Ocean Acidification: pH and the Ocean's Balance

The Big Question

What happens to ocean animals when the ocean's pH changes?

What's This All About?

When we burn fuels like gas and coal, we make a gas called carbon dioxide. About a quarter of that carbon dioxide goes into the ocean.

Carbon dioxide is an "acid gas." That means it makes the ocean more acidic (less basic). We measure how acidic or basic something is using something called pH.

Even though ocean water isn't very acidic, even a small change in pH can be a big deal for ocean animals — just like small changes can affect our own bodies too!

What You Will Learn

• pH is one way scientists check on ocean acidification (that means the ocean becoming more acidic).
• What the pH scale is, and what acids and bases are.
• A tiny change on the pH scale is actually a much bigger change in the ocean's chemistry than it looks.

Important Ideas to Remember

• The ocean is a huge part of life on Earth. It's home to sea creatures, and it helps keep humans healthy too.
• People are changing the ocean's chemical balance.
• Small pH changes can really affect sea animals. (In people, even a tiny pH drop of 0.05 can make someone sick — this is called "acidosis.")

Why This Matters

• Sea animals and humans both need to keep a careful pH balance to stay healthy.
• A small number change on the pH scale is actually a HUGE change in chemistry.
• Here's how it works, step by step:
• Burning fuel makes carbon dioxide.
• The ocean soaks up the carbon dioxide.
• Carbon dioxide is an acid gas.
• This makes the ocean more acidic.
• Even a tiny pH drop (just 0.1) can tip sea animals from healthy to unhealthy — just like it can in people.

What Can We Do?

The less acid gas (carbon dioxide) we put into the air, the less ends up in the ocean. People, neighborhoods, and whole cities can help by using cleaner energy and transportation.

• Find out what your town is already doing, and get involved!
• Help make a home more energy-efficient with better windows, appliances, or insulation.
• Ride the bus, bike, or walk instead of driving when you can.
• If your town doesn't have good bus service or bike paths, talk to a local leader about starting one.

Activity: Let's Explore pH!

Get Ready: Write the numbers 1 through 14 on separate sheets of paper. Lay them in a line, in order, from left to right. On a small card, write "8.1" and place it near the paper marked "8."

Steps:

1. Ask: "Do you know what an acid is? What about a base? Want to learn?"
2. Show the pH scale, which goes from 0 to 14.
3. Anything above 7 is a base. Anything below 7 is an acid. The number 7 is neutral — not an acid or a base.
4. 0 is the strongest acid. Acids usually taste sour, can sting your skin, and can wear away metal.
5. 14 is the strongest base. Bases taste bitter, feel slippery, and can dissolve fat and oil.

1. Ask: "Did you know we eat acidic and basic things every day?"
2. Pick a household item. Guess where it goes on the pH scale, then place it there.
3. Hints can help: "Is it sour?" or "You're getting warmer!"
4. Try as many items as you like. Save the "ocean" for last!

1. When it's the ocean's turn:
2. Talk about how special the ocean is.
3. A hundred years ago, the ocean's pH was 8.1. Today it's 8.0. That may seem like a tiny change, but it's not!
4. In our blood, even a change of just 0.05 (half of that ocean change) can cause headaches, tiredness, confusion, shaking, and trouble thinking. Healthy blood pH is 7.45. When it drops to 7.4, it's called "acidosis," and it can make people sick.
5. Scientists have seen ocean animals — like clownfish (think Nemo!) — get confused too. In more acidic water, they may even swim toward a predator instead of away from it!

1. Ask: "Do you know what's causing this change in the ocean?"
2. Carbon dioxide is an acid gas. It makes the ocean's pH go down (more acidic).
3. We make carbon dioxide when we:
4. Drive cars, boats, planes, and trains.
5. Use electricity at home.
6. Cut down trees (trees store carbon dioxide in their leaves, keeping it out of the ocean).

Let's Talk About It

• What can you do to help lower carbon dioxide in the air?
• For younger kids, small actions matter, like:
• Turning off lights when you leave a room.
• Unplugging things you're not using, like chargers and computers.

pH of Everyday Things

• Big battery = 2.2
• Vinegar = 2.8
• Cola = 2.5 (can be up to 4.2 for other brands)
• Lemon = 2.3
• Grapefruit = 3.0–3.3
• Orange = 3.0–4.0
• Apple = 3.5
• Banana = 5.0
• Milk = 6.5
• Bottled water = about 7 (6.5–8, depending on brand)
• Human blood = 7.4
• Ocean = 8.1 in the past, now 8.0
• Baking soda = 8.4
• Tums (stomach medicine) = 10.5
• Bleach = 12.6
• Drain cleaner = 14