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Summary
Environment Class 15

A BRIEF DISCUSSION OF THE PREVIOUS CLASS (1:05 PM)

ALGAL BLOOM (1:07 PM)

  • The rapid multiplication of different types of algae in water bodies is termed algal bloom
  • Algae in water bodies are in the form of seaweeds which are multicell large plants or they are made up of single-cell plants i.e. phytoplanktons
  • Blooms are generally because of the multiplication of phytoplanktons  and these blooms can be either toxic or non-toxic
  • Causes for algal bloom
  • The fundamental cause behind the bloom is the sharp increase in the nutrients in the water, particularly nitrogen, and phosphorus
  • This sharp increase can be because of:
  • Upwelling of bottom waters in oceans brings huge quantities of minerals and nutrients to the surface waters
  • Rivers supplying large amounts of nutrients to estuaries which are river valleys close to the coast buried under seawater
  • Surface runoff waters like the waters created by rain and also the water from temporary streams can carry out chemical action on minerals in the soils which leach out nutrients and supply these to water bodies like rivers, lakes, oceans, etc.
  • Nutrient supply can also increase very sharply because of man-related processes like
  • 1. Discharge of industrial effluents and urban waste waters without treatment into water bodies like oceans and rivers
  • 2. Transfer of warm waters created by industrial activity increases heat in the water bodies which receive these warm waters
  • The warm water favors the growth of algae
  • 3. Ocean warming because of global warming can also make the waters more warm helping the algae to multiply
  • 4. Periods of reduced rainfall can reduce the water levels in water bodies like lakes and rivers, and hence these bottom waters are rich in sediments and nutrients and are also warm as they are directly exposed to sunlight
  • This helps in the multiplication of algae
  • Freshwater blooms
  • Bluegreen algae are the most common cause of blooms in freshwater bodies
  • They do not directly harm other life forms by infecting them but produce toxins called cyanotoxins which could be harmful to life forms including man
  • These phytoplanktons made up of blue-green algae look like foam floating on water or take the form of mats covering the water's surface
  • Blooms in brackish and saline water
  • These are created by two types of phytoplankton which are made up of diatoms and dinoflagellates
  • Both are single-celled phytoplanktons and are much more common in saline and brackish water
  • When they multiply because of increased nutrient supply, the ocean water or brackish water can turn into different colors like red, white, or green as they approach the coast
  • These colors are due to the toxins released by these algal blooms
  • When it is reddish in color, the ocean water carrying these algal booms approaching the coast is termed the red tide
  • The algal blooms made up of dinoflagellates and the diatoms are considered to be more harmful to life forms because of the toxins they produce  and hence are called harmful algal blooms
  • Impact/Effect
  • 1. The growth of these algae in these blooms generates lots of organic matter
  • The decomposition/decay of this matter by bacteria uses up all the oxygen in the water
  • Therefore, these waters without oxygen kill almost all the lifeforms in these waters
  • 2. There is a sharp decrease in the sunlight below the surface waters and hence this directly harms plant life in the bottom waters due to the inability to carry photosynthesis
  • 3. Degradation in the quality of water
  • Waters become turbid, become a little toxic due to toxins released by these blooms, harmful gases are released by the slow decay of organic matter like hydrogen-sulfide (H2S), and methane which are gases harmful to life forms
  • These waters with all these characteristics are incapable of supporting ecosystems
  • 4. Bloom can cause physical harm to other life forms, e.g. when coral polyps and fish take in the water they are choked to death by the large quantity of algae in the water
  • They can block the gills of fish, and the algae mat can crush coral polyps to death
  • Toxins can become airborne when waves carrying them crashes against the coast
  • These airborne toxins can cause respiratory illness in human coastal communities
  • 5. Some toxins of these algae can cause the death of man
  • For example, toxins from Alexandrium can enter marine animals and when men consume these as seafood he is exposed to the risk of paralysis and death
  • Algal Bloom Information Service (ABIS) has been launched by INCOIS (Indian National Centre for Ocean Information Services)
  • This uses satellite imagery data to detect developing blooms and provide early warning signals for the Indian coast 

