The Chesapeake Bay Watershed is located in the USA’s mid-Atlantic coastal region ( Figure 1 ) (Goetz et al., 2004). The Bay is approximately 35 km long on an axis from north and south. Meanwhile, the width varies from 20 km in its mouth to 45 km in the middle and a few in the upper (Garzon et al., 2018). Five major rivers cover the Watershed: Susquehanna, Potomac, Rappahannock, York, and James (Du and Shen, 2017).

The socio-economic region is defined by six states and the District of Columbia. The Watershed extends into New York State in the north and contains half of Pennsylvania, most of Virginia and Maryland, parts of Delaware and West Virginia, and the whole District of Columbia (Arnold et al., 2021). The land use within the Watershed is diverse. Industrial and high-density urban development is on the west side of the Bay. Meanwhile, commercial agriculture dominates the eastern shore (DeLuca et al., 2004). Population growth is occurring near the coast and in the two bigger rivers, the Susquehanna and the Potomac (CBF-Population, 2023).

The water input from the rivers and the Atlantic Ocean set up a strong stratification, which creates long resident times for fresh water and nutrients (Kemp et al., 2005). An average of 2,300 m³/s of freshwater flows from the Watershed into its 74.4 km³ water volume, with the Susquehanna providing ~50% of the flow. The Susquehanna significantly affects the stratification, sedimentation, nutrient levels, dissolved oxygen, and pollution of the Bay (Kemp et al., 2005; Du and Shen, 2017). The high stratification, long resident time, and geometry of the Bay make this a productive system, with efficient nutrient use and a tendency for depletion of oxygen (Kemp et al., 2005).

One of the tools to identify the management of a socio-ecological system like the Chesapeake Bay Watershed eutrophication is the driver–pressure–state–impact–response (DPSIR). The framework reports and analyzes environmental problems to identify barriers and develop holistic management responses (Carr et al., 2007; Elliott et al., 2017). Elliott (2014) and Smyth et al. (2015) modified the framework to address perceived issues (Gari et al., 2015), expanding the structure to become DAPSI(W)R(M) (Elliott et al., 2017) which stands for drivers–activities–pressures–state of change–impact (on human welfare)–responses (as measures).

Elliott et al. (2017) defined the drivers as “the basic human needs” based on the early work of Maslow (1943). Maslow (1943) proposed a pyramid with the human needs of an individual as a five-tier hierarchical structure. The first two hierarchies are related to survival and safety (e.g., food, air, water, and protection from nature or predators). The third and fourth hierarchies are related to physiological needs (e.g., love, sense of belonging, and self-esteem). These first four levels are referred to as “deficiency needs” because the individual will be motivated to satisfy them. The fifth and last hierarchy is self-fulfillment, which relates more to the need for self-actualization (Maslow, 1943; Elliott et al., 2017).

The drivers lead to human activities to satisfy human necessities. The activities used in the framework are related to actions that introduce pressures on the natural ecosystem. These pressures change the state’s natural system, leading to impacts on human welfare. Finally, the impact requires responses (as measures) (Elliott et al., 2017). The expanded framework has been applied in a variety of coastal issues and environments, as well as the river mouth system such as the “Magdalena delta” (Gallo-Vélez et al., 2022).

The social actors and stakeholders of the socio-ecological system were defined according to the Newton and Elliott (2016) typology, which classifies the actors according to their roles in the system. The typology includes six types of stakeholders. “Inputters” create pressures, such as contaminants or fertilizers. “Extractors” develop activities like fishing or water extraction. “Beneficiaries” receive the benefits for their needs; the drivers, the extractors, and inputters. “Affectees” suffer an impact on human welfare because of the degradation of the system. “Regulators” are administrative bodies with legislative competency that implement the management responses as measures. “Influencers,” are the stakeholders concern about the state of natural systems that can influence change, such as scientists, researchers, teachers, nongovernmental organizations (NGOs), and the media (Newton and Elliott, 2016).

The Chesapeake Bay is a complex socio-ecological system with a background of extensive research and management, resulting in a vast body of complex, interrelated information. A comprehensive literature review with all the current quantitative and qualitative information on eutrophication was developed. Table 1 summarizes the quantitative sources. The qualitative sources are shown in the Results section.

Most of the quantitative information was taken directly from the sources and adapted for visual representation in this article. One of the primary sources of information is the Chesapeake Progress webpage (https://www.chesapeakeprogress.com/). The Chesapeake Progress’s main goal is to have accurate, up-to-date, and accessible information. Therefore, the datasets for nutrients, annual flow, and water quality were taken from this source.

