Biome and ecosystem:
• A large naturally occurring community of flora and fauna occupying a major habitat. E.g., forest or tundra. Ecosystem refers to the interaction of biotic and abiotic components.
• An ecosystem is smaller in comparison to a biome as a biome can be widely distributed all through the earth.
• Unlike an ecosystem, a biome is strongly influenced by its physical factors such as climatic conditions such as snow, temperature, rainfall etc. A biome has multiple ecosystems.
• An ecosystem is not influenced by the latitude whereas a biome is influenced.
• In an ecosystem, all animals interact in trophic interactions of food webs and chains whereas, in a biome, animals do not necessarily interact.
• Desert, grasslands, tundra, and tropical rainforests are some examples of biomes. An ecosystem includes ponds, coral reefs, etc.
Why humus content in tropical rainforest soils is poor?
• Humus content of soil is a function of how fast organic matter is produced and how fast it decays.
o Humus is highly resistant to microbial action and undergoes decomposition at an extremely slow rate.
• Highly productive tropical rainforest conditions certainly produce organic matter at a high rate, but they also decay it at a high rate, considerably higher than it is produced, thus organic matter doesn’t accumulate.
• Some conditions favor accumulation of humus.
o Cold soil - common in all high latitudes like the Arctic and high altitudes, like mountains.
o Lack of oxygen in the soil, which is usually a function of how saturated with water it is.
Swampy wet soils have very low oxygen and tend to accumulate humus, even if the temperature is warm.
High oxygen promotes faster rate of decomposition
o Type of organic matter.
Some forms of leaf or needle fall are high in lignin and tend to decay slowly, even when oxygen is adequate.
o Organic matter then accumulates in very dry conditions, like deserts, that doesn’t get blown or washed away by the wind or rain or burn in fires.
• The high rainfall and high temperature of tropical rainforests contributes to high bacterial actions in the soil so that organic material is quickly broken down, and certain minerals and nutrients are washed away along with humas and the soil become sterile.
Why temperate soils are rich in humus?
• Low temperature causes slow reactions so the decomposition process, becomes slow which is the main reason of greater humus content in temperate soils.
What makes soil in tropical rainforests so rich?
Mangroves
● Mangroves represent a characteristic littoral forest ecosystem.
● These are mostly evergreen forests that grow in sheltered low lying coasts, estuaries, mudflats, tidal creeks, backwaters (coastal waters held back on land), marshes and lagoons of tropical and subtropical regions.
● Mangroves grow below the high water level of spring tides.
● Mangroves are highly productive ecosystems, and the trees may vary in height from 8 to 20 m. They protect the shoreline from the effect of cyclones and tsunamis.
● Since mangroves are located between the land and sea, they represent the best example of ecotone.
● Mangroves are salt tolerant trees, also called halophytes, and are adapted to harsh coastal conditions.
● They contain a complex salt filtration system and complex root system to cope with salt water immersion and wave action.
● They are adapted to the low oxygen (anoxic) conditions of waterlogged mud.
● They produce pneumatophores (blind roots) to overcome the respiration problem in the anaerobic soil conditions.
● Mangroves occur worldwide in the tropics and subtropics, mainly between latitudes 25° N and 25° S.
● They require high solar radiation to filter saline water through their roots. This explains why mangroves are confined to only tropical and subtropical coastal waters.
● Mangroves exhibit Viviparity mode of reproduction. i.e. seeds germinate in the tree itself (before falling to the ground).
● This is an adaptive mechanism to overcome the problem of germination in saline water.
Wetland:
• Benefits
o Water storage
o Drought buffering
o Increases groundwater recharge
o Flood mitigation
o Less soil erosion
o Sewage will trap at the bottom since the soil is compact, while the water will penetrate down – water purification function – thus groundwater is not contaminated
o It traps sediments, pollutants and nutrients
o Supports rich biodiversity – birds
o Promotes tourism and recreation
o Local people’s livelihood
o Also regulates local climate
• Negative point
o Generates methane due to anaerobic decomposition
Sea cucumber:
• Sea cucumbers are echinoderms.
• They are marine animals with a leathery skin and an elongated body containing a single, branched gonad.
• Sea cucumbers are found on the sea floor worldwide.
• Many of these are gathered for human consumption and some species are cultivated in aquaculture systems. The harvested product is variously referred to as trepang, namako, bêche-de-mer, or balate.
• Sea cucumbers serve a useful role in the marine ecosystem as they help recycle nutrients, breaking down detritus and other organic matter, after which bacteria can continue the decomposition process.
• Like all echinoderms, sea cucumbers have an endoskeleton just below the skin.
Sea weed or macroalgae:
• Species of macroscopic, multicellular, marine algae. "Seaweed" is visible to the naked eye.
• They grow in the ocean as well as in rivers, lakes, and other water bodies. (both marine and freshwater)
• Seaweed species such as kelps provide essential nursery habitat for fisheries and other marine species and thus protect food sources; other species, such as planktonic algae, play a vital role in capturing carbon, producing at least 50% of Earth's oxygen.
