Aquatic Ecosystems: Classification, Issues, Conservation & Corals

• An ecosystem in a water body is called an aquatic ecosystem.

AQUATIC ORGANISMS

Classified on the basis of their zone of occurrence & ability to cross these zones. 

Aquatic Ecosystems: Factors limiting productivity of Aquatic Habitats 

Aquatic Ecosystems: Lake Ecology

Lake – A large water body with huge area and depth.

Aquatic Ecosystems: Lakes In India

Artificial lakes more than natural lakes.

• Natural lakes – in Himalayan regions, floodplains of Indus, Ganga and Brahmaputra.
• Lakes are also classified on the basis of salt content.
• On nutrient content basis they are classified as: – Oligotrophic (very low), Mesotrophic (moderate) and Neurotrophic (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.

Aquatic Ecosystems: Eutrophication

• Water body is 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.

EFFECTS – Toxicity, new species invasion, decreased biodiversity, decrease in species richness and diversity, Toxic Aerosols in micro environment. 

Aquatic Ecosystems: 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 nonpoint

Aquatic Ecosystems: Harmful Algal Bloom (Hab)

• Algal bloom – Excessive multiplying of algae or phytoplankton due to favorable 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.

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 the 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 the severity and impact of HAB events.

Aquatic Ecosystems: Wetland Ecosystems & Related Issues

• Transition zones between deep-water and terrestrial habitats
• Eg. Lake littorals, marshy or swampy areas.
• World Wetland Day – 2nd February

Aquatic Ecosystems: 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 water bodies for drinking water, aquaculture, salt production etc. can be notified.

 Aquatic Ecosystems: 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.

Aquatic Ecosystems: 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 

ESTUARY ECOSYSTEMS

• Areas where the 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 lives along estuaries and the coast.
• Benefits of Estuarine ecosystems: Commercial fishing + Ports and harbors + Travel and tourism + Economic and social benefits + Water purification + Breeding hotspot + Recreational and community benefits + Erosion protection + Stores and recycles nutrients.

Aquatic Ecosystems: 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.

 Aquatic Ecosystems: Mangrove Ecosystems

• 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 respiratory 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.

Aquatic Ecosystems: 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.

Aquatic Ecosystems: CORAL REEFS AND RELATED ISSUES

• Corals are living animals, which live 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 subtropical water, however there are exceptions of deep-water corals in colder regions.

ASPECTS OF CORAL REEFS: 

LOCATION AND CLASSIFICATION: 

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.

Aquatic Ecosystems: CORAL BLEACHING

• 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 occurs 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.

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