The application of the DAPSI(W)R(M) framework facilitates the process of identifying current links, structures, and dynamics of the socio-ecological system eutrophication. Table 2 summarizes the representation of the literature review analysis. Table 2 has three divisions: on the right, there is the DAPSI(W)R(M) framework; each row represents a component of the framework; and in parenthesis, there is a small description of the same. The second column is the Chesapeake Bay coastal system management issues linked with eutrophication. The number on the left, in brackets, is a way of representing the link between each row component. Finally, the last columns are the sources where each piece of data was collected.

Using the methodology of Newton and Elliott (2016), the conceptual map of Figure 13 was created for the stakeholders that participate in or are involved in the eutrophication of the Chesapeake Bay system.

In Figure 13 , the stakeholders in almost all the categories are the residents of the Chesapeake Bay Watershed. In extractors, they represent the urban/suburban development that has cleared the land for roads, homes, and businesses (Kemp et al., 2005; CBP-Dev, 2023). As inputters, the residents load nutrients from wastewater and urban/suburban discharges (CBP-Nutrients, 2023). Their benefits are food security due to the extensive agriculture and food industry, aesthetics and housing, and job security, which has high economic importance in the USA (Kemp et al., 2005; Walsh et al., 2017; Bilkovic et al., 2019). The people living in the Chesapeake Bay Watershed can also be influencers, participating in management or directly contributing to the Bay’s health (CBF, 2023; CBP-Nutrients, 2023). However, because the Watershed is very diverse, people feel more connected by the political boundaries, as there is a difference in governmental dependency on rural and urban development (McKendry, 2009).

The main activity and source of nutrients (~60%) in the Chesapeake Bay is agriculture, with 28% of cover in the Watershed (Williams et al., 2009). Agriculturalists were extractors until the mid-nineteenth century, when fertilizer use allowed the reduction of deforestation, after which they became fertilizer inputters (Kemp et al., 2005).

Living near the Bay provides a range of recreational and aesthetic activities. Real estate markets have provided this unique service and have become one of the beneficiary’s stakeholders (Walsh et al., 2017). The same activities that benefit this group also benefit tourism, which, in turn, benefits the residents. In 2009, tourists spent $58 billion in Maryland, Pennsylvania, Virginia, and Washington DC, supporting 600,000 jobs, contributing $14.9 billion in labor income, and paying $9.4 billion in taxes (Phillips and McGee, 2016). The Chesapeake Bay provides countless valuable and quantifiable economic goods and services. These include food availability, such as fish, crabs, clams, and oysters. Additionally, the last also contributes to the shipping and fishing industries. On the other hand, the beautiful scenery promotes recreation, tourism, and some of the country’s highest property values (Phillips and McGee, 2016).

Fisheries provide substantial jobs and tourism in the Bay; the estuary is home to 345 species of finfish and 173 species of shellfish, many of which have been fished commercially and recreationally for generations (CBF-Fisheries, 2023). In 2016, the Fisheries Economics of the USA report by the National Oceanic and Atmospheric Administration (NOAA) indicated that the commercial seafood industry in Maryland and Virginia contributed 1.4 billion in sales, almost 539 million in income, and more than 30,000 jobs to the local economy (CBF-Fisheries, 2023). The main commercial fisheries are blue crabs and oysters, although there are also striped bass, menhaden, and shad (Paolisso, 2007).

There are two fisheries stakeholders; the first is positioned in extractors and includes oyster fisheries. The other commercial fisheries are not presented, mainly because of their lack of relation to eutrophication. The over-extraction of oysters has impacted nutrient filtration time, which has increased eutrophication in the Bay ( Figure 10 ) (Kemp et al., 2005). However, the oyster industry, including catch, sale, shucking, packing, and shipping, has contributed millions of dollars to the region’s economy, which means the oysters have an important economic role in the socio-ecological system (CBP-Oysters, 2023).

The other fisheries stakeholders are positioned as affectees. The main cause of habitat loss in the Chesapeake Bay is eutrophication. The algae blooms deplete oxygen and block sunlight and have affected the entire Bay ecosystem with consequences for fish resources (Boesch et al., 2001; Morgan and Owens, 2001; Frankel et al., 2022). Buchheister et al. (2013) found that the increase in nutrients can lead to lower habitat availability for fish. Additionally, Morgan and Owens (2001) have linked eutrophication in the Chesapeake Bay to outbreaks of Pfiesteria, a toxin that causes lesions on fish; there is also physiological stress and death to fish species and other aquatic organisms. Moreover, the combination of ecosystem degradation and excessive fishing pressure has depleted the stocks and set the stage for a decline.

