A Review of a Decade of Local Projects, Studies and Initiatives of Atypical Inﬂuxes of Pelagic Sargassum on Mexican Caribbean Coasts

: This study collates and reviews the state of the art in the phenomenon of atypical pelagic Sargassum inﬂuxes in the coastline of the Mexican Caribbean, focusing on projects, studies and initiatives that have been conducted in the country for a decade. We integrated multisectoral and multidisciplinary knowledge and identiﬁed gaps and strengths in current knowledge. Initiatives and projects conducted in Mexico are numerous, diverse and valuable. However, interdisciplinary and transdisciplinary research and interinstitutional coordinated actions in the medium- and long-term are still lacking. Because of this, there is an imbalance of actions in different knowledge areas that prevents this phenomenon from being addressed in a comprehensive way. Furthermore, the funding opportunities for Sargassum research projects and other initiatives seem to respond to the events of massive inﬂuxes, without continuity or long-term planning. Attention is mainly focused on urban and touristic areas, so impacts to rural or uninhabited zones are unknown. This review represents a stepping-stone towards an integrated multisectoral effort to shift the perspective from Sargassum being a “national problem” to a “national resource,” considering and fully understanding the ecological importance of this macroalgae as a ﬂoating ecosystem and its potential as an economic resource once it massively arrives in Mexican coastal areas.


Introduction
Pelagic Sargassum is a genus of macroalgae (Sargassum natans and Sargassum fluitans) that constitutes an irreplaceable floating marine ecosystem in the open ocean [1]. These algae provide shelter, anchorage, food and migration routes for different marine species [2][3][4]. This ecosystem, documented in writing for the first time by Christopher Columbus in 1492, occurs in an area bounded by the North Atlantic subtropical gyre [5]. Given its ecological importance, in 2012 the Convention on Biological Diversity included the Sargasso Sea as an Ecologically or Biologically Significant Marine Area (EBSA) [6]. Moreover, in 2014, the Hamilton Declaration on Collaboration for the Conservation of the Sargasso Sea was signed. Its purpose was to provide a framework for intergovernmental collaboration to promote measures to minimize the adverse effects of human activities on this ecosystem, including overfishing, intensity of maritime traffic and pollution of water with plastic waste [7]. Which are the best strategies to collect Sargassum along the coast without environmental and ecological effects? • What is the Sargassum elemental content variation in space and time? • How could Sargassum be sustainably used as an economically valuable resource, help in its immediate remotion? • What is the potential of Sargassum as raw material? • How much Sargassum will arrive, when and where?
The purpose of this paper is to describe the state of the art research of the phenomenon of atypical pelagic Sargassum influxes, the main knowledge gaps and needs, and the technological development and innovations achieved in Mexico in a decade (2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017)(2018)(2019)(2020)(2021) to shed light on the aforementioned questions. We described the state of the art through an exhaustive search process of existing information and the selection, organization and analysis of multisectoral sources of information.

State of the Art
A state of the art considers the most up-to-date or current research in a certain area or field of study. It is a modality of a review and documentary research that presents an analytical study of knowledge [17]. Through a state of the art, it is possible to understand the current trends and the main knowledge gaps in a specific subject. To describe the present state of the art we followed the two-phase method proposed by Londoño-Palacio et al. [18]. The heuristic phase consists of the searching for and compilation of information, while the hermeneutical phase consists of explaining, interpreting and analyzing the accumulated information [18]. The stages within each of these two phases are summarized in Figure 1.

Characteristics of the Heuristic Phase
For brevity purposes, we start describing our methods from stage 5 of Figure 1. During the information compilation stage, we considered several three-word combinations of the following keywords: "Sargassum," "sargazo," "arribazón," "atypical influxes," "Caribe Mexicano," "natans," "fluitans" and "Mexican Caribbean," and we searched the results from various sources and types of information (Table 1). For stage 6, we only selected documents that met at least two of the following criteria: (a) studies, projects or initiatives carried out in Mexico between 2010 and the first trimester of 2021, (b) direct references to Sargassum atypical influxes to the Mexican Caribbean coasts, (c) mention of the species S. natans and/or S. fluitans that arrive to Mexico and (d) projects or initiatives conducted in other countries where Mexican researchers participated either as principal investigators, or as co-investigators. The rationale for limiting the search process to these criteria was to obtain a focused review of management and research actions related to these macroalgae in Mexico.

