Lesson 3.1.6.5

3.1.6.5 Marine ecosystems Quiz: AQA Geography, Unit 1

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.1.6.5, Marine ecosystems: 20 multiple choice questions for the AQA Geography (7037), Unit 1: Physical geography, written with Revision Ninja.

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The 20 questions

  1. Coral reefs are most commonly found in:

    • Freshwater lakes in continental interiors, where the water is low in salt and rich in dissolved minerals
    • Cold, deep polar seas with permanent ice cover and very low light levels throughout the year
    • Warm, shallow, clear tropical seas with sunlight reaching the seabed
    • Muddy estuaries with high sediment loads, where turbid water blocks most of the light from the surface

  2. Coral reef development requires a mean water temperature of approximately:

    • Above about 18 degrees Celsius, typically 23 to 25 degrees, for healthy growth
    • Above 60 degrees Celsius, which is the temperature at which the coral polyps can build their skeletons fastest
    • Below freezing at all times, so that the water remains cold enough to preserve the coral skeletons
    • Around 0 degrees Celsius year round, which is the temperature of most deep ocean water in polar seas

  3. The relationship between reef corals and zooxanthellae is best described as:

    • Competition for the same food resources, in which the algae and corals both try to capture plankton from the water
    • Parasitism, in which algae live inside the coral and gradually kill it by consuming its tissues over time
    • Predation, in which corals hunt and consume the algae that live within their tissues in the reef
    • Mutualism, in which algae provide energy through photosynthesis and corals provide shelter and nutrients

  4. Which natural factor is important to the health of coral reefs?

    • Snow cover on the seabed, which protects the coral skeletons from the effects of heavy seasonal storms
    • Average wind speed in the open ocean only, which determines how much wave energy reaches the reef flat
    • Water temperature, which can cause coral bleaching when it rises too high for too long
    • Distance from any landmass, since reefs that are far from land receive less sediment and are healthier

  5. Coral bleaching occurs when:

    • Corals are eaten by fish during the night, which removes the colourful tissues from the outer surface of the reef
    • Corals expel their symbiotic algae, often due to stress such as high temperature
    • Corals grow extra skeleton in cold water, which turns the colony white as the calcium carbonate builds up
    • Corals are covered by thick layers of sediment that block light and cause the tissues to turn pale over time

  6. Which human activity is most likely to damage a coral reef through sedimentation?

    • Growing seaweed along the reef edge with no runoff, which can slowly smother the coral colonies over time
    • Land clearance and dredging that increase sediment runoff into the sea
    • Tourism that involves only shallow snorkelling in clear water, which is known to leave sediment on the reef
    • Using sunlight to power reef tourism boats, which increases the amount of heat absorbed by the surface water

  7. Which statement about pollution and reefs is most accurate?

    • Pollution increases coral growth rates everywhere, because nutrients act as a fertiliser for the coral polyps
    • Pollution has no effect on coral reefs, since corals are able to remove all pollutants from the seawater naturally
    • Nutrient and chemical pollution from land can promote algal blooms that harm coral health
    • Pollution only affects the reef's fish, not the corals, which are protected by their hard calcium carbonate skeletons

  8. Which feature of a coral reef is most sensitive to changes in salinity?

    • Clouds above the reef, which are controlled by atmospheric pressure and not by the salinity of the sea
    • Sand on the beach next to the reef, which is composed of quartz grains that are not affected by salt
    • Coral and associated organisms, which need normal sea salinity to survive
    • Deep rock beneath the reef, which is formed from ancient sediments and is unaffected by changes in the water

  9. Which of these is a human impact of desalination on coral reefs?

    • Reduction of salinity that makes the reef sweeter, which benefits the fish and corals in the surrounding area
    • Creating a new coral species instantly, as the concentrated brine encourages rapid reproduction of polyps
    • Brine discharge that increases local salinity and may harm reef organisms
    • Increasing the volume of freshwater in the sea, which dilutes the water around the reef and protects the corals

  10. Which of these best describes a future prospect for coral reefs?

    • Reefs will disappear entirely within a single year, as all corals die from one event at the same time
    • Reefs face increasing threat from warming and acidification, though management can improve their outlook
    • Reefs are certain to grow faster as the climate warms, because warm water favours coral growth in all cases
    • Reefs will be unaffected by all human activity in the future, since they are protected by international law

