (The Sehima-dichanthium type)

It covers the northern portion of Gujarat, Rajasthan (excluding Aravallis), western Uttar Pradesh, Delhi and Punjab.

The topography is broken up by hill spurs and sand dunes.

senegal, Calotropis gigantia, Cassia auriculata, Prosopis cineraria, Salvadora oloides and zizyphus Nummularia which make the savanna rangeland look like scrub.

  1. dry sub humid zone (The Dichanthium- cenchrus-lasitrrus type)

It covers the whole of peninsular India (except Nilgiri).

The thorny bushes are Acacia catechu, Mimosa, Zizyphus (ber) and sometimes fleshy Euphorbia, along with low trees of Anogeissus latifolia, Soymida febrifuga and other deciduous species.

Sehima (grass)is more prevalent on gravel and the cover maybe 27%. Dichanthium (grass) flourishes on level soils and may cover 80% of the ground.

3)  moist subhumid zone(The Phragmities- sacchrum-imperata type)

It covers the Ganga alluvial plain in Northern India.

The topography is level, low lying and ill-drained.

Bothriochloa pertusa, Cypodon dactylon and     Dichanthium annulatum are found in transition zones.

The common trees and shrubs are Acacia arabica, hogeissus, latifolia, Butea monosperma,

Phoenic sylvestris and Zizyphus nummularia.

Some of these are replaced by Borassus sp in the palm savannas especially near Sunderbans.

4) The Themeda – Arundinella type

This extends to the humid montane regions and moist sub-humid axeas of Assam, Manipur,West Bengal, Uttar Pradesh, Punjab, Himachal Pradesh and. Jammu and Kashmir.

The savanna is derived from the humid forests on account of shifting cultivation and sheep grazing.

Indian Grasslands and Fodder Research Institute, Jhansi and Central Arid Zone Research institute, Jodhpur

Role of fire

fire plays, an important role in the management  of grasslands.

Under moist conditions fire favours grass over trees, whereas in dry conditions fire is often necessary to maintain grasslands against the invasion of desert shrubs.

Burning increases the forage yields, e.g. Cynodon daotylon

ESTUARY ECOSYSTEM

 

  • located where river meets the sea.
  • the most productive water bodies in the world
  • The complete salinity range from 0-35 ppt is seen from the head (river end) to the mouth (sea end) of an estuary
  • Coastal lakes which have their connection with the sea through small openings are better known as lagoons or backwaters acting as a natural water filter

 

Estuary Formation:

grouped into four geomorphic categories based on the physical processes responsible for their formation:

1) rising sea level; (2) movement of sand and sandbars; (3) glacial processes; and (4) tectonic processes.

India Estuarine Ecosystem

The Country has 14 major, 44 medium and 162 minor rivers drains into the sea through various estuaries.

Major estuaries occur in the Bay of Bengal.

Most of the India’s major estuaries occur on the east coast. In contrast, the estuaries on the west coast are smaller.

 BIOGEOCHEMICAL CYCLE

The elements or mineral nutrients are always in circulation moving from non-living to living and then back to the non-living components of the ecosystem in a more or less circular fashion. This circular fashion is known as biogeochemical cycling (bio for living; geo for atmosphere).

  1. Nutrient Cycling:

The nutrient cycle is a concept that describes how nutrients move from the physical environment to the living organisms, and subsequently recycled back to the physical environment.

It is essential for life and it is the vital function of the ecology of any region. In any particular environment, to maintain its organism in a sustained manner, the nutrient cycle must be kept balanced and stable.

 

Types of Nutrient Cycle

Based on the replacement period a nutrient cycle is referred to as Perfect or Imperfect cycle.

A perfect nutrient cycle is one in which nutrients are replaced as fast as they are utilised.

Most gaseous cycles are generally considered as perfect cycles.

In contrast sedimentary cycles are considered relatively imperfect, as some nutrients are lost from the cycle and get locked into sediments and so become unavailable for immediate cycling.

Based on the nature of the reservoir, there are two types of cycles namely Gaseous and sedimentary cycle

Gaseous Cycle — where the reservoir is the atmosphere or the hydrosphere, and

Sedimentary Cycle — where the reservoir is the earth’s crust.

 

  1. Gaseous Cycles:

Water Cycle (Hydrologic)

The hydrologic cycle is the continuous circulation of water in the Earth-atmosphere system which is driven by solar energy.

