Thursday, October 14, 2010

How Ocean Acidification is Harming Marine Life

Breanna Linn
ENVS 1020

While being too caught up about the effects that our emissions will have on us as humans, we have become oblivious to the fact that what we are producing is also affecting other species around us.

Due to the increasing levels of carbon dioxide in our atmosphere, there has been a growing concern on how this will alter marine ecosystems. Ocean acidification, a harmful process, occurs when carbon dioxide dissolves into shallow waters, causing the pH to decline and makes the water more acidic.

A recent study released by PNAS (Proceedings of the National Academy of Sciences) states that if we continue to produce high amounts of harmful emissions of carbon dioxide, atmospheric levels will greatly increase by mid-century. As a result, this will be absorbed into ocean waters and the pH will become effectively lower.

If acidity in marine ecosystems increases, this could have detrimental effects on ocean species. For calcifying organisms this may disrupt the formation of shells and skeletons. In contrast, for non¬-calcifying species, it was shown through laboratory work that increased carbon dioxide concentrations can affect key life processes.

The study showed how chemical cues for larval fish, which are essential for avoiding predators and locating suitable habitats, are harder for these organisms to perceive when confronted with high carbon dioxide levels.

In order to determine the outcomes of increased carbon dioxide in oceanic habitats, scientists’ nurtured larval clownfish in various carbon dioxide concentrated environments to see the effects that would result on their responses to sensory cues. They tested the same experiments on another species of larval fish, damselfish, to compare the results. Finally they tested the outcome of how carbon dioxide levels altered behaviour and if this would increase mortality rates when the damselfish were placed back into their natural environments.

When put in water containing 500 ppm (parts per million) of carbon dioxide, there was no effect shown on the clownfish. However, as the carbon dioxide concentrations increased to around 700 ppm and higher and for longer durations, the fish no longer avoided the predator order that they could once detect. Thus, the study showed that increased carbon dioxide levels and duration of exposure do affect behavioural responses. The same results held true for the damselfish.

Conversely, they tested the effects that exposure to increased carbon dioxide had on damselfish larvae prepared for settlement in their environments. They discovered that the fish treated with higher concentrations showed more risky behaviour when placed in natural reefs. This resulted in higher mortality rates due to predation for the fish exposed to high carbon dioxide levels when compared to the control fish that were not exposed.

Founded from these experiments were the results of what will occur to ocean species if increased amounts of carbon dioxide dissolve into marine waters. The effects are very harmful and could result in the decrease of many fish species, which in turn could have an even greater effect on the sustainability of fish, as their populations would decrease.

Ocean acidification is a major concern in our world today. The study discusses how carbon dioxide levels could dramatically increase to around 850 ppm by the end of this century, resulting in higher mortality rates of fish due to their lack of ability to sense and avoid predators.

What we tend to forget is that other species and ecosystems are effected on different levels than us. As a result, we must consider the biological capacity that oceanic organisms can withstand. From studying these trends not only do we see the harm we are creating, but it also allows us to gain a better insight on how rapid climate changes due to gas emissions are affecting different environments around us and ultimately how this could impact us.

Although the fish species didn’t seem to be too affected by the carbon dioxide in lower concentrations, due to hazardous emissions that are being created, ocean acidification will increase and eventually surpass the threshold level that aquatic organisms can withstand. Once this is reached, the biodiversity of ocean life will be threatened as fish populations will become less able to sustain their populations. Thus, something must be done to prevent the escalation of ocean acidification, as it will not only affect marine ecosystems, but will harm the coherence of the world as a whole.


Munday, P. Dixson, D. Meekan, M. Ferrari, M. and Chivers, P. 2010. Replenishment of fish populations is threatened by ocean acidification. Proceedings of the National Academy of Sciences.

No comments:

Post a Comment