Brian Barton
The Chesapeake Bay, the largest estuary in the United States, is facing severe pollution problems due to human activities. Nitrogen, phosphorus, and sediment are the three primary contributors to the poor health of the bay. High levels of nitrogen and phosphorus fuel excessive algae growth, creating low-oxygen dead zones that suffocate aquatic life. Sediment blocks sunlight from reaching underwater vegetation and smothers shellfish. These pollutants enter the bay through agricultural operations, urban runoff, septic discharges, and atmospheric deposition. Climate change, the Conowingo Dam reservoir, and agricultural pollution from Pennsylvania, which comprises almost two-thirds of the bay's watershed, have also impacted the bay's health.
| Characteristics | Values |
|---|---|
| Major Pollutants | Nitrogen, Phosphorus, and Sediment |
| Nitrogen Sources | Fertilizers, Wastewater, Septic Tank Discharges, Air Pollution, Farm/City/Suburban Runoff |
| Phosphorus Sources | Fertilizers, Wastewater, Septic Tank Discharges, Farm/City/Suburban Runoff |
| Sediment Sources | Dirt, Sand, Clay, Farm/City/Suburban Runoff |
| Other Pollutants | Chemicals, Oil, Animal Waste |
| Contributing Factors | Deforestation, Wetland Destruction, Climate Change, Atmospheric Deposition |
| Impact | Reduced Oxygen Levels, Algae Growth, Blocked Sunlight, Loss of Aquatic Life and Habitats |
| Area Covered | 64,000 Square Miles, Encompassing 6 States and D.C. |
| Progress | Slight Improvement in Water Quality, Pollution Reduction Efforts |
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What You'll Learn
Nitrogen, phosphorus, and sediment pollution
The Chesapeake Bay watershed, at its healthiest in the early 1600s, was mainly comprised of forested buffers, wetlands, and resource lands that absorbed and filtered nutrients. Haphazard development has stripped the watershed of these buffers, and today pollution flows undiluted into waterways. As land use patterns change and the watershed's population grows, the amount of nitrogen, phosphorus, and sediment entering the Bay's waters increases tremendously. Each year, roughly 300 million pounds of polluting nitrogen reach the Chesapeake Bay—about six times the amount that reached the bay in the 1600s.
The majority of nitrogen and phosphorus pollution comes from sewage treatment plants, animal feed lots, and polluted runoff from crop land, urban, and suburban areas. The largest source of pollution to the Bay comes from agricultural runoff, which contributes roughly 60 percent of the nitrogen and 45 percent of the phosphorus entering the Chesapeake Bay. The fastest-growing source of nitrogen pollution is polluted runoff. Implementing conservation measures on farms is one of the most cost-effective ways to reduce pollution in local streams, rivers, and the Bay.
To combat nitrogen and phosphorus pollution, stormwater systems and sewage treatment plants can be upgraded, septic systems can be properly operated, nitrogen removal technologies can be used on septic systems, and fertilizer applications to lawns can be decreased. Because roughly one-third of nitrogen pollution comes from the air, we can reduce nutrient loads by conserving energy and driving less, which will result in fewer emissions from power plants and vehicles that contribute to airborne nitrogen. Important natural filters such as forests, oysters, wetlands, and underwater grasses need to be protected and restored.
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Stormwater runoff
Nitrogen and phosphorus are among the leading causes of the bay's poor health. They fuel the growth of algae, which reduces oxygen levels in the water, creating dead zones where no aquatic life can survive. This process, known as eutrophication, has far-reaching consequences for the bay's ecosystem, including the loss of vital habitats for plants and animals. The excess nutrients in stormwater runoff, as well as agricultural operations, contribute to this issue.
Sediment from stormwater runoff also plays a detrimental role in the bay's health. Sediment can cloud the water, blocking sunlight from reaching underwater grasses and other aquatic plants, which rely on sunlight to survive. When sediment settles at the bottom, it can smother shellfish and other bottom-dwelling species, further reducing the biodiversity of the bay.
Agricultural activities, including the use of fertilizers and manure, are a major source of nutrient and sediment runoff into the bay. Pennsylvania, in particular, plays a significant role in the restoration of the bay as about half of the state drains into it, with the Susquehanna River being its largest tributary. Efforts are being made to involve farmers in finding solutions, as they have a vested interest in the health of the bay.
The impacts of stormwater runoff on the Chesapeake Bay are complex and far-reaching. It is important to address this issue through a combination of policy changes, community initiatives, and scientific solutions. By working together, communities, governments, and organizations can help restore the bay's health and protect its rich biodiversity.
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Agricultural pollution
Agriculture is one of the largest industries in Pennsylvania, and the state is a major contributor to the pollution of the Chesapeake Bay. The Chesapeake Bay watershed includes almost two-thirds of Pennsylvania, and the state supplies half of the bay's freshwater flow and the largest share of its agricultural pollution.
Excess nutrients and sediment runoff from agricultural operations are significant sources of water pollution. Nitrogen and phosphorus from fertilizers encourage the growth of algae, which blocks sunlight from reaching underwater grasses and creates low-oxygen dead zones, suffocating plant and animal life. Sediment coats streambeds, smothering vegetation and insects that fish need for habitat and food.
Farmers in Pennsylvania are working with Penn State's College of Agricultural Sciences to develop science-based solutions for reducing agricultural pollution in the Chesapeake Bay. By bringing together farmers, industry, and government agencies, the college is crafting a strategy to reduce pollutants in Pennsylvania's watersheds.
