Public—Private Partnership Governance for Accessible Tourism in Marine Protected Areas (MPAs)

: Tourism is a relevant sector in terms of social development, considering its contribution to the quality of life for people with special needs. Accessible tourism, by virtue of its complexity, requires the development of studies on the collaboration among different actors. This leads to this article’s research interest in the public—private partnership (PPP) as a managerial tool that allows cooperation and that can support the development of accessible tourism objectives in marine protected areas (MPAs). Applying the case study methodology, we investigate certain aspects characterizing PPPs governance. Answering the two proposed research questions, we conclude that (1) sharing similar moral values facilitates trust between the partners and (2) differing skills of the partners represent advantages in facing the complexity related to accessible tourism objectives.


Introduction
Tourism represents a sector that can play an important role in the pursuit of sustainable development [1,2] as it is able to ensure the achievement of objectives for economic growth [3], environmental conservation [4], and social development [5,6].
Under this last aspect, of particular relevance is the contribution that tourism can offer to improving the quality of life for people with special needs and, therefore, their social inclusion [7], especially in light of the benefits that they can receive from activities conducted in contact with nature [8]. Although the sector presents accessibility problems, tourism has the potential to become a valuable tool for social inclusion [9].
In this perspective, the health and well-being of disadvantaged people pass through the concept of accessible tourism [10], which refers "to the adaptation of environments and of tourism products and services so as to enable access, use and enjoyment by all users, under the principles of Universal Design" [11].
Tourist facilities for disabled people in Europe are only 9% of the total [12]; the European Union has highlighted the potential expansion of the tourism sector linked to disability (missed opportunities) which, in addition to social impacts, can also have significant economic effects (e.g., job creation).
In this respect, recognizing collaboration as a principle for directing tourism practices toward greater sustainability [13], this study focuses on the management tool represented by public-private partnerships (PPPs), to which the academic world is paying increased attention by virtue of its ability to be effectively functionalized toward the achievement of sustainable development objectives [14,15]. This is also in view of the 17th Sustainable Development Goals of the United Nations 2030 Agenda, which aims to strengthen the means of implementation and renew the global partnership for sustainable development.
Partnerships are complex and durable forms of cooperation between the public and private sectors based on the sharing of risks, costs, benefits, resources, and responsibilities and providing public services [16]. Good governance, coordinative participation, leadership, and managerial experience are the main factors that, when properly implemented, can ensure the success of the partnership formula [17].
In this regard, although public management literature has placed more emphasis on the analysis of formal relationships [18], a particular form of collaboration is constituted by informal partnerships between public bodies and non-profit organizations, ensuring the socio-economic well-being of the community of reference [19]. Although scarcely opted for by public management due to their often casual and temporary natures, the establishment of such relationships may depend on the local culture and the strength of pre-existing relationships [20].
From the above, the objective of the present study emerges, which is to investigate governance characteristics that distinguish PPPs as a managerial tool for the development of accessible tourism objectives in the context of protected natural areas. In this work, these objectives are all those goals related to make the heritage of protected natural areas accessible for people with special needs, e.g., guided tours for the elderly, activities for people with physical disabilities, scuba diving for the blind, etc.
To contribute to the managerial literature on the topic of PPPs in supporting accessible tourism in protected natural areas, this paper is structured as follows. The Section 2 contains the literature review from which the research questions arise. The Section 3 is dedicated to the description of the methodology used. The Section 4 illustrates the two case studies analyzed in this paper, and the Section 5 contains a discussion of the results of the case studies considered.
Finally, the Section 6 contains concluding remarks, as well as the limitations of the work and possible lines of future research.

Literature Review and Research Questions
The accessibility of tourist destinations is a real concern for people with special needs [21]. Nevertheless, the attention paid by the academic literature concerning social sustainability to address the needs and opinions of these people has been, over time, limited [22]. It is only in the last two decades that the academic world has shown an increased interest in tourism accessibility for people with special needs, to the point creating a real and constantly evolving field of academic research [23,24]. From research on tourism and disability, we have the conceptualization of so-called accessible tourism [25].