  11. Which of these is a common land-based impact on coral reefs from drainage basin schemes?

    • A rise in sea level that drowns reefs, as the drainage scheme raises the water table beneath the coast
    • Reduced sediment and nutrient inputs to the sea, which starves the reef of the material it needs to grow
    • A fall in ocean temperature that stops coral growth, since the drained land cools the surrounding seawater
    • Increased sediment and nutrient inputs from river systems

  12. Which statement about tourism and coral reefs is most accurate?

    • Tourism can bring income but can also damage reefs through anchoring, trampling and pollution
    • Tourism has no effect on reef ecosystems, because visitors rarely enter the water or touch the corals
    • Tourism only affects fish, not the corals, which are too hard to be damaged by anchors or divers
    • Tourism always improves reef health without any risk, since visitors fund conservation and remove pollution

  13. Which natural factor helps coral reefs recover from disturbance?

    • Permanent darkness on the reef floor, which slows the growth of competitors and allows corals to recover
    • Continuous deposition of volcanic ash, which provides nutrients for the polyps to rebuild the skeleton
    • Larval supply from healthy reefs nearby that can recolonise damaged areas
    • Constant freezing of the seawater, which kills the algae and allows the coral to grow back quickly

  14. Which evaluation of coral reef management is most accurate?

    • Local management is enough to offset all global warming effects, so action on climate change is unnecessary
    • Management is unnecessary because reefs recover quickly from every type of damage, whatever its cause
    • Global warming is irrelevant to reef management, since the effects of temperature rise are limited to deep water
    • Effective management needs to address both local pressures and global warming, since local action alone cannot offset warming

  15. A coral reef is subjected to sediment and nutrient pollution. Which outcome is most likely?

    • Reduced coral cover as algae and sediment compete with corals
    • Increased coral cover because of added nutrients, which allow the polyps to grow faster and cover more space
    • No change because pollution never reaches reefs, which are too far from the land to be affected
    • Creation of a freshwater lake on the reef, as the sediment forms a barrier that separates the water

  16. Which statement about the distribution of coral reefs is most accurate?

    • They are concentrated in polar latitudes, where the cold water supports dense coral growth on the seabed
    • They are evenly distributed across all latitudes, forming wherever the sea is shallow and calm
    • They are found only in deep ocean trenches, where the pressure favours the growth of reef-building organisms
    • They are concentrated in tropical latitudes between roughly the Tropics of Cancer and Capricorn

  17. Which factor would most increase the tolerance of a reef to rising temperatures?

    • A reef located in freshwater lakes, where the water temperature rises more quickly than in the sea
    • Corals and symbionts adapted to fluctuating temperatures, and a healthy, diverse reef
    • A reef exposed to constant pollution, which weakens the corals and reduces their resilience to heat
    • A reef with very low species diversity, which has fewer organisms to maintain the balance of the ecosystem

  18. Ocean acidification threatens coral reefs because it:

    • Raises the temperature of the water directly, which is the main cause of bleaching across the reef
    • Reduces the availability of carbonate ions that corals need to build skeletons
    • Increases the availability of carbonate ions for skeletons, which makes the coral grow too quickly and become brittle
    • Causes corals to grow faster and then weaken, as the increased acidity stimulates excessive growth

  19. Which feature of coral reef ecosystems is most important for supporting high biodiversity?

    • The complex three-dimensional structure that provides habitats for many species
    • Permanently muddy water with no light, which allows a wide variety of filter-feeding organisms to thrive
    • The absence of any predators in the reef, which allows prey species to multiply without restriction
    • A uniform, flat seabed with no structure, which allows fish to move freely across the reef surface

  20. A reef loses 40 per cent of its coral cover after a bleaching event. Which statement best evaluates the impact?

    • The loss increases biodiversity by opening new habitat, which allows more species to colonise the cleared areas
    • The loss has no effect on reef biodiversity, since the remaining coral can support the same number of species
    • The loss is significant and may reduce habitat for many reef species, though recovery is possible if conditions improve
    • The loss is permanent with no possibility of recovery, since bleached corals never regain their symbiotic algae

All AQA Geography quizzes