Global warming: Coral bleaching and ocean acidification

coral bleaching

Kee Alfian/Marine Photobank



*This article was updated April 10th, 2017

With varying reports of the oceans consuming 30-70% of the annual CO2 emissions, marine life is bound to suffer severe repercussions. The question remains easy to ask yet almost impossible to answer; how do we best address the huge responsibility of saving our oceans from ourselves?

Diving into the issue

One of the most splendid things about scuba diving are the diverse colors. The right colors carefully placed can attract mates, confuse predators, and even help land the next meal; for both flora and fauna. However, as any avid diver can attest, significant parts of the oceans are becoming a bit more mono-chromatic as of late. Typically, algae grows freely on healthy coral reefs, creating food for the coral system and giving it the beautiful color that they are known for.

The phenomenon of coral bleaching occurs when algae is stressed to the point of leaving the coral and is caused by extreme changes in ocean temperatures, pollution, and high exposure of solar irradiance. Once the coral is stressed the algae disperses, taking with it it’s color, food source and makes the coral way more susceptible to disease. The extent of coral bleaching is difficult to pinpoint, but organizations such as the XL Catlin Seaview Survey help us map the damages over time. The organization is a global effort to benchmark the destruction of coral reefs in order to bring this issue to the attention of the public and policy makers.



Ocean Acidification

As a home to phytoplankton, kelp, seaweed, algae, and many other ocean plants, the oceans naturally consume a large amount of carbon dioxide emissions. However, since the industrial revolution, the oceans have become stretched to the limit with what they can handle. On top of that, when atmospheric carbon reacts with seawater it breaks down from carbon dioxide to create carbonic acid, an element found in soda. As the name might suggest, high amounts of carbonic acid lead to more ocean acidification. In addition to simply sounding terrible, ocean acidification is detrimental to shell growth, bleaches coral, and is even thought to lead to reproductive disorders in fish. Although it is not proven, this might explain why there have recently been many unexplained cases of two-headed sharks.

Basically, there is no quick solution

The pH (standing for “potential of hydrogen”) scale is a measurement of elements solvent in water from 0-14, with lower numbers as acidic, higher numbers as basic, and 7 being neutral. For eons, the oceans have been slightly basic, with a pH balance of about 8.2 percent. Recently however, the oceans have budged to 8.1 pH. Although that doesn’t seem like a lot, that drop in the scale equals a massive 25% increase in acidification…throughout the entire ocean.

The change itself isn’t what is alarming. Previously, the ocean has seen similar shifts in acidity occurring over thousands of years, giving marine life ample time to adapt. Nonetheless, these recent changes have occurred in less than a century, an impossible timeline to expect plants and animals to adapt.

jellyfish

The winners of an acidic ocean

Although virtually all marine life has been negatively affected by ocean acidification, some (less appealing) creatures actually seem to thrive off of it. For example, have you been swimming lately and noticed that there has been a large amount more jellyfish? Well, these little guys are thriving off the acidity of the oceans. So there you go, at the rate we are headed the oceans will be one big floating jellyfish stand with more carbonic acid than a Coca-Cola in no time. In fact, the rise in acidity of the oceans is such a big issue that in one of his TED talks accomplished professor of Earth Science at Stanford University Robert Dunbar called it the biggest threat facing our oceans today(see below).

Unfortunately, the story doesn’t end there. During the last five decades, apparently the oceans have started losing large amounts of life-giving oxygen. Since the 1970’s, the oceans lost 2% of their oxygen while oceanic temperatures have risen 1 degree Celsius, and the rise in ocean temperatures increases water density. This denser water makes it difficult for oxygen to get to depths where deep sea fish call home. At the rate in which we are headed, scientists believe that the oceans could loose up to 7% of their oxygen, which could have detrimental effects on the already fragile ecosystem and fisheries.

Things appear to be getting worse

In 2017, the Great Barrier Reef hit a major milestone—it experienced significant coral bleaching for the second year in a row. Similar bleaching has happened in 1998, 2002 and 2016, but with the two most recent occurances happening in such rapid succession, things have really escalated. Currently, only the bottom third of the reef is free of bleaching, and athough the coral could return to normal, we would first need to tackle pollution and climate change, which hasn’t proven to be an easy feat.
Coral bleaching in the Great Barrier Reef

Coral bleaching in the Great Barrier Reef 2016 and 2017



Unfortunately, ocean acidification has also taken a turn for the worse. It is determined to have creeped up 300 miles from the northwest tip of Alaska to just south of the north pole. As if that wasn’t bad enough, the depth has also increased. In fact, it has more than doubled, from ~350 to ~800 feet. This, of course means an increased threat to clams, mussels, and oysters, which are integral in cleaning our waters. Bivalves are a sign of and contributor to a clean ecosystem, and can filter up to 50 gallons of water a day.

Oddly enough, fish excrement is basic in it’s pH make up. Presumably, if overfishing was curbed, the oceans could hypothetically change the tides on acidification themselves.