Students take a "coral quiz", San Salvador, Bahamas.
The Chesapeake Bay, an estuary unique to the United States, was once called “the immense protein factory” (Boesch et. al. 2001). It is the largest estuary in the United States having 150 tributaries (Karuppiah and Gupta 1996), a length of 300+ km, and a total tidal water area of 11000 km2 (Boesch et. al. 2001). The Bay watershed includes the District of Columbia and the states of New York, Pennsylvania, Maryland, Delaware, Virginia, and West Virginia (Harman-Fetcho et. al. 1999). Due to the complexity of the watershed, the Chesapeake Bay is more vulnerable to disturbance. “The Chesapeake Bay estuarine drainage area receives the highest pesticide application of any coastal area in the USA…” (Harman-Fetcho et. al. 1999). Although agricultural practices have contributed a large portion of pollutants into the Bay, large urban areas such as Baltimore, MD and Washington DC lie on the drainage basin of the Bay (Harman-Fetcho et. al. 1999) and contribute other non-point source pollutants to the water. Pollutants have taken their toll on the Bay ecosystem and have damaged once pristine waters and a number of valuable organisms such as the oyster populations, blue-crab populations, and the sea-grass beds. These pollutants not only affect the wildlife but have also begun to affect those responsible for much of the degradation, humans.
Non-point source pollution, also known as run-off, continues to be an issue for many watersheds around the country, contributing to a large portion of water quality problems. Unlike point source pollution where contaminants can be identified at their source and traced back to a single discharge area, non-point source pollution cannot be traced back to a single point because of the number of ources that contribute to it (What is non-point source (NPS) pollution 1997). Many contributors of non-point source pollution include agriculture, development, and residential practices. Forms of non-point source pollution include pesticides, fertilizers, yard litter, dog waste, sedimentation, hazardous chemicals, and garbage (Schuler 2000 and What is non-point source (NPS) pollution 1997).
The Chesapeake Bay has not escaped the negative effects of non-point source pollution. In the Bay, non-point source pollution is predominately from agricultural practices and urban runoff, which add excess nutrients to tributaries of the Bay (Staver and Brinsfield 2001) and cause over enrichment (Boesch et. al. 2001). A study found that excess nutrients were a primary factor contributing to poor water quality in the Bay (Staver and Brinsfield 2001). The two main nutrients impacting the Bay are nitrogen and phosphorous. Nitrogen and phosphorous are important for the growth of plants and animals including cellular growth and tissue production and are naturally found in soil, water, and air (Nutrient pollution 2001); however, excessive amounts create problems.
Phosphorous is particle bound, meaning it attaches to soil particles, and can be transported into waterbodies as erosion (Boesch et. al. 2001). The addition of phosphorous into the Bay is thought to depend on the geochemistry and erodibility of sediments in the watershed rather than being solely influenced by agriculture (Jordan 1997). Nitrogen is transformed into soluble nitrate and is leached through soil into groundwater. Nitrogen discharges often increase as the proportion of cropland in the watershed increases (Boesch et. al. 2001) and also are thought to depend on anthropogenic inputs. Anthropogenic inputs of nitrogen come from a variety of sources. The various forms of nitrogen contribution, many of which are considered anthropogenic, include atmospheric deposition, fertilizer applications, fixation of nitrogen by crops, denitrification, and livestock waste. Both phosphorous and nitrogen have lead to an increase in eutrophication in the Bay where plankton production increases and submerged vegetation decreases (Jordan 1997). Studies have found that phosphorous and nitrogen can limit production where phosphorous is more limiting at lower salinity levels and nitrogen is more limiting at higher salinity levels (Boesch et. al. 2001). It has been found that by using nitrogen removal technology, approximately 60% of the pollution in the Bay can be reduced (Maki 2002).
