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Phosphorus in the Chesapeake:An Overview on Nutrient Pollution in the Chesapeake Bay and Efforts to Limit Phosphorus Runoff in the Watershed

Kathleen DaleyNeil Saunders

1 May 2015

Copyright 2015 G2 Associates, Inc., Great Falls, Virginia, All Rights Reserved.

G2 Associates hereby authorizes you to copy this document for non-commercial uses within your organization only. In consideration of this authorization, you agree that any copy of these documents that you make shall retain all copyright and other proprietary notices contained herein. III. Nitrogen and Phosphorus Pollution in the Chesapeake BayIntroductionThe Chesapeake Bay is the nations largest estuary. The Bay and its tributaries cover 64,000 square miles, extending into six states: New York, Pennsylvania, Delaware, Maryland, Virginia and West Virginia, and the District of Columbia. The watershed includes a mix of urban, suburban and rural landscapes. [endnoteRef:-1] Agricultural runoff, urban and suburban stormwater runoff, vehicle emissions, and wastewater treatment plant discharges within the watershed result in millions of pounds of nitrogen, phosphorus and sediment reaching the Chesapeake Bay each year. An excess of nutrients and sediments from all this human activity has a negative impact on water quality in the bay, directly affecting plant and animal species that live in and around the estuary. [-1: Chesapeake Bay Program (CBP), 2013 estimates, http://www.chesapeakebay.net/indicators/indicator/chesapeake_bay_watershed_population. ]

Out of all of this human activity, agriculture is the largest single source of pollution for both phosphorus and nitrogen, contributing 45% of the phosphorus and 38% of the nitrogen entering the Chesapeake Bay. While agriculture is prevalent throughout the Chesapeake Bay region, certain states, such as Maryland, have come under scrutiny in recent months for their handling of waste from chicken production facilities. Hundreds of millions of chickens are produced annually in the state of Maryland. Manure from these chickens is used as fertilizer on cropland in the state, which often is already saturated with phosphorus. The excess phosphorus runs off and leaches into the Chesapeake Bay watershed, polluting the Bay and its tributaries.

Observed Changes in the Chesapeake Bay from Human ActivityHumans within the Chesapeake Bay region have had an enormous impact on water quality in the mainstem of the Bay, and in the numerous streams and rivers that make up the watershed. Deforestation, urban development, and agricultural activity contribute millions of pounds of nutrients and sediment to the Bay each year. In the 400 years since European colonization in the region, there have been significant changes to water quality and species composition in the Bay, as result of human activity and land use changes. According to a report released by the National Research Council, nitrogen and phosphorus levels in the Bay in the mid-1980s were 7 and 16 times higher, respectively, than when English colonists arrived in the region.[endnoteRef:0] [0: National Research Council, Achieving Nutrient and Sediment Reduction Goals in the Chesapeake Bay, 2011, 15-16.]

Since the mid-twentieth century, the population within the watershed has grown at an accelerated rate, and will continue to grow, according to recent projections.[endnoteRef:1] Eight million people lived in the Bay watershed in the 1950s; the current population is 17.8 million people. There are expected to be an additional 1.7 million people in the watershed each decade.[endnoteRef:2] Urban development has grown with the population. Between 1982 and 1997, over 750,000 acres in the Bay watershed were cleared to make way for the construction of infrastructure, and residential and commercial buildings associated with urban sprawl. Currently, about 35% of private forests in the region are available for development, which will likely result in greater sprawl, forest fragmentation and deforestation in the watershed.[endnoteRef:3] [1: According to the Chesapeake Bay Program, an estimated 17.8 million people lived in the Bay watershed in 2013, up from 17.7 million in 2012. Population numbers are expected to keep rising, and by 2040, there will be an estimated 21.4 million people living in the watershed. Chesapeake Bay Program, 2014, http://www.chesapeakebay.net/indicators/indicator/chesapeake_bay_watershed_population. ] [2: Tom Horton, Growing, Growing, Gone! The Chesapeake Bay and the Myth of Endless Growth, (Baltimore: The Abell Foundation, 2008), 2. ] [3: CBP, 2014, http://www.chesapeakebay.net/issues/issue/development#inline. ]

