- An ecosystem in a water body is called aquatic ecosystem.
|Classification of aquatic ecosystems based on salt content (parts per thousand – ppt)|
|Fresh water ecosystems||Marine ecosystems||Brackish water ecosystems|
|Less than 5 ppt||35 ppt or above||5 to 35 ppt|
|Eg. Lakes, ponds, springs, rivers||Eg. Seas, oceans||Eg. Estuaries, mangroves|
Classified on the basis of their zone of occurrence & ability to cross these zones.
|Unattached||Attached to stems||Locomotive power||Swimmers||Attached to bottom|
|Live at air-water interface||Live submerged in water||Live submerged in water||Live under water. Large & powerful||Live at bottom of water mass|
|Eg. Floating plants||Eg. Sessile algae||Eg. Algae, crustaceans||Eg. All sea animals||—|
Factors limiting productivity of Aquatic Habitats:
|4 main factors are:
Lake – A large water body with huge area and depth.
Snow cover of ice on water body can effectively cut off light, plunging the waters into darkness. Hence photosynthesis stops but respiration continues. Thus, in shallow lakes, the oxygen gets depleted. Fish die, but we won’t know it until the ice melts and we find floating fish. This condition is known as winterkill.
|LAKES IN INDIA:|
Artificial lakes more than natural lakes.
- Natural lakes – in Himalayan regions, floodplains of Indus, Ganga and Brahmaputra.
- Lakes also classified on the basis of salt content.
- On nutrient content basis they are classified as: – Oligotrophic (very low), Mesotrophic (moderate) and Eurotrophic (high rich).
CLEANING OF LAKES/REMOVAL OF NUTRIENTS TECHNIQUE: Deep water abstraction + Flushing + Algae skimming + Plants to suck nutrients + Harvest fish & macrophytes + Sludge removal + Filters for algae removal.
- Water body overly enriched with nutrients, leading to plant life growth.
- Nitrates and phosphates leached into water bodies from fertilizers, industrial waste, sewage, etc. resulting in algal bloom.
- The nutrient enrichment of the lakes promotes the growth of algae, aquatic plants and various fauna. This process is known as natural eutrophication.
|POINT SOURCE||NON-POINT SOURCE|
EFFECTS – Toxicity, new species invasion, decreased biodiversity, decrease in species richness and diversity, Toxic Aerosols in micro environment.
|POLICIES & MITIGATION FOR CURBING EUTROPHICATION:|
- Restoration and preservation of ecosystems + Create buffer zones for sediments to collect + Nitrogen testing + Industrial waste treatment and efficiency + Reduce livestock densities + Reduce non-point
|HARMFUL ALGAL BLOOM (HAB)|
- Algal bloom – Excessive multiplying of algae or phytoplankton due to favourable environmental conditions.
- Harmful algal bloom – When such algal bloom produces toxins, it affects marine organisms thus making it difficult to breathe. Produces – diatoms, cyanobacteria, dinoflagellates, filamentous algae.
- Blooms can be due to a number of reasons. Two common causes are nutrient enrichment and warm waters.
|PRODUCING HIGH BIOMASS/ “GREEN TIDES”||PRODUCING TOXINS/ “RED TIDES”|
Are HABs dangerous to fish and humans?
- Oxygen levels drop, fish suffocate and die.
- O2 level drops due to decomposition of dead algae.
- Potent neurotoxins that are produced can enter food web thus reaching animals, fish and even humans.
- Some toxins become airborne.
- People tend to breathe aerosolized HAB toxins near the beach.
- Changes in climate can change severity and impact of HAB events.
|WETLAND ECOSYSTEMS & RELATED ISSUES|
- Transition zones between deep-water and terrestrial habitats
- g. Lake littorals, marshy or swampy areas.
- World Wetland Day – 2nd February
|Ramsar Convention defines wetland as – “areas of marsh, peatland or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water, depth of which at low tides, does not exceed 6 meters.|
Recent alterations in Wetland rules 2017:
- States can alter activities prohibited in wetlands.
- Delineate wetlands, development of integrated plans.