The Chesapeake Bay’s governance is divided into six states in the USA, so it is important to elaborate on the regulator’s stakeholders. The system was the first estuary in the nation targeted by Congress after the rapid loss of wildlife and aquatic life. Since then, several written agreements have guided the efforts to reduce pollution and restore the ecosystem, led by the CBP. The CBP partners include federal and state agencies, local governments, nonprofit organizations, and academic institutions (CBP-Who, 2023).

In 2009, the CBP began drafting a new agreement to accelerate restoration and align federal directives with state and local goals to create a healthy Bay. The partners gathered input from citizens, stakeholders, academic institutions, local governments, and more to draft an inclusive, goal-oriented document that addresses current and emerging environmental concerns, the CBWA (CBP-Who, 2023). The initiative to incorporate, consult, and lead new stakeholders to participate in management has been rising to benefit the system’s well-being.

Millions of dollars have been spent researching eutrophication and water quality in the Chesapeake Bay. This has yielded an enormous amount of data, information, and knowledge. Water quality improvements are evident (Frankel et al., 2022), but improvements have been slow despite numerous restoration activities (Chang et al., 2021). Solutions that will result in the improvements required to achieve restoration goals remain elusive. The DAPSI(W)R(M) analysis summarized and synthesized the extensive research, management, and governance around the Chesapeake Bay issue of eutrophication. Furthermore, the results of the stakeholder typology analysis defined their role in a participatory process.

Good water quality and a healthy watershed are vital to human welfare and well-being, which is why there is robust environmental management in the region. This has allowed social benefits such as food security for the agriculture, fishing, and food industries; housing and aesthetics; and job security (Kemp et al., 2005; Walsh et al., 2017; Bilkovic et al., 2019). The current governance structure and economy are based on growth (Hickel et al., 2022) without sufficient attention to sustainability. Under “business as usual,” the degradation of ecosystem services will continue until it has a significant IMPACT on human welfare, the economic sectors of fisheries and tourism, as well as the well-being of residents (Phillips and McGee, 2016; Hickel et al., 2022).

Overall, there is extensive ecosystem-based management with significant engagement of stakeholders, which benefits the management of water quality. There are existing laws, policies, implementation, and accountability tools based on scientific knowledge. Despite all this, the issue of eutrophication has not yet been resolved. There are several theories about this, mostly attributed to the lag time and climate change context (Meals et al., 2010; Du et al., 2018), but also societal barriers and obstacles (Boesch, 2019).

Challenges for stakeholders and regulators remain. Science and policy working together can bridge these barriers, broaden and diversify management options, and assess the implementation and effectiveness of management measures. An adaptive management tool such as DAPSI(W)R(M) can be used in a cyclical manner to periodically monitor management success.

Most of the drivers identified in the Chesapeake Bay have fundamental biological and physiological needs. The increase in pressures is mainly linked to population growth, which will keep growing beyond the carrying capacity of the ecosystem. This is mainly because many stakeholders are unaware of the valuable ecosystem services and the externalities from the multiple activities that exert pressure on the system. This is a classic case of the tragedy of the commons (Hardin, 1968). A bridge is needed that links ecosystem health to the well-being of residents. Part of the solution may be more active community-based management for governing the commons, as advocated by Ostrom (1990) and his followers. These are not new ideas; however, they continue to be difficult to put into practice in large systems with many social actors and powerful economic sectors. In this context, financial tools and mechanisms, such as economic incentives or tax reduction, may be an attractive mind-set changer and more effective than taxes and fines, which engender counter-lobbies and expensive lawsuits. Furthermore, social benefits can be added to the environmental benefits. Moore et al. (2007) found that involvement in the management of land for conservation helps mental health, social capital, feeling safer in the local community, and the development of skills. This was particularly true for the male members of the study, who had higher levels of health and better satisfaction with daily activities.

There have been extensive research, management, and governance responses to the economic sectors and activities that contribute to the eutrophication of the Chesapeake Bay. The focus has been to decrease the nutrient runoff from point/nonpoint sources through land protection in the watershed and restoration projects of vital habitats at the coast. There are BMPs for agriculture activities and management for fisheries. There is the Clean Water Act, Clean Air Act, TMDL, and WIP document to follow for management plans. Additionally, there are accountability tools to follow the management plans. The Chesapeake Bay Foundation has been highly effective in advocating for environmental protection and rehabilitation. The report cards have kept the stakeholders, manager, and public informed about the overall ecological health.

