AQUATIC ECOSYSTEM

An aquatic ecosystem is an ecosystem in and surrounding a body of water. Aquatic ecosystems contain communities of organisms dependent on each other and their environment.

Ecosystems consisting of water as the main habitat are known as aquatic ecosystems. Aquatic ecosystems are classified based on their salt content.

• Freshwater ecosystem- The salt content of fresh bodies is very low, always less than 5ppt(parts per thousand). Example- lakes, ponds, pools, springs, streams and rivers.
• Marine ecosystem- The water bodies containing salt concentration equal to or above that of seawater (35ppt). Example- shallow seas and open ocean.
• Brackish water ecosystem- These water bodies have salt content between 5-35ppt. Examples- estuaries, salt marshes, and mangrove swamps.

1. Aquatic Organisms

The aquatic organisms are classified based on their zone of occurrence and their ability to cross these zones. The organisms in the aquatic ecosystem are unevenly distributed but can be classified based on their life form or location into the following groups.

2. Factors Limiting The Productivity of Aquatic Ecosystem

Sunlight and oxygen are the most important limiting factors of aquatic ecosystems whereas moisture and temperature are the main limiting factors of terrestrial ecosystems.

Sun Light: 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 the light penetration and plant distribution they are classified as photic and aphotic zones.

Photic Zone: It is the upper layer of the aquatic ecosystem, up to which light penetrates and within which photosynthetic activity is confirmed. The depth of this zone depends on the transparency of water. Both photosynthesis and respiration activity take place. Photic(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 ecosystem, where light penetration and plant growth are restricted, form the aphotic zone. Only respiration activity takes place. The aphotic zone is positioned below the littoral and photic zones to the bottom of the lake where light levels are too low for photosynthesis. Respiration occurs at all depths so the aphotic zone is a region of oxygen consumption. This deep, unlit region is also known as the profundal zone.

Winter Kill: Snow cover of ice on the water bodies can effectively cut off the light, plunging the waters into darkness. Hence photosynthesis stops but respiration continues. Thus in shallow lakes, the oxygen gets depleted. Fish die, but it is not known until the ice melts and the floating fish is found. This condition is known as winter kill.

Dissolved Oxygen

• In aquatic ecosystems oxygen is dissolved in water, where its concentration varies constantly depending on factors that influence the input and output of oxygen in water.
• In freshwater the average concentration of dissolved oxygen is 0.0010(10 pm) by weight, which is 150 times lower than the concentration of oxygen in an equivalent volume of air.
• Oxygen enters the aquatic ecosystem through the air, and water interface and by photosynthetic activities of aquatic plants.
• The quantity of dissolved oxygen present in an ecosystem depends on the rate at which the aforementioned two processes occur.
• Dissolved oxygen escapes the water body through the air-water interface and respiration of organisms.
• The amount of dissolved oxygen retained in water is also influenced by temperature. Oxygen is less soluble in warm water. Warm water also enhances decomposing activity. Therefore, increasing the temperature of a water body increases the rate at which oxygen is depleted from water.
• When the dissolved oxygen level falls below 3-5ppm, many aquatic organisms are likely to die.

Other limiting factors which influence on aquatic productivity are-

Transparency: Transparency affects the extent of light penetration. Suspended particulate matters such as clay, slit, phytoplankton etc., make the water turbid. Consequently, it limits the extent of light penetration and photosynthetic activity in a significant way.

Temperature: The water temperature changes less rapidly than the temperature of air because water has considerably higher specific heat than air, i.e., larger amounts of heat energy must be added to or taken away from water to raise or lower its temperature. Since water temperatures are less subject to change, aquatic organisms have a narrow temperature tolerance limit. As a result, even small changes in water temperature are a great threat to the survival of aquatic organisms when compared to the changes in air temperatures in terrestrial organisms.

The classification of organisms and limiting factors discussed here apply in general to all aquatic ecosystems-lakes, ponds, rivers, streams, estuaries, oceans, and seas.

Lake Ecology: A body of standing water, generally large enough in area and depth, irrespective of its hydrology, ecology and other characteristics is generally known as a lake. A lake ecosystem or lacustrine ecosystem includes biotic as well as abiotic physical and chemical interactions. Lake ecosystems are prime examples of lentic ecosystems, which include ponds, lakes and wetlands.

Ageing of Lakes: Like any organism, lakes are born as they originate from various geological and geomorphic events and grow with time to change in their various morphological and functional characteristics and eventually die. They receive their water from surface runoff(sometimes also groundwater discharge) and along with it various chemical substances and mineral matter eroded from the land. Over periods spanning millennia, ‘ageing’ occurs as the lakes accumulate mineral and organic matter and gradually, get filled up.

Eutrophication: 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 (discharge of waste waters or agricultural runoff) and the consequent ageing phenomenon is known as cultural eutrophication.

3. Lakes in India

• In India, natural lakes(relatively few) mostly lie in the Himalayan region, the floodplains of Indus, Ganga and Brahmaputra.
• In the semi-arid and arid regions of western and peninsular India, tens of thousands of water bodies have been constructed over millennia.
• Lake ‘Sudharshan’ in Gujarat’s Girnar area was perhaps the oldest man-made lake in India, dating back to 300 BC.
• Lakes are also classified based on their water chemistry. Based on the levels of salinity, they are known as Fresh water, Brackish or Saline lakes(similar to that classification of aquatic ecosystems.)
• based on their nutrient content, they are categorized as Oligotrophic(very low nutrients), Mesotrophic(moderate nutrients) and Eutrophic(highly nutrient rich).
• The vast majority of lakes in India are either eutrophic or mesotrophic because of the nutrients derived from their surroundings or organic wastes entering them.

General Characteristics of Oligotrophic and Eutrophic Lakes

Type of Lakes   

Removal of the Nutrients From Lake

• Flushing with nutrient lower sometimes -poor waters.
• Deep water abstraction.
• On-site P-elimination by flocculation/floatation with water backflow or floating plant Nessie with adsorbents.
• On-site algae removal by filters and P-absorbers.
• On-site algae skimming and separator thickening.
• Artificial mixing / Destratification ( permanent or intermittent).
• Harvest of fishes and macrophytes.
• Sludge removal.

