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).

Target Field Trip Grants

Itching to come to SERC for a field trip but challenged by funding? There a lot of opportunities out there for grants for field trips. Here’s one from Target! Check it out by clicking the image!

Feel free to use the comment box below as a space to share with us and other teachers.

Was this useful? Let us know about your experiences with Target Field Trip Grants.

Know of any other organizations that teachers like you might be interested in checking out?


If you come and visit us at the Reed Center, you will be greeted by the newest resident of our 550-gallon tank: a Northern Snakehead fish. An object of lore and legend, the Northern Snakehead is known for being a foreboding invasive species of the Chespeake Bay’s rivers. Between the ability to eat fish up to a third of their body size (which can get up to 2 feet), and their ability to survive out of water if kept moist for up to four days (due to gills that resemble primitive lungs), these fish have acquired quite a reputation.

The Northern Snakehead that inhabits our large tank at the Reed Center. Say Cheese!
Photo Credit: Marlene Plumley (SERC Education Docent)

The Snakehead Saga:

The Northern Snakehead, Channa argus, originates from China, and was first spotted in Chesapeake waters in May of 2002, in Crofton, MD. Scientists quickly noticed that snakeheads had the potential to seriously disrupt natural food web systems, because as top-level predators, snakeheads were eating anything they could fit in their mouth. Snakeheads were quickly marked as an invasive species and eradication began. MDDNR posted signs telling the public to kill any snakehead they found and to alert MDDNR.

After two years of relatively no news of the snakeheads, they showed up in the Potomac River. However, because snakeheads prefer fresher waters, it was thought that the saltier waters of the Bay would keep the snakeheads from leaving the Potomac and spreading through the Bay. Essentially, the saltier waters of the Bay were to act like a barrier, made up of intolerable waters. However, increased spring runoff caused the salinity of the Bay to decline, expanded the area that the snakeheads’ could tolerate, and opened the opportunity for them to invade other tributaries.

This past summer (2011), SERC scientists and interns found a pregnant female snakehead in the Rhode River, here at SERC. Of course it made the news, and worried scientists that there was probably more than just the one individual present in the Rhode River and similar tributaries.

What’s going on now

Snakeheads are still found in the Potomac River, and MDDNR still offers a monetary reward for catching, killing, and reporting a snakehead catch. At SERC’s Family Day this year, the Fish and Invertebrate Lab had a Northern Snakehead from the Potomac River on display in a tank. Now, we have inherited the fancy fish and are telling everyone. By having the snakehead available for the public to view at the Reed Center, you can come by and see what a real one looks like, increase awareness of Northern Snakeheads, and drum up conversations about the ecological impacts of invasive species. Plus, the fish looks pretty cool (the name alludes to the awesome patterned coloration). Stop by and check it out!

Click here to view the blog post on SERC’s blog Shorelines about the snakehead they caught last summer, and here to read first-hand accounts of the people who caught it.

Our camouflaged companion is no longer featured at the Reed Center. The Fish and Invertebrate lab here at SERC has used the snakehead fish as part of an ongoing project to catalog all of the fish and bottom-dwelling invertebrates in the Chesapeake Bay. As part of the International Consortium for the Barcode of Life, Rob Aguilar of the Fish and Invertebrate lab has been collecting samples of fish and bottom dwellers in Chesapeake Bay. Each time a specimen is collected, a piece of DNA is sent to a genetics laboratory, where it gets recorded, sorted, and given a barcode. The project’s goal is to compile a library of DNA to help with species identification. Read more here.

Oysters and Carbon Dioxide?

If you’ve been to SERC lately, you may have seen this strange plot off the right side of the dock:

Maybe you thought, ‘Why are those blue and green pool noodles arranged so elegantly in square formation? Why are there interns in SCUBA gear pulling up oyster shells? What is going on?!’

Thanks to Chesapeake Quarterly, we have answers. That square plot is the where Whitman Miller, a SERC scientist, is doing research on how ocean acidification affects oyster populations.