Characteristics of the Heuristic Phase
For brevity purposes, we start describing our methods from stage 5 of Figure 1. During the information compilation stage, we considered several three-word combinations of the following keywords: "Sargassum," "sargazo," "arribazón," "atypical influxes," "Caribe Mexicano," "natans," "fluitans" and "Mexican Caribbean," and we searched the results from various sources and types of information (Table 1). For stage 6, we only selected documents that met at least two of the following criteria: (a) studies, projects or initiatives carried out in Mexico between 2010 and the first trimester of 2021, (b) direct references to Sargassum atypical influxes to the Mexican Caribbean coasts, (c) mention of the species S. natans and/or S. fluitans that arrive to Mexico and (d) projects or initiatives conducted in other countries where Mexican researchers participated either as principal investigators, or as co-investigators. The rationale for limiting the search process to these criteria was to obtain a focused review of management and research actions related to these macroalgae in Mexico. During this stage, experts were also identified and cataloged within the academic, private, civil, foreign and government sectors. Experts with at least two projects, initiatives or studies on Sargassum as principal investigators (or project leader) were included in this database. Additionally, previously existing directories in CONACYT and other federal government agencies (e.g., Instituto Nacional de Ecología y Cambio Climático (INECC)) were also compiled.

Characteristics of the Hermeneutic Phase
During stage 1 of the hermeneutic phase, two databases were generated, one for projects, studies and initiatives, and the other for experts. The first database (Supplementary File S1) provides an in-depth overview of the diversity of actions that have been conducted in Mexico to address the pelagic Sargassum in the country since 2010. The fields' description of this database can be consulted in Supplementary File S1.1. The second database (Supplementary File S2) provides a list of stakeholders (researchers, businesspeople, Non-Governmental Organizations (NGOs) founders, private consultants, government officials, etc.) who are experts in different areas related to the Sargassum phenomenon. Fields' description can be consulted in Supplementary File S2.1.

Findings on the Mexican Government Strategy to Address the Phenomenon
Based on the generated databases and interviews with subject-experts, we distinguished three historical stages of actions to address the phenomenon in Mexico from the federal, state and local governments: (1) Awareness of the problem: The massive influxes of Sargassum began to represent a social problem in Quintana Roo until 2015, when there was media coverage about these influxes for the first time; however, they were presented as a transitory event. This stage was characterized by an awareness that Sargassum is not a temporary situation with a limited impact, but will be a recurring wide-spread problem. The solutions implemented during this period were characterized by beach cleaning interventions by local and hotel authorities, with minimal intervention from the state and federal government, as well as very limited funding to generate new scientific knowledge.
(2) First actions: The massive influxes of 2015 and 2018 reframed the situation and its definition as a comprehensive, permanent and multinational challenge. The federal government invested 62 million Mexican pesos (~3 million USD) from the Fondo Nacional de Emergencias (FONDEN) and an additional budget of 240 million Mexican pesos (~12 million USD) for the Secretaría de Medio Ambiente Estatal de Quintana Roo (SEMA) for the removal of Sargassum from touristic beaches [19]. In 2018, CONACYT addressed the phenomenon from a scientific and technological development perspective. The same year, the congress of the state of Quintana Roo approved the "environmental sanitation tax" which is applied to tourists for hotel occupancy in Cancun. This tax seeks to guarantee beach cleaning and beach conservation financial resources for the municipality [20].
(3) The SEMAR decree: The Secretaría de Marina (SEMAR) has been coordinating Sargassum containment and management efforts by government decree since 2019 [21]. In support of this decree, CONACYT defined a scientific, technological and innovation agenda for the attention, adaptation and mitigation of the massive influxes of Sargassum on the Mexican coasts in 2019 [22]. This Agenda was published as a collaborative effort between various federal and local government institutions, as well as specialists and experts in different disciplines and areas of knowledge (https://conacyt.mx/sargazo/images/Agenda/ 2020/Agenda_Conacyt_Sargazo-2020_.pdf, accessed on 18 April 2022) [22]. This Agenda defines nine strategic and multidisciplinary lines to address the Sargassum phenomenon in a comprehensive manner at different timescales: (1) origin and ecological importance, (2) monitoring, modeling and early warning, (3) socioeconomic and environmental impacts, (4) containment, harvest and disposal, (5) potential uses, (6) restoration of affected ecosystems, (7) regulations, (8) communication and education and (9) international cooperation.