Ameenpur Lake First Biodiversity Heritage Site 

Under the Green India Mission(GIM), perspective plans and annual plans of operations of six states have been approved in the first sitting of the National Executive Council held in May 2015.

Ameenpur Lake gets the status of the first Biodiversity Heritage Site in the country under the Biodiversity Act, 2002. It is an ancient, man-made lake in the western part of Telangana. A Biodiversity Heritage site is an area of biodiversity importance, which harbours rich biodiversity, and wild relatives of crops or areas, which lie outside the protected area network. Biodiversity Management Committee funds for its protection.

4. Eutrophication

• In the Greek language, Eutrophia means adequate and healthy nutrition.
• Eutrophication is a syndrome of ecosystem, response to the addition of artificial or natural nutrients like nitrates and phosphates through fertilizer, sewage etc., that fertilize the aquatic ecosystem.
• It is primarily caused by the leaching of phosphates and nitrate-containing fertilizers from agricultural lands into lakes or rivers.
• The growth of green algae which we see in the lake surface layer is the physical identification of an Eutrophication.
• Some algae and blue-green bacteria thrive on the excess ions and a population explosion covers almost the entire surface layer known as an algal bloom. This growth is unsustainable.
• As Algal Bloom covers the surface layer, it restricts the penetration of sunlight.
• Oxygen is required by all respiring animals in the water and it is replenished by diffusion and photosynthesis of green plants.
• The oxygen level is already low because of the population explosion and further oxygen is taken up by micro-organisms which feed off the dead algae during the decomposition process.
• Due to reduced oxygen levels, fishes and other aquatic organisms suffocate and die.
• The anaerobic conditions can promote the growth of bacteria which produces toxins deadly to aquatic organisms, birds and mammals.
• All this eventually leads to the degradation of the aquatic ecosystem and the death of its organisms.
• It often leads to changes in animal and plant populations & degradation of water and habitat quality.

Types of Eutrophication 

Sources: There are two different sources of eutrophication.

Point Source: Directly attribute to one influence. Point sources are easy to regulate. In point source, nutrient waste travels directly from source to water.

Non-Point Source: It is from various ill-defined and diffuse sources. Vary spatially and temporarily and are difficult to regulate.

Process of Eutrophication

• Agricultural runoff, untreated sewage, etc,
• Transportation to the aquatic ecosystem.
• Nutrient accumulation and enrichment.
• Overgrowth of algae.
• Algal bloom.
• Algae covering the aquatic surface layer.
• Restricts the sunlight penetration, and diffusion of dissolved oxygen.
• Underground aquatic algae, plants die.
• Bacterial decomposition consumes the available oxygen in the aquatic ecosystem
• Anoxia condition- devoid of oxygen
• All aquatic organisms die due to lack of dissolved oxygen.
• Degradation of aquatic ecosystem.

Effects

Change in Ecosystem: Eutrophication eventually creates a detritus layer on the ponds, and lakes and produces a successively shallower depth of surface water. Eventually, the water body is reduced into a marsh whose plant community is transformed from an aquatic environment to a recognizable terrestrial ecosystem.

Decreased Biodiversity: Algal blooms restrict the sunlight from penetrating and affect the photosynthesizing plants. It causes the death of plants. Bacteria consumes all the oxygen on decomposition & results in devoid of oxygen. Eventually, it leads to the death of all living organisms in the aquatic ecosystem. New Species Invasion- Eutrophication may make the ecosystem competitive by transforming the normal limiting nutrients to abundant levels. This causes shifts in the species composition of the ecosystem.

Toxicity

• Some algal blooms when die or are eaten, release neuro & hepatotoxic which can kill aquatic organisms and pose a threat to humans. (Shellfish poisoning)
• Depletion of dissolved oxygen level.
• Increased incidents of fish kills and loss of desirable fish species and reduction in harvesting.
• Loss of coral reefs.
• Decrease in water transparency and increased turbidity.
• Color(yellow, green, red), smell and water treatment problems.
• Increased biomass of inedible toxic phytoplankton.
• Increase in bloom of gelatinous zooplankton.
• Increased biomass of benthic and epiphytic algae.
• Unsuitable for aesthetic recreation and reduction in value of water body.

Mitigation

• Riparian buffer- it is an area adjacent to a stream, lake or wetland that contains a combination of trees, shrubs, and other perennial plants and is managed differently from the surrounding landscape, primarily to provide conservation benefits.
• Interfaces between a flowing body of water and land created near the waterways, farms, roads, etc,.in an attempt to filter pollution.
• Sediments and nutrients are deposited in the buffer zones instead of deposition in water.
• Minimize the non-point pollution.
• Nitrogen testing and modelling.
• N-testing is a technique to find the optimum amount of fertilizer required for crop plants. It will reduce the amount of nitrogen lost to the surrounding area.
• Treatment of Industrial effluents.
• Organic farming & integrated farming system.
• Reduction in livestock densities.
• Improving the efficiency of the use of fertilizer.
• Treatment of runoff from street and storm drains.
• Reduction in nitrogen emission from vehicles and power plants.
• Increase in efficiency of nitrogen & phosphorus removal from municipal wastewater.

Policies

• Multi-dimensional in nature should include.
• Education & awareness.
• Research, monitoring & evaluation.
• Regulations
• Fiscal & economic incentives.
• Ecosystem preservation & restoration.

Harmful Algal Blooms

• Algae or phytoplankton are microscopic organisms that can be found naturally in coastal waters. They are major producers of oxygen and food for many of the animals that live in these waters.
• When environmental conditions are favourable for their development, these cells may multiply rapidly and form high numbers of cells and this is called an algal bloom.
• A bloom often results in a colour change in the water. Algal blooms can be any colour, but the most common ones are red or brown. These blooms are commonly referred to as red or brown tides.
• Most algal blooms are not harmful but some produce toxins and affect fish, birds, marine mammals and humans. The toxins may also make the surrounding air difficult to breathe. These are known as Harmful Algal Blooms(HABs).