• Mechanical dredging of kelp destroys the resource and dependent fisheries.
• Seaweeds are rich in nutrients, such as fiber, iodine and vitamin K, and have been an important source of food, animal feed and fertilizer for coastal communities for thousands of years.
• Seaweed farming has become a global agricultural practice, providing food, source material for various chemical uses, cattle feeds and fertilizers.
• Because of their importance in marine ecologies and for absorbing carbon dioxide, recent attention has been on cultivating seaweeds as a potential climate change mitigation strategy for bio-sequestration of carbon dioxide, alongside other benefits like nutrient pollution reduction, increased habitat for coastal aquatic species, and reducing local ocean acidification.
• Seaweeds are also termed as the ‘Medical Food of the 21st Century’
• Several studies have shown that seaweed contain a range of bioactive substances with diverse pharmacological potential, such as antiviral, antibiotic and antiendotoxic, antifungal, antiparasitic, antioxidant, anti-ageing, antinociceptive, anti-tumor, anti-diabetic, anti-inflammatory, and immunomodulatory effects. Among all, the anti-inflammatory activity of compounds derived from seaweed is one of the largest bioprospecting areas in marine natural products
• Seaweed cultivation is a highly remunerative activity involving simple, low cost, low maintenance technology with short grow-out cycle.
• In India there are 46 seaweed-based industries, 21 for Agar and 25 for Alginate production.
• Seaweeds are abundant along the Tamil Nadu and Gujarat coasts and around Lakshadweep and Andaman & Nicobar Islands.
• Suitable sites for seaweed cultivation will be selected based on the following criteria:
o Stable seawater with not less than 30 ppt salinity
o Sandy/ rocky bottom with transparent water
o Ideal temperature 26-30 degree C.
o The area should have minimum 1.0 m water depth during low tide.
o Area with mild water currents are preferred.
Seagrass:
• Seagrasses are the only flowering plants which grow in marine environments. Seagrasses evolved from terrestrial plants which recolonized the ocean.
• Found across the world. The global distribution of seagrass is remarkably consistent north and south of the equator and found in all 6 continents except Antarctica
• The name seagrass stems from the many species with long and narrow leaves and often spread across large "meadows" resembling grassland.
• Like all autotrophic plants, seagrasses photosynthesize, in the submerged photic zone, and most occur in shallow and sheltered coastal waters anchored in sand or mud bottoms.
• Most species undergo submarine pollination and complete their life cycle underwater.
• While it was previously believed this pollination was carried out without pollinators and purely by sea current drift, this has been shown to be false for at least one species, Thalassia testudinum, which carries out a mixed biotic-abiotic strategy.
• The plant produces nutritious mucigenous clumps of pollen to attract and stick to them instead of nectar as terrestrial flowers do.
• Seagrasses form dense underwater seagrass meadows which are among the most productive ecosystems in the world.
• They function as important carbon sinks and provide habitats and food for a diversity of marine life comparable to that of coral reefs.
• Distribution of seagrass in India
o More in east coast than west coast due to the shallow coast
Gulf of Mannar and Palk Bay > Lakshadweep > A&N
• Benefits
o It maintains stable sea bottom – extraordinary root system
o It traps sediments and nutrients and slows down water movement
o Thus it maintains water quality
o It absorbs the shocks of waves and tides because of extensive root system.
o It is food and shelter for many organisms. Some take refuge here
o Supports rich biodiversity –
o Sea cow consumes on sea grass – similar organism is Manatee
o It has got extraordinarily high rate of primary productivity
o Sea grass will capture CO2 35 times faster than tropical rain forests.
o Sea grass can be used as fertilizer, furniture, etc.,
Peatlands:
• Peatlands are a type of wetland which occur in almost every country and are known to cover at least 3% of global land surface. The term ‘peatland’ refers to the peat soil and the wetland habitats growing on the surface.
• In these wetlands, plant debris sinks into shallow, slightly acidic water. The debris doesn't decompose in this oxygen-poor environment and instead turns into carbon-storing peat.
• Peatlands are critical for preventing and mitigating the effects of climate change, preserving biodiversity, minimizing flood risk, and ensuring safe drinking water.
• Peatlands are the largest natural terrestrial carbon store. They store more carbon than all other vegetation types in the world combined. The world's peatlands account for about a third of the total CO2 absorbed by soil.
• Peatland landscapes are varied from temperate blanket of Scotland to swamp forests in Southeast Asia. The world’s largest tropical peatland was identified beneath the forests of the Congo Basin in 2017.
• In peatlands, year-round water-logged conditions slows down the plant decomposition to such an extent that dead plants accumulate to form peat. This stores the carbon the plants absorbed from the atmosphere within peat soils, providing a net-cooling effect and helping to mitigate the climate crisis.
• Draining peatlands exposes the layers underneath to oxygen, triggering a decomposition process that releases CO2 and nitrous oxide.
• Damaged peatlands are a major source of greenhouse gas emissions, responsible for almost 5% of global anthropogenic CO2 emissions. Degradation and overexploitation of peatland landscapes release huge quantities of greenhouse gasses.