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Ocean bottom topography, ocean temperature, salinity, deposits, and the basics of coral reefs
Require warm, tropical waters with temperatures generally above 20°C.
Thrive at depths not exceeding 200–250 feet for adequate sunlight penetration.
Need average salinity around 35 parts per thousand.
Must have sediment-free water to prevent blockage of polyp mouths and tentacles.
Require a solid platform such as a continental shelf or a submerged feature (e.g., guyot) to attach and expand.
Occur between 30°N and 30°S latitudes in warm, shallow, and clear ocean waters.
Absent along regions affected by cold ocean currents (e.g., western margins of continents in tropical latitudes).
Rare near large river deltas due to influxes of freshwater and sediment.
Major regions include:
Coral Triangle: Southeast Asian islands, the Great Barrier Reef, and many South Pacific islands
Western Indian Ocean: Red Sea, Persian Gulf, areas around Madagascar, Mauritius, the Maldives, and Lakshadweep
Caribbean: Stretching from the Greater and Lesser Antilles to the Bahamas
Fringing Reefs
Develop close to the coastline in discontinuous patches.
May lack a lagoon or have a very narrow one.
Example regions include parts of the western coast of India and around the Andaman & Nicobar Islands.
Barrier Reefs
Located farther offshore and separated from land by a lagoon.
Form continuous, extensive structures over long time spans.
The largest example is Australia’s Great Barrier Reef.
Atolls
Ring-shaped reefs encircling a lagoon, often formed around a submerged volcanic island or guyot.
Common in Lakshadweep, the Maldives, the Caribbean, and many Pacific islands.
Andaman & Nicobar Islands: Host some of the most pristine reef systems with rich biodiversity.
Lakshadweep: Volcanic islands topped by coral atolls, forming circular reef structures.
Gulf of Mannar and Gulf of Kutch: Notable reef complexes along India’s southeastern and northwestern coasts, respectively.
Minor reef patches also exist near certain western coastal areas and offshore banks (e.g., Angria Bank off Maharashtra).
Involves loss of the symbiotic algae (zooxanthellae) that give corals their color and supply food via photosynthesis.
Occurs when corals experience stress from factors like temperature spikes, pollution, salinity changes, or sedimentation.
Stress causes coral polyps to expel zooxanthellae, leaving white skeletal frameworks exposed.
Ocean Warming: Even slight temperature rises can induce bleaching, especially during marine heatwaves.
Ocean Acidification: Increased CO₂ lowers pH, inhibiting corals’ ability to absorb calcium carbonate.
Sedimentation & Freshwater Influx: Excessive sediment or decreased salinity hampers coral feeding and respiration.
Pollution: Chemicals, plastics, and untreated waste disrupt coral health.
Unsustainable Tourism: Certain sunscreens and human contact damage reefs.
Thermal Pollution: Heated effluents from power plants alter surrounding water temperatures.
Storm Surges & Cyclones: Physical damage and abrupt environmental changes stress reef systems.
El Niño Events: Heighten ocean warming and trigger large-scale bleaching episodes.
Reducing global warming through lower greenhouse gas emissions.
Limiting pollution from industrial, agricultural, and urban sources.
Restoration initiatives, such as the Biorock method, which uses low-voltage electric currents to enhance coral settlement and growth.
House around 25 percent of all marine species despite covering under 1 percent of the ocean floor.
Serve as essential nurseries and habitats for numerous fish and invertebrates.
Help protect coastlines from wave action and storm surges.
Are key indicators of ocean health and ancient climate history through their layered limestone structures.
Large-scale water movements within oceans in specific directions.
Act like rivers in the sea, influencing global climate by distributing heat and moisture.
Warm Currents: Flow from equatorial (low latitudes) to higher latitudes.
Cold Currents: Flow from higher latitudes toward the equator.
Steady planetary winds (e.g., trade winds, westerlies) drag surface water, creating and sustaining flow.
The continuous push over large distances sets up prominent current systems.
Variations between warm, less dense tropical waters and cold, denser polar waters create a pull driving water movement.
Salinity differences also contribute to density gradients that guide currents.
Continental shapes, shelves, and submerged features redirect flows.