Red Tide

• ”Red Tide” is a common name for such a phenomenon where certain phytoplankton species contain pigments and “bloom” such that the human eye perceives the water to be discoloured.
• Blooms can appear greenish, brown and even reddish orange depending upon the type of organism, the type of organism, the type of water and the concentration of the organisms.
• The term red tide is thus a misnomer because blooms are not always red, they are not associated with tides, they are not usually harmful and some species can be dangerous at low cell concentrations that do not discolour the water.
• They are scientifically referred to as Harmful Algal Blooms (HABs).

Causes of Algal Blooms

• Blooms occur when several colonies start combining rapidly when conditions like nutrient concentration, salinity and temperature are optimal.
• Blooms can be due to several reasons. Two common causes are nutrient enrichment and warm waters.
• Nutrient enrichment of water, especially phosphates and nitrogen, is often the result of pollution and can cause algal blooms.
• Water temperature has also been related to the other occurrence of algal blooms, with unusually warm water being conducive to blooms.

Dangerous Effects of HABs 

• HABs can deplete oxygen in the water and lead to low dissolved oxygen levels.
• When masses of algae die and decompose, the decaying process can deplete oxygen in the water, causing the water to become low in oxygen. Thus oxygen is depleted by HABs.
• When oxygen levels become too low, fish suffocate and die.
• Some algal species in blooms produce potent neurotoxins that can be transferred through the food web where they affect and even kill the higher forms of life such as zooplankton, shellfish, fish, birds, marine mammals and even humans that feed either directly or indirectly on them.

HABs as Environmental Hazard

• HABs are an environmental hazard because they make people sick when contaminated shellfish are eaten or when people breathe aerosolized HAB toxins near the beach.
• In addition, HAB events can result in the closure of shellfish beds, massive fish kills, death of marine mammals and seabirds and alteration of marine habitats.
• As a consequence, HAB events adversely affect commercial and recreational fishing, tourism and valued habitats, creating a significant impact on local economies and the livelihood of coastal residents.

Exposure to HAB Toxins: Most illness associated with HAB exposure is the result of consuming toxins that are present in shellfish or finfish. Some HAB toxins can become airborne during bloom and people can become ill by inhaling toxins.

Seafood-Safety: Usually, it is safe to eat seafood. Consuming shellfish that have been harvested from waters with high levels of harmful algae and consuming fish that have lesions or that were caught in an area during an algal bloom can result in illness.

HABs-Climate Change: Because the growth, toxicity and distribution of harmful algal bloom(HAB) species are all tied to the environment, climate changes can change the occurrence, severity and impacts of HAB events.

5. Wetland Ecosystem

• Wetlands are areas intermediate in character between deep water and terrestrial habitats, also transitional in nature and often located between them.
• These habitats experience periodic flooding from adjacent deep water habitats and therefore support plants and animals specifically adapted to such shallow flooding or water logging of the substrate, were designated as wetlands.
• They included lake littorals(marginal areas between the highest and lowest water level of the lakes), flood plains and other marshy or swampy areas where water gets stagnated due to poor drainage or relatively impervious substrate and bogs, ferns and mangroves due to similar ecological characteristics.
• Flood plains include areas lying adjacent to the river channels beyond the natural levees(a levee is a natural or artificial wall that blocks water from going where we don’t want it to go) and periodically flooded during high discharge in the river.e

Definition

Areas of marsh, fen (low & marshy or frequently flooded area of land), peatland/water, whether natural or artificial, permanent or temporary with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide does not exceed 6 meters.

Characteristics: Covered by water or has waterlogged soil for at least seven days during the growing season. Adopted plant life(hydrophytes). Hydric soils(not enough oxygen available for some plants)

Wetlands Classification

Wetlands are classified into 

1. Inland wetland—two types

• Natural- lakes, ponds, ox-bow lakes, waterlogged, seasonal, swamp/marsh.
• Man-made reservoirs, tanks, waterlogged, ash ponds.

1. Coastal wetland—-two types

• Natural- estuary, lagoon, creek, backwater, bay, coral leaf, tidal flat, mangroves, salt marsh
• Man-made- salt pans, aquaculture

Functions of Wetlands 

• Habitat to aquatic flora and fauna, as well as numerous species of birds, including migratory species.
• Filtration of sediments and nutrients from surface water.
• Nutrient recycling
• Water purification
• Flood mitigation
• Maintenance of streamflow
• Groundwater recharging
• Provide drinking water, fish, fodder, fuel.
• Control the rate of runoff in urban areas.
• Buffer shorelines against erosion.
• Comprise an important resource for sustainable tourism, recreation and cultural heritage
• Stabilization of local climate
• Source of livelihood for local people
• Genetic reservoir for various species of plants(rice)
• Supporting specific diversity

Reasons For Depletion

• Conversion of lands for agriculture
• Overgrazing
• Removal of sand from beds
• Aquaculture
• Habitat destruction and deforestation
• Pollution
• Domestic waste
• Agricultural runoff
• Industrial affluents
• Climate change

Mitigation

• Survey and demarcation
• Protection of natural regeneration
• Artificial regeneration
• Protective measures
• Afforestation
• Weed control
• Soil conservation measures and afforestation
• Wildlife Conservation
• Removal of encroachments
• Eutrophication abatement
• Environmental awareness

Distinction from Lakes

• Although the Ministry of Environment and Forests has not adopted a clear distinction between Lakes and wetlands, the National Lake Conservation Program(NLCP) considers lakes as standing waterbodies which have a minimum water depth of 3 meters, generally cover a water spread of more than 10 hectares, and have very little aquatic vegetation. (macrophytes)
• These water bodies are used primarily for drinking water supplies, irrigation and recreation.
• Excessive growth of macrophytes generally present in wetlands, affects the water quality adversely and interferes with the utilization of the water body.
• However, marginal aquatic vegetation (wetlands), particularly comprising of emergent plants and those inhabiting waterlogged soils, is not only desirable but is to be promoted because it checks erosion, serves habitat for wildlife and helps improve water quality.
• Wetlands(generally less than 3 m deep over most of their area) are usually rich in nutrients (derived from surroundings and their sediments) and have abundant growth of aquatic macrophytes.
• They support high densities and diversity of fauna, particularly birds, fish and macroinvertebrates, and therefore, have high value for biodiversity conservation. These shallow lakes are rightfully categorized as wetlands.
• Lakes are generally less important compared to wetlands from the viewpoint of ecosystem and biodiversity conservation.

