Wetland Ecosystem
Wetland Ecosystem
Wetlands are ecotones or transition zones between terrestrial and aquatic ecosystems. These areas have distinct environmental features, including hydric soils (with low oxygen levels), periodic flooding from nearby deepwater habitats, and hydrophytes—plants adapted to waterlogged soils.
Wetland Definition (Ramsar Convention and Indian Rules)
Under the Ramsar Convention and Wetlands (Conservation and Management) Rules, 2017, a wetland is defined as:
- An area of marsh, fen, peatland, or water—natural or artificial, permanent or temporary.
- Water may be static or flowing, fresh, brackish, or salty.
- Includes marine areas with water depths not exceeding six meters at low tide.
Difference Between Oligotrophic and Eutrophic
Estuarine
Definition and Formation
- An estuary is a partially enclosed coastal area with brackish water (salinity of 0-35 ppt) formed where freshwater from rivers or streams meets the ocean. Examples of estuaries include river mouths, coastal bays, tidal marshes, lagoons, and deltas.
- Estuaries are shaped by rising sea levels, movement of sand and sandbars, glacial processes, and tectonic activity, and they experience tidal influences that bring periodic seawater flooding. In narrow estuaries, tidal bores can significantly impact the ecosystem, sometimes causing ecological damage.
Importance of Estuaries
- Ecological Importance
- Ecotone Zone: Estuaries serve as transition zones between river and marine environments, creating highly productive ecosystems where freshwater meets saline water.
- Biodiversity Refuge: Minimal wave action provides a calm environment, supporting diverse aquatic species. Mangrove forests on estuary coasts help reduce wind damage during storms.
- Sediment Accumulation: Saline water encourages the precipitation of fine alluvium, aiding in delta formation. Mangroves trap suspended mud and sand, filtering the water.
- Natural Filtration: Estuaries store and recycle nutrients, trap sediments, and detoxify pollutants, acting as natural water filters for surrounding ecosystems.
- Economic Importance
- Human Settlement: Approximately 60% of the world’s population resides along estuaries and coasts due to rich resources and accessibility.
- Ports and Harbors: Estuaries, with their protected waters, are ideal for constructing ports and harbors, making them economically significant areas.
- Rich Resources: Estuarine ecosystems support various natural resources, such as fisheries and seagrass beds, which contribute to local economies.
Estuarine Vegetation and Biodiversity
- Adaptive Species: The brackish water and fluctuating salinity in estuaries support plants and animals that can osmoregulate. Salinity and tidal range influence the distribution and diversity of organisms.
- Dynamic Ecosystem: Due to variable river flow, tides, and sediment distribution, estuaries are dynamic and support diverse habitats such as mangroves, salt marshes, seagrass, and mudflats.
- Species Diversity:
- Terrestrial: Includes wood storks, pelicans, coniferous and deciduous trees, and butterflies.
- Aquatic: Estuaries house unique species like sea turtles, sea lions, salt grasses, and bulrushes.
- Phytoplankton and Vegetation: dominant phytoplankton include diatoms, dinoflagellates, green algae, and blue-green algae, with seagrasses near the coast and mangrove forests at river mouths and deltas.
Indian Estuarine Ecosystem
- India has 14 major, 44 medium, and 162 minor rivers that drain into the sea through estuaries, with the most large estuaries on the east coast.
- Estuaries on the west coast tend to be smaller. Major estuaries often house important seaports, such as Mormugao Port on the Zuari Estuary.
Threats to the Indian Estuarine Ecosystem
- Water Flow Modifications: Alterations in river catchments impact estuarine water flow (e.g., Hooghly, Godavari, Pulicat).
- Pollution: Discharge from industries and urban sewage contributes significantly to estuarine pollution.
- Navigation and Dredging: Heavy dredging for navigation and shipping, especially in areas like Hooghly, disrupts estuarine habitats.
- Urbanization and Industrialization: Expansion of settlements, agriculture, and solid waste dumping in catchment areas cause habitat degradation.
- Intensive Aquaculture: Fish and prawn farming obstruct migratory paths of species in areas like Chilka and Pulicat.
- Environmental Pollution in Pens: Feeding practices in aquaculture contribute to pollution (e.g., Chilka).
- Destruction of Biodiversity: Practices like prawn seed collection using fine mesh nets harm biodiversity in regions such as Hooghly, Chilka, and Pulicat.
- Rising Water Levels: Submergence of catchment areas due to increasing water levels poses a long-term threat.