Israeli [26] was one of the first authors to highlight the critical issues, in terms of accessibility, that disadvantaged people face when visiting tourist sites. Subsequently, Darcy and Dickson [27] articulated the first definition of accessible tourism as tourism that enables people with special access needs to act independently through universal tourism services. To emphasize the interaction between stakeholders as a factor likely to improve accessibility, Darcy and Buhalis [28] later adapted this definition: "accessible tourism is a form of tourism that involves collaborative processes between stakeholders that enables people with access requirements, including mobility, vision, hearing and cognitive dimensions of access, to function independently and with equity and dignity through the delivery of universally designed tourism products, services and environments".
More recently, accessibility has been considered in the literature as an element of competitiveness for tourist destinations [29,30], given the better quality of tourist offerings that more accessible environments can provide. In any case, greater accessibility of tourist destinations, in addition to being relevant from a financial point of view (there is a genuinely accessible tourism market), has the potential to promote the achievement of social objectives [31], confirming Wearing and Darcy's [32] claim that the effective pursuit of social sustainability requires tourism management to adopt more inclusive management principles and practices.
Considering the benefits that people with special needs derive from activities conducted in close contact with nature [33], a key role in terms of promoting barrier-free tourism can be played by protected natural areas, which can profitably integrate the in-stitutional aims of environmental protection with the achievement of relevant objectives for social sustainability [34]. This function of protected natural areas seems more important if we consider that natural heritage is a universal good that everyone should be able to enjoy and that participation in the activities of a protected area can create greater awareness of environmental issues and, therefore, lead to responsible behavior toward the environment [35].
A shared orientation in the accessible tourism literature is that stakeholder collaboration can positively influence the implementation of accessible tourism solutions [23,36,37], including, as stated by Michopoulou and Buhalis [38], organizations of people with special needs. Establishing relationships with such entities may be a valid approach for the implementation of tourism policies that integrate the expectations of disadvantaged people [39], thus ensuring the involvement of these people in effectively accessible tourism experiences [31].
In this perspective, PPPs are tools essentially focused on collaboration between different stakeholders [16], as collaboration through multi-stakeholder partnerships can be an effective way to support initiatives aimed at developing greater sustainability in tourism [40].
Indeed, with specific reference to partnerships implemented within protected natural areas, such collaborations not only contribute to the creation of a different attitude toward biodiversity conservation issues [41] but also improve the understanding of the values of protected areas and bring social benefits to local communities [42]. The latter, appropriately involved in the management of the protected area, can guarantee a greater effectiveness of the environmental protection policies implemented by the managing bodies [43], also contributing, more generally, to the pursuit of sustainable tourism [44]. This confirms what Lockwood [45] asserted, namely the opportunity of an inclusive governance of protected natural areas.
Moreover, considering what Sica et al. [34] asserted, protected natural areas represent tourist destinations that are scarcely used by people with special needs, mainly due to accessibility problems. The relevance of the partnership formula appears more evident if considered as a tool to support the implementation of more accessible tourism. Indeed, partnerships have the potential to increase universal accessibility with regard to tourist sites in general [46][47][48][49][50], and with specific reference to protected natural areas [51,52].
The significant role of the partnership model in the promotion of accessible tourism is confirmed by the World Tourism Organization (UNWTO) in the Manual on Accessible Tourism for All-Public-private Partnerships and Good Practices [53]. The UNWTO highlights the capacity of PPPs to allow disadvantaged persons to independently enjoy the tourist services designed for all and to contribute to the management of tourist demand in such a way as to guarantee the conservation of the cultural, environmental, and social resources that are the object of the tourist offering.