India's Wetlands

• Wetlands are areas of critical ecological significance, as they support biodiversity, support millions of people directly and indirectly, protect from storms, and flood control, improve water quality, and supply food, fiber and raw materials.
• India has a total of 27,403 wetlands of which 23,444 are inland wetlands and 3,959 are coastal wetlands. Wetlands occupy 18.4% of the country’s area of which 70% are under paddy cultivation.
• Natural wetlands in India range from high altitude wetlands in the Himalayas; flood plains of the major river systems; saline and temporary wetlands of the arid and semi-arid regions; coastal wetlands like lagoons, backwaters, estuaries, mangroves, swamps coral reefs etc.,

National Wetlands Conservation Program (NWCP) 

• NWCP was implemented in the year 1985-86.
• Under the program, 115 wetlands (annexure) have been identified by the Ministry which require urgent conservation and management interventions.

Aim: Conservation of wetlands to prevent their further degradation and ensure their wise use for the benefit of local communities and overall conservation of biodiversity.

Objectives 

• To lay down policy guidelines for the conservation and management of wetlands in the country.
• To provide financial assistance for undertaking intensive conservation measures in the identified wetlands.
• To monitor the implementation of the program and to prepare an inventory of Indian wetlands.
• The Central Government is responsible for the overall coordination of wetland conservation programs and initiatives at the international & national levels. It also provides guidelines and financial & technical assistance to the state government.
• Since the land resources belong to them, the state governments / UT administrations are responsible for the management of wetlands and implementation of the NWCP to ensure their wise use.

Criteria for Identification of Wetlands of National Importance

Criteria for identification of wetlands of national importance under NWCP are the same as those prescribed under the “Ramsar Convention on Wetlands “ and are as given below:

1. If it contains a representative, rare or unique example of a natural or near-natural wetland type found within the appropriate biogeographic region.
2. If it supports vulnerable, endangered or critically endangered species; or threatened ecological communities.
3. If it supports populations of plant or animal species important for maintaining the biological diversity of a particular biogeographic region.
4. If it supports plant or animal species at a critical stage in their life cycles or provides refuge during adverse conditions.
5. If it regularly supports 20,000 or more water birds.
6. If it regularly supports 1% of the individuals in a population of one species or subspecies of water birds.
7. If it supports a significant proportion of indigenous fish subspecies, species or families, life-history stages, species interactions or populations that are representative of wetland benefits or values and thereby contribute to global biological diversity.
8. If it is an important source of food for fishes, spawning ground, nursery or migration path on which fish stocks, either within the wetland or elsewhere depend. Specific criteria based on water/life and culture.
9. If it is an important source of food and water resources, increased possibilities for recreation and eco-tourism, improved scenic values, educational opportunities, and conservation of cultural heritage.

6. Montreux Record

Montreux Record is the principal tool under the Ramsar Convention and is a register of wetland sites on the list of wetlands of international importance.

It highlights those sites where adverse changes in ecological character have occurred, are likely to occur as a result of technological developments, pollution or other human interference and are therefore in need of priority conservation attention. It is maintained as part of the Ramsar List.

Montreux Records are employed to identify priority sites for positive national and international conservation attention. Sites may be added to and removed from the Record only with the approval of the Contracting Parties in which they lie.

Montreux Record Sites in India 

Chilika Lake, Odisha was placed on the Montreux Record in 1993 due to siltation, which was choking the mouth of the lake. Following the rehabilitation efforts of the government, it was removed from the record in 2002. For this achievement, the Chilika Development Authority received the Ramsar Wetland Conservation Award in 2002.

Loktak Lake, Manipur was included on the Montreux Record 1993, as a result of ecological problems like deforestation in the catchment area, infestation of water hyacinth and pollution. The construction of a hydroelectric power plant has caused the local extinction of several native fish species.

Keoladeo National Park, Rajasthan was placed on the Montreux Record in 1990 due to water shortage and an unbalanced grazing regime around it. The invasive growth of the grass Paspalum distichum has changed the ecological character of large areas of the site, reducing its suitability for certain water bird species, notably the Siberian crane.

Loktak Lake and Keoladeo National Park are the two Montreux Record sites in India.

Neknampur Lake

The Neknampur lake, Hyderabad is the largest floating treatment wetland in the country. Floating treatment wetland works based on hydroponics technique. Hydroponics permits plants to grow on water with the help of sunlight without soil. A floating island unit is essentially a platform designed using styrofoam, bamboo, gunny bags and coir and, it performs the function of a wetland.

7. Estuary Ecosystem

Characteristics

• An estuary is a semi-enclosed coastal body of water with one or more rivers or streams flowing into it.
• It has a free connection with the open sea.
• The complete salinity range from 0-35 ppt is seen from the head(river end) to the mouth(sea end) of an estuary.
• An estuary has very little wave action, so it provides a calm refuge from the open sea. It provides the shelter for some of the animals.
• It is the most productive region as it receives a high amount of nutrients from fresh and marine water.
• Estuaries are the most heavily populated areas throughout the world, with about 60% of the world’s population living along estuaries and the coast.
• Coastal lakes which have their connection with the sea through small openings are better known as lagoons or backwaters.
• They exhibit a gradient in salinity from freshwater to marine depending upon the extent of influence of the seawater.

Most estuaries can be grouped into 4 geomorphic categories based on the physical processes responsible for their formation.

1. Rising sea level
2. Movement of sand and sandbars
3. Glacial processes
4. Tectonic processes

• Estuaries are typically classified by their geomorphological features or by water circulation patterns and can be referred to by many different names, like bays, harbours, lagoons, inlets, etc,
• The banks of estuarine channels from a favoured location for human settlements, which use the estuaries for fishing and commerce, but nowadays also for dumping civic and industrial waste.
• Estuaries are usually biologically highly productive zones.
• They also act as a filter for some dissolved constituents in river water; these precipitate in the zone where river water meets seawater.