Findings on Knowledge Generation
A total of 185 projects, initiatives or studies concerning the pelagic Sargassum in Mexico were generated between 2010 and 2021. We identified nine additional projects with a starting date or results expected after 2021 (Supplementary File S1). Most were review articles (30%) (Figure 2). A considerable number of projects (137) did not reach the peer-review publication stage. The project "Sistema de Información y Análisis Marino Costero (SIMAR)" of the Comisión Nacional para el Conocimiento y Uso de la Biodiversidad (CONABIO) was the only identified project with databases for free download or public access. Of all the projects, 68% were developed by the academic sector ( Figure 3). Almost 30% of the projects were developed by four academic institutions: CICY, CINVESTAV, ECOSUR and UNAM ( Figure 4). Of all the projects, 68% were developed by the academic sector ( Figure 3). Almost 30% of the projects were developed by four academic institutions: CICY, CINVESTAV, ECOSUR and UNAM (Figure 4). Of all the projects, 68% were developed by the academic sector ( Figure 3). Almost 30% of the projects were developed by four academic institutions: CICY, CINVESTAV, ECOSUR and UNAM ( Figure 4).  Most projects (41%) were found under the strategic line of potential uses. We identified a total of eight Mexican granted patents, four within this line and four within the containment, harvest and disposal strategic line (Supplementary File 1). The second most common strategic line was that of socioeconomic and environmental impacts, with 18% of the total projects ( Figure 5). The less developed strategic lines, with longer temporal scales to achieve outputs, were those concerning the development of regulations and res- Most projects (41%) were found under the strategic line of potential uses. We identified a total of eight Mexican granted patents, four within this line and four within the containment, harvest and disposal strategic line (Supplementary File S1). The second most common strategic line was that of socioeconomic and environmental impacts, with 18% of the total projects ( Figure 5). The less developed strategic lines, with longer temporal scales to achieve outputs, were those concerning the development of regulations and restoration efforts of affected ecosystems. These accounted for only 1% of the identified projects ( Figure 5).
Next, we describe the content of each of these strategic lines and provide an overview focusing on what has been accomplished in Mexico and what the current consolidation needs are. Next, we describe the content of each of these strategic lines and provide an overview focusing on what has been accomplished in Mexico and what the current consolidation needs are.

Origin and Ecological Importance
The origin and causes of massive growth of Sargassum in the last decade are still being studied worldwide [11]. Blooms in the open ocean have been associated with changes in wind circulation and ocean currents [23]. Other hypotheses, such as the input of iron-and phosphorous-rich sand dust of the Sahara Desert [24] and the input of nutrients from river discharges [11], are still being tested. The identification and characterization of Sargassum species is also a critical component to understanding the bloom formations [25,26].
This strategic line also entails the importance of Sargassum in macro-and micro-ecological processes. For example, Sargassum is one of the main carbon sinks in the ocean, forming a trophic link between pelagic and benthic habitats [27][28][29]. Sargassum also forms important biological associations with many marine organisms [2][3][4].
Studies in this line were initiated in Mexico in 2010 (Supplementary File 1). Many (37%) of the identified projects regarding the origin of Sargassum atypical influxes are review articles (Supplementary File 1). Most of the studies (52%) are related to the ecological and environmental importance of Sargassum at the coastal scale and the identification and characterization of different morphotypes. Based on the compiled information, summarized by subarea, we described the existing knowledge and what is needed to consolidate this strategic line ( Table 2). These studies, projects and initiatives are further described in Supplementary File 3. Table 2. Knowledge advances from projects, studies and initiatives regarding the strategic line of origin and ecological importance.