In view of the value of the partnership instrument highlighted above, it is advisable to pay adequate attention to the issue of governance when implemented. Indeed, good governance is a critical factor for any type of partnership, on which the success or failure of public-private cooperation may depend [54][55][56]. In this sense, with particular reference to partnerships developed within protected natural areas, the contribution of Eagles [57] is relevant. In identifying and comparing the possible management models of protected natural areas, he considered collaboration between public entities and non-profit organizations as the management approach that comes closest to the ideals of good governance.
In particular, one of the elements necessary for effective governance of public-private partnerships is mutual trust between the partners [58,59]. Defined as "confident reliance on a person, group, organization, or system in the face of risk and uncertainty" [60], mutual trust between members of a partnership is a condition that does not arise spontaneously. Instead, mutual trust must be built, managed, and strengthened over time through regular collaborative interactions, considering that it can be achieved if all parties involved perceive the opportunity to derive value from the cooperation [61]. Furthermore, where the operational context does not facilitate the building of this condition, the ability of partnerships to generate the desired outcomes may be compromised [62].
In this respect, the actors entrusted with leadership within the PPP play a key role, as it is they who are entrusted with the task of developing a collaborative culture and ensuring that the components of the partnership trust each other [63].
In this regard, the sharing of objectives, actions, and information between partners is a basic prerequisite for building the mutual trust that Panchapakesan et al. [64] considered necessary to improve the performance of the partnership, to increase the commitment of the parties involved, to limit the risk of opportunistic behavior, and to reduce transaction costs, thus ultimately ensuring long-term public-private relations. Moreover, the development of trust allows the transfer of time and resources generally dedicated to the process of monitoring behavior (aimed at reducing uncertainties and opportunism in the pursuit of objectives) toward a more productive use, such as the satisfaction of mutual expectations and the resolution of problems and conflicts potentially arising from the implementation of the partnership model [65].
Panchapakesan et al. [64] and Abdullah and Khadaroo [65] identified three dimensions in which trust is articulated: competence, integrity, and benevolence.
The competence dimension of trust relates to the trustor's perception of the resources and capabilities that the trustee will employ to meet the expectations of the trusting party. The integrity dimension of trust, conversely, concerns the observance of the shared moral principles accepted by the partners. Finally, the benevolence dimension of trust refers to the trustor's positive expectation that the trustee is well-intentioned and, therefore, will refrain from opportunistic behavior.
In addition to this, Gazley [18] believed that the development and maintenance of trust is an essential condition on which the realization of so-called informal partnerships rests, acting as an element on which public management can leverage to manage and direct partnerships without formal agreements. Pozil and Hacker [19] also leaned in this direction: the establishment of informal partnerships is due to the creation of trust, acting as a force that guides the relationship between the parties toward the achievement of a common goal.
In this paper, focused attention is on a particular type of natural protected area represented by marine protected areas (MPAs). These areas play important roles not only in the conservation of marine environments [66,67] but also socially [68]. MPAs, besides contributing to the well-being of people and communities [69,70], can play equally relevant roles in meeting the needs of disadvantaged people and, therefore, in achieving accessible tourism objectives, for example, by providing underwater routes that allow disabled people to enjoy marine environments [71].
Consequently, considering that the lack of trust can weaken PPPs implemented in protected natural areas [72] and that, as is clear from the literature, the partnership tool can support the development of accessible tourism, the first research question that this contribution aims to answer is the following.
RQ (1): How is it possible to facilitate trust between partners for the pursuit of accessible tourism objectives within MPAs?
As mentioned above, a further element for the successful functioning of PPPs in support of accessible tourism is the competence of the partners, which, in practice, can facilitate the establishment of mutual trust. Although benevolence and integrity take time to emerge, competence can be assessed at the initial stage of the public-private relationship [65].
Generally, the choice of public institutions to partner with the private sector stems from the awareness that these forms of cooperation, if properly implemented, make it possible to functionalize the specific technical expertise that private actors usually possess into the provision of public goods and services [73,74]. A technically competent private partner is an essential prerequisite for achieving a successful partnership [75].
