Coral
Coral is a colony of innumerable tiny, fleshy sea anemones called polyps. one of the most diverse and productive marine ecosystem on Earth housing millions of marine species. Favourable conditions
• Temperature: Annual range ‐ 23°C and 30°C.
• Depth: The coral needs shallow water not survive beyond 200‐250 feet (60‐77m) below sea level due to lack of sufficient amount of sunlight
• Saltwater: Corals need saltwater to survive and require a certain balance in the ratio of salt to water. This is why corals don’t live in areas where rivers drain fresh water into the ocean. The salinity requirement is 27%0 – 30%0
• Nutrients and oxygen supply are provided by vigorous cleansing wave action. They die in small enclosed sea and lagoons. Hurricanes, cold currents, upwelling zones, fresh water from rivers –all impede their growth
• Clean, sediment free ambient water as turbidity clogs the mouth of polyps leading to their demise
• diverse underwater ecosystems held together by calcium carbonate structures secreted by corals.
• classified into Warm and Cold water coral reefs.
• Depth of water ‐ not exceed 180 feet as the sunlight is too faint for photosynthesis ‐ survival of microscopic algae on which coral polyps depend.
• cannot survive for too long out of water.
• Corals are best developed on the seaward side of the reef, where constantly moving waves, tides and currents maintain an abundant supply of clear,
oxygenated water.
Distribution of Coral reefs
• within 30° of equator and Indo‐Pacific region accounts for 91.9% of the global distribution of coral reefs.
• South east Asia: 30% of world’s coral; coral triangle (extending from southern Philippines to eastern Indonesia and western New Guinea).
• Pacific ocean: 25% of world’s corals, especially on west part; great barrier reef, Micronesia, Papua New guinea, Vanuatu
• Indian ocean: 24% of world’s coral; gulf of Mannar, Lakshadweep, Andaman and Nicobar
• Persian gulf & Red sea –miniscule percentage
Coral reefs
Conditions conducive to Warm water/Tropical coral reefs:
• limited to tropical and sub‐tropical zones.
• will not flourish in areas of cold currents but thrive in warm current regions.
• generally absent on western coasts of continents. E.g. Due to the Gulf Stream, corals are found far to the north of West Indies in Atlantic Ocean.
Conditions conducive to Cold Water Corals:
• They are commonly found where current flow is fast.
• They are found on continental shelf, and also in deepsea areas with topographic highs, such as seamounts, mounds, ridges, and pinnacles.
• no symbiotic algae living in their polyps‐ no need sunlight to survive ‐ can occur at greater depth.
•
Their polyps are bigger hence they can capture food particles from lesser nutrient holding water. Anthropogenic factors that have resulted in decline of corals:
• Increase in temperature due to climate change and pollution.
• With climate change, acidity of oceans increases because of dissolution of carbon dioxide. This is the major cause of death of corals.
• Impact of global warming: High water temperature and solar irradiance causes disruption of enzyme system in zooxanthellae that offers protection to corals against oxygen toxicity. Photosynthesis pathways in zooxanthellae are also impaired. Ocean acidification form the skeletons of coral.
• Runoff from agricultural land and chemical pollution: Results in eutrophication and subsequent oxygen depletion.
• Overfishing: Leads to an average decrease in size of the fish and a reduction in predatory target fish, thus, resulting in large‐scale ecosystem change. This affects coral ecosystem.
• Destructive fishing and boating practices: Leads to habitat destruction and disintegration of reef ecosystem. introduction of mechanized fishing.
• Marine Pollution: increase in sea transport, oil spill etc. destroy coral reefs
• Uncontrolled tourism activities: Lead to breakage of coral colonies and leads to tissue damage.
• Coastal construction and shoreline development: Results in heavy sedimentation, which can lead to coral reef destruction.
• Introduction of invasive species in the ocean by humans too lead to change in the coral ecosystem.
• Coral mining: Live coral is removed from reefs for use as bricks etc.
• Many coral islands are small and near sea level, so they are at constant threat from cyclones, storms and rising sea levels.
• Construction of groynes, breakwaters, and jetties, and anchor damage and siltation caused by speedboats cause considerable damage to coral
islands.
• human activities such as species introduction, phosphate mining and even bomb testing.
• Other threats include pollution, increased shipping traffic, risk of oil spills and dumping, inadequate waste disposal, and the overuse of water pumps and
fertilisers for agriculture.
About 60% of the world's reefs may be at risk due to destructive, human‐related activities and climate change. Further, by 2030s, 90% of reefs are expected to be at risk; and
by 2050, it is predicted that all coral reefs will be in danger.
