How Blue Crabs Molt

If you have visited SERC and participated in an Estuary Chesapeake Field Trip, you learned about the life cycle of a Blue Crab. As a Blue Crab grows, it sheds its old shell as it goes through a process called molting. Have you ever wondered how a Blue Crab grows its new shell?


The crab forms a new and soft shell underneath the old one before it molts. Once the crab molts and has left its exoskeleton, its new shell begins to grow very quickly. While the shell is growing the crab pumps calcium and carbonate ions into the shell. Once these ions are pumped to the shell, the crab uses a protein to create calcium carbonate and the shell is hard.

Take a look at the articles below for more information about molting and the creation of crab shells!


Learn More About Chesapeake Bay Oysters and Their History

Helpful Resources for Teaching About Oysters

NOAA illustration

A Natural History Resource about Oysters

Oysters are a keystone species of the Chesapeake Bay, and an important indicator of the health of our waters. During your Estuary Chesapeake Field Trip your students will participate in a parent-teacher lead rotation station about oysters and their oyster bar community.

Oyster reefs: When the oysters are alive (and even deceased) they offer a wide variety of ecological services, these include habitat for micro organisms (fish, shrimp, worms, and mud crabs), water filtration, slowing energy from waves and water, and food for Bay organisms.

Here are some great resources to help you prepare for your field trip:

What Can We Learn From Crab Eyes?

Scientists Have Found Female Crab Eyes Have Hormones That Help Them Mature

There’s More to Crabs Than Just Catching Their “Eye”


Frontal view of blue crab eye stalks. (Photo: Mark Haddon)

Scientists at the University of Maryland have discovered that the eyes of immature female blue crabs have a specific hormone in them that contributes to their final maturation, and growth of reproductive body parts. These hormones allow them to proceed from an immature female, to growing sexual structures, and then proceeding into their final molt. Female blue crabs mate only once in their life, the time right after their final molt, which makes this information of particular interest to scientists. Check out the release of this research article online.

Spring 2014 Workshop Training Schedule

Training Opportunities for Parents and Teachers for Spring 2014, in Preparation for Field Trips to the Smithsonian Environmental Research Center


Students participating in the Estuary Chesapeake field trip, at the Water Testing station.

Below is a listing of dates to visit SERC for training. Please be sure to register with Jane Holly ( to let us know you’re coming. If you do not RSVP we can not guarantee staff available to train. Thanks!

You can download a copy of this schedlue here: Estuary Chesapeake Workshop dates 2014

Estuary Chesapeake Workshop Schedule
Spring 2014
All workshops are free, but you must register with Jane Holly ( You will receive an e-mail to confirm your registration.
11am-1 pm 4-6 pm 11am-1 pm 10 am-Noon
March 19th
March 25th March 27th March 29th
April 10th
April 15th April 16th April 17th
April 22nd April 23rd
May 6th May 8th

Plankton Breath Activity for the Classroom (Grades 3rd-8th)

Plankton Laboratory Activity for Your Classroom

Post-Field Trip Follow-Up All About Plankton

After students learn at SERC about how much of the oxygen we breathe comes from Plankton here’s an activity that can be done in the classroom on the topic!

Background Information

Prochlorococcus and other ocean phytoplankton are responsible for 70 percent of Earth’s oxygen production. However, some scientists believe that phytoplankton levels have declined by 40 percent since 1950 due to the warming of the ocean.

Plankton SERC

Zooplankton from the Chesapeake Bay (Photo: SERC)

Ocean temperature impacts the number of phytoplankton in the ocean. Phytoplankton need sunlight and nutrients to grow. Since phytoplankton depend on photosynthesis, they have to live near the ocean surface. Nutrients come to the surface as a result of the global conveyor belt—an upwelling current that circulates cold water and nutrients from deeper waters to warmer surface waters. As the oceans warm, there is less circulation of warm and cold water by the global conveyer belt. As a result, less mixing and circulation is occurring between the ocean depths. As the ocean water gets warmer, there are less nutrients for the plankton to eat. This means less photosynthesizing, which decreases phytoplankton’s carbon dioxide absorption and oxygen production.