However, the structural complexity of the partnership formula requires that the public side also possesses adequate skills for the activation [76] and governance [77] of partnership projects to structure and execute sustainable partnership contracts [78]. Therefore, when recognizing partner expertise as a key factor for successful partnerships [79] the public and private sides of the partnership must have the necessary skills to steer the collaboration toward achieving positive outcomes [80].
In this perspective, it is crucial that the public and private actors entrusted with the management of the partnership have the managerial skills that Mohd Som et al. [63] claimed were essential for good negotiation skills, for the correct identification of the responsibilities that each member has in the partnership scheme, and therefore, for the construction of solid and lasting relationships. Interpreters of the partnership are also required to possess the necessary competencies to be aware of the different cultures and goals underlying the actions of the public and private sectors.
From the above emerges the second research question that guides this contribution. RQ (2): How can the different competencies of the partners impact on the realization of accessible tourism objectives within MPAs?

Methodology
The research methodology applied is that of multiple case studies [81], which is particularly indicated in situations such as the one considered in this paper, characterized by the analysis of several elements.
The prerequisite for the case choice is represented by the identification, based on previously analyzed literature, of two aspects that constitute important elements for the use of partnerships as a tool for accessible tourism. The first variable is represented by mutual trust between partners [58,59] as a preparatory element to the implementation of the partnership. The second variable relates to the different competencies [75,80] that, through the partnership, need to be implemented to oversee the complexity inherent in the sustainable tourism objectives that are being pursued.
Consequently, the cases chosen are: the partnership between the MPA of Porto Cesareo and the Albatros association; and the partnership between the MPA of Porto Cesareo, the University of Salento, and the European Research Centre for Technologies Design and Materials (CETMA). Table 1 below summarizes the variables and the related selected cases. The research design included two units of analysis: the first unit of analysis examined the elements connected to trust between partners and the impact this had in terms of achieving the objectives of accessible tourism, which are the object of the partnership; and -the second unit of analysis examined the system of competencies generated through the instrument of the partnership and how they had repercussions in terms of the pursuit of accessible tourism objectives.
The information source used for the analysis of the cases is represented, first, by documentary analysis, for which official documents were consulted (partnership agreement, final reports, etc.). In addition, a further source of information is represented by semi-structured interviews [82] conducted by telephone between 2020 and 2021, lasting between 40 and 60 min and addressed to the MPA's top management and its partners.
The use of the case study methodology, using different units of analysis, made it possible to analyze the object of the research from different points of view, integrating the data and information gathered from the different sources mentioned above.

Partnership and Accessible Tourism: The Case of the Porto Cesareo Marine Protected Area
Established by a Ministry of the Environment decree on 12 December 1997, the Porto Cesareo MPA is located in Puglia, a region in southern Italy. More precisely, the MPA covers the coastline of the Porto Cesareo and Nardò municipalities, both in the province of Lecce in the eastern part of the Gulf of Taranto, which is the northernmost area of the Ionian Sea.
With its 16,654 hectares of protected marine area and 32 km of coastline, the Porto Cesareo MPA is the largest in the Puglia region and the third largest in Italy. Since 2011, it has been included in the list of Specially Protected Areas of Mediterranean Importance.
This MPA, whose management is entrusted to a consortium formed by the province of Lecce and the two municipalities in whose territory the reserve lies (Porto Cesareo and Nardò), is characterized by two A zones of integral reserve, two B zones of partial reserve, and a C zone of general reserve.
Preservation of the marine environment, promotion of compatible socio-economic development, and implementation of environmental education and scientific research projects are the main institutional aims pursued by the MPA.
In addition, the MPA aims to implement a management of anthropogenic activities that improves the environmental and social quality of tourism in the area and enhances stakeholder awareness and competence. In this sense, the MPA adheres to the European Charter for Sustainable Tourism as an operational tool to increase the involvement of local stakeholders operating in the tourism chain for the realization of more environmentally and socially sustainable tourism.