Consequences
• impact marine ecosystem, as coral reefs ‐ most bio diverse and productive ecosystems.
• Act as natural barriers to shorelines, protecting them from the effects of moving water.
• coastlines become more susceptible to damage and flooding from storms, hurricanes, and cyclones.
• Without coral reefs, ocean will not be able to absorb as much CO2, leaving more CO2 in the atmosphere.
• Loss of the coral reefs will have a devastating impact on tropical countries’ economies, food supplies, and safety of their coastal communities.
• Livelihood Concerns‐Atolls have few natural resources. Soil quality on atolls is very poor, and erosion is a constant threat. Most native residents on atolls practice subsistence agriculture and fishing. Fisheries and support for the shipping industry help support communities on remote atolls.
• Hence, it is important that efforts be taken to conserve them else thousands of years of natural
change, will not survive.
Coral islands
Coral islands develop from coral reefs either by uplift or by accretion. Coral islands may also be formed from atoll reefs wherein they manifest as a string of roughly circular islands with shallow lagoons. Examples of coral islands include
Maldives, Kiribati islands, Lakshadweep etc.
Measures to protect coral island:
• Political measures. For example Maldives often leads international conferences on the impacts of global warming, which is associated with sea level rise. Maldives and Kiribati have also taken steps to outline a permanent evacuation process should sea level rise threaten to drown inhabited atolls.
• Geo‐engineering solutions‐ For example Island nations such as Maldives and Kiribati are fortifying their atolls by dredging the seafloor. Sand elevates certain areas and widens others, creating a more stable landmass.
• Switching to sustainable livelihood measures‐ Recognize the carrying capacity of each coral island ecosystem and limit population growth, tourist foot fall etc. at these islands.
• Developing alternative livelihoods like establishing sustainable fisheries
Some atoll communities have taken advantage of their equatorial location and established launch sites for low‐orbit satellites. Eg:Tuvalu, receives millions of dollars for use of its
".tv" Internet domain name.
Geysers and Springs
• Geysers are fountains of hot water & superheated steam that may sprout up to a height of 150 feet from the earth beneath. Usually emitted with an explosion & is often triggered off by gases seeping out of heated rocks.
• Some major geysers are found in Iceland, New Zealand, Russia & Yellowstone park of USA. The world's best known Geyser is 'Old Faithful' in Yellowstone National Park,
Wyoming.
Springs
• Hot springs or thermal springs are produced by the emergence of geothermally heated groundwater that rises from the Earth's crust.
• These generally contain dissolved minerals in water that may have medicinal value. Iceland has thousands of hot springs.
Difference between Springs & Geysers
• In contrast to geysers, water rises to surface without any explosion in Springs.
• Springs are more common than geysers which are quite rare.
• Springs are not associated with volcanic origin but geysers usually are.
• Springs may not be heated to beyond boiling point but geysers are superheated bodies.
Areas conducive to their development
Springs:
• They occur where very deep groundwater, heated in warm bedrock at depth, flows up to the ground surface.
• Second, hot springs develop in geothermal regions, places where magma & very hot rock resides close to the Earth’s surface.
Geyser:
• The phenomena are generally associated with a thermal or volcanic region in which water below is being heated beyond boiling point (100 C or 212 F).
Major grasslands of the world
Definition: lands dominated by grasses rather than large shrubs or trees. It is largest ecosystems in the world & comprise 40.5 percent of the terrestrial area.
There are two main divisions of grasslands–
Tropical Grasslands (Savannas):
• transitional regions between the equatorial forests & the trade wind hot deserts.
• located in semi‐arid to semi‐humid climate regions of subtropical & tropical latitudes.
• practically treeless & the grasses are much shorter.
Temperate Grasslands (Steppes):
• they occupy interior of the continents in the mid‐ latitude zone of 40 & 55 North & South.
• occupy vast areas in the NH where their east‐west extension is broader. In Southern Hemisphere, the grasslands are small in extent.
• ‘granaries of the world’. They are the largest wheat exporters.
The conditions responsible for this are‐
• The cool, moist spring stimulates early growth & the light showers in the ripening period help to swell the grains to ensure a good yield.
• The summer is advantageous for harvesting & enables the straw to be dried for farm use.
• The levelness of the Steppes makes ploughing & harvesting a comparatively easy job.
• Marked specialization in wheat monoculture, high degree of mechanization, strong forward linkages are some of the other reasons.
Performance of Temperate Grasslands vis‐à‐vis Tropical
Grasslands
• Low yield per acre: Temperate area have large land compared to tropical areas, where greater attention to small piece of land is given.
• High yield per man: Since the temperate regions are marked by high degree of mechanization
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