The runoff of fertilizer and animal waste can rob the Chesapeake Bay of oxygen that blue crabs need — and so can sewage from small towns, suburbs and cities.

Three decades ago, scientists working on Maryland's Patuxent River showed how sewage discharges robbed the river of oxygen, creating dead zones that can kill fish and crabs. Their discoveries set the stage for the current campaign to clean up the Chesapeake Bay.

In this video you can see a small seine boat from the 80-foot-long snapper rig "Hush Puppy" as it surrounds a school of menhaden.

The Corsica River on Maryland's Eastern Shore is a little waterway with big problems. But it is also the site of one of the most intensive restoration efforts ever mounted in the Chesapeake watershed. Take a tour with some of the Corsica’s champions to learn about efforts on the ground.

Video by Matthew Ellis, Maryland Sea Grant.

Who invents new oysters? Stan Allen does. He not only breeds disease-resistant oysters by speeding up the familiar process of natural selection, but he's also created a new kind of oyster, an oyster nature never designed. His invention is called a triploid oyster. It carries extra chromosomes and in the right conditions, it can grow nearly twice as fast as natural oysters. Widely grown on oyster farms along the west coast and in other countries, the triploid oyster is now coming to the Chesapeake.

Video by Michael Fincham, Maryland Sea Grant.

Oyster gardening, growing baby oysters off a dock, keeps growing in popularity among Bay-area residents interested in restoring water quality in Chesapeake Bay. Most of those dockside oysters will end up on sanctuary reefs where they will go to work filtering water at the rate of 50 gallons a day. Maryland residents can now get oysters and gear and training from a number of environmental organizations around the state. Here's how one organization trains and equips new gardeners.

Video by Michael Fincham, Maryland Sea Grant.

The Ocean City Beach Patrol began in 1930 with one lifeguard watching over several blocks of swimming beach. The beach patrol now numbers nearly 200 lifeguards watching over 10.5 miles of public beach.

Video by Michael Fincham, Maryland Sea Grant.

Terrapin populations seem to be booming out on a new, largely rebuilt island on the eastern side of Chesapeake Bay. When biologist Willem Roosenburg began monitoring terrapin nests on Poplar Island, he found hatchling survival rates as high as 70 to 80 percent. The Army Corps of Engineers has been diking and filling this site to create a large manmade island out of several small, separate islets that were dwindling away, the victims of erosion and subsidence. The new island is now the disposal site for dredge material dug out of the shipping channels of Chesapeake Bay, but it also holds several wetland cells where female terrapins can dig their nests, lay eggs and have high hopes their offspring will survive. The reasons: few predators, little boat traffic, no highway traffic, no commercial harvesting.

Video by Michael Fincham, Maryland Sea Grant.

Diamondback terrapins became the unofficial mascot for the University of Maryland teams as early as 1924, though "Testudo" would not become the official mascot for the school until 1933. For decades Testudo was often a comic or a combative cartoon character. In 2003, University Marketing and Communications began its well-publicized "Fear the Turtle" campaign that created a handsome, charismatic, roaring terrapin.

Produced by Mac Nelson and University Video.

When the University of Maryland wanted to highlight its continuing rise to prominence as an academic and research institution, it turned again to its terrapin mascot and sent "Testudo" rocketing into space in this 2004 television spot.

Produced by Mac Nelson and University Video.

"Fear the Turtle" began as a T-shirt slogan, coined by a fan, to celebrate Maryland's sports teams, but it grew into a well-funded marketing campaign to publicize the University of Maryland's high rankings for academics and research. Marching terrapins were unleashed in a 2005 television spot.

Produced by Mac Nelson and University Video.

The University of Maryland grew out of small agricultural college in College Park where cadets, many of them engineering students, began forming baseball and football teams in the 1890s, largely against the wishes of the faculty who saw sports as a distraction from study. The teams were often called "The Aggies" or "The Farmers," and they lost more than they won until 1905 when a student named H.C. "Curley" Byrd began to star as a pitcher for the baseball team, a quarterback for the football team and a sprinter for the track squad. In 1912, he returned as a football coach with big plans for his little alma mater.

From Keeping the Promise: The Rise of the University of Maryland.

