A Changing Ocean

How climate change is altering the world’s largest ecosystem

Climate change has had many names and connotations since I first learned about it. Originally, it was taught as “global warming” and the not-so-well understood implications of it seemed too far in the future to be concerned with in the present. In fact, I had many peers who welcomed the idea of a climate a few degrees warmer in a part of the United States that could experience some brutal fall and winter conditions. Thankfully, the science surrounding what is happening to our climate is much more robust than it used to be and it is well understood that the time frame climate change is acting on is no longer a future phenomenon for our great-great-grandchildren to deal with, it is for us to manage.

Climate change is believed to be caused by excess anthropogenic carbon dioxide (CO2) and steps need to be taken to mitigate the effects on natural systems because the science is clear- we as a collective planet, will not easily adapt if things stay on course. The ocean in particular, in all of its vastness, is especially struggling to keep up with a changing climate. You may be surprised how much even the most land-locked person relies on a well-functioning ocean. Below, I look at some of the big ways oceans are changing in response to increased atmospheric CO2.

Ocean Acidification

Image via Climate Commission, Image Source on Flickr
Image via Climate Commission, Image Source on Flickr

Ocean acidification (decreasing pH) occurs when an excess of carbon dioxide in the atmosphere is exchanged with the top layer of the ocean (oceans are our largest natural carbon ‘sink’). When this happens, the water becomes more acidic and corrodes the shells of ocean animals like mollusks, such as oysters and clams, and ties up carbonate so the same shell in-habiting animals can’t use it to repair or build their homes. The result is ocean animals that are more vulnerable to predation and less apt to survive, reproduce and adapt to a changing environment.

Ocean acidification is also associated with coral erosion, slowing of growth and activity in some animals such as seahorses and alterations in the ocean food web due to deleterious effects on carbonate-reliant plankton.

An unexpected consequence of excess carbon dioxide in the environment is actually localized basification (increasing pH) of ocean waters. Basification is the opposite of ocean acidification and occurs in areas more near to shore that are prone to pollution from runoff. Nutrients from urban runoff combined with excess atmospheric carbon dioxide lead to perfect conditions for phytoplankton blooms that consume excess carbon dioxide and can lead to basic ocean waters. In a study conducted earlier this year, it was found that localized basic and global acidic conditions cause stress for some ocean animals that will need to adapt to a wide range of pH values throughout the ocean and potentially alter the dynamics of regional tropic levels by adversely affecting the growth of plankton.

Ocean Warming

Image courtesy GLORES partner photographer Cristian Dimitrius

The warming of ocean water is a response to a warming atmosphere caused by excess atmospheric greenhouses gases. While the ocean’s temperature may have only risen an average of 0.1 degree centigrade, it is important to emphasize the magnitude of energy it takes to raise the temperature of something as massive as the ocean; a small incremental increase in temperature has a large impact on marine life.

Due to current warming trends, researchers have noticed quite a few marine species migrating towards the poles to escape the heat. Once an animal is outside its range, the effect it has on the ecosystem can resemble that of an invasive species. Other marine animals are very specialized to their habitat (reef fish) or lack the anatomy to swim long distances (seahorses) so they can’t escape the heat and have no choice but to try and adapt, which means dealing with an increased metabolism driven by warming waters.

Researchers believe this could have big implications for the dynamics of the food web, as rising temperatures cause the metabolism of some fish to increase. A heightened metabolism drives marine animals to seek out and compete for more food, resulting in decreased prey populations. It is considered unlikely that all ocean species will be able to increase predation and reproduction to meet the increased metabolic demand a warming ocean will have, leading to severely altered ocean food webs.

Sea Level Rise

Image courtesy GLORES partner photographer David Doubilet

Resulting from a warming ocean, rise in sea level is the most visible consequence of climate change on the ocean. Sea level rise happens in three ways: expansion of the ocean by warming waters, melting polar ice and mountain glaciers, and sea ice loss form Greenland and Antarctica. The result of these mechanisms are the same: flooding and inundation of low-lying land, erosion, drowning of coastal plants, increased vulnerability to storms and, for some unfortunate areas, permanent loss of land. The degradation and loss of ice in the poles will make it difficult for species such as polar bears and penguins to reproduce, find food and safety. Ultimately, sea level rise will result in a loss of habitat for humans and animals alike.

Climate change is affecting the entire planet, but for life in the ocean, the effects are largely invisible to us. But just because we can’t see it, doesn’t mean it isn’t there. It is projected that some animals will adapt to the changes happening to the ocean, but many will not. For even those animals considered robust enough to survive most anything (like jellyfish), they may struggle because their habitat or prey are affected greatly by a changing ocean, or their proliferation in an ocean without predators may be detrimental to the other animals trying desperately to survive.

We depend on the ocean for food, oxygen, and a livable climate. It is time we strongly protect the ocean, for us and for marine life.

Image courtesy GLORES partner photographer Paul Nicklen 

The best way to maintain our oceans’ biological diversity, abundance and resilience is by protecting marine life and their ecosystems in marine reserves – areas that have the strictest and strongest level of protection. Marine scientists recommend that 20-30% of the oceans need to be strongly protected to alleviate stress where possible. Currently, only 1% of the ocean is safeguarded in this manner. Many of the most important and vulnerable marine ecosystems are not yet protected, and others are vastly under protected and underrepresented.

The Global Ocean Refuge System (GLORES) is a Marine Conservation Institute initiative designed to catalyze protection for at least 20% of the ocean by 2030. These types of protections act as safe havens for marine life, even in the face of climate change. Read more about our GLORES initiative here.


Cover photo via GLORES partner photographer Joe Platko


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