Earth's oceans are a carbon sink, which is a place where carbon is stored long term. Oceans absorb carbon dioxide from the atmosphere. It reacts with seawater, creating carbonic acid, which in turn lowers the pH of the ocean. This phenomena is known as ocean acidification. It will only get worse as we release more carbon dioxide into the atmosphere. Oceans currently have a pH of around 8.1, but it is projected to lower to 7.7 by the year 2100.

What is the impact of ocean acidification on marine life?
Research is still being conducted on this, but there are a few things we know for sure. First, organisms that rely on carbonate to build their shells and exoskeletons will have less available. These organisms include coral, mollusks, sea urchins, starfish, and zooplankton to name a few. If they struggle to build shells, they are more likely to be eaten by predators and it can create a trophic cascade up the food chain. Other impacts could include lowering the blood pH of fish, changes in reproductive ability of marine life, and impeding with organisms ability to send chemical signals.

Ocean Acidification Lab
An easy way to show students the impact of ocean acidification on marine life is by soaking seashells in ocean water with various pH levels.
For this lab you will need (per group): 3 cups or beakers, 3 seashells, water, salt, vinegar, an electronic scale, and pH paper. Seashells can be purchased at craft stores, and I've even found them at the dollar store in the craft aisle.

Start by mixing up simulated ocean water (3.5% saltwater solution). Students will put ocean water in the first beaker, 75mL of ocean water and 25mL of vinegar in the second beaker, and 50mL ocean water and 50mL of vinegar in the third beaker. Next, have students take the mass of the seashells over the course of 3 days and calculate the percent change in mass. They will see the vinegar eat away at the seashell and a large reduction in mass. You can also have them measure the pH of the liquids over 3 days and see how it changes as carbonate is released (enter discussion on buffers!)

Following the activity you can discuss ways students can lower their carbon footprint so we can slow the rate of acidification in the future. If you are interested in a powerpoint lesson on ocean acidification and a lab write up for this activity, you can find it HERE.

Students often struggle to understand what aquifers are and how they work. Since they are located underground we can't see them, so it can be hard to visualize in our minds what they look like.

In this quick video you can see how I built a model of an aquifer. So many light bulbs went off after this activity! Check it out:

Interested in some lesson ideas to teach the water cycle? Check out this blog post!

The water cycle is taught starting in elementary school. It seems like in high school biology when I get to the biogeochemical cycles (water, carbon, nitrogen, and phosphorus) the water cycle gets glossed over because we assume the students know it and it's too basic. But water is vital to life! It's important to take some time to dig a little deeper with the water cycle and there are ways to ramp up the rigor. Check out a few activities you can use to take a deep dive into the water cycle:

TAKE A RIDE THROUGH THE WATER CYCLE
Even though this activity is good for younger grades, older kids still enjoy it. In this activity, students roll cubes that tell them how to move through the water cycle. It allows students to review the steps of the process but also realize where more water is stored within the biosphere. You can download the game cubes here.

WATER FOOTPRINT
How much water do students use each day? At watercalculator.org, they can calculate their water footprint.

EVAPOTRANSPIRATION AND URBAN HEAT ISLANDS
In this free lab from ASU, students see first hand how evapotranspiration from trees can cool down an area and have an impact on the urban heat island effect. You will need clay terra-cotta pots and thermometers. You can download the lab for free HERE. If you would like to see more resources dealing with urban heat islands, check out this blog post.

WHERE DID EARTH'S WATER COME FROM?
Water has been around on our planet for a very long time. But where did it come from in the first place? You can students this Ted YouTube video:

SCALED MODEL OF EARTH'S WATER
We tell students that the amount of fresh water we have available is very small compared to the total amount of water on earth, but does it really sink in? In this lab, students create a scaled model of where the water on Earth is located. There are 4 different versions of this lab so you can differentiate based on the amount of inquiry and math you would like your students to do. By the end of the lab, students will see that our freshwater supply is very small and hopefully realize how important water conservation is.

VIRTUAL WATER
What is virtual water? It is the amount of water used to produce a product. In this activity from California Academy of Science, students learn about the hidden water footprint of different products. You can download the lesson here.

THE GRACE SATELLITES
How do scientists monitor groundwater levels? NASA tracks water levels from space using the Grace satellites- super cool! They orbit the Earth and scientists measure the gravitational pull on the satellites in order to monitor how much water is underground (more groundwater = more dense = more gravitational pull).
You can find free lessons on them here, and check out some interactive maps with satellite data here.

ICE CORE LAB
What can we learn from ice cores? In this lab, students learn about how ice cores form, what we can learn from them, and how they are analyzed. It takes about 4 days to set up on your part, but the students love looking at these simulated ice cores. You can read a full blog post on how I made them here.

WATER DOCUMENTARY
There are a ton of documentaries out there on water shortages and conservation. I showed my students one titled "Beyond the Mirage" that is available on YouTube. I chose it because it is centered around Colorado River water, which feeds into my home state of Arizona. If you live in one of the 7 states that uses Colorado River water, I recommend this video. If you would like video questions to accompany the video, click here.

I hope these help and you spend an extra day or two digging a little deeper into the water cycle. If you have any other favorite activities, leave them in the comments!

At the end of every school year we end our life science curriculum with geologic time. It's one of my favorite units because I get to bust out my fossil collection (If you know me, that's a big deal).
It's hard to talk about geologic time, mass extinctions, and evolution of species without bringing up climate change. All these topics are fascinating but there aren't a ton of hands on labs you can do with them. I decided to try something different this year and make my own ice cores for students to analyze. Most students had never heard of ice cores, and when I asked them how we learn about shifts in climate I got a lot of blank stares. It was a great opportunity to bring up a new topic.

Some background on ice cores:

• The best ice cores are taken from places where the snow doesn't melt. Over the years the snow layers on top of each other, compacts, and freezes into thick layers of ice. 
• ​Ice cores are generally drilled from Antarctica and Greenland. The oldest ice cores date back to 800,000 years ago. 
  
• Ice core layers are similar to tree rings- new layers form on top of the last each year.
  
• When analyzing the layers, winter snow layers appear lighter than summer snow layers. This is because the snow melts slightly in the summer, refreezes, and is more dense than the winter layer. When we count years in an ice core, a light band and a dark band make up 1 year of snowfall (see image below).
• As snow falls, particles from the atmosphere get trapped in the snow. We can use this ash, pollen, and even radioactive atoms to make inferences about what occurred during that year. 
• Air bubbles are trapped in ice core layers. Scientists can melt small layers of ice cores, trap the gas that is released, and measure the gas components to infer what the climate was like the past 800,000 years. Higher levels of greenhouse gases such as carbon dioxide and methane mean the climate was warmer.  
  

Overall the students enjoyed looking at their simulated ice cores and I was glad I got to throw in an extra lab during our geologic time unit. If you are interested in checking out the powerpoint and lab worksheet I used for this lesson, click here. If you would like to look at additional ice core information and dig through real data, check out this site. Have fun!