Origin and Ecological Importance
The origin and causes of massive growth of Sargassum in the last decade are still being studied worldwide [11]. Blooms in the open ocean have been associated with changes in wind circulation and ocean currents [23]. Other hypotheses, such as the input of iron-and phosphorous-rich sand dust of the Sahara Desert [24] and the input of nutrients from river discharges [11], are still being tested. The identification and characterization of Sargassum species is also a critical component to understanding the bloom formations [25,26].
This strategic line also entails the importance of Sargassum in macro-and microecological processes. For example, Sargassum is one of the main carbon sinks in the ocean, forming a trophic link between pelagic and benthic habitats [27][28][29]. Sargassum also forms important biological associations with many marine organisms [2][3][4].
Studies in this line were initiated in Mexico in 2010 (Supplementary File S1). Many (37%) of the identified projects regarding the origin of Sargassum atypical influxes are review articles (Supplementary File S1). Most of the studies (52%) are related to the ecological and environmental importance of Sargassum at the coastal scale and the identification and characterization of different morphotypes. Based on the compiled information, summarized by subarea, we described the existing knowledge and what is needed to consolidate this strategic line (Table 2). These studies, projects and initiatives are further described in Supplementary File S3. Table 2. Knowledge advances from projects, studies and initiatives regarding the strategic line of origin and ecological importance.

Subarea What It Is Known Needs
Origin of the phenomenon The transport of Sargassum from the ocean to coastal areas is not well understood and several variables are [30]. The nutrient input from rivers is not likely the main explanatory variable of atypical influxes [31] Scientific evidence to support different hypothesis associated with massive growth; open-access databases of variables to support models Changes in biological and genetic structure of floating biomass (morphotypes) Sargassum morphotypes in Mexico differ from those reported in the Sargasso Sea [32] Systematized identification of species Morphology shows phenotypic variations according to habitat and season [25,26] Carbon sink and sediment supply to the deep sea and coasts Sargassum fixate CO 2 and it is a vital carbon sink and calcium carbonate producer for the coasts [33,34] Calcite production mechanisms in Sargassum and its epiphyte communities; Sargassum carbon flux measurements to deep ecosystems

Biological associations
Biological associations between Sargassum and various taxa vary in diversity and abundance according to the size of the Sargassum raft and its distance from the beach [3,4,35,36] Characterization of biological associations in open ocean, nearshore waters, and on the beach

Monitoring, Modeling and Early Warning
The use of remote sensors has helped to detect Sargassum rafts in the open ocean [37]. However, Sargassum tracking and quantification still present technical challenges. For example, satellite information is limited by cloudiness, which means that information on the presence and route of Sargassum may be lost for several days. Another limitation is the spatial and temporal resolution provided by satellites. High spatial resolution satellites (e.g., Sentinel-2, Landsat-8, Planet) do not collect data over large areas and their temporal resolution can be low compared to satellites of lower spatial resolution. Low spatial resolution satellites (e.g., MODIS, Sentinel-3) limit the detection of small and isolated Sargassum rafts and are not suitable for detection in coastal areas [38].
Numerical models that can predict when and where Sargassum rafts that are detected in the open ocean may arrive are needed. Current models have not been highly effective in predicting influxes, since Sargassum is not just a floating particle but a living organism that interacts with and responds to a changing and complex environment [39]. In the coastline, nested models at fine resolutions are still required [40].
An effective Sargassum early warning system must be based on robust remote and in situ monitoring that feed highly predictive numerical models to determine the probability of beach strandings. This would allow for a system akin to hurricane forecasting [41], with a major impact on containment, harvesting and other management strategies [37,42].
Mexican efforts in Sargassum detection and the development of a monitoring and an early warning system began in 2014 (Supplementary File S1). The federal government and academic sectors are currently working to solve the technical limitations of both remote sensing and numerical models (Supplementary File S3). There are also important civil society initiatives to produce "Sargassum traffic lights", a widespread tool to inform tourists about the amount of the macroalgae in touristic beaches (Supplementary File S3). What we know and have accomplished in Mexico in the main subareas of this strategic line, as well as the main requirements in order to consolidate it, are summarized in Table 3. Some of these studies, projects and initiatives are further described in Supplementary File S3. Continuous and systematic records of the occurrence of the phenomenon at fine temporal (i.e., daily) and spatial (i.e., meters) scales Sargassum population dynamics [50] Citizen Science for in situ monitoring [51,52] Improvements in statal telecommunication infrastructure (i.e., widespread free internet access) and massive informative campaigns