A Healthy Estuary

• A healthy estuary supports a host of plants and animals. It stores and recycles nutrients, traps sediment and forms a buffer between coastal catchments and the marine environment.
• It also absorbs traps and detoxifies pollutants, acting as a natural water filter. When all such processes remain functional an estuary is considered to be healthy.
• Estuaries support diverse habitats, such as mangroves, salt marshes, seagrass, mudflats etc.

Life in Estuary

• Only certain types of plants and animals specially adapted to the “brackish” estuarine waters flourish in the estuaries.
• Factors influencing the growth and distribution of organisms in an estuary are its salinity and the amount of flooding.
• Estuaries are homes to all kinds of terrestrial or land-based plants and animals, such as wood storks, pelicans, coniferous and deciduous trees and butterflies.
• Estuaries are also home to unique aquatic plants and animals like turtles, sea lions, sea catfish, saltworts, eelgrass, salt grasses, cord grasses, sea grass, sedge and bulrush.
• Predators are important to the estuary because of their end position in most consumer food chains.

Benefits of Estuarine Ecosystem

• Water quality regulation and groundwater recharge
• Habitat, breeding and nursery grounds for plants and animals
• Biological productivity
• Social benefits
• Community values
• Indigenous values
• Recreation values
• Research/knowledge values
• Economic benefits
• Commercial fishing
• Ports and harbours
• Tourism
• Navigation
• Storm and erosion
• Agriculture, aquaculture and industry

Estuary Ecosystem in India 

• The country has 14 major, 44 medium, and 162 minor river drains into the sea through various estuaries.
• Estuaries are an important and distinct component of the coastal landscape with highly complex ecosystems, varying physical-chemical properties and highly diverse flora and fauna.
• Major estuaries occur in the Bay of Bengal. Many estuaries are locations of some of the major seaports.
• Most of India’s major estuaries occur on the east coast. In contrast, the estuaries on the west coast are smaller.

Issues of Indian Estuarine Ecosystem

The specific issues which have affected the estuarine environment in the country are :

Water Flow: Changes in water flow in various estuaries, either far in excess or much lower than required (Hooghly, Godavari, Pulicat, Krishna, Narmada etc,.) Modifications of the estuarine catchments(most of the Indian estuaries)

Pollution and Water Quality: Pollution through industries and combined city sewage (for example, all the Indian estuaries)

Tourism and Recreation: Recreational boating (Hooghly in West Bengal, Chilika Lake in Orissa), Recreational fishing ( Chilika) and Navigation (Hooghly). 

Shipping and Ports: Dredging (Hooghly) and Shipping (Hooghly)

Land Use

• Expansion of urban and rural settlements (Krishna, Pulicat, Hooghly, Cauvery)
• Marinas, groynes, land reclamation and other structures (Pulicat, Hooghly)
• Mining and industries (Zuari, Goa, Hooghly)
• Agriculture (all the estuaries)
• Dumping of solid wastes (all the Indian estuaries)

Commerical Fishing and Aquaculture

• Over-exploitation of target fish stock due to increased demand (ex: all the Indian estuaries)
• Reclaiming the fringed areas for intensive aquaculture in pens(an enclosure to keep domesticated animals.)
• Obstructing the migratory routes of fish and prawn recruitment (ex: Chilika, Pulicat)
• Polluting the environment through feeding of stocked fish and prawns in pens (Chilika)
• Destruction of biodiversity through prawn seed collection and operation of small-meshed nets (ex: Hooghly, Chilika, Pulicat)

Climate Change: Submergence of catchment areas due to rise in water level (ex: all the major Indian estuaries). Change in biodiversity profile, affecting the production and productivity (ex: all the major Indian estuaries)

8. Mangroves

Mangroves are the characteristic littoral plant formation of tropical and subtropical sheltered coastlines. Mangroves are trees and bushes growing below the high water level of spring tides which exhibit a remarkable capacity for saltwater tolerance.

Characteristics of Mangroves

• They are evergreen land plants growing on sheltered shores, typically on tidal flats, deltas, estuaries, bays, creeks and barrier islands.
• The best locations are where abundant silt is brought down by rivers or on the back shore of accreting sandy beaches.
• Their physiological adaptations to salinity stress and water-logged anaerobic mud are high.
• They require high solar radiation and have the ability to absorb fresh water from saline /Degraded brackish water.
• It produces pneumatophores (blind roots) to overcome respiration problems in anaerobic soil conditions.
• Mangroves occur in a variety of configurations. Some species (Rhizophora) send arching prop roots down into the water. While others (Avicennia) send vertical “pneumatophores” or air roots up from the mud.
• Most mangrove vegetation has a lenticellated bank which facilitates more water loss and produces coppices. Leaves are thick and contain salt-secreting glands.
• Mangroves exhibit viviparity mode of reproduction, i.e., Seeds germinate in the tree itself(before falling to the ground). This is an adaptive mechanism to overcome the problem of germination in saline water.
• Some secret excess salt through their leaves, if you look closely you can see crystals of salt on the back of the leaves, others block the absorption of salt at their roots.
• The adventitious roots that develop from the base of stem nodes are called stilt roots. They grow in the downward direction and join the soil substratum.
• Usually they provide mechanical support to the weaker stems. They also facilitate faster vertical growth of the stem.

