Many organisms that form the basis for the marine food chain are going to be affected by ocean acidification. It turns out that changing the pH of the ocean is not the only impact from this phenomenon. There is another, equally impactful side effect. When carbon dioxide (CO2) mixes with water molecule (H2O) it forms carbonic acid (H2CO3) that then breaks down easily into hydrogen ions (H+) and bicarbonate (HCO3-), those available hydrogen ions bond with other carbonate ions to form more bicarbonate. The problem here is that marine organisms possessing shells (many mollusks, crustaceans, corals, coralline algae, foramaniferans) need available carbonate ions to form the calcium carbonate (CaCO3) that comprises their shells. In essence, ocean acidification is robbing these organisms of their necessary building blocks.
There have been scientific experiments focusing on how the projected acidity of the oceans will affect different organisms. Marine pteropods already have thin shells, and these shells literally dissolve over 30 days in seawater with a 7.8 pH. Studies on sea urchins and mollusks show similar results.
There are many resources included in this lesson, and many of them are going to say the same things, but each resource does a good job of explaining a certain part of the ocean acidification story.
- Start with the pdf slideshow called Ocean Acidification: effects on marine organisms. It is the best overview and it has informative slides which can be presented or printed. It covers the whole topic and even has some great solution pages.
- Ocean Acidification is a short 2-minute video from North Carolina Aquarium that explains how marine organisms build shells from calcium carbonate, and how ocean acidification impedes that process.
- NOAA's Ocean Acidification: The Other CO2 Problem video is 4 minutes long and shows the results of acidifying water on marine pteropods, one of the delicate creatures at the bottom of the food chain.
- NOAA Ocean Acidification Intro and Classroom Demonstrations is a 15-minute video that has some really great hands-on and visual representations of calcium carbonate dissolving in acid, and of CO2 turning water more acidic.
- For a more hands-on approach, or if you're interpreting for the classroom or in a lab-like setting, download the Lab Activities pdf. The third experiment "Group Demonstration: I'm Melting! Seashells in Acid" is focysed on the effects of increased acidity on seashells.
- Watch the 6-minute Acid Oceans video to get a good feel for how Ocean Acidification will affect sea urchins. There are scientists doing research on the effects of acidity on urchin larval development.
- Climate Training Activities shows some actual interpretation from Aquarium staff, using props and visuals to show visitors about the impacts of ocean acidification to shellfish and corals.
In addition to decreasing ocean pH, ocean acidification also causes a reduction in available carbonate ions which are essential to shell-building across many different groups of marine organisms. Many of these organisms form the very basis of the marine food chain, and their disappearance could potentially lead to a domino-like effect that will impact everyone.
This is a slideshow in pdf format provided by National Marine Sanctuaries and NOAA. It does an excellent job of summarizing ocean acidification, posing questions, clarifying rumors and illustrating the effects on different types of marine organisms. It also demosntrates the effects on the marine food chain, as well as socio-economic impacts. There are some solutions mentioned here too, so people can learn some things they can do to help slow the rate of ocean acidification.
This short animation from North Carolina Aquarium at Fort Fisher is one of the best visual representations of what exactly is involved in the ecological interactions impacted by increased carbon dioxide in the atmosphere.
Fundamental changes in seawater chemistry are occurring throughout the world's oceans. Since the beginning of the industrial revolution, the release of carbon dioxide (CO2) from humankind's industrial and agricultural activities has increased the amount of CO2 in the atmosphere. The ocean absorbs almost a third of the CO2 we release into the atmosphere every year, so as atmospheric CO2 levels increase, so do the levels in the ocean. Initially, many scientists focused on the benefits of the ocean removing this greenhouse gas from the atmosphere. However, decades of ocean observations now show that there is also a downside — the CO2 absorbed by the ocean is changing the chemistry of the seawater, a process called ocean acidification. This change in the ocean's chemistry will have profound effects on life in the ocean, and those who depend on it.
NOAA Administrator Dr. Lubchenco presents a 15-minute video about ocean acidification. She specifically references the effects of ocean acidification on pteropods and corals. There are two demonstrations featured in this video which would work well in the classroom or with visitors at an aquarium. One shows the rapid acidification of water when carbon dioxide is introduced. The other shows how calcium carbonate (in the form of chalk) dissolves in acidic conditions. This is a good analogy for how ocean acidification will affect animals with calcium carbonate shells.
This pdf resource contains three fantastic classroom lab activities provided by the Ocean Acidification Subcommittee of the Ocean Carbon & Biogeochemistry Program. The first activity is about the pH scale, and how to test solutions to determine whether they are acids or bases. The second activity simulates the chemical process of ocean acidification in a cup using human-generated carbon dioxide! The third activity goes a step further and demonstrates the effects of ocean acidification on seashells using vinegar as the acid.
This is a six-minute video presentation by the American Museum of Natural History. It focuses on the effects of ocean acidification on sea urchins and other marine life forms. There are interviews with scientists who are studying larval urchin development in different simulated ocean acidities.
As we add more carbon dioxide (CO2) to the atmosphere, the ocean absorbs about a quarter of it. This changes the basic chemistry of the ocean, shifting it towards the more acidic end of the pH spectrum. Ocean acidification makes it more difficult for shelled organisms to make their shells. This activity takes the complex chemistry of ocean acidification and makes it physical. It is designed for any age, with pictures and graphs to make the science deeper, richer, and easier to grasp.
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