Socioeconomic and Environmental Impacts
Atypical influxes of Sargassum have ecological, economic and social impacts that need to be described and quantified. These impacts have multisectoral effects at the local, state and national levels [53]. Economic and social activities such as tourism and fishing are affected [54].
Decomposing Sargassum in coastal waters or on beaches release toxic gasses such as methane and hydrogen sulfide [55] that have detrimental effects on human health [56]. In the reef lagoon, decomposing Sargassum produces high loads of organic material leading to eutrophication, where the water contains low levels of oxygen, high concentrations of nutrients, hydrogen sulfide and tannins [57]. Eutrophication of the water and leachates containing arsenic and other heavy metals has an effect on population structure and mortality of marine organisms [12,58]. The Sargassum that is transported and discarded inland contaminates the aquifer and cenotes (sinkholes) with leachates [59].
These impacts have been studied in Mexico since 2010 (Supplementary File S1). Most (61%) of these studies have been focused on ecological effects (e.g., mortality of marine organisms, detrimental effects on coral reefs and seagrasses). Effects on human health, commercial fisheries and beach erosion have been poorly documented. What we know in Mexico in the main subareas of this strategic line, and the main requirements of consolidating it, are summarized in Table 4. Some of these studies, projects and initiatives are further described in Supplementary File S3.

Subarea What It Is Known Needs
Tourism Not all indicators reflect a clear trend in relation to atypical influxes [53] Continuous and systematic monitoring of tourism indicators that allows to distinguish Sargassum-related fluctuations from other variables (e.g., inefficient tourism promotion, local insecurity) Commercial fisheries During atypical influxes, fishermen reduce or alter their activity [60] Documenting social impacts; a socio-economical perspective of the phenomenon Human health and air pollution Toxic gas emissions from decomposing Sargassum and the potential growth of pathogenic bacteria [61] Documenting of health impacts; a public health perspective of the phenomenon

Leachates, eutrophication and contamination of aquifers and cenotes
Coastal eutrophication leads to mortality of marine organisms [12,57] Management strategies that allow to contain and harvest Sargassum at sea; determination of disposal sites with adequate infrastructure to prevent leachates pollution; banning clandestine dumping; regulations compliance; studies outside touristic areas; restoration of beaches; long-term monitoring program The region's aquifer, including the cenotes, are contaminated because of leachates [59]; indirect contamination of cenotes also occurs due to a shift in tourism activities from the sea to coastal areas [14] Species of the reef lagoon and coastal zone Oxidative damage in turtles [62]; fewer turtle hatchlings [63] Loss of the seagrasses and the seafloor [12] Total or partial mortality of coral reefs [64][65][66] Fish and crustaceans' massive mortality [13] Erosion of beaches Heavy machinery used to collect Sargassum affects the coastal dynamics by removing and compacting the sand [67] Documenting containment and harvest technologies' impacts