Agriculture, which is needed to feed and support the 17.8 million people who live within the watershed, takes up almost a quarter of the land within watershed boundaries. In total there are about 8.5 million acres of farmland, and 87,000 farming operations in the region.[endnoteRef:4] All of these human activities- development, deforestation, and agriculture- contribute nutrient and sediment pollution, which has a detrimental effect on fish, shellfish, and plant species in the Chesapeake Bay and its tributaries. [4: CBP, 2014, http://www.chesapeakebay.net/issues/issue/agriculture#inline. ]

Hypoxia and Dead ZonesNutrient and sediment pollution can cause hypoxia, or dead zones in the Bay. Dead zones are underwater areas with low oxygen levels, in which aquatic organisms find it difficult to survive. Sediment, phosphorus and nitrogen feed algae throughout the watershed. Excessive loads of phosphorus and nitrogen entering the Chesapeake result in algal blooms, reducing dissolved oxygen levels in the estuary. This leads to dead zones in the Bay over the summer months, a problem that has been occurring in the mainstem of the Bay for decades.[endnoteRef:5] Hypoxic conditions in the Bay lead to habitat loss for marine species in shallow and deep waters, fish and shellfish die-offs, and disruptions to energy transfer and production in the food chain.[endnoteRef:6] [5: Rebecca R. Murphy, W. Michael Kemp, and William P. Ball, Long Term Trends in Chesapeake Bay Seasonal Hypoxia, Stratification, and Nutrient Loading, Coastal and Estuarine Research Federation, 2011, ] [6: Murphy, et. al., ]

Submerged Aquatic VegetationExcess nutrients and sediments in streams, rivers, and the Bay block sunlight from reaching submerged aquatic vegetation, preventing the growth and survival of these underwater grasses. Submerged aquatic vegetation, or SAV, act as a source of food for waterfowl, and as a habitat for fish and shellfish species in the Chesapeake Bay. Decomposing SAV feed species on the Bay floor. SAV filters polluted runoff by taking up nitrogen and phosphorus, and improves water quality and clarity in the Bay. Underwater grasses also absorb wave energy and protect shorelines from erosion.[endnoteRef:7] [7: VIMS, 2014, http://web.vims.edu/bio/sav/AboutSAV.html.]

While submerged aquatic vegetation takes up nitrogen and phosphorus, excess levels of these nutrients impair the ability of underwater grasses to filter polluted runoff. Sedimentation, and nitrogen and phosphorus pollution have contributed to massive die-offs of SAV. Poor water quality is listed as the chief threat for SAV by the Virginia Institute of Marine Science (VIMS).[endnoteRef:8] VIMS estimates that the Chesapeake Bay once had over 600,000 acres of SAV.[endnoteRef:9] As of 2012, the Chesapeake Bay Program estimates a total of 48,191 acres of SAV are in the Bay.[endnoteRef:10] [8: VIMS, 2014, http://web.vims.edu/bio/sav/AboutSAV.html. ] [9: VIMS, 2014. ] [10: CBP, 2013, http://www.chesapeakebay.net/presscenter/release/bays_underwater_grasses_decline_for_third_year. ]

Reduction of submerged aquatic vegetation acreage occurred at a steady rate in the last century. VIMS states: Since the 1950s, there has been a tremendous decline in SAV due to degraded water quality.[endnoteRef:11] Another source claims that SAV beds in the Chesapeake Bay declined by 50% after 1960.[endnoteRef:12] In 1972, Tropical Storm Agnes resulted in massive amounts of rainfall and nutrient runoff, and killed off many grass beds in the Bay.[endnoteRef:13] The reduction of SAV acreage has continued into the present day. Aerial surveys conducted by VIMS show that acreage of one SAV species in the Bay, eelgrass, has declined by about 50% since the early 1990s.[endnoteRef:14] [11: VIMS, 2014. ] [12: Virginia Places, Blue Crabs in Virginia, 2014, http://www.virginiaplaces.org/natural/crabs.html. ] [13: VIMS, 2014. ] [14: Maryland Department of Natural Resources, 2008, http://www.dnr.state.md.us/bay/sav/download/grass_beds_capital.pdf.]