ECOTONE (2:35 PM)

  • An ecotone is a transitional area between two or more adjacent ecosystems.
  • It is often characterized by a high diversity of plants and animals, as species from both ecosystems meet and interact.
  • Ecotones are often very productive areas, as they receive nutrients from both of the ecosystems that they connect.
  • They play an important role in the environment by providing a buffer between ecosystems and helping to regulate climate.
  • Ecotones are also important for human use, as they provide a variety of resources such as food, water, and timber

WETLANDS (3:08 PM)

  • They are ecotone between dry terrestrial ecosystem and true aquatic ecosystem
  • Types of ecosystems based on location/geographic setting
  • Types Examples
    Riverine

    Floodplains, ox-bow lakes, water bodies within river basins
    Lacustrine

    Freshwater lakes, brackish waters lakes
    Marine

    Lagoons (e.g. Lake Pulicat), creeks, part of the sea cut off by coral reefs
    Palustrine

    Swamp, bog, and marshes
    Man-made

    Reservoir lakes, aquaculture ponds/tanks, tanks
    Estuarine settings

    Deltaic regions, bays, estuaries
    Coastal wetlands

    Tidal marshes, mangroves
  • Characteristics of wetlands
  • Wetlands have the characteristics of eutrophic lakes unlike oligotrophic lakes
  • Oligotrophic water bodies have deep clear waters, they are low in sediments and therefore low in nutrients
  • Low nutrients imply a low presence of plants including phytoplanktons and other aquatic vascular plants
  • Therefore, dead organic matter is generated in fewer quantities reflected in low BOD (Biological Oxygen Demand)
  • Hence, they are rich in oxygen which is capable of supporting large sized-fish species and other invertebrates which require huge oxygen
  • Eutrophic water bodies are shallow because they get sediments from temporary streams and surface runoff depositing their sediments into them
  • Hence,  they are rich in nutrients and therefore have a large collection of plant life including phytoplanktons
  • These phytoplanktons and the algae support large fish populations
  • Since dead organic matter is generated in large quantities, the oxygen in these lakes is less
  • Peatlands
  • They are partly decomposed organic matter mixed in the soil
  • They have moderating effect on global warming as they act as carbon sinks
  • Peatlands which are wetlands are called palustrine wetlands
  • Palustrine wetlands are of the following types:
  • Bogs
  • These peatlands receive water only from rain
  • Their soil is acidic
  • They have vegetation in the form of grass and weeds
  • Fens/Fenlands
  • They get water from surface sources
  • The soils are always alkaline in nature
  • Swamps
  • They have temporarily or permanently submerged trees
  • Marshes
  • They have grasses submerged temporarily or permanently
  • Plant communities found in wetlands
  • Submerged plant communities
  • They have roots attached to the soil and are completely submerged
  • A few examples include seagrass/eelgrass
  • Emergent plant communities
  • Their roots are buried in soils but parts of plants grow above the water surface
  • A few examples include cattails
  • Floating plant communities
  • Their roots are not buried in water and they float over water
  • A few examples include water lilies
  • Dominant animal communities are insect/invertebrates
  • Function of wetlands
  • Protect coastal areas from shore erosion
  • Water hyacinth, duckweed, and water lettuce absorb heavy metals like iron, cadmium, lead, mercury
  • They slow down the water flow, thus allowing the deposition of suspended particles filtering sediments and pollutants thus are commonly referred to as the kidneys of the environment
  • It helps in nutrient recycling
  • It helps in groundwater recharge, as the water slows down here where it sinks and percolates into the ground
  • It supports a large variety of life and provides a rich biodiversity, thus acting as a bank for species and stabilizing the food web
  • It provides drinking water and foods like fish, vegetables, and rice
  • It helps in climate mitigation through carbon sequestration

Topics for the next class: Characteristics of Ramsar wetlands, India's strategy to protect wetlands, Mangrove ecosystem, Estuarine ecosystem, Coral ecosystem