Bryozoans and ocean acidification
Oceans are becoming more acidic due to increased levels of carbon dioxide (CO2) in the atmosphere. Tiny marine animals called bryozoans may help monitor the impact of ocean acidification on the marine ecosystem.
Preserved colony of bryozoans
Biogeochemist Abby Smith needs to carefully prepare bryozoans for her research. This small colony has been preserved and bleached and is now ready for a number experiments.
Ocean acidification has the potential to affect many marine organisms that make shells and skeletons out of calcium carbonate. Associate Professor Abby Smith and the Carbonate Geochemistry and Sedimentology research group at the University of Otago are investigating bryozoans as a way to monitor the impacts of ocean acidification. Bryozoans may be the ‘canary in the coalmine’ for our oceans.
Understanding ocean acidification
The world’s oceans currently absorb as much as one-third of all CO2 emissions in our atmosphere. This causes the pH to decrease, resulting in the ocean becoming more acidic. Scientists have long understood that an increase in carbon dioxide in the atmosphere will result in higher levels of dissolved CO2 in seawater. However, a relatively recent discovery is that even small changes in water pH can have big impacts on marine biology. Ocean acidification is a worldwide issue. However, as CO2 is more soluble in colder water, it is of particular concern in New Zealand’s temperate oceans.
Ocean acidification
Our oceans are absorbing about one-third of the carbon dioxide in the atmosphere. As a result, they are becoming more acidic. Associate Professor Abby Smith, from the University of Otago, is researching the role that bryozoans can play in monitoring these changes in pH.
Point of interest
Discuss what is meant by the term ‘canary in the coal mine’.
The effect of ocean acidification on marine ecosystems
Many marine species rely on calcium carbonate to build a shell or skeleton. One of the effects of ocean acidification is a reduction in the availability of carbonate. This means that any animal that produces a calcium carbonate skeleton will find it much more difficult to do so as CO2 levels in the atmosphere rise and oceans become more acidic. Organisms could grow more slowly, their shells could become thinner or they might dispense with shells altogether.
Many of these organisms, such as bryozoans, may no longer be able to form thickets that currently provide an important shelter and nursery area for other marine animals such as sea stars and many fish species. It is difficult to predict the overall impact on the marine ecosystem, but many scientists fear that ocean acidification has the potential to decrease marine biodiversity on a very large scale. Climate change, overfishing and pollution also threaten the health of our marine ecosystems, and ocean acidification is likely to increase vulnerability to these pressures.
Nature of science
Scientists can play an important role in informing policy decisions. Abby’s role has been working with other scientists to better understand the potential impacts of ocean acidification. This research will help policy-makers make decisions about the issue.
Bryozoans can help monitor ocean acidification
Abby Smith is a biogeochemist who leads the Carbonate Geochemistry and Sedimentology group at the University of Otago. Abby and her students investigate carbonate sediments in temperate waters and geochemical signals in shells and skeletons. A major focus of their work is New Zealand’s bryozoans – their identification, classification, growth and production, ecology and geochemistry. With growing concern over ocean acidification, the work with bryozoans is becoming more important. This is because bryozoans have the potential to act as environmental indicators and provide information about the effects of ocean acidification.
Bryozoan experiment
This experiment is comparing how bryozoan skeletons respond to solutions with different pH levels. This research is important to better understand the potential impacts of ocean acidification.
Part of Abby’s research involves working on different bryozoan species and investigating how they respond when they are placed in solutions with different pH levels. The results have shown that a decrease in pH affects the skeletons of bryozoan species differently, depending on what they are made of and the shapes formed by their colonies. These results mean that some species of bryozoans have the potential to act as ‘a canary in the coal mine’ and provide early warning signs for areas that are at greatest risk from ocean acidification.
Ocean acidification has caused Abby to change some of her views and approaches to scientific research. Over the past couple of years, she has started to collaborate more with researchers in other fields and work harder on the practical applications of her science research, rather than just focusing on the intellectual challenge. As part of her role as a scientist, Abby is now becoming involved in things like policy, government response and advocacy.
Our role in ocean acidification
In this video, Associate Professor Abby Smith, from the University of Otago, talks about what we can do to help reduce ocean acidification.
Point of interest
Make links to other initiatives to reduce carbon emissions that students may have heard of.
Activity idea
In this activity, students observe how chicken eggs can be used to simulate the potential effects of increasing ocean acidity on marine animals with calcium carbonate shells or skeletons, for example, bryozoans and cockles.
Useful links
Read this New Zealand Geographic article by Veronica Meduna to learn more about research into the effects of ocean chemistry change on marine organisms, particularly those that use calcium carbonate as a building block – Acid Seas.
The New Zealand Ocean Acidification Observing Network (NZOA-ON) is a nationwide network of stations to monitor coastal pH.
Find out more about NIWA's work investigating ocean acidification.
See the StatsNZ website for information, resources and data on ocean acidification.