Both nutrients enter the Bay directly through oceanic inputs, atmospheric precipitation, shipping and recreational vessels, and erosion, or indirectly through stream and groundwater inflow. Atmospheric input is the greatest direct source of nitrogen and oceanic inputs is the greatest direct source of phosphorous. Land-based inputs are the most indirect sources for both phosphorous and nitrogen and are the largest source of both the direct and indirect inputs. Land-based inputs are primarily in the form of non-point sources (Pionke et. al. 2000).
Agricultural practices and urban runoff are prime culprits for contributing to the excess of phosphorous and nitrogen in the Chesapeake Bay (Pionke et. al. 2000). The Chesapeake Bay watershed has 7.2 million acres of cropland (Biemer 2002), which produce major crops including soybeans, corn, wheat, tobacco, and barley (Harman-Fetcho et. al. 1999). According to studies, croplands “receive higher anthropogenic inputs of nitrogen than do pastures and nonagricultural lands” (Jordan et. al. 1997). Agriculture practices including cropland, pasture, hay land, and non-point confined animal sources make up 33% of the land area of the Chesapeake Basin. These practices are the largest land-based contributors to nitrogen and phosphorus inputs into the Bay (Pionke et.al. 2000) contributing approximately 30% of the nitrogen and phosphorous to the watershed (Biemer 2002). The reasons agriculture is such a large contributor of nutrients is due to the amount of land area (94%) relative to the size of the body of water (6%) and because it is the “largest intensive land use in the Chesapeake Basin” (Pionke et.al. 2000). On the Delmarva Peninsula agriculture uses approximately “3 million pounds of herbicides, insecticides, and fungicides annually” (Karuppiah and Gupta 1996), and the Peninsula is one of the largest concentrations of poultry farms in the United States (Jordan et. al. 1997). Poultry waste contributes nitrogen and phosphorous as well as trace heavy metals to Bay waters and tributaries (Karuppiah and Gupta 1996).
Along with agriculture, the Chesapeake Bay continues to be used by millions of people (Woodard 2001) for a number of activities including crabbing, fishing, sailing, trading, oyster harvesting, and wildlife watching. There are a number of people that reside in the watershed itself as well as directly on the Bay. As development around the Bay continues to increase, so do the amount of nutrients going into the Bay. Due to this, urban runoff contributes a large portion of non-point source pollution to the Bay (Woodard 2001). Urban runoff could become a larger contributor to non-point source pollution above agriculture because agriculture is declining and nutrient management strategies are being implemented by farmers (Nutrient pollution 2001).
The most common practices and everyday activities of the public are contributing to watershed pollution. Dog walking may appear to be the most surprising activity since it would seem to cause the least amount of water pollution; however, it has been found that in many urban watersheds dog waste has been a major source of fecal coliform and pathogens (Schuler 2000). Common activities including gardening, yard upkeep, car washing, automobile use, and construction contribute to various forms of pollutants including yard fertilizers, pesticides, sediments, metals, oil, and toxic chemicals, many of which run off with surface water or percolate into groundwater (Schuler 2000). Faulty septic systems are also contributors to water pollution. These systems contribute large amounts of nutrients to groundwater due to waste not being treated or only partially treated (Schuler 2000). In some rural areas, and most likely many more, groundwater contamination is largely due to faulty septic systems (Maki 2002).
Surface runoff is a major contributor to poor water quality because of paved surfaces. Paved surfaces have taken the place of forests, wetlands and grasslands. These surfaces do not allow water and hence pollutants to be absorbed at slow rates, rather water will accumulate and run off in large amounts. This has a major impact on streams by increasing erosion, destroying vegetation, and widening stream channels all of which impact the Bay ecosystem (EPA 1997).
The nutrients inflicted on the Bay from agriculture and urban practices create a chain reaction of events. Overall increases in nutrients promote eutrophication. Large algal blooms are the result of eutrophication which decreases dissolved oxygen levels in the water and in turn decreases aquatic vegetation, harms wildlife, damages water supplies, decreases the aesthetic value, and overall weakens the Bay ecosystem (Nutrient pollution 2001). Along with eutrophication, sedimentation and runoff reduce the amount of sunlight needed by aquatic plants. Sedimentation covers spawning grounds, clogs fish gills, increases water levels during wet periods, lowers water levels during drier periods, increases sediment loads, and increases water temperatures. Overall, many native organisms will have to relocate because they cannot survive in the altered environment (EPA 1997).
