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Aquatic ecosystem - (Part - 2) | Environment & Additional Topics for State PSC Exams - BPSC (Bihar) PDF Download

Harmful Algal Blooms

➤ What are 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 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).

➤ Why Red Tide is a misnomer?

  • "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 water, and the organisms' concentration. 
  • The term "red tide" is thus a misnomer because blooms are not always red. They are not associated with tides. They are usually not harmful, and some species can be harmful or dangerous at low cell concentrations not discolour the water. 
  • They are scientifically referred to as Harmful Algal Blooms (HABs).

➤ What are the causes of these blooms?

  • Blooms occur when several colonies start combining rapidly when conditions such as nutrient concentrations, 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 occurrence of algal blooms, with hot water being conducive to blooms.

➤ How are HABs dangerous to fish and humans?

  • HABs can deplete oxygen in the water and lead to low dissolved oxygen levels. 
  • How it depletes oxygen? When masses of algae die and decompose, the decaying process can deplete oxygen in the water, causing the water to become low in oxygen. 
  • When oxygen levels become too low, fish suffocate and die. 
  • Some algae 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.

Question for Aquatic ecosystem - (Part - 2)
Try yourself:Which are the major producers of oxygen in marine ecosystem?
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➤ Is HAB's an environmental hazard?

  • Yes, these events can make people sick when contaminated shellfish are eaten, or when people breathe aerosolized HAB toxins near the beach. 
  • Besides, HAB events can result in the closure of shellfish beds, massive fish kills, death of marine mammals and seabirds, and marine habitats' alteration. 
  • Consequently, 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.

➤ How do we get exposed to HAB toxins?

  • Most illness associated with HAB exposure results from 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.

➤ Is it safe to eat seafood?

  • In general, it is safe to eat seafood. 
  • However, 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 and 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.

Wetland Ecosystem

  • Wetlands are 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 supports plants and animals specifically adapted to such shallow flooding or waterlogging of the substrate, were designated as wetlands. 
  • They included lake littorals (marginal areas between highest and lowest water level of the lakes), floodplains (areas lying adjacent to the river channels beyond the natural levees and periodically flooded during high discharge in the river) and other marshy or swampy areas where water gets stagnated due to poor drainage or relatively impervious substrata & Bogs, fens and mangroves due to similar ecological characteristics

➤ 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 O2 available for some plants)

Wetlands Classification

Aquatic ecosystem - (Part - 2) | Environment & Additional Topics for State PSC Exams - BPSC (Bihar)

➤ 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 
  • Nutrients recycling 
  • Water purification 
  • Floods mitigation 
  • Maintenance of streamflow 
  • Groundwater recharging 
  • Provide drinking water, fish, fodder, fuel, etc. 
  • Control 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 to local people 
  • Genetic reservoir for various species of plants (especially 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 effluents 
  • Climate change

➤ Mitigation

  • Survey and demarcation 
  • Protection of natural regeneration 
  • Artificial regeneration 
  • Protective measures 
  • Afforestation (percentage survival to be indicated) 
  • Weed control 
  • Soil conservation measures & 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 Programme (NLCP) considers lakes as standing water bodies which have a minimum water depth of 3 m, generally cover a water spread of more than ten hectares, and have no or very little aquatic vegetation (macrophytes). 
  • These water bodies are used primarily for drinking water supplies, irrigation and/or recreation. 
  • Excessive growth of macrophytes (both submerged and free-floating) generally present in wetland, affects the water quality adversely and interfere 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 when compared to the wetland from the viewpoint of ecosystem and biodiversity conservation.

Question for Aquatic ecosystem - (Part - 2)
Try yourself:Which of the below doesn’t belong to Coastal wetland?
View Solution

➤ India's Wetlands

  • Wetlands are areas of critical ecological significance: as they support biodiversity, support millions of people, directly and indirectly, protect from storms, flood control, improve water quality, supply food, fibre and raw materials. 
  • India has 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 lagoons, backwaters, estuaries, mangroves, swamps and coral reefs, and so on.

Question for Aquatic ecosystem - (Part - 2)
Try yourself:Which of the following factor does not affect depletion of wetlands?
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➤ National Wetlands Conservation Programme (NWCP)

  • NWCP was implemented in the year 1985-86. 
  • Under the programme, 115 wetlands (Annexure) have been identified by the Ministry, requiring urgent conservation and management interventions.


Conservation of wetlands to prevent their further degradation and ensure their wise use benefits local communities and overall biodiversity conservation.