Containment, Harvest and Disposal
Efforts to contain Sargassum at sea before it can reach the beaches are conducted through the installation of barriers. These barriers stop and aggregate Sargassum to be collected by "Sargassum trawlers" or be redirected away from the coast [68]. Incipient Sargassum harvest at sea is conducted by vessels, trawlers or small coastal boats [21]. Some vessels have pre-processing systems such as milling to reduce Sargassum volume [69].
Once the Sargassum strands on the beach, it is collected with wheelbarrows and rakes by hotel staff, municipal brigades or local people [67]. In months of atypical influxes, mechanical machinery is used [69]. Sargassum collected at sea and on land is transported to collection points and then transported to treatment stations or final disposal sites with towing vehicles. The facilities of Sargassum treatment stations must be adequate to prevent leachates from reaching the aquifers [69].
Most management efforts to date in Mexico are focused on Sargassum containment in coastal waters and harvest at beaches [22]. These strategies have been conducted since 2015 (Supplementary File S1). The containment and harvest actions are centralized by the state government through the different municipalities and by the federal government through SEMAR. Furthermore, most of the technological developments and innovations (i.e., barriers, trawlers, pre-processing equipment, beach clean-up equipment, etc.) are conducted by the private sector (Supplementary File S3). The document "Lineamientos Técnicos y de Gestión para la Atención de la Contingencia Ocasionada por Sargazo en el Caribe Mexicano y el Golfo de México"(https://www.gob.mx/cms/uploads/attachment/ file/636709/SEMARNAT-INECC-SARGAZO-2021.pdf accessed on 18 April 2022) [69] describes the characteristics that these developments must meet. What we know and have done in Mexico in the main subareas of this strategic line, and the main things needed to consolidate it, are summarized in Table 5. Some of these studies, projects and initiatives are further described in Supplementary File S3.

Potential Uses
Several uses for pelagic Sargassum have been explored in the last decade [70]. These are based on the biological, physical and chemical characteristics of the macroalgae [71].

Agriculture Industry and Livestock Goods
Composting has been explored for the conservation and enhancement of soil as one of the most economical and practical methods for the exploitation of fresh and dry Sargassum [72]. Sargassum has also been explored as a growth substrate for plants and as an additive to substrates due to its antifungal, antimicrobial and antiviral properties [73]. The use of Sargassum as a biofertilizer has become visible worldwide [70]. Biostimulants and biofertilizers are compounds that stimulate plant growth by providing nutrients, improving soil quality and creating a natural microbial environment [74].

Chemistry, Pharmaceutics and Nutritional Supplements
Macroalgae are an important source of alginates, fucoidans and fucoxanthins [70]. The compounds are used in the food industry as emulsifiers and gelling agents [75]; as food or dietary supplements with antioxidant, anticoagulant, antithrombotic, anti-inflammatory, antiviral, antilipidemic, antidiabetic and anticancer properties [76], and in the cosmetics industry as they contain important levels of nutrients and minerals [77,78].

Ecomaterials
Ecomaterials are economically viable products with a minimal ecological footprint that use existing local raw materials combined with existing technologies [79]. Sargassum has been used as a material (i.e., in concrete and bricks) for construction, for textile fiber production (i.e., in footwear), for bioplastics production and for paper manufacturing [70].

Livestock Feed
The suitability of Sargassum use in animal feed supplement is highly questioned due to potential toxic effects of heavy metals [70,80].

Bioenergetics
Sargassum that arrives on beaches or that becomes a residue from other industrial processes has a promising potential use as an energy source (i.e., bioethanol, biogas and biodiesel). It does not require fresh biomass like other processes (e.g., biofertilizers production) [71]. Limitations for this use are the high concentrations of recalcitrant components in Sargassum, such as sulfates, sodium chloride and heavy metals, which can act as inhibitors of anaerobic digestion, a process necessary for bioenergy production [81]; additionally, the amount of lignin found in Sargassum cell walls acts as a barrier to the microorganisms needed in the biofuel conversion process [82]. Other isolated efforts to produce bioenergy from Sargassum used direct pyrolysis of waste biomass. However, the high content of Sargassum ash leads to a low gross calorific value, resulting in a lower energy yield than that given by land-based plant biomass [83] and a large atmospheric impact with the release of several pollutants [84].

Advanced Materials
Sargassum can be used to obtain biocarbon and nanocarbon for the generation of electrocatalysts and specialized goods for high-tech industries. It has also shown great potential for the green synthesis of metal nanoparticles with multiple applications [85][86][87].

