SW1 – The Effects of Ocean Acidification on Pteropods

Filed Under (SW1) by David Rosenberg on 03-09-2011 and tagged , ,

The Effects of Ocean Acidification on Pteropods

While there is a wide range of negative effects expected in the future due to ocean acidification, there are some cases that have much more potential fallout than others. One of these cases is plankton. Plankton plays a crucial role in food webs, and therefore any damage done to plankton species will have a ripple effect that spreads throughout the ecosystem. A prime example of plankton that is at risk due to ocean acidification is the pteropod. While much uncertainty remains regarding the severity of future damage to pteropods, the prospect of a losing a key part of the food web is frightening. The ocean’s changing chemistry will inhibit pteropods’ ability to grow and survive, subsequently creating imbalance (decreasing biodiversity) among the various plankton species and creating problems further up the food chain.

Pteropods are snail-like plankton that float through ocean waters consuming smaller plankton. They, like many other marine organisms, rely on the process of calcification to grow their shells (which consist of aragonite and calcium carbonate). Thus, the saturation of carbonate ions in the water is vital to their survival. The increased amount of carbon dioxide in ocean water has shifted the chemical equilibrium such that there is a decreasing concentration of carbonate ions. Studies have shown that pteropods tend to have a slower rate of calcification when placed in water with a high concentration of carbon dioxide. To make matters worse, the decrease in carbonate ions also pushes the saturation horizon closer to the surface of the ocean, reducing the amount of water that pteropods are able to inhabit (calcium carbonite and aragonite will dissolve if placed below the saturation horizon). In addition to problems with building shells, pteropods face a few other potential roadblocks due to ocean acidification. First, they might have to adjust to a new diet; phytoplankton, pteropods’ main food source, will also be negatively affected by ocean acidification, and therefore pteropods could potentially have to deal with either a lack of phytoplankton or a change in what types of phytoplankton they are limited to consuming. Second, they, like many other marine organisms, will have to work harder to regulate bodily processes. The changes in pH of ocean water make it more difficult for pteropods to maintain the proper internal pH; acclimating to the new environment requires energy (which could be put towards other important processes). The combination of all of these roadblocks puts pteropods at risk.

Unfortunately, the risk extends beyond just pteropods. Ocean acidification ultimately threatens the balance of existing plankton species. Studies have shown that some species of plankton are less susceptible to changing ocean chemistry than others; this means that there will be winners and losers amongst plankton species over the next series of decades, resulting in a decrease in biodiversity. This, in turn, will send waves up the food chain. For example, pteropods make up a major part of the diets of certain types of salmon in the arctic (over 60% in some cases), so a decrease in the pteropod population could potentially do serious damage those salmon populations. Possibilities such as this are frightening, especially when considering that it is just one example of what ocean acidification is capable of changing; the situation that pteropods face is a mere microcosm of what could happen to the ocean’s ecosystem as a whole.




National Research Council. Ocean acidification: a national strategy to meet the challenges of a changing ocean. Washington, D.C: National Academies Press, 2010. Print.

3 Comments Already, Leave Yours Too

Barbara Blachut on 3 September, 2011 at 12:00 pm #

It is honestly really alarming to see how a disastrous effect on even a non-producer organism can go on and affect the whole marine food chain. I thought your explanation was very well written, especially when you extended the effects beyond pteropods.

Sandra on 4 September, 2011 at 2:26 pm #

I agree with the Barbara that your post was well-written for a non-specialist readership. Using the word “frightening” twice might jump out at some readers, but you also mention the uncertainty involved in predicting future effects.

Monica Turewicz on 4 September, 2011 at 3:26 pm #

I also agree that your post is well written. Its ridiculous how when acidification effects one tiny organism, it ultimately effects everything else associated with it and shows major shifts in the species survival and food chains.