- All wetlands except river channels, paddy fields, human-made waterbodies for drinking water, aquaculture, salt production etc. can be notified.
|NATIONAL PLAN FOR CONSERVATION OF AQUATIC ECOSYSTEMS (NPCA):|
- NPCA is a single conservation programme for both wetlands and lakes.
- Centrally sponsored scheme, currently being implemented by the Union Ministry of Environment and Forests and Climate Change.
- Formulated in 2015 by merging of the National Lake Conservation Plan and the National Wetlands Conservation Programme.
- NPCA seeks to promote better synergy and avoid overlap of administrative functions.
|Functions of wetlands
|Habitat to various species, sediment filtration, water purification, pollution control, disaster management, nutrients recycling, ground water recharge, prevents erosion, species diversity, stabilize local climate, natural heritage.|
|Reasons for depletion
|Land use changed for agriculture, sand removal from beds, overgrazing, deforestation, pollution, domestic waste, climate change, agricultural runoff, hazardous industrial waste, aqua culture.|
|Eutrophication abatement, environmental awareness, afforestation, soil conservation, weed control, artificial regeneration, wildlife conservation, heritage management.|
|Acc. to NLCP – minimum depth 3 mts||Acc. To NLCP – minimum depth < 3 mts|
|Origin from multiple sources||Origin due to Geomorphic processes|
|Minor water level changes||Major water level changes|
|Small pelagial ratio||Large pelagial ratio|
|No waste treatment occurs||Waste treatment occurs|
|Low productivity||High productivity|
|Low biodiversity||High biodiversity|
|Oligo trophic status||Eutrophic status|
|Does not manage flood control||Very significant in managing floods|
|Thermal stratification||No Thermal stratification|
|Management objectives – Control of eutrophication and High-Water quality||Biodiversity conservation Specific Functions|
|RAMSAR criteria for wetland identification:|
- Sites containing rare or unique wetland types.
- Criteria based on species and ecological communities
- Specific criteria based on water birds: If it supports 20,000 or more & if it supports 1% individuals of a single species.
- Specific criteria based on fish.
- Ramsar Convention works with the collaboration of the following organizations: International Union for Conservation of Nature (IUCN) + Birdlife International + International Water Management Institute (IWMI) + Wetlands International + Wildfowl & Wetlands Trust (WWT) + WWF International.
|Management objectives – Control of eutrophication and High-Water quality|
|NEWLY ADDED RAMSAR SITES|
|Asan Barrage||Uttarakhand||21 July 2020|
|Kanwar Taal or Kabar Taal Lake||Bihar, Begusarai||21 July 2020|
|Sur Sarovar||Uttar Pradesh, Agra district||13 November 2020|
|Lonar Lake||Maharashtra, Buldhana district||13 November 2020|
|Tso Kar||Ladakh, Leh district||17 November 2020|
|MONTREUX RECORD SITES IN INDIA:
- Areas where river meets the sea (exhibiting gradient in salinity), resulting in mixture of fresh river water with salty ocean water, subject to tidal variations.
- Conditions for Estuary Formation: (1) rising sea level; (2) movement of sand and sandbars; (3) glacial processes; and (4) tectonic processes.
- Characteristics: Filter for river water + Traps mud & sands + Semi-enclosed coastal body + Connection with open sea + Salinity range – 0 to 35 ppt + Heavily populated + Little wave action.
- Biologically most productive region à Receives the high amount of nutrients from fresh and marine water.
- Flora: homes to unique aquatic plants and animals, such as sea turtles and sea lions, sea catfish, saltworts, eelgrass, salt grasses, cord grasses, sea grass, sedge and bulrush.
- About 60% of the world’s population living along estuaries and the coast.
- Benefits of Estuarine ecosystems: Commercial fishing + Ports and harbours + Travel and tourism + Economic and social benefits + Water purification + Breeding hotspot + Recreational and community benefits + Erosion protection + Stores and recycles nutrients.
|ESTUARIES IN INDIA:
India has 14 major, 44 medium and 162 minor rivers. Major estuaries occur in the Bay of Bengal region. West- flowing rivers are generally fast-moving ones giving rise to formation of estuaries.
