Anne Kuckertz
Ocean Warming: it’s killing our coral, coastlines, and fishing industries.
By Anne Kuckertz
Katrin Gray goes by “Mermaid Kat” and makes her living as a professional mermaid. She swims in oceans around the word wearing a custom silicone tail as she advocates for marine awareness and protections. Since she started scuba diving in 2007, she witnessed the ocean change in some disheartening ways. “The damage was just crazy” she says, “all the coral reefs are pretty much gone from coral bleaching and were pretty much dead. I mean, you kind of had a few little fish that were left around, but none of these beautiful colorful reefs, that you would see in documentaries and movies.”
The coral bleaching that Mermaid Kat describes is causing coral to lose their vibrant pinks, reds, and oranges and leave behind white ghostly skeletons in their place. Believe it or not, coral is not inherently brightly colored. Coral’s striking appearance is thanks to the many tiny marine algae it hosts called zooxanthellae.
Zooxanthellae are like the tenants of an apartment complex. They pay the coral for a home with the sugars, fats, and oxygen they release as a byproduct of photosynthesis. The coral then uses the fatty sugary treats in order to grow, thrive, and reproduce. It is a mutually beneficial relationship. That is, until excess carbon dioxide and increased ocean temperatures put stress on the coral’s system. When coral becomes overly stressed, they can no longer support the algae, forcing the coral to kick the zooxanthellae out of its dwelling. Without its algae inhabitants, all that is left of the coral is a white shell, barely holding on to life, devoid of the necessary fats and sugars. If the zooxanthellae are not able to move back in quickly enough, the coral dies, destroying the habitat of not only the zooxanthellae but also of the many marine species that depend on reefs for food and shelter.
While a bleaching event does not necessarily mean death for coral, it does mean susceptibility to disease and an unsure recovery timeline. When all stressors are removed, some corals can fully recover within a year. But for some it can take decades, and others just do not survive at all. For example, in 2016, 90% of The Great Barrier Reef’s coral experienced a bleaching event and 20% of the population died within the year. Sometimes a reef is lucky, and a bleaching event occurs just in one spot on a reef, surrounded by healthy coral. The coral that is still thriving can help its bleached neighbors recover and restore the reef’s overall health, but this is not always the norm. Considering that coral bleaching not only affects the coral as a species itself, but the many types of aquatic animals that need the reef habitat in order to thrive, this is major cause for concern.
In fact, the ocean is home to many diverse species and covers seventy percent of the Earth’s surface and is the biggest absorber of energy. This energy is usually mostly solar, but it also comes from clouds, water vapor and greenhouse gases, including carbon dioxide. Under normal conditions, the earth’s oceans have the ability to take in a large amount of thermal energy without experiencing a noticeable change in its own temperature. Because the ocean is so deep there are a lot of places for heat to go and waves and ocean currents help mix up the warm water with the cooler deeper water, letting the heat spread out. Because of its super mixing abilities, the ocean plays a large role in keeping climate conditions stable for the whole earth. However, this heat does not stay in the ocean forever, it usually takes decades, but eventually this energy is released back into the atmosphere.
Steven Goodbred Jr., an oceanographer at Vanderbilt University describes this process of CO2 turnover in Antarctica and the Greenland seas saying that, due to the CO2 they absorb, “surface waters get dense enough to sink down into the deep ocean.” He continues saying, “there's a significant fraction of the carbon dioxide that humans have been putting in the atmosphere that's been getting drawn down into the deep ocean. And that circulation time down there is on the order of hundreds of years.” He asserts that eventually all that CO2 will start releasing back into the atmosphere and the ocean will stop absorbing a lot of the new CO2 we produce.
Unfortunately, the amount of energy on the earth increased drastically over the past century. Since 1972 carbon emissions increased by 90%. Increased CO2 emissions driven by human activity is causing the ocean to absorb heat quicker than it can release it, leading to an increase in temperature overall.
Now, ocean warming is not just causing a decrease in coral but in livable coastal land as well. As the ocean heats up, it expands, leading to rising sea levels. Mean global sea levels rose 8-9 inches since 1880, damaging coastal infrastructure such as power plants, landfills, and modes of transportation (roads, subways, etc.). According to the US National Ocean Service, around 40% of the US population lives in an area that is vulnerable to negative effects of rising sea levels. For example, without human intervention, Miami beach is projected to see 94.1% of its habitable land go underwater by 2100. That represents more than 19.6 billion dollars’ worth of property. That is almost a whole city. Gone.