In addition to the importance of the MPA from an environmental point of view, the area in which it is located has a rich heritage of historical and architectural interest that increases its potential for tourism. For example, in the bay of Porto Cesareo, at a shallow depth and not far from the coast, it is possible to observe monolithic columns of cipolin marble dating back to Roman times, when the port called Portus Sasinae existed in the area. Moreover, one of the most striking features of the area is the system of fortified towers along the coast that were once used by the local population to defend the territory from Saracen attacks.
These peculiarities make the area in question a place with a strong vocation for not only tourism but also history, art, and culture.
These aspects make the Porto Cesareo MPA particularly interesting both for its potential as a tourist attraction and for the relations it develops with other subjects to conduct its activities.

Accessibility of the Seabed: The Partnership with the Albatros Paolo Pinto Project Association
The Albatros Paolo Pinto Project Association was developed to commemorate the sporting activity of Paolo Pinto, a world champion long-distance swimmer who, in the last years of his life, was tormented by the progressive loss of sight. The association conducts activities aimed at pursuing social, moral, sporting, recreational, and leisure objectives, with the ultimate aim of improving the lives of blind people and their social integration.
Albatros Paolo Pinto Project Association, together with diving instructor Manrico Volpi, developed a new teaching method for teaching scuba diving to the blind. Thanks to its effectiveness, which has been consolidated over the years, the World Confederation of Underwater Activities has recognized this method as an international teaching method for the blind.
To promote "diving for all", this association organizes courses, with the issue of licenses, for blind students, instructors, assistant instructors, dive masters, guides and companions, following the abovementioned methodology, recognized as Albatros Scuba Blind International (ASBI).
In this regard, the Albatros Paolo Pinto Project Association and the MPA of Porto Cesareo have created a partnership aimed at training ASBI-qualified environmental guides capable of offering blind divers the opportunity to enjoy the natural beauty of the MPA. In particular, from the interview with the referents of the two institutions involved, it emerged that the partnership was aimed at training not only underwater guides able to accompany blind persons during dives in the waters of the MPA but also blind persons, so that they can acquire the necessary skills to conduct underwater visits.
The training courses covered by the partnership were held at the MPA's underwater territories in Porto Cesareo, with the involvement of candidates identified by their needs and available professionalism and in compliance with the minimum standards envisaged and required by the ASBI regulations. During the courses reserved for blind people and technical divers, great emphasis was placed on the knowledge and protection of the marine environment and its species. During these courses, the blind diver dives very close to the substrate and, due to the environmental knowledge of the accompanying guide, is able to recognize, with a delicate and non-invasive tactile approach, many species that populate the seabed. The immediate recognition of the encountered species' scientific name is possible for the visually impaired due to a special underwater binder with Braille captions that the guide brings with him and allows the diver to read, such that the diver can mentally reconstruct every single species encounter.
The training of local divers has enabled the creation of a permanent network in the area of subjects specialized in making the marine and historical-architectural heritage of the MPA accessible to blind tourists. The initiative has allowed people with special needs to enjoy an innovative and inclusive tourist service and, moreover, has strengthened the MPA's image of inclusion, usability, and professionalism, thus increasing its profile of tourist accessibility.
From the interviews with the referents of those involved in the partnership, it emerged that "the technical and practical exchanges that took place between the association and the MPA biologists made it possible to develop ideas, expand services, and increase specific knowledge regarding the usability of diving and ways of reducing environmental impact". In addition, an aspect emerged that was fundamental for the solidity of the partnership between the two institutions and for the effectiveness of the training course undertaken. As stated by the interviewees, this aspect is that "the values and objectives pursued by the association have a clear affinity with the principles and aims concretely pursued by the Porto Cesareo MPA".