By 1920 the aggie college had become the home campus of a new University of Maryland. By 1924, the football coach began calling his football teams "The Maryland Terrapins," and by 1935, the coach was president of the university. During his 19-year tenure, H.C. Curley Byrd raised funds for expanding the campus and redesigned it with Georgian-style architecture that reflected the colonial era in American history.

From Keeping the Promise: The Rise of the University of Maryland.

After World War II, President Curley Byrd opened the University of Maryland to all returning veterans with a high school degree and used funds from the G.I. bill to fund the building of Byrd Stadium and Cole Fieldhouse. He also hired a coach who would take his Maryland Terrapins to the top of college football.

From Keeping the Promise: The Rise of the University of Maryland.

This slender channel between Kent Island and the Eastern Shore was once a seafood center where 14 busy seafood houses bought oysters and crabs from hundreds of watermen. Only one seafood house and one shipping house are still open, but a new Maryland Watermen's Monument has now gone up here to honor all the men and women who once worked these waters — and the few dozen who still do.

Barnacles grow on pilings, boats, rocks, and even other animals. They have hard outer plates that, once submersed, open to reveal featherlike legs called cirri, that whisk plankton from the water column into an internal cavity. This very short video shows the barnacle feeding.

Attached to rocks and other surfaces by fine fibers called byssal threads, hooked mussels open their shells during high tide to draw in water and filter out food particles over their gills. The hooked mussel grows prolifically on oyster reefs, often outnumbering the oysters themselves by several fold. Although the filtration capacity of the hooked mussel has not been calculated directly, the combined filter power of the oyster and hooked mussel together can be quite significant. This video shows the hooked mussel feeding and mud worms that live nearby.

Often mistaken for the invasive zebra mussel, dark false mussels are native to the Chesapeake Bay. In the summer of 2004, a population explosion of dark false mussels in the Magothy, Severn and South rivers on the Bay's western shore cleared local waters with its filtering power. The mussel attached itself to pilings, boats, cages, ropes, and every other hard surface it encountered. This video chronicles a large-scale community science initiative, led by Richard Carey of the Magothy River Association, to survey the size of populations in 2004 and to calculate how much water they could filter.

One of only a few true filter-feeding worms in the Bay, the parchment worm feeds on suspended organic material. The video shows the parchment worm in the laboratory, outside the tube that it creates to live in, so we can see its anatomy and feeding structures. Winglike notopodia pump sea water through its tube and the notopodia secrete mucus that is drawn back, forming a bag. The mucus bag filters the water to retain finer particles. Periodically, the particles are transported back to the mouth by the dorsal ciliated groove and ingested.

Still the go-to filter feeder in the Bay, this native oyster can process water at rates 2-3 times that of other bivalves. Beating cilia draw water over the gills where plankton and other particles are trapped in mucus and sent to the mouth. Follow the link to see this video on YouTube, from the Chesapeake Bay Foundation, which shows time-lapse photography of the capacity of oysters to clear the water.

When watermen find wounded fish along a lonely river in Maryland, they kick off a scientific debate and an environmental crisis focused on a mysterious microbe that may — or may not — cause sick fis and sick people. Watch the title sequence from this award-winning film.

Scientists come up wiht conflicting evidence about the life cycle and fish-killing powers of the dinoflagellate called Pfiesteria piscicida. Features JoAnn Burkholder, Wayne Litaker, Wolfgang Vogelvein and Andrew Gordon.

When a Maryland Bay pilot brings a big ship up the Chesapeake Bay to Baltimore, he (or she) is making the longest single-pilot passage in America. When Captain Randy Bourgeois boards his ship, he is 8 miles from shore, 150 miles from Baltimore.

His job: guide a deep draft ship through a long, shallow estuary. And do it without incident, accident or environmental catastrophe.

From Baltimore to the Chesapeake and Delaware Canal is a short, tricky run: 40 miles with narrow channels and oncoming ship traffic.

Can students raise striped bass in their high school and middle school classrooms? Only if they can tackle and solve a slew of research questions and technical problems, ranging from water quality to food supply to fish disease. At South Carroll High School, science teacher Bob Foor-Hogue set up aquaculture projects for his students and the result was a pioneering, problem-solving approach to science education. Working with Foor-Hogue Sea Grant educators Adam Frederick and Jackie Takacs are now exporting his approach and their fish to other schools around the state.