Water moves from one reservoir to another by the processes of evaporation,

transpiration, condensation, precipitation, deposition, runoff,

infiltration, and groundwater flow.

 

  1. The Carbon Cycle

without carbon dioxide life could not exist, because it is vital for the production of carbohydrates through photosynthesis by plants. It is the element that anchors all organic substances from coal and oil to DNA(deoxyribonudeic acid: the compound that caries genetic information) Carbon cycle involves a continuous exchange of carbon between the atmosphere and organisms. Carbon from the atmosphere moves to green plants by the process   of photosynthesis, and then to animals. By process of respiration and decomposition of dead organic matter it returns back to atmosphere.

 

  1. The Nitrogen Cycle

an essential constituent of protein and is a basic building block of all living tissue. It constitutes nearly 16% by weight of all the proteins.

There is an inexhaustible supply of nitrogen in the atmosphere but the elemental form cannot be used directly by most of the living organisms needs to be ‘fixed’, that is, converted to ammonia, nitrites or nitrates, before it can be taken up by plants. on earth it is accomplished in three different ways:

(i) By microorganisms (bacteria and blue-green algae)

 

(ii) By man using industrial processes (fertilizerfactories) and

(iii) To a limited extent by atmospheric phenomenon such as thunder and lighting

The amount of Nitrogen fixed by man through industrial process has far

exceeded the amount fixed by the Natural Cycle.

As a result Nitrogen has become a pollutant which can disrupt the balance of

nitrogen. It may lead to Acid rain, Eutrophication and Harmful Algal Blooms.

Certain microorganisms are capable of fixing atmospheric nitrogen into

ammonium ions. These include free living nitrifying bacteria (e.g. aerobic

Azotobacter and anaerobic Clostridium) and symbiotic nitrifying bacteria living in  association with leguminous plants(pulse etc) and symbiotic bacteria    living in non leguminous root nodule plants (e.g. Rhizobium) as well as blue green algae (e.g. Anabaena, Spirulina).

Ammonium ions can be directly taken up as a source of nitrogen by some plants, or are oxidized to nitrites or nitrates by two groups of specialised bacteria:

Nitrosamines bacteria promote transformation of ammonia into nitrite. Nitrite is then further transformed into nitrate by the bacteria Nitrobacter.

The nitrates synthesised by bacteria in the soil are taken up by plants and converted into amino acids, which are the building blocks of proteins.

These then go through higher trophic levels of the ecosystem.

During excretion and upon the death of all organisms nitrogen is returned to the soil in the form of ammonia.

Certain quantity of soil nitrates, being highly soluble in water, is lost to the system by being transported away by surface run-off or ground water. In the soil as well as oceans there are special denitrifying bacteria (e.g. Pseudomonas), which convert the nitrates/nitrites to elemental nitrogen. This nitrogen escapes into the atmosphere, thus  completing the cycle.

The periodic thunderstorms convert the gaseous nitrogen in the atmosphere to ammonia and nitrates which eventually reach the earth’s surface through precipitation and then into the soil to be utilized by plants.(Better if You Check Diagram)

  1. Sedimentary Cycle

Phosphorus, calcium and magnesium circulate by means of the sedimentary cycle.

(a) Phosphorus Cycle

Phosphorus plays a central role in aquatic ecosystems and water quality.

Phosphorus occurs in large amounts as a mineral in phosphate rocks and enters the cycle from erosion and minning activities.

This is the nutrient considered to be the main cause of excessive growth of rooted and free-floating microscopic plants in lakes.

The main storage for phosphorus is in the earth’s crust.

On land phosphorus is usually found in the form of phosphates.

By the process of weathering and erosion phosphates enter rivers and streams that transport them to the ocean.

In the ocean once the phosphorus accumulates on continental shelves in the form of insoluble deposits

After millions of years, the crustal plates rise from the sea floor and expose the phosphates on land.

After more time, weathering will release them from rock and the cycle’s

geochemical phase begins again.

(b) Sulphur Cycle

The sulphur reservoir is in the soil and sediments where it is locked in organic

(coal, oil and peat) and inorganic deposits (pyrite rock and sulphur rock) in the

form of sulphates, sulphides and organic sulphur.

