This coral reef, in Sogod Bay, Philippines, is thriving with biodiversity. Coral, algae, fish, and crustaceans such as crabs inhabit the reef. The large white organism in this photograph is bubble coral. Bubble corals have large, water filled tubes (called vesticles) that expand during the day to look like white grapes. At night these vesicles deflate and the tentacles of the coral appear.

Photograph by Michael Keller, MyShot
  • Coral reefs are among the most diverse ecosystems in the world. This biodiversity makes them a high priority for conservation. The brilliant corals of Sogod Bay, above, live in one of more than 400 marine protected areas (MPAs) in the Philippines.

    MPAs help to conserve biodiversity by preventing practices like coral harvesting and dynamite fishing. Unfortunately, there are also global dangers facing coral reef habitats that cannot be withheld by MPA boundaries.

    The impact of ocean acidification on corals is one of these dangers. Oceans absorb carbon dioxide (CO2) from the atmosphere. Carbon dioxide reacts with seawater to form carbonic acid. Due to increases in carbon emissions, more CO2 is entering the world’s oceans, which creates additional carbonic acid in the water.

    The more acidic seawater becomes, the less calcium carbonate it can hold. Many marine species, including coral, need calcium carbonate to build their protective shells and exoskeletons. Without it, shells grow slowly and become weak. Coral reefs with breakable, slow-growing corals erode more quickly than they accrete. Reefs can disappear, and the extinction of entire species is possible.

    Efforts are being made in the Philippines to increase awareness of the potential impacts of ocean acidification. However, it will take global action to decrease our carbon emissions and help to protect the world’s fragile coral reef ecosystems.

    • Sogod Bay, Philippines, where this beautiful photo was taken, is actually a collection of MPAs. Besides coral, the areas are home to animals as small as pygmy seahorses and as large as whale sharks.
    • Coral reefs cover approximately 26,000 square kilometers (10,039 square miles) around the Philippines.
    • Only 5% of corals in the Philippines are considered to be in excellent condition.
    • Coral reef ecosystems cover only 1% of the ocean, but 25% of marine creatures live in them.
    • Corals can be animal, mineral, and plant all at once! The actual coral polyps are animals. Their calcium carbonate shells are mineral. Algae, which are sometimes considered plants, live with corals and give them their bright colors.
  • Term Part of Speech Definition Encyclopedic Entry
    accrete Verb

    to build up or grow together.

    atmosphere Noun

    layers of gases surrounding a planet or other celestial body.

    Encyclopedic Entry: atmosphere
    biodiversity Noun

    all the different kinds of living organisms within a given area.

    Encyclopedic Entry: biodiversity
    calcium carbonate Noun

    chemical compound (CaCO3) found in most shells and many rocks.

    carbon dioxide Noun

    greenhouse gas produced by animals during respiration and used by plants during photosynthesis. Carbon dioxide is also the byproduct of burning fossil fuels.

    carbon emission Noun

    carbon compound (such as carbon dioxide) released into the atmosphere, often through human activity such as the burning of fossil fuels such as coal or gas.

    carbonic acid Noun

    chemical produced as carbon dioxide dissolves in water.

    conservation Noun

    management of a natural resource to prevent exploitation, destruction, or neglect.

    Encyclopedic Entry: conservation
    coral Noun

    tiny ocean animal, some of which secrete calcium carbonate to form reefs.

    coral reef Noun

    rocky ocean features made up of millions of coral skeletons.

    diverse Adjective

    varied or having many different types.

    dynamite fishing Noun

    practice of using explosives to stun or kill entire schools of fish. Also called blast fishing.

    ecosystem Noun

    community and interactions of living and nonliving things in an area.

    Encyclopedic Entry: ecosystem
    erode Verb

    to wear away.

    exoskeleton Noun

    the hard external shell or covering of some animals.

    extinction Noun

    process of complete disappearance of a species from Earth.

    fragile Noun

    delicate or easily broken.

    habitat Noun

    environment where an organism lives throughout the year or for shorter periods of time.

    Encyclopedic Entry: habitat
    MPA Noun

    (marine protected area) area of the ocean where a government has placed limits on human activity.

    ocean acidification Noun

    decrease in the ocean's pH levels, caused primarily by increased carbon dioxide. Ocean acidification threatens corals and shellfish.