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Abiotic Ecosystem Factors in Marine Life

Unlike many terrestrial species, most aquatic life forms are very sensitive to small changes in their habitat. They require precise living conditions to thrive. Abiotic factors, or "nonliving" factors, can affect the quality of a marine ecosystem in many ways. Even minute adjustments to these factors can determine the organisms that live in the region.

  1. Temperature

    • Marine organisms require specific temperatures in their environment. Most can only tolerate a few degrees of variability on either side of this temperature. Heat pollution from factories, generators or global climate change can make certain bodies of water uninhabitable for some sensitive species. For example, a rise in ocean temperatures of just one or two degrees could cause coral reefs worldwide to bleach and die out. A shift to cooler water can have similar effects on aquatic creatures.

    Salinity

    • Marine ecosystems are often defined by the salinity of their water. Some species can survive only in freshwater, while others prefer extremely salty or "super-saline" waters. Many organisms favor a balance between the two, occupying the brackish waters where streams or rivers meet oceans, gulfs or seas. Most freshwater species cannot tolerate salty water, and most saltwater species cannot stand freshwater. The organisms living in a particular ecosystem can only withstand a range of a few parts per million (ppm) in salinity.

    pH Levels

    • Another abiotic factor that tends to affect marine ecosystems exclusively is the pH level of the body of water. The pH level of a substance measures how acidic or basic it is. In recent years, pH levels have been dropping in lakes, streams and oceans worldwide due to an increasing concentration of carbon dioxide in the atmosphere. This corresponds to more carbonic acid in the Earth's waters and acid rain from sulfur dioxide given off by factories and industry.

    Sunlight

    • In many bodies of water, multiple different ecosystems can exist one over the other, at differing depths. Because light can only penetrate so far into the water, the deeper the water, the less light that reaches the organisms living there. Some aquatic plant species prefer more light, while some can tolerate less light, just like terrestrial plant species. The plants that survive at each level in turn affect the other organisms that live there.

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