 

It is released by weathering of rocks, erosional runoff and decomposition of organic matter and is carried to terrestrial and aquatic ecosystems in salt solution.

The sulphur cycle is mostly sedimentary except two of its compounds hydrogen sulphide

(H2S) and sulphur dioxide (SO2) add a gaseous component to its normal sedimentary cycle.

Atmospheric sulphur dioxide is carried back to the earth after being dissolved in rainwater as weak sulphuric acid.

sulphur in the form of sulphates is take up by plants and incorporate through a series of metabolic processes into sulphur bearing amino acid which is incorporated in the  proteins of autotroph tissues. It then passes through the grazing food chain.

Sulphur bound in living organism is carried back to the soil, to the bottom of ponds and lakes and seas through excretion and decomposition of dead organic material.

FOREST ECOSYSTEM

 

 

FOREST ECOSYSTEM includes a complex assemblage of different kinds of biotic communities. Optimum conditions such as temperature and ground moisture are responsible for the establishment of forest communities.

Forests may be evergreen or deciduous which are distinguished on the basis of leaf into broad-leafed or needle leafed coniferous forests in the case of temperate areas. classified into three major categories: coniferous forest, temperate forest and tropical forest.

All these forest biomes are generally arranged on a gradient from north to south latitude or from high to lower altitude

 

Coniferous forest (boreal forest):

Cold regions with high rainfall, strong seasonal climates with long winters and short summers

evergreen plant species such as Spruce, fir and pine trees, etc and by animals such as the lynx, wolf, bear, red fox, porcupine, squirrel, and amphibians like Hyla, Rana, etc.

Boreal forest soils are characterized by thin podozols and are rather poor. Both because, the weathering of rocks proceeds slowly in cold environments and because the litter derived from conifer needle (leaf  is decomposed very slowly and is not rich in nutrients.

These soils are acidic and are mineral deficient.

This is due to movement of large amount of water through the https://exam.pscnotes.com/soil”>Soil, without a significant counter-upward movement of Evaporation, essential soluble nutrients like calcium, nitrogen and potassium which are leached sometimes beyond the reach of roots. This process leaves no alkaline oriented cations to encounter the organic acids of the accumulating litter.

The productivity and community stability of a boreal forest are lower than those of any other forest ecosystem.

Temperate deciduous forest:

The temperate forests are characterised by a moderate Climate and broad-leafed Deciduous trees, which shed their leaves in fall, are bare over winter and grow new foliage in the spring.

The Precipitation is fairly uniform throughout.

Soils of temperate forests are podozolic and fairly deep.

Temperate evergreen forest:

Parts of the world that have Mediterranean type of Climate are characterised by warm, dry summers and cool, moist winters. low broad leafed Evergreen trees.

Fire is an important hazardous factor in this ecosystem and the adaptation of the Plants enable them to regenerate quickly after being burnt.

Temperate rain forests:

seasonality with regard to temperature and rainfall

Rainfall is high, and fog may be very heavy. It is the important source of water than rainfall itself

The biotic diversity of temperate rain forests is high as compared to other temperate forest.

the diversity of plants and animals is much low as compared to the tropical rainforest.

 

Tropical rain forests:

 

Near the equator.

Among the most diverse and rich communities on the earth.

Both temperature and humidity remain high and more or less uniform.

The annual rainfall exceeds 200 cm and is generally distributed throughout the year.

The Flora is highly diversified The extreme dense vegetation of the tropical rain  forests remains vertically stratified with tall trees often covered with vines, creepers,   lianas, epiphytic orchids and bromeliads.

The lowest layer is an understory of trees,  shrubs, herbs, like ferns and palms.

Soil of tropical rainforests are red latosols, and they are very thick

Tropical seasonal forests:

also known as monsoon forest occur in regions where total annual rainfall is very high but segregated into pronounced wet and dry periods.

This kind of forest is found in South East Asia, central and south America, northern Australia, western Africa and tropical islands of the pacific as well as in India.

Subtropical rain forests:

Broad-leaved evergreen subtropical rain forests are found in regions of fairly high rainfall but less temperature differences between winter and summer

Epiphytes are common here.

Animal life of subtropical forest is very similar to that of tropical rainforests.

 

INDIAN FOREST TYPES

Forest types in India are classified by Champion and Seth into sixteen types.