Shellfish: Pollutions Impact on Crabs and OystersUnderwater grass beds are a source of food and habitat for many regional marine species, including the iconic Chesapeake blue crab (Callinectes sapidus). Juvenile blue crabs rely on underwater grasses for protection from predators, such as striped bass. SAV beds have been found to contain 30 times more juvenile crabs than uncovered water floors. The blue crab is more susceptible to predation in areas where these SAV beds have been significantly reduced. [endnoteRef:15] A loss of SAV habitat, associated with nutrient and sediment pollution, has led to the decline in the blue crab population in the Bay over the past several years.[endnoteRef:16] [15: Maryland Department of Natural Resources, 2008, http://www.dnr.state.md.us/bay/sav/download/grass_beds_capital.pdf. ] [16: Chesapeake Bay Program, http://www.chesapeakebay.net/issues/issue/bay_grasses#inline. ]

Overfishing and the reluctance of state regulatory agencies to limit crab harvesting, are also possible explanations for this population decline. However, habitat loss associated with nutrient and sediment pollution has likely contributed the most to the blue crab die offs in recent years. The 2014 State of the Bay report from the Chesapeake Bay Foundation attributes the most recent decline in crab numbers to poor water quality associated with pollution. They state:Factors other than harvest are evidently also limiting the crab population. The large numbers of juvenile crabs produced in 2011 did not mature into large numbers of adults as expected. Continued low levels of underwater grasses habitat probably exposed small crabs to high predation by striped bass and other predatory fish.[endnoteRef:17] [17: Chesapeake Bay Foundation (CBF), State of the Bay, 2014, http://www.cbf.org/about-the-bay/state-of-the-bay-report-2014. ]

The blue crab population in the Chesapeake Bay has been declining since the late-twentieth century. Population numbers have fallen to particularly low levels in the past couple of years. In 2014, the Bays blue crab population dropped to less than half of what it was in 2012. (See Figure 7 below).

Figure 7: Total crab population from 2007 to 2014 based on winter dredge surveys in the Bay, (http://virginiaplaces.org/natural.crabs.html).

Annual harvests and winter dredge surveys are indicators of population health in the Bay. The average annual catch of blue crabs from 1968 to 2001 was 75 million pounds. [endnoteRef:18] Although this number fluctuates year to year, crab harvest decline was drastic in the last decade of the twentieth century, when harvests dropped from 113 million pounds in 1993 to 49 million pounds in 2000.[endnoteRef:19] (See Figure 8 below). More recent numbers show an even greater decline. According to the Chesapeake Bay Blue Crab Advisory Report on the 2013 harvest, Bay-wide commercial harvest, including catches from Maryland, Virginias Chesapeake region and the Potomac River, was only 37 million pounds. The report labeled this harvest the lowest recorded in 25 years. Mirroring the population drop from 2012 to 2014, Marylands 2013 harvest had a decline in 41% from 2012 numbers, while Virginias harvest had a 24% drop in the Bay and 44% drop in the Potomac River from 2012 numbers.[endnoteRef:20] The 2014 harvest numbers will be released later this year, but numbers are expected to be similar or lower to the previous year. [18: VIMS, 2002, http://www.fisheries.vims.edu/bcar/. ] [19: http://www.virginiaplaces.org/natural/crabs.html.] [20: Chesapeake Bay Stock Assessment Committee, Chesapeake Bay Blue Crab Advisory Report, 2014. ]

Figure 8: Decline in total crab population (in blue), in millions of crabs, from 1990 to 2007. (http://virginiaplaces.org/natural.crabs.html).