Bioremediation and Purification Mechanisms
The use of Sargassum in the production of activated carbon for biofilters that remove pollutants (dyes, ions, heavy metals, nitrogen, phosphorus, phenols, chlorine, etc.) from air, land, gas and water [88] has been explored.
The potential uses of Sargassum have been explored in Mexico since 2014 (Supplementary File S1). Most of these initiatives (76%) are focused on the development of biostimulants and biofertilizers, extraction of fucoidans and alginates, development of materials for bioconstruction and the generation of energy. Within this strategic line, we also determined a Technology Readiness Level (TRL) for applicable projects through interviews with subject matter experts. There are nine levels of TRLs, ranging from the basic principles of creating a new technology (TRL = 1) to the successful testing in a real-world environment and subsequent commercial availability (TRL = 9) [89][90][91]. (Figure 6). The TRLs of the projects were averaged to determine the TRL of each major product as presented in Figure 6. In Mexico, the industries with the most immediate potential, based on the highest TRL, are the biostimulants and biofertilizers, fucoidan and alginates, textile materials, bioconstruction materials and paper production. What we know and have done in Mexico in the main subareas of this strategic line, and the main needs to consolidate it, are summarized in Table 6. Some of these studies, projects and initiatives are further described in Supplementary File S3.
Phycology 2022, 2, FOR PEER REVIEW 14 Figure 6. TRL Scale (Adapted from [89]) and an averaged TRL value for each major product or development in Mexico. Table 6. Technological and scientific advances in the strategic line of potential uses.

Subarea What It Has Been Done Needs
Agriculture industry and livestock goods

Development of compost (Supplementary File 3)
Change adverse perception of stranded Sargassum; intra and interannual characterization studies and bromatological analysis; determine suitability and safety of products and by-products; harvesting and Sargassum-based substrates are rich in potassium magnesium and sodium. High salinity is a challenge for plant cultivation, but these substrates are suitable for the growth of commercial mushrooms [92,93] Development and commercialization of biostimulants and biofertilizers (Supplementary File 3) Figure 6. TRL Scale (Adapted from [89]) and an averaged TRL value for each major product or development in Mexico. Table 6. Technological and scientific advances in the strategic line of potential uses.

Subarea What It Has Been Done Needs
Agriculture industry and livestock goods

Development of compost (Supplementary File S3)
Change adverse perception of stranded Sargassum; intra and interannual characterization studies and bromatological analysis; determine suitability and safety of products and by-products; harvesting and processing (i.e., drying, pressing, desalination, milling) logistics; disposal procedures that facilitate technically, ecologically and economically viable conservation and storage for a permanent supply; Sargassum biomass pre-treatment with fungi and other microorganisms to increase energy efficiency Sargassum-based substrates are rich in potassium magnesium and sodium. High salinity is a challenge for plant cultivation, but these substrates are suitable for the growth of commercial mushrooms [92,93] Development

Advanced Materials
Sargassum aqueous extracts for electrocatalysts and the synthesis of platinum, gold and silver nanoparticles that can be used in the construction of electrochemical glucose sensing platforms, in the catalytic activity for blue methylene degradation and as antibacterials for Staphylococcus aureus and Pseudomonas aeruginosa) [85][86][87][101][102][103] Bioremediation and purification mechanisms Effectiveness of a Sargassum-based bioremediation system for the removal of metal ions and toxic dyes in water [104] 3.

Regulations and Other Strategic Lines
The strategic line referring to the legal framework and regulations for all activities associated with Sargassum management is crucial to establishing consolidated industries around the use of the macroalgae and reducing socioecological risks associated with macroalgae decomposition at shallow coastal waters and on the beaches. However, this strategic line has very limited information and coordinated technical efforts for its consolidation.
The development of communication and education strategies on the Sargassum phenomenon is necessary in order to move from a problem perspective to a resource perspective and to promote a culture of care for the oceans. The Sargassum phenomenon affects several nations in the Western tropical Atlantic and the Caribbean region. Thus, it is necessary not only to have a comprehensive national strategy to address this phenomenon, but also a multilateral strategy that brings together the solution-oriented knowledge and experiences of different countries and sectors [22].
Finally, as described above, the extent of the direct and indirect environmental impacts of atypical Sargassum influxes is not known at this time. Thus, restoration efforts in affected areas are incipient or nonexistent. Moreover, there is no adequate coastal regionalization that would allow differentiated, zoned Sargassum management plans (e.g., marine protected areas, uninhabited areas, fishing areas) [22].
In Mexico, these strategic lines have been addressed, with limited tangible results, since 2019 (Supplementary File S1). In terms of regulations and legal instruments, most of the initiatives are ongoing efforts by different governmental entities (Supplementary File S3). Further actions are needed in all population sectors to consolidate these lines. What we know and have done in Mexico in terms of the main subareas of these strategic lines and the main requirement of consolidating them are summarized in Table 7. Some of these studies, projects and initiatives are further described in Supplementary File S3. Table 7. Advances in the strategic lines of regulation, international cooperation, communication and education and restoration.