 

Tropical Wet evergreen forests

are found along the Western Ghats, the Nicobar and Andaman Islands and all  along the north-eastern region.

It is characterized by tall, straight evergreen trees.

The trees in this forest form a tier pattern:

Beautiful fern of various colours and different varieties of orchids grow on the trunks of the trees.

Among the following States, which one has the most suitable climatic conditions for the cultivation of a large variety of orchids with minimum cost of production, and can develop

Tropical Semi-evergreen forests

found in the Western Ghats, Andaman and Nicobar Islands, and the Eastern

Himalayas.

Such forests have a mixture of the wet evergreen trees and the moist

deciduous trees. The forest is dense

Tropical Moist deciduous forests

found throughout India except in the western and the north -western regions.

The trees are tall, have broad trunks, branching trunks and roots to hold them firmly to the ground.

These forests are dominated by sal and teak, along with mango, bamboo, and rosewood.

Littoral and swamp

found along the Andaman and Nicobar Islands and the delta area of the Ganga and the Brahmaputra.

They have roots that consist of soft tissue so that the plant can breathe in the water.

Tropical Dry deciduous forest

The northern part of the country except in the North-East. It is also found in Madhya Pradesh, Gujarat, Andhra Pradesh, Karnataka, and Tamil Nadu. The canopy, of the trees does not normally exceed 25 metres.

The common trees are the sal, a variety of acacia, and bamboo.

Tropical Thorn forests

This type is found in areas with black soil: North, West, Central, and South India. The trees do not grow beyond 10 metres. Spurge, caper, and cactus are typical of this region.

Tropical Dry evergreen forest

Dry evergreens are found along Tamil Nadu Andhra Pradesh and Karnataka coast. It is mainly hard-leaved evergreen trees with fragrant flowers, along with a few  deciduous trees.

Sub-tropical Broad-leaved forests

Broad-leaved forests are found in the Eastern Himalayas and the Western Ghats, along the Silent Valley.

There is a marked difference in the form of vegetation in the two areas.

In the Silent Valley, the  poonspar, cinnamon, rhododendron, and fragrant grass are predominant.

In the Eastern Himalayas, the flora has been badly affected by the shifting cultivation and forest fires.

There are oak, alder, chestnut, birch, and cherry trees. There are a large variety of orchids, bamboo and creepers.

Sub-tropical Pine forests

found in Shivalik Hills, Western and Central Himalayas, Khasi, Naga, and Manipur Hills.

The trees predominantly found in these areas are the chir, oak, rhododendion, and   pine as well as sal, amla, and laburnum are found in the lower regions.

 

Sub-tropical Dry evergreen forests

hot and dry season and a cold winter. It generally has evergreen trees with shining

leaves that have a varnished look.

found in the Shivalik Hills and foothills of the Himalayas up to a height of 1000 metres.

Montane Wet temperate forests

In the North, found in the region to the east of Nepal into Arunachal Pradesh, receiving a minimum rainfall of 2000 mm. In the North, there are three layers of    forests: the higher layer has mainly coniferous, the middle layer has deciduous trees such as the oak and the lowest layer is covered by rhododendron and champa.

In the South, it is found in parts of the Niligiri Hills, the higher reaches of Kerala.

The forests in  the northern region are denser than in the South. Rhododendrons and a

variety of ground flora can be found here.

Himalayan Moist temperate Forest

This type spreads from the Western Himalayas to the Eastern Himalayas. The trees

found in the western section are broad-leaved oak, brown oak, walnut,

rhododendron,

Eastern Himalayas, the rainfall is much heavier and therefore the vegetation is also more lush and dense. There are a large variety of broad-leaved trees, ferri, and  bamboo.

Himalayan Dry temperate Forest

This type is found in Lahul, Kinnaur, Sikkim, and other parts of the Himalayas.

There are predominantly coniferous trees, along with broad-leaved trees such as the oak, maple, and ash. At higher elevation, fir, juniper, deodar, and chilgoza are found.

 

Sub alpine forest

Sub alpine forests extend from Kashmir to Arunachal Pradesh between 2900 to 3500 metres.

In the Western Himalayas, the vegetation consists mainly of juniper, hododendron, willow, and black currant.

In the eastern parts, red fir, black juniper, birch, and larch are the common trees.