Sediment and nutrient pollution affect the Bays oyster population as well. Since the mid-twentieth century, the Chesapeake oyster, (Crassostrea virginica), has come back from numerous set-backs.[endnoteRef:21] Disease, overfishing, sedimentation, and nutrient pollution contributed to reductions in population numbers in the Chesapeake and its tributaries. (See Figure 9 below). Nutrient and sediment pollution, associated with changes in land use and deforestation, contribute to poor water quality in the Bay, which makes oysters more susceptible to disease. Excess sediment in the water stifles oysters, while excess nutrients can create oxygen-depleted dead zones, suffocating oysters and limiting the growth of larvae.[endnoteRef:22] [21: Catch loads in Maryland, for example, declined from 1884 to 1992, from 615,000 tons to 12,000 tons. (B.J. Rothschild, et. al., Decline of the Chesapeake Bay oyster population: a century of habitat destruction and overfishing, Mar. Ecol. Prog. Ser., 1994). Catch trends in Virginia were quite similar. It is thought that Bay-wide, less than 1% of the original 17th century population remains in the watershed. (Newell, R.I.E. 1988. Ecological changes in Chesapeake Bay: are they the results of overharvesting the American oyster, Crassostrea virginica? In: M. Lynch and E.C. Krome (eds.) Understanding the estuary: advances in Chesapeake Bay research, Chesapeake Research Consortium, Solomons MD pp.536-546).] [22: CBP, 2014, http://www.chesapeakebay.net/issues/issue/oysters#inline. ]

Figure 9: Virginia and Maryland oyster landings from 1880 to 2000. The graph, from a report in Chesapeake Quarterly documents the great decline of the Bays oyster population over the twentieth century. Overfishing and disease are credited as having the greatest impact on the Chesapeake oyster, however, nutrient and sediment pollution have played a large role in this decline as well. (Jack Greer, Killer from Across the Sea, Chesapeake Quarterly 8:2, 2009).

Phosphorus, Nitrogen Loads Entering the BayNutrients and sediment enter the Chesapeake Bay at rates that exceed levels the EPA deems healthy for the watershed. The EPA determined that annual nutrient loads to the Bay should not exceed 12.5 million pounds of phosphorus and 185.9 million pounds of nitrogen. However, average annual loads, calculated from 1990 to 2013, exceed these levels. Average phosphorus loads during this period were estimated to be over 21.1 million pounds, and nitrogen estimated at 338 million pounds.[endnoteRef:23] [23: CBP, 2014, http://www.chesapeakebay.net/indicators/indicator/nitrogen_loads_and_river_flow_to_the_bay1. ]

In the Chesapeake Bay, the major sources of nutrient and sediment pollution are agriculture; urban and suburban development; vehicle emissions; and wastewater treatment and industrial site emissions. For Bay-wide nitrogen loads, sewage treatment plants, industry wastewater, and private septic systems account for 23% of the nitrogen entering the watershed. Air pollution, mainly from car and industrial emissions, account for 21% of the nitrogen polluting the Bay. Stormwater runoff in urban and suburban areas is another 16%, while agriculture contributes 38% of the nitrogen in the Chesapeake[endnoteRef:24] (See Figure 10 below). [24: CBF, 2014, http://www.cbf.org/about-the-bay/issues/dead-zones/nitrogen-phosphorus. ]

Figure 11: Sources of phosphorus loads to the Chesapeake Bay. Image source: National Research Council, Achieving Nutrient and Sediment Reduction Goals in the Chesapeake Bay, 29.Figure 10: Sources of nitrogen loads to the Chesapeake Bay. Image source: CBF, www.cbf.org/about-the-bay/issues/dead-zones/nitrgoen-phosphorus.Percentages of phosphorus loads entering the Bay, divided up by source, are similar to nitrogen. Urban and suburban stormwater runoff accounts for 31% of phosphorus entering the Bay, sewage and industrial wastewaster is 21% and forest is 3%.[endnoteRef:25] [endnoteRef:26] Almost 50% of phosphorus in the Chesapeake Bay and its tributaries comes from agriculture. Out of this source, 26% is from manure runoff from farms, and 19% from chemical fertilizers.[endnoteRef:27] In 2013, out of 17 million pounds of phosphorus that reached the Chesapeake, approximately half of the phosphorous load came from agriculture, according to models created by the Chesapeake Bay Program.[endnoteRef:28] (See Figure 11 above). [25: According to the EPA: Sources of nonpoint source (NPS) pollution associated with forestry activities include removal of streamside vegetation, road construction and use, timber harvesting, and mechanical preparation for the planting of trees. Road construction and road use are the primary sources of NPS pollution on forested lands, contributing up to 90 percent of the total sediment from forestry operations, (EPA, Forestry, http://water.epa.gov/polwaste/nps/forestry.cfm). ] [26: CBP, 2014. ] [27: National Resource Council, 29. ] [28: CBP, 2014, http://www.chesapeakebay.net/indicators/indicator/reducing_phosphorus_pollution. ]