Mangroves in India

• The mangroves of Sundarbans are the largest single block of tidal holophytic mangroves in the world. The major species of this dense mangrove forest include Herritiera fames, Rhizophora species, Avicennia species, Bruguiera species, Ceriops decandra, and sonneratia species are found along the creeks.
• This mangrove forest is famous for the royal Bengal tiger and crocodiles. Mangrove areas are being cleared for agricultural use.
• The mangroves of Bhitarkanika(Odisha), Which is the second largest in the Indian subcontinent, harbour a high concentration of typical mangrove species and high genetic diversity.
• Mangrove swamps occur in profusion in the intertidal mud flats on both sides of the creeks in the Godavari- Krishna deltaic regions of Andhra Pradesh.
• Mine grows of Pichavaram and Vedaranyam are degraded mainly due to the construction of ponds and salt pans.
• On the West Coast of India, mangroves, mostly scrubby and degraded occur along the intertidal region of estuaries and creeks in Maharashtra, Goa and Karnataka.
• The mangrove vegetation in the coastal zone of Kerala is very sparse and thin.
• In Gujarat, mangroves Avicennia marine, Avicennia officinalis and rhizophora mucronata are Found mainly in the Gulf of Kuchchh and the Kori Creek.
• Mangroves are scrubby types with stunted growth, forming narrow, discontinuous patches on soft clay mud.
• The condition of the mangrove is improving especially in the Kori Creek region which is a paleo delta of the Indus River.
• In size mangroves range from bushy stands of dwarf mangroves found in the Gulf of Kuchchh to taller stands found in the Sundarbans.
• On the Andaman and Nicobar islands the small tidal estuaries, neritic inlets and the lagoons support a dense and diverse undisturbed mangrove flora.

Role of Mangroves

• Mangrove plants have special roots like prop roots, and pneumatophores which help to impede water flow and thereby enhance the deposition of sediment in areas, stabilize the coastal shores, and provide a breeding ground for fishes.
• Mangroves moderate monsoon tidal floods and reduce inundation of coastal lowlands.
• It prevents coastal soil erosion.
• It protects coastal lands from tsunamis, hurricanes and floods.
• Mangroves enhance the natural recycling of nutrients.
• Mangrove supports numerous flora, avifauna (birds)and wildlife.
• Provide a safe and favourable environment for the breeding, spawning, and rearing of several fishes.
• It protects coastal inland from adverse climatic elements.
• It supplies wood, firewood, medicinal plants and edible plants to local people.
• It provides numerous employment opportunities to local communities and augments their livelihood.
• Fine, anoxic sediments, deposited under mangroves act as sinks for a variety of heavy metals which are scavenged from the overlying seawater by colloidal particles in the sediments.
• By cleaning our air, they take in carbon dioxide, store the carbon in their roots, leaves, branches and surrounding silt and release oxygen back to the atmosphere along with a little methane gas.

Threat

They are destroyed for conversion of area for agricultural purposes, fuel, fodder and Salinization, mining, oil spills, aquacultural use of chemical pesticides and fertilizers, and industrial purposes.

9. Coral Reefs

• Coral is a living animal. Coral has a symbiotic relationship with ‘Zooxanthellae’, microscopic algae which lives on coral (Instead of living on the sea floor, the algae lives up on the coral which is closer to the ocean surface so that the algae gets adequate light).
• Zooxanthelle assist the coral in nutrient production through its photosynthetic activities. These activities provide the coral with fixed carbon compounds for energy, enhance calcification, and mediate elemental nutrient flux.
• The tissues of corals themselves are not the beautiful colours of the coral reef, but instead clear. The corals receive their colouration from the zooxanthellae living within their tissues.
• The host coral polyp in return provides its Zooxanthelle with a protected environment to live within and a steady supply of carbon dioxide for its photosynthetic process.
• There are two types of corals- hard corals and soft corals like sea fans and gorgonians. Only hard corals build reefs.
• The builders of coral reefs are tiny animals called polyps. As these polyps thrive, grow, and then die, they leave their limestone(calcium carbonate)skeletons behind.
• The limestone is colonized by new polyps. Therefore, a coral reef is built up of layers of these skeletons covered ultimately by living polyps.
• The reef-building, hermatypic corals can form a wide range of shapes. Coral reefs may be branched, table-like, or look like massive cups, boulders or knobs.
• While the majority of coral reefs are found in tropical and subtropical water, there are also deep-water corals in colder regions.
• Cold water coral inhabit deep, cold(39 to 50^o Fahrenheit) water. The United Nations Environment Program reports that there are more cold-water coral reefs worldwide than tropical reefs.
• There are only about six different coral species associated building with these reefs. The largest cold-water coral reef is the Roast Reef of Norway.

Features

• They occur in shallow tropical areas where the seawater is clean, clear and warm.
• The coral reef cover in Indian waters is roughly estimated up to 19,000 square kilometres.
• Coral reefs are one of the most productive and complex coastal ecosystems with high biological diversity.
• The high productivity is owing to the combination of its own primary production and support from its surrounding habitat.
• Reef-building coral or a symbolic association of polyps and zooxanthelle.
• The quote also generally slow-growing colonies of animals while zooxanthellae are fast-growing plants.
• Even though corals live in nutrient-poor waters, their capability to recycle scarce nutrients is enormous.
• In the coral reef ecosystem, many invertebrates, vertebrates and plants live in close association with the corals, with tight resource coupling and recycling, allowing coral reefs to have extremely high productivity and biodiversity, such that they are referred to as ‘the tropical rainforests of the oceans.’

Classification

• The coral reefs are classified depending on their locations into fringing, patch, and barrier.
• The fringing reefs are contagious with the show and they are the most common-by occurring reef form, found in Andamans.
• Patch reefs are isolated and discontinuous patches, lying shoreward of offshore reef structures as seen in the Palk Bay, Gulf of Mannar and Gulf of Kutch.
• Barrier reefs are linear offshore reef structures that run parallel to coastlines and arise from submerged shelf platforms. The water body between the reef and the shore is termed a lagoon. Barrier Reefs are seen in Nicobar and Lakshadweep.
• Atolls are circular or semi-circular reefs that arise from subsiding sea floor platforms as coral reef building keeps ahead of subsidence. The examples are the atolls of Lakshadweep and Nicobar.
• When the reef-building does not keep pace with subsidences, reefs become submerged banks as seen in Lakshadweep.
• Seagrasses grow on Kavaratti atoll, and mangroves are prevalent on Andaman and Nicobar coral reefs.
• Four major reef areas of India, Andaman and Nicobar Islands are found to be very rich in species diversity followed by the Lakshadweep Islands, the Gulf of Mannar and finally the Gulf of Kuchchh.

Functions of Coral Reefs

• Coral reefs are natural protective barriers against erosion and storm surge.
• The coral animals are highly adapted for capturing plankton from the water, thereby capturing nutrients.
• Largest biogenic calcium carbonate producer.
• They provide substrate for mangroves
• Coral reefs provide habitat for a large variety of animals and plants including avifauna.