Teachers have to learn before they can teach, and if they are going to teach aquaculture they have a lot to learn. Bob Foor-Hogue of South Carroll High School and Adam Frederick of Maryland Sea Grant Extension have been organizing summer workshops for teachers since 1998. They claim an aquaculture project is one of the best ways to get American students to plug into serious science. Here's what some of the teachers who plugged into the workshop have to say about the experience.

When Adam Frederick taught high school biology he got his students into science by getting them out of the classroom - out into the woods and fields and streams where they could see biology at work. Environmental science leads to better scores in science, according to Frederick, now a Marine Science Educator with Maryland Sea Grant Extension. And it's a teaching tool that can be used across all disciplines.

A biologist dives into his work. Ken Paynter on the damage from heavy fishing and devastating disease epidemics.

At the Horn Point Environmental Lab, Don Meritt turns out seed oysters full of oyster spat, and Charlie Frentz of the Oyster Recovery Partnership plants them in Chesapeake Bay.

Seafood growers and packers are calling for replanting the Chesapeake with oysters from China. But scientists have formed cautious and sometimes conflicting opinions about the promise and perils of planting non-natives. Can Crassotrea ariakensis revive the tidewater seafood economy? Can it create ecological benefits for the ecosystem? Here in their own words are an oyster packer, an oyster grower and two oyster scientists.

Oceanographer Bill Boicourt uses the Scanfish, an underwater flying wing, to document a new discovery in Chesapeake Bay: a Hydraulic Control Zone just north of the Rappahannock Shoals. Like a valve on a water faucet, the Hydraulic Control can regulate the flow of salty ocean water into the northern Bay. As the Scanfish glides up and down through the Bay, it can take tens of thousands of readings per hour, measuring salinity, chlorophyll, dissolved oxygen and plankton.

A pioneer in estuarine paleoecology, Grace Brush has been charting the history of environmental change in the Chesapeake watershed. Her technique: dig up cores from the bottom of the Bay's rivers, marshes and mainstem. Her hypothesis: the sediment holds a history of ancient and recent events that altered the estuary. On May 6, 2004, Grace Brush became the first woman to be awarded the Mathias Medal for research that has a significant impact on public policy.

Do the watermen of the Chesapeake Bay share similar values? A common culture? A collective worldview? Is their outlook rooted in their work, their sense of community, their sense of place? Anthropologist Michael Paolisso took those questions to Deal Island, an isolated enclave along Maryland's Eastern Shore. Here he talks about his work, and watermen Robert Daniels, Dickie Webster and Art Daniels talk about their lives.

Every Labor Day is race day on Deal Island. Watermen in skipjacks and workboats compete for trophies and glory. David Horseman of Chance gets to fire the starter's horn for the Workboat Docking Contest.

Julius Lowery remembers earlier days on a cleaner river: swimming and cat fishing and hanging out along the river banks in Washington, DC. From "Endangered Species," a documentary by the Earth Conservation Corps, a nonprofit environmental organization that puts the city's young people to work cleaning up the river.

The work and words of young volunteers with the Anacostia Watershed Society. Filmed for the Society by Todd Clark.

Since the 1890s watermen have been dredging oysters under sail on skipjacks - "two-sail bateaux" that were first built in dozens of small boatyards along the Eastern Shore of Maryland and Virginia.

The oldest oyster captain, Art Daniels Jr., remembers his first boyhood sail on his father's skipjack.

Dredging oysters under sail with Captain Art Daniels Jr. of Deal Island, Maryland.

"As long as you don't get afraid and stick with the boat, she'll stand by you." (Art Daniels, Jr.)

The day Captain Daniels found his skipjack, City of Crisfield, drowned at the dock in Cambridge harbor.

Sail rigger Rich Schofield and boat builder Mike Vlahovich go to work rebuilding the City of Crisfield.

A skipjack goes down to the bay again - the first success in an ambitious project at the Chesapeake Bay Maritime Museum to restore the last working sail fleet in the country.