At the water testing station of Estuary Chesapeake, we measure the pH of the Rhode River and discuss how any deviation from neutral conditions can have a negative effect on aquatic biological processes. Whitman has taken this question and turned it into a full-blown scientific investigation.

Here’s a link to a preliminary study:

Let’s break down his study into the 6 parts of the scientific method:
Question, Background Research, Hypothesis, Test the Hypothesis/Method, Analyze, Report your findings 

Question: Since all good scientific study starts with a question, here’s Whitman’s: What would happen to oysters in an acidifying Chesapeake? 

Background Research: What information and observations lead him to ask this question?

SERC is home to the longest running CO2 study on plant communities. In that study scientists created marsh chambers with elevated levels of CO2 to simulate what the atmosphere could be like in the future.  Now Tom Arnold, a chemical ecologist from Dickinson College, and Whitman Miller are taking the same idea and applying it to an aquatic animal: the oyster.

Research has revealed that higher levels of CO2 in the atmosphere are changing Earth’s climate. About a third of that CO2 ends up getting absorbed into the world’s oceans, causing reactions to change the chemistry of the water. When CO2 absorbs into water, it creates carbonic acid, which could make it hard for organisms like oysters to form their shells made of calcium carbonate. Here’s how it works:

To make matters worse, in areas like the Chesapeake Bay, an excess of nutrients like nitrogen and phosphorus can cause higher levels of CO2. Studies have investigated this issue in a marine (or ocean) settings, but there isn’t enough research on coastal and estuarine settings (like the Rhode River).

Hypothesis: If the acidity of the Bay’s waters continue to increase, then the growth rate of young oyster shells will decrease.

Test the Hypothesis/Method: Whitman and Tom used tanks to pump CO2 into the river bottom where baskets of young oysters were set up in order to raise the CO2 levels and simulate future conditions. They then measure the surface area of the shells, how fast the shells are growing, how fast the larvae are growing, and the chemical makeup of the shells.

Analyze: Data has shown that estuarine shell-forming organisms are vulnerable to the effects of more CO2 in the water, and that the effects are different across species- meaning, the conditions affect different types of oysters and other shelled organisms differently. However, Whitman has had to postpone research due to increased precipitation in early summer.

Report Your Findings: When charting the data he has so far, Whitman has found a 16% decrease in how fast native oyster mature in conditions simulating CO2 levels of the year 2100, and a 42% decrease in the amount of calcium in the shells. Whitman is still collecting data, so more conclusions will come in the future.

This kind of study deserves a lot of attention. For one, it attacks a hole in aquatic chemical ecology. Before this study, research on acidification in oceans had been just beginning, but acidification in coastal and estuarine zones was barely existent.

The study also deserves attention because it has implications for both economic and restoration efforts surrounding the Bay’s oyster populations. If oysters aren’t going to be able to grow their shells as strong or large, there will be less to sell AND there will be less places for new baby oysters to hook onto (check out this video to learn more about the life of oysters).

On the Estuary Chesapeake Field trip, we tell you how you are investigating an estuary alongside SERC researchers. This study shows you just that-

We test pH, they test pH— Scientists use some of the same methods we use to test pH to answer some of the questions we hypothesize about in our discussions at Station 2: Water Testing.

We use oyster baskets, they use oyster baskets— The same kinds of baskets we use, the ones that are hanging off the dock at Station 3: Oyster Bar Community, are the same kinds that Whitman and his team used to house the young oysters that were receiving extra CO2 gas.

We examine oyster shells, they examine oyster shells— The way we carefully make observations about the shape, size and organisms present on the oyster shells at Station 3: Oyster Bar Community is similar to how researchers examine the oysters that are part of their study.

If you and/or your class are interested in learning more about Whitman’s study, comment and ask some questions. We challenge you to trail blaze the issue of acidification in estuaries: come up with some great science questions that could lead to new research questions. Let these few questions get your brain moving…..

What other organisms might be affected? What other processes and conditions could make the situation worse? What can we do to help?

(Check out the original article published in Chesapeake Quarterly: An Acidifying Estuary? The “Other CO2 Problem”)