Ocean acidification impacting population demography and hindering adaptation potential

January 29, 2016
Carbon dioxide bubbles at the volcanic vent in the Mediterranean. Credit: Demetris Kletou, Plymouth University

Ocean acidification may be impacting upon the population dynamics of marine species and hindering their ability to genetically adapt to future climate change.

These are the findings of a team of scientists, whose report is published in the journal Scientific Reports, following an investigation into how the gastropod Hexaplex trunculus has responded to over multiple generations.

The project, led by Aberystwyth University, in conjunction with a number of European partners, including the Institute of Marine Research, Bergen, Norway; Plymouth University; and the University of Palermo, found evidence that individuals have to trade-off maintaining their shells in order to compensate for a higher cost of living in acidified conditions.

But going further, they discovered that that these changes to the energy budget may not be the same for males and females, and at a population-level, those individuals contributing to reproduction change year-on-year, resulting in a genetic drift that could hinder the potential for genetic adaptation to ocean acidification.

Ben Harvey, of the Institute of Biological, Environmental, and Rural Sciences, at Aberystwyth, said: "Despite growing evidence for direct impacts on specific species, few studies have simultaneously considered the effects of ocean acidification on individuals and population level demographic processes. By using carbon dioxide vents as natural laboratories, we have found that ocean acidification may hamper normal breeding habits and reduce the potential for species to adapt."

A specimien of Hexaplex trunculus found at one of the research sites. Credit: Demetris Kletou, Plymouth University

H. trunculus, which grows to nearly 10cm, is a commercially valuable species of mollusc, one widely consumed in African countries that border the Mediterranean. In the course of the project, the scientists looked at communities clustered at three sites off the coast of Isola Vulcano in Sicily characterised by different levels of CO2.

Those at the CO2-rich site were found to have a significantly lower mean shell length, and smaller, thinner shells than those at the two neutral sites. They also found significantly fewer females present in the Low pH site (32.26%), while the sex ratio in the control pH sites was around 50%.

As part of the research, the team relocated some specimens from one site to another and after a 14-day period of exposure, extracted them to the laboratory to analyse the physiological response through its metabolic rate. They found notably higher metabolic rates for those that had been exposed to acidic waters, pointing to evidence of acclimatisation.

"Acclimatisation can buffer populations against the immediate impacts of ocean acidification, and even provide time for adaptation," said Samuel Rastrick, of the Institute of Marine Research. "However, it can also result in stress-induced energetic trade-offs, and unless organisms can compensate for the extra costs caused by ocean acidification, then they may suffer negative consequences in the form of reduced growth, development and reproduction."

Pippa Moore, also of Aberystwyth University, added: "Should organisms be unable to maintain their energy budgets, then they may lack the necessary energy to contribute to future generations."

Professor Jason Hall Spencer, of Plymouth University, concludes: "Overall, this study demonstrates that ocean acidification is driving individual and population level changes that will impact eco-evolutionary trajectories, and highlights the need for deeper understanding of the links between individual effects and (often unknown) population demographics in order to predict and manage the consequences of climate change."

Explore further: West Coast study emphasizes challenges faced by marine organisms exposed to global change

More information: Ben P. Harvey et al. Individual and population-level responses to ocean acidification, Scientific Reports (2016). DOI: 10.1038/srep20194

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2 / 5 (4) Jan 29, 2016
Can we sue the Deniers for impeding us from saving the Earth?

Takeaway their "things".
not rated yet Jan 29, 2016
While the need to accomplish ocean acidification studies is certainly real and pressing, we need well designed experiments wherein variables are actually controlled. "Ocean acidification may be impacting upon the population dynamics of marine species and hindering their ability to genetically adapt to future climate change." Understand that when the authors uses the term "may be" in the sentence - it make this a theory, not conclusive data or fact.

Additionally, "By using carbon dioxide vents as natural laboratories..." - there is no control of pH as the animals are exposed to pH being varied by currents. This is why we do dosage and exposure tests in real labs so that we know exactly what the animals are exposed to and can control any potential variations. The lack of scientific experimental design and control of potential variables here is absolutely scary.
not rated yet Jan 30, 2016
lacking any information on the actual PH levels at the sites, the food available at the sites and the temperatures at the sites in relation to other none CO2 sites the piece as written useless in deciding anything about CO2. We do know one thing the ocean is not getting acid, it is simply less basic at the vent sites. If it was actually acid, than the volcano vents are dumping H2S into the water. If you wiki ocean PH levels they vary a lot during the seasons, the source of the ocean waters and where you take your sample. Lacking any PH reading from this article it is basically political trash.
3 / 5 (2) Jan 30, 2016

You obviously didn't follow the link at the bottom of the article otherwise you wouldn't
be asking questions. The paper is open access.

Uncle Ira
3 / 5 (2) Jan 31, 2016
Can we sue the Deniers for impeding us from saving the Earth?

This is not the "Ask-The-Lawyer" place Cher. You might try asking Google-Skippy and see if he knows about that.

Takeaway their "things".

Be careful there Skippy. They might choot you with one of their "things".

What is the difference between their "things" and their things anyway?
1 / 5 (1) Feb 03, 2016
In the chemistry dictionary BUFFER is defined as
A solution that resists changes in pH when acid or alkali is added to it. Buffers typically involve a weak acid or alkali together with one of its salts.
Ocean water is a buffer.
This means there is no way you can change the acidity of this huge water system.
3 / 5 (2) Feb 03, 2016

"Seawater has a pH of 8.2 on average because it contains naturally occurring alkaline ions that come primarily from weathering of continental rocks. When seawater absorbs carbon dioxide from the atmosphere, carbonic acid is produced (see Box 1), reducing the water's pH. Since the dawn of industrialization, average surface ocean pH has decreased to about 8.1."

"Because the pH scale is logarithmic (a change of 1 pH unit represents a tenfold change in acidity), this change represents a 26 percent increase in acidity over roughly 250 years, a rate that is 100 times faster than anything the ocean and its inhabitants have experienced in tens of millions of years."

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