Alewives swim against the current in a tributary of the Chesapeake Bay in Cecil County, Maryland, where thousands of river herring gathered to spawn on April 20, 2017.
River herring—alewives and their close relatives, blueback herring—are anadromous: as adults, they live off the Atlantic coast, but they return to freshwater to spawn. For the most part, river herring return to the same streams in which they were born. Scientists aren’t quite sure how the fish manage this migratory feat, but tend to attribute their homing instincts to a sensitivity to polarized light, magnetic signals and the unique characteristics of the waters where they were born.
As water temperatures warm and days lengthen each spring, river herring are spurred to begin their spawning runs. Years ago, some rivers seemed to turn silver or appeared to flow backwards as millions of river herring migrated upstream. The river herring fishery was once one of the most valuable in the Bay—alewives can be eaten fresh, smoked, salted or pickled, as well as used for pet food, as bait for lobster and snow crab or in fishmeal and fish oil. But habitat loss, harvest pressure and migration-restricting barriers like dams and culverts led to a sharp drop in river herring abundance, resulting in harvest moratoriums in Maryland, Virginia and the Potomac River, as well as other states along the East Coast.
These days, river herring populations continue to struggle, and adults must navigate a maze of obstacles to reach their spawning grounds. Sometimes their long journey ends at a dam or other barrier that blocks their access to upstream habitat. By clearing blocked waterways, or by installing fish ladders and lifts that help fish get over or around larger barriers, managers can help river herring recover. “Last month they were out in the Atlantic Ocean somewhere,” said Jim Thompson, a fisheries biologist with the state of Maryland, as he observed last week’s spawning run. “That’s why it’s really important to build these [fish] ladders or take these dams out to get them over that last little speed bump so they can spawn.”
Learn more about the Chesapeake Bay Program’s work to open the region’s streams to the migration of fish.
Image by Will Parson
An estimated 97,433 acres of underwater grasses were mapped in the Chesapeake Bay in 2016, the highest amount ever recorded in more than 30 years of aerial surveys by the Virginia Institute of Marine Science. The total marks a 53 percent achievement of the 185,000-acre goal adopted by Chesapeake Bay Program partners in the Chesapeake Bay Watershed Agreement.
In addition, even more underwater grasses likely grew in the region than the estimate suggests. Due to weather conditions and security restrictions, researchers were unable to collect aerial imagery over a portion of the Potomac River. In 2015, the portion supported almost 2,000 acres of grasses, and trends suggest that—had it been mapped—the area would have put the Bay-wide total at 99,409 acres.
Experts attribute the rise in underwater grass abundance to a strong increase in the tidal freshwater and moderately salty regions of the Bay, with widgeon grass in particular expanding in the latter region. However, because widgeon grass is a “boom and bust” species—its abundance can rise and fall from year to year—a widgeon-dominant spike is not guaranteed to persist in future seasons.
Underwater grasses—also known as “submerged aquatic vegetation,” or SAV—are critical to the Bay ecosystem. They provide food for small invertebrates and migratory waterfowl and maintain clear and healthy waters by absorbing nutrients, trapping sediment and slowing shoreline erosion. Although sensitive to pollution, underwater grasses are quick to respond to improvements in water quality, making their abundance a good indicator of Bay health.
“As a bay grass biologist, it is thrilling to see SAV recovering in the Chesapeake. Bay grasses exceeded our 2017 midterm goal of 90,000 acres for the second year, with reports of recovering SAV species diversity in areas throughout the Bay as well,” said Maryland Department of Natural Resources Biologist and Submerged Aquatic Vegetation Workgroup Chair Brooke Landry in a media release. “With continuing commitments to further reduce pollutants entering the Bay’s waters, I believe it’s possible to reach records every year and foster thriving SAV beds throughout the Bay—SAV beds that will promote ecological resilience and provide economic and recreational opportunities for generations to come.”
Because grass beds provide shelter for young fish and blue crabs, underwater grass abundance is also one of several factors influencing the health and stability of blue crab populations. Earlier this month, data collected by Maryland and Virginia through the Blue Crab Winter Dredge Survey showed that, while the overall blue crab population fell 18 percent between 2016 and 2017, the abundance of adult female crabs increased from 194 million to 215 million: the highest amount ever recorded by the Winter Dredge Survey.
In addition to financially supporting the aerial surveys used to monitor underwater grasses, the Chesapeake Bay Program has funded a citizen science project in which local riverkeepers, watershed organizations and volunteers can collect data on underwater grasses. As part of this project, Chesapeake Commons is expanding its Water Reporter app to include underwater grass monitoring features. By downloading the app and joining the Chesapeake Bay SAV Watchers group, anyone with a smartphone can help monitor underwater grasses whenever and wherever they are on the water.
Images by Will Parson
Nestled between Washington, D.C., and Baltimore, Maryland, the Patuxent Wildlife Research Center boasts native gardens, picturesque benches next to flowering trees that hum with bees, study sites for the center’s biologists and plenty of rivers, forests and walking trails for the public. Last Wednesday, the refuge played a role in ensuring a new generation of research scientists and nature lovers by hosting the Chesapeake Bay Program’s Leadership Summit on Environmental Literacy.