Organisms that are most commonly impacted by poor water quality in the Bay include the American oyster, Crassostrea virginica, the blue crab, Callinectes sapidus, and bay grasses. At one point in history oysters were so plentiful that they were harvested in the millions of bushels rather than in the thousands of bushels, which they are currently harvested at. Oysters are important organisms to the Bay. They provide valuable habitat to other organisms due to the reefs they form and also act as filters, keeping the Bay’s water healthy. When the oyster populations were healthy they were able to filter the entire Bay every three to four days, which kept nutrients at proper levels. However, today the oyster population is now only “one percent of its historic level” and filtering the Bay takes approximately one year to complete. Oyster populations are being predominately threatened by pollution. Excess nutrients causing eutrophication and algal blooms impact oyster larvae development. Pollutants such as metals are toxic to juvenile oysters, and an increase in sediments limits their feeding (Chesapeake Bay Program 2002). Diseases including those from the parasites MSX and Dermo have also threatened oyster populations (Woodard 2001 and Surowiec 2002).
The blue crab population has been impacted by the affects of non-point source pollution. This organism is valued highly in the Chesapeake Bay and is “the object of the most productive commercial and recreational fishery in the Chesapeake Bay” (Blue crab 2002). Over a 20-year time period the crab population has decreased by 70 percent (Woodard 2001) as a result of low oxygen levels created by nutrient pollution and the decline of sea grass beds, which serve as important protective habitat for blue crabs (Blue crab 2002 and Hyland 2001).
Sea grasses, which are an important habitat for many organisms and important nutrient filters, are declining due to non-point source pollution as well. These grasses provide food, protective cover, and oxygen to organisms and remove nutrients from the water. However due to excess nutrients from runoff of fertilizers, pesticides, and animal wastes, which contribute to eutrophication, the amount of sunlight these grasses need in order to survive has been severely limited. Sediments also block sunlight and add nutrients, which are attached to soil particles (Bay grasses 2001). Historically, there were 600,000 acres of sea grass that lined the Bay’s shoreline (Bay grasses 2001). The Chesapeake Bay Foundation estimates that nutrient pollution has alone “depressed grass growth in the Bay, leaving coverage at just 12 percent of its historic level” (Hyland 2001). Also, “grass beds yield greater fish density and diversity than grass-free areas and provide the needed protection to small fish” (Hyland 2001). In whole, sea grass beds are an important component in the Bay ecosystem.
Overall, non-point source pollution causes a chain reaction of events in the Chesapeake Bay. Whether it is the oyster populations, the blue crabs, the sea grasses, the small minnow, the heron, or the microorganisms, everything is impacted by the Bay’s health including humans. Although health risks can occur due to poor water quality and because there is not a clear relationship between regulatory, conservation, and public health efforts, it has been difficult to develop a clear understanding of the overall status of the watershed in evaluating the impacts on public health. The Chesapeake Bay is one of the most studied ecosystems in the world; however, the level of knowledge is limited in regards to the influence pollution has on public health (Boesch 2000).
As with any area that suffers from pollution there is always the potential for human health to be impacted. The Chesapeake Bay is no exception. The growing concern over public health is due to the increase in population, development, and consumption of the resources the watershed provides (Burke et. al. 1999). The risk to human health either increases or decreases depending on exposure to toxic chemicals, risk of infection from pathogens, and the level of biotoxins produced by harmful algae (Boesch 2000). Over the past century health issues that have impacted the Bay include acute infectious diseases, cumulative risks of chronic diseases, issues concerning diseases related to contaminated drinking water, shellfish contamination, and fish consumption advisories to name a few (Burke et. al. 1999). Seeing that eutrophication is one main concern of the Chesapeake Bay, it is suggested that this type of condition can increase various microorganism pathogens, which can cause human infection such as the bacteria Vibrio spp. There is however uncertainty as to whether human health risk is increased by degraded ecosystems. This uncertainty is partially due to the effort in protecting public health and the unclarity in the prediction that eutrophication and climatic warming increase human risk to pathogens (Boesch 2000).