Due to heavy rainfall and high humidity the timberline in this part is higher than that in the West.

Rhododendron of many species covers the hills in these parts.

Moist Alpine scrub

Moist alpines are found all along the Himalayas and on the higher hills near the Myanmar border. It has a low scrub, dense evergreen forest, consisting

mainly of rhododendron and birch. Mosses and ferns cover the ground in patches. This region receives heavy snowfall.

Dry alpine scrub

Dry alpines are found from about 3000 metres to about 4900 metres. Dwarf plants predominate, mainly the black juniper, the drooping juniper, honeysuckle, and willow.

Key Initiatives To Protect Marine And Coastal Environments

 

 

  1. Coastal Ocean Monitoring and Prediction System (COMAPS)
  • Being implemented from 1991. Assesses the health of coastal waters and facilitates management of pollution-related issues
  • Programme was restructured and modified in 2000 2001 to include pollution monitoring; liaison, regulation and legislation; and consultancy services.

2.Land Ocean Interactions in the Coastal Zone (LOICZ)

 

  • Launched in 1995. Investigates the effects of global change on the coastal zone
  • Aims to develop, on a scientific basis, the integrated management of coastal environments
  1. Integrated Coastal and Marine Area Management (ICMAM)
  • Launched in 1998
  • Aims at integrated management of coastal and marine areas.
  • Model plans for Chennai, Goa and Gulf of Kutch being prepared
  1. Society of  Integrated Coastal Management (SICOM)
  • Launched in 2010
  • Major national initiative to protect coastal ecosystems
  • A professional body with experts in various aspects of coastal science and management
  1. Institutions for Coastal Management
  • The Notification on Coastal Regulation Zone (CRZ), 1991 (as amended from time to time) aims at protecting coastal stretches in India.
  • India has created institutional mechanisms such as National Coastal Zone Management
  • Authority (NCZMA) and State Coastal Zone Management Authority (SCZMA) for enforcement and monitoring of the CRZ Notification.
  • These authorities have been delegated powers under Section 5 of the Environmental (Protection) Act, 1986 to take various measures for protecting and improving the quality-of the coastal environment and preventing, abating  and controlling environmental pollution in coastal areas.

Niche

 

Niche:- a  description  of  all  the  biological,  physical  and  chemical  factors  that  a  species needs to survive, stay healthy and reproduce. No two species have exact identical niches. Niche plays an important role in conservation of organisms.

Types of Niche

  1. Habitat niche – where it lives
  2. Food niche – what is eats or decomposes & what species it competes with
  3. Reproductive niche -how and when it reproduces.
  4. Physical & chemical niche – temperature, land shape, land slope, humidity & other requirement.

India’s action against Desertification

India as a signatory to United Nations Convention to Combat Desertification (UNCCD) has submitted four National Reports to UNCCD  in the years 2000, 2002, 2006 and 2010

Some of the major programmes currently implemented that address issues related to land degradation and desertification is:-

  1. Integrated Watershed Management Programme (IWMP),
  2. National Afforestation Programme (NAP),
  3. National Mission for Green India (GIM),
  4. The Mahatma Gandhi National Rural Employment Guarantee Scheme
  5. (MGNREGS),
  6. Soil Conservation in the Catchment of River Valley Project and Flood Prone River,
  7. National Watershed Development Project for Rainfed Areas (NWDPRA),
  8. Desert Development Programme (DDP)
  9. Fodder and Feed Development Scheme-component of Grassland Development including
  10. Grass Reserves, Command Area Development and Water Management (CADWM)  programme etc

 

AQUATIC ECOSYSTEM

 

Fresh water ecosystems- The salt content of fresh bodies is very low, always less than 5 ppt  (parts per thousand). E.g lakes, ponds, pools, springs, streams, and rivers

Marine ecosystems – the water bodies containing salt concentration equal to or above that of sea water (i.e., 35 ppt or above). E.g shallow seas and open ocean   Brackish water ecosystems- these water bodies have salt content in between 5 to 35 ppt. e.g. estuaries, salt marshes, mangrove swamps and forests.

 

AQUATIC ORGANISMS

The aquatic organisms are classified on the basis Of their one of occurrence and their ability to cross these zones. can be classified on the basis of their life form or location into five groups

  1. Neuston:

These are unattached organisms which live at the air-water interface such as floating plants, etc.