Agriculture in the Chesapeake Bay Watershed In the Chesapeake Bay watershed, about a quarter of the land is dedicated to farming, making agriculture the second largest land use in the region, behind forested areas. Agricultural activities contribute the largest percentage of phosphorus levels in the Bay. Phosphorus pollution in the Bay can be partly attributed to the over-application of animal manure to farmlands. The Chesapeake Bay was ranked as one of the highest priority watersheds in the country needing protection from manure nutrients at the beginning of this century.[endnoteRef:29] [29: Catma, et. al. ]

How Manure Pollutes the BayAnimal waste is often used throughout the watershed as a fertilizer on croplands. Whether manure is collected and distributed as fertilizer, or manure is left on fields where it was naturally deposited, the animal waste poses a major risk to water quality in nearby streams, rivers, and the Chesapeake Bay. Plants need nutrients, such as phosphorus and nitrogen, to grow. Phosphorus applied to cropland in the form of manure can meet these needs, however soils can already have sufficient levels of the nutrient. Phosphorus applied in excess does not help the plant. Instead, when extra phosphorus is applied, the phosphorus remains in the soil. Heavy rain and snowmelt cause the excess nutrients in soil to runoff into local streams. This occurs directly, when manure is applied too close to the edge of a field, or when a vegetative buffer does not exist along a waterway. Phosphorus can also enter a waterway indirectly through soil erosion, leaching, or when rain and snowmelt carry soil to drainage ditches; the phosphorus in the soil gradually makes its way into streams, rivers and the Bay.[endnoteRef:30] [30: Frontier Group, An Unsustainable Path: Why Marylands Manure Pollution Rules are Failing to Protect the Chesapeake Bay, 2011, p. 9. ]

Manure comes from a variety of animals in the watershed. Animal production of beef cattle, dairy cattle, swine, and the three main poultry types: layers, broilers, and turkeys, are most common in the Chesapeake Bay watershed.[endnoteRef:31] Poultry production is especially prevalent along the Bay in the state of Maryland and on the Delmarva Peninsula.[endnoteRef:32] Chicken litter is a popular form of manure on farms in this region. About 1.5 billion pounds of chicken manure are produced annually on the Delmarva Peninsula and used on farms throughout the region.[endnoteRef:33] This manure is a contributor to nutrient pollution in the Chesapeake Bay. Ten percent of the total phosphorus in the Bay is estimated to come from the Eastern Shore, as a result of large-scale chicken production and chicken litter runoff.[endnoteRef:34] [31: Catma et. al., 122. ] [32: The Delmarva Peninsula is on the Eastern Shore of the Chesapeake Bay, and is made up of parts of Delaware, Maryland, and Virginia. ] [33: Public Broadcasting System, Whos Responsible for that Manure? Accessed 2015, http://www.pbs.org/wgbh/pages/frontline/poisonedwaters/themes/chicken.html. ] [34: EPA, 2010, 4-4. ]

Chicken production in Chesapeake Bay watershedThe Delmarva Peninsula is home to large national chicken production companies. Perdue Farms, Mountaire Farms and Tyson Foods run poultry production facilities throughout the peninsula. In 2010, 786 million chickens were produced regionally, two-thirds of which came from Delmarva.[endnoteRef:35] With these production rates, Delmarva is one of the nations highest poultry producing regions, and two counties on the Peninsula- Delawares Sussex County and Marylands Wicomico County- are listed as two of the twenty top poultry producing counties in the country.[endnoteRef:36] [35: Frontier Group, pg. 8] [36: EPA, 2010, 4-29.]