Urban sprawl from urban development sectors in the Chesapeake Bay Watershed is another activity that has limited regulation, rather than regulation for limitation and sustainability. Substantial segments of the US population continue to distrust science-based solutions (Krause et al., 2019), especially in the context of private property, so this becomes a social–political barrier to many science-policy solutions. Inadequate urban development regulations result in land-use change, urban sprawl, and more infrastructure. Limits to urban development are lacking, and there is poor accountability for the consequences of urban growth along tributaries and shorelines. This increases pressures from effluents from housing and industry and NO _x emissions from transportation and industry and decreases connected forest and other nutrient buffers. Bibri et al. (2020) proposed a bridge to decrease sprawl by applying “compact city growth,” a relatively high-density, mixed-use city with efficient public transport that encourages walking and cycling, with obvious health and fitness benefits as well as an improved environment. Furthermore, compact city growth can be beneficial to decreasing car dependency, increasing connected forests, and enhancing social activities by reducing social exclusion (Saif et al., 2018).

The Chesapeake Bay Program has regulated the pressures on the ecosystem from point and nonpoint sources. However, there is a lot of uncertainty about the total nutrient input from nonpoint sources. Numerical models have reconciled nonpoint source calculations with observation (Frankel et al., 2022). The numerical model results have conveyed a sense of confidence in the implementation and effectiveness of the management (Meals et al., 2010; Boesch, 2019). However, these results have not met the stakeholders’ expectations (Meals et al., 2010; Boesch, 2019; Frankel et al., 2022). Frankel et al. (2022) attribute the lack of expected results to the increase in temperature because of climate change. A bridge proposed by Boesch (2019) is that numerical models must be as complex as necessary and be constantly compared with observations.

The bridge to manage expectations is to clearly understand the difference between models and observation results. There are BMPs and CASTs in agriculture. The latter one is a Web-based nitrogen, phosphorus, and sediment load estimator tool that helps apply the BMP in an area. This provides users with the most cost-effective practices to reduce pollutant loads. Since 2014, agriculturists have voluntarily implemented many BMPs as they feel responsible for the water quality (Fox et al., 2021). The application has generally been well received by farmers, as it shows significant cost savings (Ator et al., 2020).

Significant nutrient reduction could be achieved by improving in agricultural practices. Farmers commonly exceed fertilizer application rates with no extra crop yield (Boesch, 2019). Unpopular (Guo et al., 2021), but effective accountability tools can be applied to estimate the cost of damage this is causing and apply tariffs or fines according to the “polluter pays” principle (Ambec and Ehlers, 2016). Policies and regulations limiting farming subsidies to those using lower application rates can reduce nutrient pressure significantly. Such regulations benefit economic sectors that depend on the Chesapeake’s water quality and ecosystem health, such as fisheries, real estate, and tourism. They also save the farmers money on excessive and expensive agrochemicals.

Other mutually beneficial “win–win” options are possible. For example, livestock operation in the Watershed has increased the nutrient input from manure (Kleinman et al., 2012). This excess manure can be managed, up to a point, as natural fertilizer in crop production (Kleinman et al., 2012; Yılmaz et al., 2019). The farmers that apply manure could reduce the application of synthetic fertilizers and maintain regional food security while reducing environmental pressures. The main barrier is the lack of financial support for lower-income farms (Fox et al., 2021). Once more, financial instruments, such as progressive taxation of agrochemicals, could provide a bridge of financial support and subsidies to farms to implement the BMPs.

In this context, nutrient buffers, e.g., riparian vegetation and wetland conservation, are cost-effective management measures for nonpoint sources. Currently, the management of vital habitats is increasing, but with little improvement in the water quality (CP-VitalHabitats, 2023). Hence, clear management plans and realistic goals are needed.

There are no clear accountability responses when laws and policies are violated (Ostrom, 2011). Engaging responsible parties at the highest governance level is an important bridge to achieving the desired outcomes (Boesch, 2019). Once again, financial mechanisms, such as fines and incentives, may be useful. Menold (2021) proposed three governance solutions: improve incentives, courts to handle violations, and fines for violations. A good example of this is the over-extraction of bivalves, especially oysters, which has degraded an important ecosystem service provided by the biofiltering of oyster reefs. The collected fines could be used for research on sustainable oyster harvest methods or oyster cultivation. The incentives could support fishermen or residents from the Watershed that foster oyster reefs on their property or fishermen that have developed their own sustainable harvest methods. Oyster restoration seems to be increasing; however, the population is less than 1% of the original, and there is also a high risk of diseases and mortality due to climate change and decreased reef habitats (Boesch, 2006; Najjar et al., 2010; NOAA-Fisheries, 2023). So, the management questions remain: What extent of oysters’ reefs is needed to significantly improve the water quality? Where is the best place to locate them to ensure their natural growth? How many have died since the restoration started? How many are still alive since the restoration started?

