Ocean acidification is an emerging problem for environmental scientists.

While the effects of ocean acidification have not yet become noticeable enough to warrant an environmental crisis, experts expect that this may occur within the century.

With current technology and predictive models, it is not possible to describe the overall effects that the ocean’s gradually decreasing pH level will have over time. The only thing that scientists can do is pinpoint small, localized effects and conjecture an overall pattern from that information.

Eventually, better, more complete models for describing climate change may change that. For now, we must look at the four biggest effects and correlate them to what we already know.

Four Effects of Ocean Acidification on Marine Ecosystems

Since the industrial revolution, the average pH level of the ocean has fallen by a factor of 0.1. This may not seem like much, but the pH scale is a logarithmic scale, which means that this corresponds to a 30 percent decrease. The main culprit for this level of acidification is absorption of carbon dioxide.

If nothing changes, by the end of the century the ocean may be 150 times more acidic than it is now, resulting in sweeping changes to marine life as we know it.

1. Tropical Coral Reefs May Die

The EPA estimates that 25 percent of all marine life is dependent on coral reef structures. Throughout the biological history of Earth, coral reefs have served as “cradles of evolution”, creating environments that produced many of the biological adaptations responsible for life as we know it today. Furthermore, about 500 million people rely on coral reef ecosystems for food and income.

Coral reefs rely on calcification to build their hard, stony outer surfaces. Reef calcification slows when exposed to lower pH levels. This slowing effect is already visible on the Great Barrier Reef, which is uniquely sensitive to oceanic water chemistry because of its enormous size. Corals also rely on calcification to reproduce, which a more acidic ocean would make impossible.

2. Less (or Completely Different) Plankton Species

This is one of the more mysterious changes that ocean acidification may produce within the century. Currently, plankton occupy the lowest rung on the marine ecosystem’s food chain – they produce small amounts of energy through chemical processes and are consistently eaten by a huge variety of other creatures, from tiny protists to blue whales.

If all the ocean’s plankton were to die, the resulting environmental catastrophe would disrupt the foundation of all life and civilization on the planet. Ocean acidification is not likely to have that powerful an effect, but it can change the overall constitution of plankton species in the ocean.

Since plankton are so diverse – scientists have described 4,000 individual species discover more every year – and since they largely subsist on chemical reactions, it’s impossible to tell which species would survive acidification and which would not. It’s also impossible to tell how the increased presence of the acid-friendly plankton would further affect the planet’s global ecosystem.

If, for instance, only the plankton responsible for consuming greenhouse gases die off, then ocean acidification could hugely accelerate global warming, melting ice shelves and flooding coastal cities in the process.

3. Commercially Important Coastal Ecosystems Would Suffer

The vast majority of commercially important marine ecosystems – the ones the produce food and other products for human consumption – are likely to change radically as a result of ocean acidification. Not only will the ecosystems suffer as a result of the changing environment, but ecosystem engineers may be less capable of building habitats for commercial fishery.

Oyster reefs, kelp beds, and sea grass beds may no longer be feasible in the areas where they are most needed. Unwanted algae species may dominate ecosystems and ruin commercial attempts at farming. The effects of ocean acidification on specific coastal environments is yet unknown, however, because each coastal environment is unique.

4. Deep Water Ecosystems Become Less Diverse

Scientists are least capable of describing the changes acidification may provoke in deep sea ecosystems. This is largely because the scientific community knows so little about how these ecosystems work. Some deep benthic organisms seem to be resistant to differences in pH level, but others, such as cold-water corals, are likely to suffer.

These cold-water corals are ecologically significant for a huge number of seamount ecosystems. Scientists have identified over 30,000 seamounts that serve as bastions for deep-sea life, and which could be threatened by increasing acidification. These ecosystems can only become less diverse as a result of acidification threatening the corals they rely on.

What We Can Do

The largest contributor to ocean acidification is fossil fuel combustion. Everyday people contribute by using flushing harmful acids down the drain, as well. Only by lessening our general carbon footprint can we reduce the effects of ocean acidification in the long run.

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