In fact, as previously mentioned, the association's action aims to promote equal opportunities in carrying out recreational activities by reducing the physical and social barriers that all too often affect the world of the blind, thus favoring immersion experiences with a high cognitive value. In turn, one of the founding purposes of the Porto Cesareo MPA is to promote social development compatible with the naturalistic features of the protected area, as well as to disseminate and divulge knowledge on the characteristics of marine environments.
This confirms the evidence emerging from the literature analysis on the importance of trust between partners. In this specific case, the affinity of the partners' reference values induced a mutual trust that allowed them to cooperate effectively for the achievement of a common objective.

The Partnership for the Puglia Seascapes Project: Accessible Tourism and Technology
The main objective of the Puglia Seascapes-Porto Cesareo project, which took place in 2020, was to create a model for the technological use of one of the most evocative archaeological contexts of the Porto Cesareo MPA, namely the remains of the navis lapidaria wreck (which ran aground around the 2nd-3rd century A.D. near the coast of Torre Chianca) and its cargo of five Roman cipolin marble columns lying on the sandy bottom at a depth of a few meters. Specifically, to transfer playful and educational information to all visitors, the project envisaged the creation of immersive and interactive multimedia content related to the most important moments of the stranding of the boat and its cargo from Euboea (an island in Greece) using virtual reality visors and touch monitors placed in specific and dedicated spaces. In this way, the accessibility of the underwater cultural heritage is guaranteed for disabled and elderly people, for whom diving is impractical.
The realization of the project saw the collaboration of three main partners: From the interviews with the referents of the partners, it emerged that a strong point of the partnership is represented by the different competences that the three partners have similarly put in the developed collaboration, which have allowed for its success through technology to make the archaeological heritage in the Porto Cesareo MPA accessible to all visitors (especially those with special needs).
The MPA of Porto Cesareo has its own means and marine operators available, and the University of Salento provided the scientific documentation necessary for the digital restitution of the morphology of the territory, the navis lapidaria, and its cargo. In particular, the University of Salento provided data, reconstructive hypotheses of the grounding, and a photogrammetric analysis, due to which CETMA researchers, using special software, were able to reconstruct the three-dimensional (3D) geometric model of the vessel and the columns it carried.
For its part, CETMA, in collaboration with the MPA and the University of Salento, conducted complex survey campaigns of the five cipolin marble columns lying at a depth of approximately 5 m. The digital acquisition campaigns of the submerged asset were conducted using innovative instrumentation dedicated to 360 • video filming, which made it possible to arrive at an exact representation of the columns' current state.
Based on the reconstructive hypotheses provided by the archaeologists of the University of Salento and using Autodesk Maya software, CETMA then proceeded to define the 3D model of the vessel. The production of the digital contents followed two main operational phases: 3D modeling/geometry control and definition of texture mapping, shading, and displacement to be applied to the single 3D models. Subsequently, the CETMA team returned the 3D digital model of the Roman columns and conducted the 3D analysis and modelling of the morphology of the coastline of Torre Chianca in the 2nd-3rd century AD.
After digitally translating the scientific data, the next step was to identify the points of interest on which to focus the development of the 3D 360 • scenes. Then, the storyboard was developed to define the guidelines for the digital narrative.
To support the narration and storytelling, an ad hoc virtual reality application was designed and developed using "game-based learning" methodologies, with the aim of promoting the user's learning, entertainment, and emotional involvement. Finally, during the implementation phase, CETMA's IT developers prepared a detailed diagram of the processes, describing in a precise way all the graphic functions, the possible interactions of the users with the environment, and the methods the model could evolve during the realization. The user of this experience, totally immersed in the scene, can look around with 360 • of freedom and choose which scene to explore through a 3D user interface that connects the different views.
As stated by the interviewees, "the achievement of this result was possible thanks to the different skills of the partners, which, appropriately functionalized, allowed the development of a virtual reality application with undoubted potential in terms of accessible tourism".