Loss of coastal land is not the only drain that ocean warming is taking on our economy. The commercial fishing industry is taking a big hit as well. William Cheng, a marine scientist, and director of the Changing Ocean Research Unit at The University of British Columbia in Canada recalls growing up in Hong Kong and watching fish populations decline in his own community. He explains, “when I was young, and I visited the local fish market in Hong Kong there was an abundance of fish. All the fish were fairly big in size. And the price of it was really reasonable.” He continues, “but now, when I visit the market, there's a really big change in the kinds of fish that are available there, the size of fish, as well as the price.” As the ocean got warmer the fish got smaller and pricier.
In fact, one study published in the peer reviewed journal Plos One in 2020 predicts that, with continued ocean warming and acidification, the Artic Cod fishing industry will collapse. Another study published in Science Magazine in 2019 found that in the past 80 years, the total amount of fish that could be caught without damaging the local ecosystem decreased by 4%. That is equivalent to 1.4 million metric tons of fish product.
Ocean warming is a major contributor to the drastic decrease in fish population we are seeing. This is because different species of fish like to live at certain temperatures (much like how coral does not thrive when it is too warm) and will therefore stay in regions of the ocean that are their preferred temperature. This means that, for some species of fish, global warming actually made previously uninhabitable waters viable food sources. Black sea bass, for example, a species that hangs out on the US East Coast, could expand its home farther North as the previously too cold water warmed up. This is great for Black sea Bass (juvenile herring and sprat in the Baltic sea are experiencing similar habitat expansion), not so great for the rest of the fish who are adapted to cool water and whose livable ocean space is getting smaller and smaller. This means an increase in competition for food sources and, therefore, a decrease in population. Ocean warming provides an explanation for the many changes Cheng saw in his local fish market growing up in Hong Kong. It accounts for the skeletal coral Mermaid Kat witnesses all the time as she swims throughout the world’s oceans. It accounts for decreased marine habitats, coastal land, and increased fish prices.
If these changes are not enough to give a human pause, then it is important to remember that the ocean is currently acting as a carbon sponge, soaking up the CO2 we emit from our agricultural industry, our coal burning, our factory production, and our modes of transportation. Without the ocean taking away all the CO2, our planet would be unlivable. We would not have enough oxygen to breathe. Something that some marine life is already experiencing.
Seasonally, between late May and early September places called “dead zones” appear in the ocean. In these marine regions, the oxygen is overpowered by other things such as nitrogen and methane. Any fish still around when these dead zones pop up suffocate from the lack of oxygen. This is especially prevalent in the Gulf of Mexico where many major US rivers end up. These rivers carry with them fertilizer runoff from farms throughout the country, mixing in with the ocean water and making it impossible for fish to breathe.
So, what’s a human to do? Well, those working in the agricultural industry can decrease their use of fertilizer, plant more biodiverse crops, and use a ring of trees as a buffer zone to catch fertilizer runoff. As for the rest of us, Mermaid Kat has some advice. She urges people to reduce their consumption of animal products as much as they can. Which is sound advice because the agricultural industry is a big producer of greenhouse gases. Just cows’ burps on their own contribute a significant amount of methane that could eventually wind up in the ocean.
Goodbred argues, that while lifestyle changes on an individual level can add up in meaningful ways, what we really need are systemic government policy changes. An example GoodBred gives is increasing the amount of renewable energy sources our power grids draw from. That way, every house that takes in power will be using cleaner energy without even thinking about it.
Cheng agrees that policy change should be a priority and has published many papers on the topic. A possible policy change he suggests is setting up protected marine environments. Currently, a method of fishing called “bottom churning” is causing a lot of harm. Bottom churning involves dredging up the settled sediment at the bottom of a body of water to attract fish that like to feed on things left behind in the sediment. The dangerous part of this is that this sediment contains CO2 that the ocean absorbed previously and by disturbing it, humans are causing the CO2 to circulate faster than it is meant to. This can often take the CO2 on an early journey back to the atmosphere. Cheng urges governments to set protected areas where bottom churning will not be allowed in order to mitigate this effect.
Even Mermaid Kat has seen differences between the health of protected marine areas vs nonprotected ones. In French Polynesia for example, where there are more marine protections, she says that the coral reefs there are “really nice and much more colorful.”
This gives us some hope that we can repair some of the damage we have done to the oceans. However, Goodbred urges us to keep in mind that climate change is a long game. He says that the damage we are doing now has “lag effects.” And that “the impacts are going to be playing out in the next decade or century, and our actions now are setting that in motion.” Meaning that we cannot get frustrated if we do not see immediate effects, but we still need to make the changes where we have the ability. Goodbred suggests we focus on “things like environmental degradation, our policies at the coast and how we use fertilizers, on landscapes on our lawns, things like that. These are in our direct control.”
We can not expect climate change to unfold at a fast pace. The earth is ancient and slow moving. We must be patient, make changes now, and know that it will take some time for the ocean to recover from all the damage we caused.