Marylands Contribution to Phosphorus Pollution in the ChesapeakeAgriculture97% of Marylands streams, creeks, and rivers empty into the Bay or its tributaries, making Maryland the state with the highest percentage of its bodies of water within the watershed (excluding the District of Columbia).[endnoteRef:37] Many of these waterways carry nutrient and sediment into the Bay from agricultural fields. According to a report released by the Department of Agriculture, in 2013, there were 12,400 farms, making up 2,050,000 acres in Maryland.[endnoteRef:38] Runoff from these farms accounts for 41% of the phosphorus that enters the Bay from Maryland.[endnoteRef:39] [37: Catma, et. al., 122. ] [38: USDA, 2013. ] [39: Frontier Group, ]

Chicken farming Maryland, both on its Eastern Shore, and throughout the state, produces chickens on a massive scale. The state is currently ranked eighth nationally in the number of broiler chickens produced, and has one of the highest concentrations of chickens per acre of farmland, in the country.[endnoteRef:40] [endnoteRef:41] In 2013, over 300 million chickens were raised in Maryland.[endnoteRef:42] Production results in hundreds of millions of pounds of manure each year. For instance, 296 million broiler chickens raised in 2007 generated over 1.2 billion pounds of chicken litter.[endnoteRef:43] [endnoteRef:44] Much of the phosphorus from this manure is entering the Chesapeake Bay, directly or through its tributaries. [40: USDA, 2013. ] [41: Frontier Group, 8. ] [42: USDA, 2013. ] [43: Frontier Group. ] [44: Chicken litter refers to chicken manure mixed with feathers. Waste is collected from chicken production organizations and often spread on fields as litter. ]

Figure 12. : Poultry production for each state in the Chesapeake Bay watershed in 2007. Maryland produces the greatest amount of poultry compared to the other watershed states.Perdue Farms, headquartered in Salisbury, Maryland, employs poultry farmers throughout the state. Many of these farmers produce a variety of other crops, and use chicken litter as fertilizer on their agricultural lands. Excess manure is distributed to nearby farms. However, unequal distribution of chicken manure in the state has led to high levels of phosphorus in Marylands soils. According to recent soil tests, over three-quarters of fields on Marylands Eastern Shore, and half of the fields throughout the state are over-saturated with phosphorus. A 2002 study, which looked at soil samples from four counties in the state where large-scale chicken production takes place, showed that over half of samples had phosphorus levels that exceed crop needs, and pose water quality risks to the Chesapeake Bay.[endnoteRef:45] [45: Frontier Group]

Phosphorus levels increased in the Bay in recent years.[endnoteRef:46] The 2014 State of the Bay report from the Chesapeake Bay Foundation (CBF) found that phosphorus levels rose in areas in the Potomac and James River, and off of Marylands Eastern Shore. Given that large-scale chicken production is prevalent on Marylands Eastern Shore, CBF attributes higher phosphorus levels in this area to manure-related phosphorus pollution. This same report awarded the Chesapeake Bay a health index score of D+.[endnoteRef:47] The state of the Bay may be slowly improving, but it is a long way from healthy. Limiting pollution runoff from agriculture and chicken manure, one of the biggest contributors to poor water quality in the Bay, will go a long way toward upgrading the Bays health score. Maryland, with high production levels of poultry and chicken waste, could lead the way in improving Bay health by enforcing new proposed phosphorus regulations for its farms and agricultural lands. [46: Karl Blankenship, Long Term Improvements of Phosphorus Reduction in Chesapeake Bay Fading Away, Bay Journal, February 1, 2015, http://www.bayjournal.com/article/water_quality_monitoring_shows_some_long_term_improvements_fading_away ] [47: CBF, State of the Bay, 2014, http://www.cbf.org/about-the-bay/state-of-the-bay-report-2014. ]

Chapter III Endnotes