Discussion
From the analysis of the cases, certain reflections arise regarding the two aspects that emerged from the literature and that led to the formulation of the two research questions and the selection of the case studies: trust and different competences. These are two factors of particular importance in the implementation of partnerships [18,79], which, in this work, are studied as a tool for the development of accessible tourism.
Regarding the first factor, the literature review has shown that mutual trust between partners is an essential condition [19], which, not arising spontaneously, must be built over time [61]. For this to happen, it is also necessary for the operational context to be conducive to the establishment of this condition [62].
In this regard, in order to answer the first research question, from the analysis of the first case study, it was possible to deduce that collaboration between subjects with similar values can facilitate the achievement of mutual trust. In other words, the partners did not need long periods to establish that their respective operational contexts could be effectively functionalized toward a common goal and that, consequently, they could trust each other. The mutual trust that the collaborating parties placed in each other's partners made it possible for the partnership to be fruitful from the outset and, therefore, for an accessible tourism service to be developed.
With reference to the shared values, the first case study highlights the relevance of the integrity defined as the observance of the shared moral principles [65]. These principles are represented by the honesty of the partners, their efforts in fulfilling agreements, observing contractual rules, complying with ethical standards, realizing information useful to the partnership and sharing socio-cultural context.
The examined case showed that it is possible to assess integrity in advance, albeit formally and based on the simply expressed values. In other words, it must be considered that the partnership's social character, the involved partners' nature and activity, what the partners declared in their constitutive documents or on their institutional websites (e.g., regarding their behavior in partnerships already implemented or their ethical values) allowed, already upstream of the cooperation to positively assess the reciprocal intentions pursued and, therefore, the attitude to refrain from opportunistic behavior. This consideration is valid for the integrity by which is meant the observance of those moral principles shared and accepted by the partners that are at the basis of the affinities that emerged from the analyzed case.
Although integrity takes time to emerge, it follows that, in a partnership in which the subjects involved pursue similar values, it can be formally ascertained from the initial stages of cooperation. Consequently, the sharing of values facilitates greater initial trust between the partners, allowing them to reduce their focus on monitoring each other's behavior and to focus on improving the level of accessibility of the tourism experience offered.
It is believed that less attention paid to monitoring reciprocal behavior, in the name of common values, should not result in unconditional trust in the respective partners to avoid the perspective of one party prevailing over the other and, therefore, compromising the virtuousness of the partnership. Therefore, an aspect to be monitored in this type of partnership is the search for a balance between the trust that partners place in the affinity of reference values and the appropriate monitoring of the actual conduct implemented.
With reference to the second factor investigated, some considerations arise from the second case study on the benefit and potential criticalities that the functionalization of different competences can generate to achieve the objectives of accessible tourism. In the first place, it is considered that the cooperation at the basis of the project in question resulted in a greater usability of the knowledge. In other words, as a result of sharing competencies, the data and hypotheses derived from the research conducted by one of the partners was understood not only by the others but also by a public (especially considering people with special needs) for whom direct access to underwater environments is almost impossible. In this sense, the use of virtual reality facilitated the dissemination of archaeological research results and the dissemination of the area's historical knowledge among the disabled and elderly (i.e., among people who by virtue of reduced motor or sensory capacity would otherwise not know the historical and architectural heritage of the area).
Second, the technological partner also benefited from the sharing of competencies. The technicians were able to experiment with new techniques for digitizing the submerged archaeological heritage. Therefore, the MPA may favor the future replicability of similar accessible tourism experiences at other sites. Therefore, if it is true that public institutions generally resort to partnerships with the private sector by virtue of the specific technical skills with which the latter is endowed [73,74], it is also true that the public sector can play a central role in experimenting with technological applications capable of increasing the tourism offer's level of inclusiveness.