The Chesapeake Bay Program is also working to reduce pollution from the watershed, and experts are using a new indicator, the Chesapeake Bay Total Maximum Daily Load Indicator, to better understand how the bay is responding to installed best management practices and other watershed changes. Between 1995 and 2022, 80.95 million pounds of nitrogen and 2.4 million pounds of phosphorus were reduced through the installation of best management practices.
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Air pollution
One of the primary concerns regarding air pollution in the Chesapeake Bay is nitrogen oxide pollution (NOx). NOx is a group of highly reactive gases released into the air when fuel is burned. Elevated levels of NOx are found in regions with a high density of fuel-burning vehicles and power plants. In 2000, nitrogen oxides accounted for three-quarters of the airborne nitrogen polluting the bay, contributing significantly to ground-level ozone pollution. By 2017, nitrogen oxides still accounted for half of the airborne nitrogen pollution, with ammonia making up the other half.
Atmospheric deposition, or air deposition, is a significant contributor to the high levels of nitrogen in the bay. Air sources are responsible for about one-third of the total nitrogen loads, with direct deposition onto the tidal surface waters estimated to be 6 to 8 percent. Nitrogen deposited onto the land surface of the watershed can also be transported to the bay, accounting for approximately 25 to 28 percent of the total nitrogen load. The Clean Air Act regulations are expected to achieve significant reductions in nitrogen deposition by 2020, helping to improve the bay's health.
Other chemical contaminants polluting the Chesapeake Bay's airshed include mercury, polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHs). These contaminants, along with nitrogen oxides, have detrimental effects on the bay's ecosystem, which is home to more than 3,600 plant and animal species. To address air pollution and its impact on the bay, the Chesapeake Bay Program has developed Watershed Implementation Plans aimed at reducing nitrogen pollution from various sources, including atmospheric deposition, by 2025.
Additionally, individuals can play a role in reducing air pollution by adopting simple measures. For example, opting for walking, biking, or using public transportation can help decrease emissions from mobile sources. Similarly, using electric or manual lawn mowers and yard tools instead of gas-powered machines can contribute to lowering air pollution levels. By working together and implementing these measures, we can help improve the air quality in the Chesapeake Bay region and, in turn, enhance the health of this vital ecosystem.
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Climate change impacts
The Chesapeake Bay, the largest estuary in the United States, is facing significant environmental challenges due to the impacts of climate change. Here are some key ways in which climate change is affecting this vital waterway:
Warmer Water Temperatures: Climate change is causing an increase in water temperatures within the Chesapeake Bay. This has direct implications for the bay's ecology. Higher temperatures can lead to reduced oxygen levels in the water, creating "dead zones" where aquatic life cannot survive. Warmer waters can also promote the growth of harmful algae blooms, which can be toxic to marine life and detrimental to the overall health of the ecosystem.
Sea Level Rise and Erosion: The Chesapeake Bay region is experiencing rising sea levels due to climate change. This rise in water levels exacerbates erosion along the bay's shores, leading to the loss of critical habitats such as wetlands and coastal marshes. These habitats act as natural buffers against storms and flooding, and they also provide essential breeding and nursing grounds for many species, including blue crabs and oysters, which are vital to the bay's economy and ecosystem.
Changes in Precipitation Patterns: Altered patterns of precipitation, including more intense and frequent storms, are impacting the Chesapeake Bay watershed. Increased stormwater runoff carries higher volumes of pollutants, such as nitrogen and phosphorus, into the bay. These nutrients contribute to algae blooms and can lead to a process known as eutrophication, where excessive nutrients deplete oxygen levels, creating further dead zones. More frequent and severe storms can also lead to increased sediment runoff, smothering aquatic vegetation and further degrading water quality.
Altered Habitat and Species Distribution: As climate change affects water temperatures and currents within the bay, it also influences the distribution of habitats and species. For example, warmer waters may lead to shifts in the ranges of certain fish species, with potential impacts on the bay's food web dynamics. The timing of key ecological events, such as spawning and migration, may also be disrupted, causing imbalances in the ecosystem. These changes can have cascading effects on the bay's commercial and recreational fisheries, as well as on the overall biodiversity of the region.
Ocean Acidification: Increased carbon dioxide absorption in the ocean due to climate change leads to ocean acidification, which can have significant impacts on shellfish and other marine calcifiers in the Chesapeake Bay. Lower pH levels in the water can make it more difficult for oysters, clams, and other shell-forming organisms to build and maintain their shells, disrupting their growth and survival. Given the importance of oysters in filtering the bay's water and maintaining its ecological balance, ocean acidification can have far-reaching consequences for the entire ecosystem.
The complex interactions between climate change and the Chesapeake Bay's ecology underscore the urgent need for mitigation and adaptation strategies. Addressing these challenges requires coordinated efforts to reduce greenhouse gas emissions, improve watershed management practices, restore critical habitats, and enhance the resilience of both human communities and natural systems. By taking action to tackle climate change, we can help protect and preserve the Chesapeake Bay for future generations.
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Frequently asked questions
The three main contributors to the poor health of the Chesapeake Bay are nitrogen, phosphorus, and sediment.
Nitrogen and phosphorus enter the bay from fertilizers, wastewater, septic tank discharges, air pollution, and runoff from farms, cities, and suburbs. Sediment comes from soil, sand, and clay, and is also a byproduct of agricultural operations.
Nitrogen fuels the growth of algae, which reduces the amount of oxygen in the water, creating low-oxygen dead zones that suffocate plant and animal life.
In 2010, under an Executive Order from President Obama, the EPA set limits on nitrogen, phosphorus, and sediment pollution for the Chesapeake Bay watershed. States are working on implementing plans to achieve these limits by 2025. Additionally, organizations like the National Wildlife Federation and Penn State's College of Agricultural Sciences are working on initiatives to restore the bay and its surrounding waterways.