Theat 

• Natural causes may be due to the outbreak of reef-destroying mechanisms, “bleaching” and depletion of essential symbionts.
• Anthropogenic causes- may be due to chemical pollution (pesticides, cosmetics), industrial pollution, mechanical damage, nutrient loading or sediment loading, dredging, shipping, tourism, mining or collection, thermal pollution, intensive fishing, etc,
• Coral reef eco worldwide have been subject to unprecedented degradation over the past few decades.
• Disturbances affecting coral reefs include anthropogenic and natural events. Recent accelerated coral reef decline seems to be related mostly to anthropogenic impacts and nutrient overloading.
• Natural disturbances which cause damage to coral reefs include violent storms, flooding, high & low-temperature extremes, El Niño Southern Oscillation events, subaerial exposures, predatory outbreaks and epizootics.
• Coral reef bleaching is a common stress response of corals to many of the various disturbances.

Coral Bleaching

• Bleaching or the paling of coral colour occurs when- the densities of zooxanthelle decline, and the concentration of photosynthetic pigments within the zooxanthelle fall.
• When corals bleach, they commonly lose 60-90% of their zooxanthelle and each zooxanthelle may lose 50-80% of its photosynthetic pigments.
• If the stress-causing bleaching is not too severe and if it decreases in time, the affected corals usually regain their symbiotic algae within several weeks or a few months.
• If zooxanthelle loss is prolonged, i.e., if the stress continues and depleted zooxanthelle populations do not recover, the coral host eventually dies.
• High temperature and irradiance stressors have been implicated in the disruption of enzyme systems in zooxanthelle that offer protection against oxygen toxicity.
• Photosynthesis pathways in zooxanthelle are impaired at temperatures above 30^oC, this effect could activate the disassociation of coral / algal symbiosis.
• Low or high-temperature shocks results in zooxanthelle, low as a result of cell adhesion dysfunction.
• This involves the detachment of Cnidarian endodermal cells with their zooxanthelle and the eventual expulsion of both cell types.

Ecological Causes of Coral Bleaching

As coral reef bleaching is a general stress response, it can be induced by a variety of factors, alone or in combination.

It is therefore difficult to unequivocally identify the causes of bleaching events. The following stressors have been implicated in coral reef bleaching events.

Tempearture (Major Cause)

Coral species live within a relatively narrow temperature margin, anomalously low and high sea temperatures can induce coral bleaching. Bleaching is much more frequently reported from elevated seawater temperatures. Bleaching events also occur during sudden temperature drops accompanying intense upwelling episodes, and seasonal cold-air outbreaks.

Solar Irradiance

• Bleaching during the summer months, during seasonal temperature and irradiance maxima often occur disproportionately in shallow-living corals and on the exposed summits of colonies.
• Solar radiation has been suspected to play a role in coral bleaching.
• Both photosynthetically active radiation (PAR-400-700nm) and ultraviolet radiation (UVR-280-400nm) have been implicated in bleaching.

Subaerial Exposure

Sudden exposure of reef flat corals to the atmosphere during events such as extreme low tides, ENSO-related sea level drops or tectonic uplift can potentially induce bleaching.

Sedimentaiton: Relatively few instances of coral bleaching have been linked solely to sediment. It is possible but has not been demonstrated, that sediment loading could make zooxanthellate species more likely to bleach.

Fresh Water Dilution: Rapid dilution of reef waters from storm-generated precipitation and runoff has been demonstrated to cause coral reef bleaching. Generally, such bleaching events are rare and confined to relatively small, nearshore areas.

Inorganic Nutrients: Rather than causing coral reef bleaching, an increase in ambient elemental nutrient concentrations (ammonia, nitrate) actually increases Zooxanthelle densities 2-3 times. Although eutrophication is not directly involved in zooxanthelle loss, it could cause secondary adverse effects like lowering coral resistance and greater susceptibility to diseases.

Xenobiotics: Zooxanthelle loss occurs during exposure of coral to elevated concentrations of various chemical contaminants like copper herbicides and oil. Because high concentrations of xenobiotics are required to induce zooxanthelle loss, bleaching from such sources is usually extremely localized or transitory.

Epizootics: Pathogen-induced bleaching is different from other sorts of bleaching. Most coral diseases cause patchy, or whole colony death and sloughing of soft tissues, resulting in a white skeleton. A few pathogens have been identified that cause translucent white tissues, a protozoan.

Government Measures to Protect Mangrove Forest and Coral Reefs

• The government seeks to protect, sustain and augment mangroves and coral reefs in the country by both regulatory and promotional measures.
• Under the regulatory measures, the Coastal Regulation Zone(CRZ) Notification (2011) and the Island Protection Zone(IPZ) Notification 2011 regulate the development activities along the sea coast and tidal-influenced water bodies.
• The mangroves and coral reef areas are categorized as ecologically sensitive areas(CRZ-I) where no new constructions are permitted except projects relating to the Department of Atomic Energy, pipelines, conveying systems including transmission lines, installation of weather radar for monitoring of cyclones movement and prediction by Indian Meteorological Department and construction of trans harbour sea link and without affecting the tidal flow of water.
• To enforce and implement the CRZ and IPZ Notifications, the Ministry of Environment and Forests has constituted the National and State/UT level Coastal Zone Management Authorities.
• The Ministry of Environment & Forests also provides financial assistance to Coastal states/ Union Territories, who so request, under its Centrally Sponsored Scheme for conservation & management of mangroves and coral reefs.
• In addition Coral reef is included in Schedule 1 of the Wild Wildlife Act, 1972 which affords it the highest degree of protection.
• Further protected areas like National parks, 96 sanctuaries and 3 marine biosphere reserves have been created all over the country under the provisions of the Wildlife Protection Act, 1972 to conserve marine life including coral reefs.
• The Wildlife Crime Control Bureau has also been set up to strengthen the enforcement of the law for the control of poaching and illegal trade in wildlife and its products.