After the implementation of ecosystem-based management, there has been an improvement in the decrease in hypoxia area extent and duration (Frankel et al., 2022). However, there has been a higher expectation of the results from the stakeholders (Meals et al., 2010; Frankel et al., 2022). The reality is that it can take years to restore an ecosystem, if at all (Duarte et al., 2009; O’Higgins et al., 2014). Even complex models do not faithfully reproduce ecosystem complexity because there are always sources of uncertainty. Nevertheless, this does not mean that the management to abate eutrophication should stop. On the contrary, there should be more decisive actions and the simultaneous application of several management measures. There are positive signals that if the current reduction from TMDL in the region is met, the health of the Bay will continue to improve, even with the potential impact of climate change (Irby et al., 2018).

Climate change can change biochemical and physical flows. In Chesapeake Progress, there is a climate change category, which shows the continuous monitoring and assessment of the impacts and the start of an organization for climate adaptation (CP-Climate Change, 2023). The current projections of climate change in the Chesapeake Bay Watershed are temperature increase, accelerated SLR, and altered precipitation. These cannot be managed, so they can only be mitigated. Maryland is the leader in coastal adaptation for climate change. The Maryland coastal adaptation report cards of 2021 (RC-CoastalAdaptation, 2023) gave a score of B− (~70/100). The categories of ecosystem and planning climate change have significant investment to achieve adaptation goals, and there is progress in flooding and socio-economic adaptations. However, there are still challenges, such as more data, updated goals, and improved access to funding (RC-CoastalAdaptation, 2023). Therefore, more work is required.

The bridge to this barrier is to develop, implement, and assess climate change adaptation projects, such as green infrastructure management options. Green infrastructure has the potential to mitigate urban flooding, attenuate indoor temperatures and heat islands, improve air quality, and muffle noise (Nieuwenhuijsen, 2021). Additionally, it improves aesthetic and environmental injustices. Green infrastructure can also increase economic well-being, reduce violence, improve health, and develop a sense of belonging (Wood et al., 2017; Nieuwenhuijsen, 2021). On the coastline, the green infrastructure could focus on the oyster reefs and a “living shoreline.” Examples of these living shorelines as natural or constructed habitats include emergent marsh grasses, riparian vegetation, and coarse woody debris (Davis et al., 2006). That could be used to decrease the degradation of coastal habitats, stabilize the shoreline from the SLR acceleration, and mitigate the input of nutrients from increased precipitation.

A long-term, cost-effective bridge can be provided by science communication. This is a useful tool to educate the public and enhance their awareness of ecosystem services and benefits. A good understanding of the cost and benefits to public well-being and welfare is fundamental to gaining public support. This can lead to a better understanding by nonscientific actors of how models work, what the lag time is, and how climate change uncertainties can change the expected results.

However, the question remains as to why the management has not been able to decrease the eutrophication more rapidly. This is mainly because changing the system has costs for some or many stakeholders. However, the impacts on the social welfare of a degraded ecosystem are also multiple. They include loss of shoreline, loss of open natural space, loss of affordable food resources, and loss of job security. The main barrier is a lack of understanding of how changes in the socio-ecological system of health impact socio-economic science and policy, which requires complex interdisciplinarity (Elofsson et al., 2003).

Once more, the main bridge is education about sustainability and growth. Understanding sustainable development (Keeble, 1988) makes the implementation of regulatory requirements and accountability more acceptable to stakeholders and stimulates engagement in participatory processes. Unfortunately, most residents of the Bay do not feel a “sense of place” related to the environment (Ardoin, 2014). Developing a sense of place would mean that residents would feel a greater responsibility for environmental health and be more active in community-based management. This could improve mental health and a sense of accomplishment (Moore et al., 2007).

Using a range of synergetic environmental management measures requires multi-stakeholder engagement and changes in the socio-economic culture. For example, “citizen science” actions to engage residents to be more involved in the management of the region relieves cost burdens on regulatory agencies for environmental monitoring (Tulloch et al., 2013).

Multiple bridges are necessary to solve the complex issue of eutrophication. The coordination of communication between stakeholders is critical. It is therefore vital for the science stakeholders to communicate science and knowledge at all levels, from schoolchildren to decision-makers, so the long-term benefits of changing “business-as-usual” practices are fully understood in the science-policy context (Tambe et al., 2023). The government also has a vital role in encouraging holistic management that considers the benefits of the ecosystem health, increases accountability and incentives, and creates new projects to develop the social benefits.