The summit centered on the environmental literacy outcome of the Chesapeake Bay Watershed Agreement, in which Bay Program partners—which include federal and state agencies, local governments, non-profit organizations, communities and academic institutions—committed to the goal to “enable every student in the region to graduate with the knowledge and skills to act responsibly to protect and restore their local watershed.”
Attendees were delegates from the education departments, environmental or natural resource departments and school districts of D.C., Delaware, Maryland, Pennsylvania, Virginia and West Virginia. Representatives from federal agencies, nonprofits, outdoor centers, and educational organizations throughout the Chesapeake Bay watershed joined in discussion and collaborated at each table.
Remarks from Nick DiPasquale, Director of the Chesapeake Bay Program, and Brad Knudsen, Patuxent Research Refuge Manager, kicked off the day. Both began by reminiscing spending sunrise-to-sunset childhood days playing outdoors, with Knudsen expressing concern over whether today’s children would be able to do the same.
“Most kids now experience the outdoors through sports,” Knudsen said. “Sports are great, but what are the odds that at 60 they’ll still be playing soccer? If they are exposed to birdwatching, nature hikes, [nature becomes] a lifelong love and activity.”
To give today’s children outdoor memories and ensure a robust outdoors in which to have them, education leaders from across the watershed shared stories and discussed how to foster success in each jurisdiction. “Me – We” is the handily descriptive pronunciation for Meaningful Watershed Education Experiences (MWEE), the formal environmental education component in place in elementary, middle and high schools and which has been shown to increase overall academic performance. MWEEs—which last weeks to months and morph from classroom learning to outdoor experiences and back again—give students a sense of place within the watershed as a whole, while providing real-world applications for science, math, history, reading and art.
The afternoon concluded with attendees discussing how best to tackle environmental literacy in their particular locality. A major component of environmental literacy is establishing a sense of the full watershed. Covering some 64,000 square miles, the Chesapeake Bay watershed stretches from New York down to Virginia and includes land-locked areas of Pennsylvania and West Virginia. A school in coastal Virginia might create a Bay-focused MWEE in partnership with a local nonprofit, while a class in rural Pennsylvania might work with a local farm, a conservancy and their conservation district to develop a sense of pollution prevention and groundwater protection on their own school grounds. Watershed protection works when people understand the interworking nature of the system and decide to act locally: each area taking pride in their own land, their own streams, their local community. Environmentally literate citizens result in healthier communities; healthier local communities result in a healthier bay.
Researchers studying historic pollution levels in the Chesapeake Bay found their answers in a somewhat out-of-the-ordinary subject: oyster shells. A recent study from the University of Alabama looked at nutrient levels in Bay oyster shells dating back over three thousand years, finding that humans have been polluting the Chesapeake Bay since the early 19th century.
Because they live stationary lives, oysters can make useful study subjects, serving as snapshots of environmental conditions in one location. As filter feeders—they eat by pumping water through their gills—the bivalves remove nutrients from the water, absorbing much of it into their shells. This study was one of the first to use oyster shells, commonly found at archaeological sites in the region, to backdate nitrogen levels. Using that data, researchers could determine when nitrogen levels increased and what role humans may have played.
Studying oyster shells dating back to 1250 BC, researchers found a dramatic increase in nitrogen content that began in the early 1800s and increased almost exponentially until present day. That timeline corresponds what is known about human activities in the Chesapeake Bay region at that time: dramatic increases in population, agriculture and forest clearing. While American Indians altered their environment and contributed to higher nitrogen levels in the water, the effects were local. Beginning in the 17th century, an influx of European colonizers led to an increase in agriculture and forest clearing— but it wasn’t until the 19th century that human effects began to dramatically alter nitrogen levels in oysters.
Industrialization and population increases in the 1800s left their mark on the Chesapeake Bay. Between 1830 and 1880, the area’s population tripled. As a result, over 80 percent of forests surrounding the Bay were cleared for farming and development. Plowing and erosion increased the amount of sewage and sediment entering the water, increasing nitrogen levels in the water as well. Oyster populations also declined, thus limiting the ability of the Bay to filter out this influx of pollution.
While this research focused on historical nitrogen levels, nutrient pollution is still a problem in the Chesapeake Bay today. Nitrogen is necessary for plants and animals to survive, but too much of it can lead to algal blooms, which create harmful conditions for underwater life. Manure and fertilizers can wash off of agricultural fields into nearby waterways, and stormwater runoff can pick up nutrients from excess lawn and garden fertilizers, pet waste and other sources in urban areas. Chesapeake Bay Program partners work with states, local governments, farmers, businesses and many more stakeholders to implement practices that can reduce and even eliminate pollution entering waterways.
The study, “δ15N Values in Crassostrea virginica Shells Provides Early Direct Evidence for Nitrogen Loading to Chesapeake Bay,” is available online in Scientific Reports.