The Chesapeake Bay does contain a number of algae that produce toxins. One in particular, Pfiesteria piscicida, has been found to cause fish kills and could be harmful to humans. This dinoflagellate has caused lesions on fish but has caused short-term memory impairment in fisherman and those workers involved with sampling the rivers that have had the outbreaks (Boesch 2000). In general, human illness from Pfiesteria is the result of the toxins that this algae releases into the water (What you should know about Pfiesteria piscicida 2002). Although it is thought that Pfiesteria was due to the over-enrichment of tributaries (Boesch 2000), research continues to be conducted and uncertainty still remains regarding the reasons for Pfiesteria particularly in relation to current outbreaks of the dinoflagellate (Haas 2002).
In order to understand the relationship between pollution and disease a number of things need to be understood. These include “identifying the source of pollution, tracking pollutants through the environment, identifying pathways and degree of population exposure, understanding the exposure level that is harmful to human health, and measuring the incidence of adverse health effects in the population.” Also by understanding both the frequency of disease in the population and the health status of Bay communities, the health impacts of the Bay will be better understood (Burke et. al. 1999). In general, to minimize public exposure to harmful pollution and poor water quality it is important to minimize non-point source pollutants entering the Bay and to maintain the Bay ecosystem.
In order to protect human health and the ecosystem of the Bay, extensive monitoring programs continue on the Bay waters and tributaries. A multi-group and state effort to maintain the health of the Bay has helped to keep the Bay from declining anymore than it already has. The Chesapeake Bay Program has been conducting extensive monitoring of water quality since the 1980’s (Boesch 2000). Various inventories of the land and water and seafood products are taken in order to observe how human activities influence the water quality but also to monitor pathogens and toxins in the water to prevent negative impacts. The extensive monitoring program measures all aspects of water quality and organisms in the water including nutrient levels, suspended sediments, toxins, temperature, salinity, freshwater inflow, dissolved oxygen, submerged aquatic vegetation, benthos, fish and shellfish and also includes not only habitats but also recreational areas. Results are made available to the public (Boesch 2000).
Along with monitoring the Bay a number of additional strategies are being implemented to help reduce nutrient inflow. Such strategies include a Farm bill aimed to increase water quality by reducing nitrogen in the Bay from agriculture (Biemer 2002) and the Chesapeake Bay Agreement, which originally aimed to reduce nutrients at their source, has shifted to control land sources and nutrient sources along with increasing non-point source control particularly in agriculture (Pionke et. al. 2000). Restoration plans are being adapted and improved in order to reach goals of reducing urban sprawl, preserving more land, and reducing nitrogen inputs into the Bay as well as improving oyster populations. Nitrogen levels have currently been reduced by clean-up efforts; however, the levels are still too high and need to be further reduced to improve water quality (Woodard 2001). Extensive public education outreach programs are also being implemented to inform the public of their influence on the Bay watershed.
In sum, a number of factors have contributed to the degradation of the Bay. However, it can be concluded that the pressures from human activity have been at the fore front of this degradation influencing nutrient loads and sedimentation as well as the risk to their own health. There is an overall connection between polluted ecosystems and human health; however, uncertainties continue to remain as to the degree of risk to human health by contaminated water sources. All in all, if human pressures are reduced, the Bay may be able to recover on its own (Woodard 2001). Hope is not lost for the recovery of the Bay. The Chesapeake Bay is a valuable ecosystem that through the combined efforts of state and federal governments as well as a number of committed organizations and individuals, has begun to recover from the pressures it has faced for decades.
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