Issues relating to Indian Estuarine Ecosystems:
Modification of catchment areas + Pollution + Recreation & unsustainable tourism + Increased dredging and shipping + unstainable Land-use pattern + Fishing & aquaculture + Climate change.
- Mangroves are littoral plants like trees and bushes having exceptional capacity for salt water tolerance (Halophytic adaptability), growing below high-water level of spring tides.
|CHARACTERISTICS OF MANGROVES:|
- Evergreen land plants growing on tidal flats, deltas, estuaries, bays, creeks and barrier islands.
- High adaptation to salinity (Halophytic adaptability) and water logging.
- Ability to absorb fresh water from saline water and require high solar radiation.
- Produce pneumatophores/blind roots to overcome respiration problem.
- Have lenticulate banks that facilitate water loss.
- Secrete excess salts through leaves or block absorption of salts at their roots.
- Adventitious roots, also called stilt roots.
- Reduce inundation and moderate monsoonal tidal floods. + Prevent coastal soil erosion and enhance nutrient recycling. + Source of firewood, medicinal plants and edible plants to locals.
- Provides employment opportunities.
Mangroves are destroyed and converted for the use of agriculture, aquaculture, fuel, industrial purposes and chemical fertilizers.
|MANGROVES IN INDIA:
|UTILITY OF MANGROVES:|
- Protect shorelines from storm, hurricane winds, waves, and floods + Prevent erosion by stabilizing sediments with tangled root systems + Maintain water quality and clarity, filtering pollutants and trapping sediments + Provide nursery habitat for many commercial fish.
|CORAL REEFS AND RELATED ISSUES|
- Corals are living animals, which lives in a Symbiotic relationship with ‘zooxanthellae’. Both have a mutual type of relation.
- There are 2 types of corals: Hard and soft — only hard corals build reefs.
- Majority coral reefs are found in tropical and sub-tropical water, however there are exceptions of deep-water corals in colder regions.
|ASPECTS OF CORAL REEFS:|
|LOCATION AND CLASSIFICATION:|
|FRINGE REEFS||PATCH REEFS||BARRIER REEFS||ATOLL|
|Most common, contiguous with shore||Isolated and discontinuous lying shoreward of offshore reef||Linear offshore structures. Run parallel to coastline.
Water body between reef & shore is called ‘lagoon’
|Circular or semi – circular reefs, arise from subsiding sea floor platform|
|Seen in Andamans||Seen in Palk Bay, Gulf of Mannar & Kachchh||Seen in Nicobar and Lakshadweep||Seen in Nicobar and Lakshadweep|
|ADVANTAGES OF CORAL REEFS:|
Natural protective barriers against storms and soil erosion + Food + Medicine + Tourism + Meteorology + Capture nutrients and plankton from water + Largest biogenic calcium carbonate producer + Home to variety of animals and plants + Sources of new medicines being developed to treat cancer, arthritis, human bacterial infections, Alzheimer’s disease, heart disease, viruses, and other diseases + Tourism & meteorology + More than 1 billion people depend on food from coral reefs.
- Without algae, coral loses its major source of food, turns white or pale and is more susceptible to diseases and eventually starves to death.
- Bleaching of corals occur when densities of zooxanthellae decline and/or concentration of photosynthetic pigments within zooxanthellae fall.
- Global Warming Induced Threats To Corals: Unsustainable fishing + Water Pollution + Marine Debris + Habitat Destruction.
|Ongoing bleaching events worldwide:
|ECOLOGICAL CAUSES OF CORAL BLEACHING:|
- TEMPERATURE – Anomalously low and high temperatures induce bleaching
- SOLAR IRRADIANCE – Bleaching during summers occurs on exposed and shallow-living corals
- SUBAERIAL EXPOSURE – Sudden exposure to air during sea level drop/tectonic movements affect corals
- SEDIMENTATION – Few instances of bleaching linked to sediments
- FRESH WATER DILUTION – Though rare, rapid dilution from storm surges and runoffs cause bleaching
- INORGANIC NUTRIENTS – Increase in ambient elemental nutrient content indirectly causes bleaching
- XENOBIOTICS – Exposure to chemicals like Cu, herbicides and oil leads to zooxanthellae loss
- EPIZOOTICS – It is a type of pathogen induced bleaching