Phytoplankton are extremely important to the Earth’s carbon cycle; they help to process and store carbon. In addition to oxygen production, phytoplankton are responsible for most of the transfer of carbon dioxide from the atmosphere to the ocean. Carbon dioxide is consumed during photosynthesis and the carbon is incorporated and stored in the phytoplankton. This is similar to how trees store carbon in their leaves and wood. Worldwide, this plankton “biological carbon pump” transfers about 10 gigatonnes (1 gigatonne=1 billion tons) of carbon from the atmosphere to the deep ocean each year. Even small changes in the growth of phytoplankton may affect atmospheric carbon dioxide concentrations, which would cause further climate change and speed up the warming of surface temperatures.

Humans can protect plankton and help overall ocean health by decreasing pollution, overharvesting, and habitat destruction.

1. Discuss Earth’s oxygen resources.
Ask: Where does the oxygen we breathe come from? Explain to students that rainforests are responsible for roughly one-third (28%) of the Earth’s oxygen but most (70%) of the oxygen in the atmosphere is produced by marine plants. The remaining 2 percent of Earth’s oxygen comes from other sources. The ocean produces oxygen through the plants (phytoplankton, kelp, and algal plankton) that live in it. These plants produce oxygen as a byproduct of photosynthesis, a process which converts carbon dioxide and sunlight into sugars the organism can use for energy. One type of phytoplankton, Prochlorococcus, releases countless tons of oxygen into the atmosphere. It is so small that millions can fit in a drop of water. Prochlorococcus has achieved fame as perhaps the most abundant photosynthetic organism on the planet. Dr. Sylvia A. Earle, a National Geographic Explorer, has estimated that Prochlorococcus provides the oxygen for one in every five breaths we take.

2. Have students collect and analyze data.
Distribute a copy of the worksheet Breath Calculations to each student. Then divide students into small groups of three to measure and record the number of breaths taken in 30 seconds. Ask them to assign roles: timer, breather, and data recorder. After all groups have collected and recorded their data, have students independently calculate how many breaths they take in one minute, one hour, and one day. Finally, have students calculate the number of breaths that come from the phytoplankton, Prochlorococcus.

3. Discuss the importance of phytoplankton and ways humans can positively influence phytoplankton levels and overall ocean health.
Explain to students that phytoplankton form the base of the marine food web. The health of all organisms in the ocean is connected to the health of phytoplankton. Use the provided Carbon Cycle illustration and information in the Background & Vocabulary tab of this activity to build students’ content knowledge about phytoplankton’s role in oxygen production and the carbon cycle. Ask: Why is it important that we protect our oceans and the plankton that live in them? What are some ways we can protect the ocean? Explain to students that they can help protect plankton by decreasing pollution, using less energy, urging individuals and companies to stop destroying habitat on land and in the ocean, and encouraging others to stop overharvesting ocean wildlife. An important part of saving the ocean is working together and educating others about why it is important.

4. Have students create a t-shirt or bumper sticker.
Have students create a t-shirt or a bumper sticker to increase public awareness about the problem with their own ocean health outreach slogan; for example, Save the Phytoplankton—Breathe More Air!


Informal Assessment

Assess student comprehension by evaluating the accuracy of their calculations and their contributions to the class discussion.

Extending the Learning

Have students research and compare the volume of air used by a human in one day to the volume of air that algae output (about 330 billion tons per year). Have students blow one breath of air into a balloon. Place the balloon in a 2,000 milliliter beaker partially filled with water. Measure the displacement that occurs.

What You’ll Need

Materials You Provide

  • Balloon
  • Beaker
  • Pencils
  • Stopwatch
  • Water

Resources Provided

The resources are also available at the top of the page.


  • The Carbon Cycle

Handouts & Worksheets

Required Technology

  • Tech Setup: 1 computer per classroom, Projector

Physical Space

  • Classroom


  • Large-group instruction
  • Small-group instruction

Need More Resources?