Finally, in the context of the case examined, the different skills of the partners represented a strong point of the partnership. At the same time, the operational phase of the partnership and the different competences (i.e., scientific, biological, technological, etc.) might have led to conflicting approaches. In this sense, the mediation capacity of the partners becomes of relevant importance to establish an effective collaboration, with the ultimate goal of achieving the expected results of the partnership. This highlights that while the different competencies of the partners represent an element of strength of the partnership, they must be carefully monitored to avoid contrasts that may have a negative impact on the achievement of accessible tourism objectives.

Conclusions and Managerial Implications
The PPP tool is an increasingly important solution in ensuring inclusive tourism services and, therefore, in increasing the accessibility profile of tourist destinations [47,50].
Among the different types of tourism sites, protected natural areas represent entities that can play a relevant role in achieving social objectives in tourism. Indeed, as institutions, they have the task of making their resources available for the promotion of a more inclusive tourism [34].
Hence, the research interest was toward PPPs as a tool to support accessible tourism [48,49] within a particular category of protected natural areas, namely MPAs. Specifically, this paper focused on two types of partnerships implemented in the Porto Cesareo MPA and aimed at ensuring accessible tourism experiences for people with reduced motor or sensory capacity.
Two research questions guided the present work. RQ (1): How is it possible to facilitate trust between partners for the pursuit of accessible tourism objectives within MPAs?
RQ (2): How can the different competencies of the partners impact the realization of accessible tourism objectives within MPAs?
With reference to the first research question, the analysis of the partnership between the Porto Cesareo MPA and the Albatros Paolo Pinto Project Association showed that trust between the partners could be facilitated through collaborations between subjects with similar values. Integrity facilitates the establishment of mutual trust, which, in turn, makes it possible to reduce the attention paid to controlling the respective behaviors and to focus on strengthening the level of accessibility of the tourism service offered. This allows the establishment of partnerships effectively oriented toward tourism accessibility in which the priority, deriving from shared values, is represented by the disadvantaged person and the ways in which he or she can use tourism services.
With regard to the second research question, from the analysis of the partnership between the Porto Cesareo MPA, the University of Salento, and CETMA, it emerged that the different skills of the partners represent an undoubted advantage in support of the achievement of accessible tourism objectives. The functionalization of the different competences toward accessible tourism purposes allows the achievement of advantages, such as the greater usability of scientific and historical knowledge by subjects with special access needs or the possibility of experimenting with new technological applications. Moreover, considering that accessible tourism has relevant effects from social, environmental, and economic points of view [31,36,83,84], the involvement of various competences in the partnership makes it possible to oversee all the intrinsic dimensions of accessible tourism effectively. At the same time, it is essential that the distinct competencies be appropriately managed to avoid clashes between partners that may ultimately compromise the successful achievement of accessible tourism goals.
From the above concluding remarks, certain managerial implications arise: 1. the relevance of the sharing of common values highlights the need for pre-partnership analyses of the moral values which characterize partners. Managers need to pay close attention to the partners' moral values through various types of surveys (communicated values, activity already conducted, network of acquaintances, etc.). In this way, the appropriate value prerequisites are verified for the functioning of the partnership and, ultimately, for the pursuit of accessible tourism objectives; 2.
the sustainability of the partnership based on shared integrity underlines the importance of ongoing monitoring of the correspondence between previously known moral values and the moral values followed during the partnership. This is in order to keep the relationship between partners transparent and oriented toward common values that facilitate the achievement of the results of tourism accessibility; 3.
the positive impact that different competencies can have on the sustainability of partnerships implies the need for managers to develop skills both in identifying necessary and complementary competencies for accessible tourism and in maintaining a balance of these competencies such that they can be effectively integrated.
The main limitation of the contribution is represented by the focus on accessible tourism experiences resulting from partnerships implemented within a specific MPA. Therefore, it will be interesting if future research analyzed similar partnership experiences implemented in other MPAs. This will make it possible to broaden knowledge regarding the management of partnership tool with a view to achieving accessible tourism objectives.

Conflicts of Interest:
The authors declare no conflict of interest.