Currents typically follow contours or are deflected at abrupt changes in coastline orientation.
Deflects currents to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.
Combined with wind patterns, helps determine major current loops (gyres).
North Equatorial Current
Driven westward by trade winds above the equator.
Flows from the eastern Atlantic toward the Caribbean.
South Equatorial Current (Northern Branch)
Part of the South Equatorial Current that splits and joins the North Equatorial Current.
Converges near the Caribbean islands.
Counter Equatorial Current
Moves eastward near the equator, formed by water piling up in the west and flowing back across calm equatorial zones.
Antilles Current
Forms from the combined flow approaching the Caribbean.
Curves around island arcs (Greater and Lesser Antilles).
Florida Current
Arises when water passes through the Gulf of Mexico and rejoins flows near Florida.
Continues northeast along the United States coastline.
Gulf Stream
A major warm current that follows the eastern coast of North America.
Swings northeast past Newfoundland under the influence of westerlies and Coriolis force.
North Atlantic Drift
Continuation of the Gulf Stream across the North Atlantic from west to east.
Splits near northwestern Europe into:
One branch veering north as the Norwegian Current
Another flowing southward as part of a broader loop.
Canary Current
Cold current moving south along the northwest coast of Africa.
Eventually rejoins equatorial flows, completing the northern Atlantic gyre.
Labrador Current
Cold current descending between Greenland and northeastern Canada.
Merges with the Gulf Stream near Newfoundland, creating a convergence of warm and cold waters.
East Greenland Current
Carries cold Arctic waters south between Greenland and Iceland.
Interacts with portions of the North Atlantic Drift.
Irminger Current
Warm current branching toward Iceland.
Merges with cold flows near Greenland/Iceland boundary zones.
Sargasso Sea
Region of relatively stagnant water enclosed by surrounding currents (North Equatorial, Gulf Stream, North Atlantic Drift, and Canary Current).
Characterized by floating seaweed (Sargassum) thriving in calmer circulation.
South Equatorial Current (Southern Branch)
Moves west in the southern tropical Atlantic.
Splits upon reaching South America into two segments.
Brazilian Current
Warm branch flowing south along Brazil’s east coast.
Deflected eastward by westerlies and Coriolis effect.
South Atlantic Drift (part of West Wind Drift)
Formed by merging of the Brazilian Current with strong west-to-east circulations around Antarctica.
Some flow returns northward up Africa’s western side.
Benguela Current
Cold current flowing north along Africa’s southwest coast.
Rejoins the South Equatorial Current, completing the South Atlantic gyre.
Falkland Current
Cold current near the Falkland Islands, merging with the Brazilian Current.
Influences marine life and regional climate off Argentina’s southern coasts.
Flows west under the influence of the northeastern trade winds.
Begins in the eastern Pacific, carrying water toward Southeast Asia.
Moves eastward in equatorial latitudes, balancing water buildup in the western Pacific.
Kuroshio Current
Warm current flowing along the east coasts of the Philippines and Japan.
Deflects northeast under Coriolis force and westerlies.
Oyashio Current
Cold current from the Bering Sea region merging with the Kuroshio near Japan.
Transition zone fosters productive fishing grounds and varied marine life.
North Pacific Drift
Continuation of the Kuroshio across the open Pacific from west to east.
Splits off near North America, sending a portion north and another south.
Alaska Current
Warm branch moving north along the Gulf of Alaska’s coast.
Transitions into cooler, subarctic waters at higher latitudes.
California Current
Cold current flowing south along the U.S. west coast.
Eventually loops westward to rejoin the North Equatorial Current.
South Equatorial Current
Driven westward by the southeasterly trade winds south of the equator.
East Australian Current
Warm branch following the east coast of Australia.
Turns east under westerlies and enters the West Wind Drift.
South Pacific Drift (part of West Wind Drift)
Cold flow encircling Antarctica.
Shifts northward along the west coast of South America.
Humboldt (Peru) Current
Strong cold current running north from Chile to Peru.
Rejoins the South Equatorial Current, completing the gyre in the southern Pacific.
Ocean currents of the Indian Ocean and their specific circulation patterns.