Check out the SERC Phytoplankton Ecology Lab’s free online photo guide to plankton of the Chesapeake Bay.

Phytoplankton guide SERC image

Click here to visit the SERC Phytoplankton Guide.

A surprising benefit of oyster reefs in the Chesapeake Bay

Oysters, though not the most charismatic of marine organisms, are said to be “ecosystem engineers” as they are essential to building and maintaining healthy and functioning marine ecosystems while also providing fisheries resources. Oysters often form reefs that not only provide habitats for other organisms, like mussles, clams, shrimps and crabs, but they are also breeding areas for commercially important fish species. In addition, oysters are known for their water clearing capabilities as they filter feed algae out of the water. However, when oysters consume algae, they excrete a nitrogen based waste product, ammonia, and the fate of this nitrogenous waste product is uncertain.

Nitrogen is an element that when in excess can cause algal blooms in coastal waters. In turn, any algae that remains uneaten sinks to the bottom, where bacteria acts on it, resulting in oxygen deprived areas. Though oysters are essential to the health of ecosystems, scientists want to know what happens to the ammonia excreted by oysters. The answer is a surprising one, and it comes from scientists at the Virginia Institute of Marine Science who were conducting research on the Choptank River located on the Eastern shore of Maryland. Dr. Lisa Kellog and her colleagues have determined that oysters have the ability to denitrify, or get rid of nitrogen, in the Bay. On the Choptank River she found that one acre of healthy oyster reef could remove 534 pounds of nitrogen per year through denitrification, which is one of the highest rates in any natural system in the Bay, and one of the highest in any marine environment. Denitrification is the process by which bacteria that are living in the presence of free oxygen convert ammonia to nitrate, which is then converted to nitrogen gas by other bacteria living in an anoxic (oxygen deprived) environment. Kellog describes oyster reefs as “denitrifying machines” as oyster reefs have a multitude of microhabitats for both types of bacteria and provide the bacteria with huge amounts of nitrogen rich material to denitrify.

This has huge implications for oyster reef restoration in the Bay. Kellog claims that if all the reefs in the Choptank were rehabilitated, they could remove around 50% of the nitrogen inputs into the river. However she cautions that the results from the Choptank are probably on the high end, and denitrification rates may differ among oyster reefs based on the characteristics of the reef, including oyster density and water depth. The study reef had over 100 oysters per square meter, a high figure when compared to most restoration projects. The reef was also in deeper water. Future work is looking in to the denitrification rates of oyster reefs in shallower or even intertidal waters.

Though the denitrification power of oyster reefs is just beginning to be studied, we are reminded of the many benefits of this sessile, rock-like organism. Not only do they provide habitat, and improve water quality, oysters and the associated reefs may have an important role in denitrification, which could mean improved water quality in the Bay. With future research and restoration efforts, we may be looking at more surprises from the lowly oyster!


“Ability of oysters to denitrify Bay surprises scientists” by Karl Blankenship, Bay Journal:

For more information on oysters, and restoration projects going on in Maryland, visit the Oyster Recovery Partnership website:

Plankton Revealed! TED-Ed Explores Our World’s Oceans….

As you get to know your new classmates, get to know the about the beginnings of a fish’s life story in this AWESOME TED-Ed talk about plankton. If you thought your first day of school outfit is cool, check out the amazing colors and shapes that these microscopic life forms display. Click through to to take a short quiz and see some extra resources for when you really get into it!

(link from if youtube is blocked at your school:

Want some more? Hear David Gallo make a case for getting to know our blue planet. We’ve explored only 5% of our world’s oceans. With things like giant vampire squids with defensive capes, who wouldn’t want to know what else is down there!

(link from if youtube is blocked at your school:

Our planet’s water systems are all connected, and are controlled in one way or another by plankton. On your Estuary Chesapeake field trip at SERC, you can get a peek at that plankton- the microscopic sea creatures that run the world. You will sample the plankton community of the Rhode River and examine the what you caught under a microscope. Call to book your trip today, if you haven’t already (443. 482.2216).