10.  Initatives to Protect Marine and Coastal Environments

Coastal Ocean Monitoring & Prediction System-(COMAPS)

• Being implemented in 1991.
• Assess the health of coastal waters and facilities management of pollution-related issues.
• Program was restructured and modified in 2000-2001 to include pollution monitoring; liaison, regulation and legislation and consultancy services.

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.

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 the Gulf of Kuchchh are being prepared.

Society of Integral 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.

Institutions for Coastal Management- The notification on Coastal Regulation Zone (CRZ), 1991 aims at protecting coastal stretches in India. India has created institutional mechanisms like the 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.

Ganga Action Plan

The Ganga Action Plan was launched on 14^th January 1986 with the main objective of pollution abatement, to improve water quality by interception, diversion and treatment of domestic sewage,  toxic and industrial chemical wastes present, from identified grossly polluting units entering into the river.

After reviewing the effectiveness of the “Ganga Action Plan “, the government announced the “Mission Clean Ganga” project on 31^st December 2009 with the objective that by 2020, no municipal sewage and industrial waste would be released in the river without treatment.

The Government also established the National Ganga River Basin Authority (NGRBA), chaired by the Prime Minister, to ensure effective abatement of pollution and conservation of the river Ganga, by adopting a river basin approach for comprehensive planning and management.

Namami Ganga Program

• Accordingly, an integrated Ganga Conservation Mission called “NAMAMI Gange”  has been proposed to be set up and a sum of Rs. 2,037 crores has been set aside for the conservation and improvement of the Ganga.
• In addition a sum of Rs. 100 crores have been allocated for the development of Ghats and beautification of River fronts at Kedarnath, Haridwar, Kanpur, Varanasi, Allahabad, Patna and Delhi.
• Accordingly, NAMAMI Gange approaches Ganga rejuvenation by consolidating the existing ongoing efforts and planning for a concrete action plan for the future.
• The interventions at the Ghats & river fronts will facilitate better citizen connections and set the tone for the river-centric urban planning process.

Proposals to be taken up Under Namami Ganga Program

• Nirmal Dhara- ensuring sustainable municipal sewage management.
• Project prioritization in coordination with the Ministry of Urban Development.
• Incentive for states to take up projects on Ganga Main-stem by providing an additional share of central grants for sewage infrastructure.
• Uniform Standards for both MoUD scheme and Namami Ganga program, 10 years mandatory O & M by the same service provider at par with NGRBA program and PPP, mandatory reuse of treated water.
• Expanding coverage of sewerage infrastructure in 118 urban habitations on banks of Ganga estimated cost by MoUD(Ministry of Housing & Urban Development )is Rs. 51,000 crores.
• Nirmal Dhara- managing sewage from Rural areas- ministry of drinking water and sanitation scheme for all Ganga bank Gram Panchayats (1632) free from open defecation by 2022, for Rs. 1700 crores as central share.
• Nirmal Dhara- managing industrial discharge-
• Making zero liquid discharge mandatory
• Rationalized water tariff to encourage reuse
• Real-time water quality monitoring
• Aviral Dhara-
• Enforcing river regulatory zones on Ganga banks
• Rational agricultural practices, efficient irrigation methods
• Restoration and conservation of wetlands
• Ensuring ecological rejuvenation by conservation of aquatic life and biodiversity.
• Promotion of tourism and shipping rationally and sustainably.
• Knowledge management on Ganga through the Ganga knowledge centre leading to a Ganga University of River Sciences.

NRI Ganaga Fund

NRIs Have been a very important contributor to the development process in India, in areas like education, health and preservation of culture. In this context, to harness their enthusiasm to contribute towards the conservation of the river Ganga, the NRI fund for Ganga will be set up which will finance special projects. NRI Ganga fund could be Set up under the aegis of the Ministry of Overseas Indian Affairs or Ministry of Finance with a focus on funds sourcing and corpus management.

Clean Ganga Fund

The main features of a “clean GANGA fund” are :

Considering that there is a need to increase people’s participation from across the country and abroad, it is proposed to set up a “clean Ganga fund”(CGF) with voluntary contributions.

• CGF We have the objective of contributing to the national effort of improving the cleanliness of the river Ganga with the contributions received from the residents of the country, NRIs and others.
• CGF Will be operated through a bank account by a trust to be headed by the finance minister.
• The secretariat of the trust will be set up in the Ministry of Resources, River Development and Ganga Rejuvenation under the Mission Director, clean Ganga.
• Domestic donors to the fund shall be eligible for tax benefits as in the case of ”Swachch Bharath Kosh”. Foreign donors could get suitable tax exemptions in domestic law wherever permissible.
• CGF will explore the possibility of setting up daughter funds in other jurisdictions/countries of high donor interest like the USA, UK, Singapore, UAE, etc., to enable tax benefits to donors in their respective jurisdictions.
• CGF we’ll be catalytic in nature and will identify and fund specific projects which could be pilot projects, R & D projects, innovative Projects or other focused projects. The fund will define specific and measurable objectives to form the basis for planning funding and evaluation.

Broad Activities that will be Financed From the Clean Ganga Fund are

• Activities outlined under the “NAMAMI Gange” program for cleaning of river Ganga.
• Control of non-point pollution from agricultural runoff, human defecation, cattle wallowing.
• Setting up waste treatment and disposal plants along the river around the cities.
• Conservation of the biotic diversity of the river.
• Community-based activities to reduce polluting human interface with the river.
• Development of public amenities including activities like Ghat redevelopment.
• Research and development and innovative projects.
• Research and development projects and innovative projects for new technology and processes for cleaning the river.
• Independent oversight through intensive monitoring and real-time reporting.
• Any other activity as approved by the Trust.

Recent Measures

• Union Environment Ministry has taken up a new strategy for the conservation and rejuvenation of major river water systems. The new strategy takes into account the entire river basin, which is contributing its flow to the particular river stretch for conservation.
• The present strategy for the conservation of rivers is limited only to tackling pollution load from domesticated wastewater and regulation of industrial pollution.
• The new approach is a holistic one for the rejuvenation of rivers, wherein water management and environment management are taken together for implementation to restore the lost ecology of the polluted stretches of the rivers.