➤ 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 implementation of the programme, and to prepare an inventory of Indian wetlands. 
  • The Central Government is responsible for overall coordination of wetland conservation programmes and initiatives at the international and national levels. It also provides guidelines, financial & technical assistance to state govt. 
  • Since the land resources belong to them, the State Governments/UT Administration are responsible for managing the wetlands and implementing 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: 
  • Sites containing representative, rare or unique wetland types
  • If it contains a representative, rare, or unique example of a natural or near-natural wetland type found within the appropriate biogeographic region. 
  • Criteria based on species and ecological communities
  • If it supports vulnerable, endangered, or critically endangered species; or threatened ecological communities.
  • If it supports populations of plant and/or animal species important for maintaining a particular biogeographic region's biological diversity.
  • If it supports plant and/or animal species at a critical stage in their life cycles, or provides refuge during adverse conditions. 
  • Specific criteria based on waterbirds 
  • If it regularly supports 20,000 or more water birds.
  • If it regularly supports 1% of the individuals in a population of one species or subspecies of waterbirds. 
  • Specific criteria based on fish 
  • If it supports a significant proportion of indigenous fish subspecies, species or families, life-history stages, species interactions and/or populations that are representative of wetland benefits and/or values and thereby contributes to global biological diversity.
  • If it is an important source of food for fishes, spawning ground, nursery and/or migration path on which fish stocks, either within the wetland or elsewhere, depend. Specific criteria based on water/life and culture
  • If it is an important source of food and water resource, increased possibilities for recreation and eco-tourism, improved scenic values, educational opportunities, conservation of cultural heritage (historical or religious sites).

Montreux Record

Montreux Record is the principal tool under the Ramsar Convention, 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 occurring, or are likely to occur as a result of technological developments, pollution or other human interference and which are therefore in need of priority conservation attention.
It is maintained as part of the Ramsar List. Montreux Record is 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 Contracting Parties' approval in which they lie.

➤ Montreux Record sites in India

  • Chilika lake, Orissa was placed on the Montreux Record in 1993 due to siltation, which was choking the lake's mouth. 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 for 2002. Loktak lake, Manipur was included on the Montreux Record in 1993 (signifying habitat degradation) due to ecological problems such as deforestation in the catchment area, an infestation of water hyacinth and pollution. 
  • The construction of a hydroelectric power plant has caused the local extinction of several native fish species. 
  • The Keoladeo national park, Rajasthan was placed on the Montreux Record in 1990 due to water shortage and the unbalanced grazing regime. 
  • 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 - First FTW 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 the water with sunlight's help (no need of 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.

The document Aquatic ecosystem - (Part - 2) | Environment & Additional Topics for State PSC Exams - BPSC (Bihar) is a part of the BPSC (Bihar) Course Environment & Additional Topics for State PSC Exams.
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FAQs on Aquatic ecosystem - (Part - 2) - Environment & Additional Topics for State PSC Exams - BPSC (Bihar)

1. What causes harmful algal blooms?
Ans. Harmful algal blooms are caused by an excessive growth of certain types of algae in aquatic ecosystems. This rapid growth is often fueled by an abundance of nutrients, such as nitrogen and phosphorus, in the water. These nutrients can come from various sources, including agricultural runoff, wastewater treatment plants, and stormwater runoff.
2. How do harmful algal blooms affect aquatic ecosystems?
Ans. Harmful algal blooms can have detrimental effects on aquatic ecosystems. The excessive growth of algae can block sunlight from reaching underwater plants, leading to their decline. As the algae die and decompose, they consume oxygen in the water, which can create areas of low oxygen or "dead zones" that are harmful to fish and other aquatic organisms. Some types of algae also produce toxins that can harm or even kill wildlife, leading to ecosystem imbalances.
3. Can harmful algal blooms impact human health?
Ans. Yes, harmful algal blooms can pose risks to human health. Some species of algae produce toxins known as harmful algal toxins (HABs). These toxins can contaminate drinking water sources, recreational waters, and seafood. Exposure to these toxins can cause a range of health issues, including skin rashes, respiratory problems, gastrointestinal illnesses, and even neurological effects in severe cases.
4. How can harmful algal blooms be prevented or controlled?
Ans. Preventing and controlling harmful algal blooms involve various strategies. One approach is to reduce the input of nutrients into aquatic ecosystems, as excess nutrients often contribute to algal growth. This can be achieved through better wastewater treatment, improved agricultural practices to minimize nutrient runoff, and implementing stormwater management measures. Monitoring and early detection of algal blooms is also crucial to implementing timely control measures, such as applying algaecides or using techniques like aeration to increase oxygen levels in affected areas.
5. Are harmful algal blooms a widespread issue?
Ans. Yes, harmful algal blooms are a widespread issue that affects many aquatic ecosystems around the world. They can occur in freshwater bodies like lakes and rivers, as well as in marine environments. The frequency and severity of harmful algal blooms have been increasing in recent years, partly due to human activities that contribute to nutrient pollution. This issue is of great concern due to its ecological impacts and potential risks to human health. Efforts are being made globally to better understand and address the causes and consequences of harmful algal blooms.
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