Some organisms spend most of their lives on top of the air-water interface such as water striders, while others spend most of their time just beneath the air-water interface and obtain most of their food within the water.

E.g., beetles and back-swimmers.

  1. Periphyton:

These are organisms which remain attached to stems and leaves of rooted plants or substances emerging above the bottom mud such as sessile algae and their associated group of animals.

  1. Plankton

This group includes both microscopic plants like algae (phytoplankton) and

animals like crustaceans and protozoans (zooplankton) found in all aquatic

ecosysteins, except certain swift moving waters

The locomotory power of the planktons is limited so that their distribution is

controlled, largely, by currents in the aquatic ecosystems.

  1. Nekton:

This group contains animals which are  swimmers.

The nektons are relatively large and powerful as they have to overcome the water currents.

  1. Benthos:

The benthic organisms are those found living in the bottom of the water mass.

Practically every aquatic ecosystem contains well developed benthos

Factors Limiting the Productivity of Aquatic Habitats

  1. Sunlight :

Sunlight penetration rapidly diminishes as it passes down the column of water.

The depth to which light penetrates a lake determines the extent of plant distribution.

Based on light penetration and plant distribution they are classified as photic and aphotic zones

Photic zone:

It is the upper layer of the aquatic ecosystems, up to which light penetrates and within which photosynthetic activity is confined.

The depth of this zone depends on the transparency of water.

photic (or .”euphotic”) zone is the lighted and usually well-mixed portion that extends from the lake surface down to where the light level is 1% of that at the surface.

Aphotic zone:

The lower layers of the aquatic ecosystems, where light penetration and plant growth are restricted forms the aphotic zone.

Only respiration activity takes place.(photic-both respiration and photosynthesis take place )

Aphotic zone is positioned below the littoral and photic zones to bottom of the lake where light levels are too low for photosynthesis.

This deep, unlit region is also known as the profundal zone.

Dissolved oxygen:

Oxygen enters the aquatic ecosystem through the air water interface and by the photosynthetic. average concentration of dissolved oxygen as 10 parts per million by weight.

Dissolved oxygen escapes the water body through air-water interface and through respiration of organisms (fish, decomposers, zooplanktons, etc )

The amount of dissolved oxygen retained in water is also influenced by temperature.

Other limiting factors which influence on aquatic productivity are

Transparency:

Transparency affects the extent of light penetration.

Suspended particulate matters such as clay, silt, phytoplankton, etc make the water turbidity. Consequently it limits the extent of light penetration and the photosynthetic activity in a significant way.

Temperature:

The water temperature changes less rapidly than the temperature of air because water has a considerably higher specific heat than air.

Since water temperatures are less subject to change, the aquatic organisms have narrow temperature tolerance limit.

LAKE ECOLOGY

 

Any – body of standing water, generally large enough in area and depth, irrespective of its hydrology, ecology, and other characteristics is generally known as lake.

Ageing of Lakes

The nutrient enrichment of the lakes promotes the growth of algae, aquatic plants and various fauna. This process is known as natural eutrophication.

Similar nutrient enrichment of lakes at an accelerated rate is caused by human activities and the consequent ageing phenomenon is known as ‘cultural eutrophication’.

In India, natural lakes (relatively few) mostly ile in the Himalayan region, the floodplains of Indus, Ganga and Brahmaputra.

Lake ‘Sudarshan’ in Gujarat’s Girnar area was perhaps the oldest man-made lake in India, dating back to 300 BC.

Lakes are also classified on the basis of their water chemistry. Based-on the levels of salinity, they are known as Freshwater, Brackish or Saline lakes (similar to that of classification of aquatic ecosystem).

On the basis of their nutrient content, they are categorized as Oligotrophic (very low nutrients), Mesotrophic (moderate nutrients) and Eutrophic (highly nutrient rich).

Removal of the nutrients from a lake

  • Flushing with nutrient-poor waters.
  • Deep water abstraction.
  • On-site P-elimination by flocculation/flotation with water backflow, or floating Plant
  • NESSIE with adsorbents.
  • On-site algae removal by filters and P-adsorbers.
  • 0n-site algae skimming and separator thickening.
  • Artificial mixing / Destratification (permanent or intermittent).
  • Harvest of fishes and macrophytes.
  • Sludge removal