Subarea What It Has Been Done Needs
Regulations and legal framework Regarding the geographic representativeness, 72% of the projects, studies or initiatives provided analyses at the state or regional level (Caribbean), and only 28% indicated sitespecific analyses. For the latter, most of the sampling sites are in the northern region of the state of Quintana Roo, between Playa del Carmen and Cancun (Figure 7). In terms of timing, 87% of the projects or studies have been developed since 2018, with a peak in 2019, one year after the most impactful influx of Sargassum ever registered. Phycology 2022, 2, FOR PEER REVIEW 17 Figure 7. Number of projects conducted per study site.

Findings on Key Experts and Multisectoral and Interinstitutional Collaboration
We identified a total of 261 experts in the topic of pelagic Sargassum in Mexico (Supplementary File 2). Of these, 177 were assigned to a specific strategic line. The others were assigned to an additional classification called "comprehensive attention" due to their inherent multidisciplinary work; most of them were from the government sector. Most experts work within the strategic lines of potential uses, socioeconomic and environmental impacts and monitoring. Most of them work in the academic sector, followed by the private sector. The smallest number of experts was associated with the lines of regulations and restoration of affected ecosystems (Figure 8). The four institutions with the highest number of experts are UNAM, SEMARNAT, CICY and CINVESTAV, with an average of fourteen experts per institution (Figure 9). In

Findings on Key Experts and Multisectoral and Interinstitutional Collaboration
We identified a total of 261 experts in the topic of pelagic Sargassum in Mexico (Supplementary File S2). Of these, 177 were assigned to a specific strategic line. The others were assigned to an additional classification called "comprehensive attention" due to their inherent multidisciplinary work; most of them were from the government sector. Most experts work within the strategic lines of potential uses, socioeconomic and environmental impacts and monitoring. Most of them work in the academic sector, followed by the private sector. The smallest number of experts was associated with the lines of regulations and restoration of affected ecosystems ( Figure 8).

Findings on Key Experts and Multisectoral and Interinstitutional Collaboration
We identified a total of 261 experts in the topic of pelagic Sargassum in Mexico (Supplementary File 2). Of these, 177 were assigned to a specific strategic line. The others were assigned to an additional classification called "comprehensive attention" due to their inherent multidisciplinary work; most of them were from the government sector. Most experts work within the strategic lines of potential uses, socioeconomic and environmental impacts and monitoring. Most of them work in the academic sector, followed by the private sector. The smallest number of experts was associated with the lines of regulations and restoration of affected ecosystems ( Figure 8). The four institutions with the highest number of experts are UNAM, SEMARNAT, CICY and CINVESTAV, with an average of fourteen experts per institution (Figure 9). In The four institutions with the highest number of experts are UNAM, SEMARNAT, CICY and CINVESTAV, with an average of fourteen experts per institution (Figure 9). In terms of geographical representation, the largest number of experts were located in Quintana Roo (89), followed by Mexico City (85) and Yucatan (35), while the rest were dispersed in seventeen other states of Mexico.
2, FOR PEER REVIEW 18 terms of geographical representation, the largest number of experts were located in Quintana Roo (89), followed by Mexico City (85) and Yucatan (35), while the rest were dispersed in seventeen other states of Mexico. At least one national or international collaboration was identified in 87 of the projects. The average number of collaborations was three within each project. From these, 76% were national academic, private, civil or governmental collaborations, while 24% were international academic and private collaborations (Supplementary File 1). The academic institutions with more established collaborations were UNAM and CINVESTAV, while the government agencies that collaborated the most were CONACYT, SEMAR and CONABIO (Supplementary File 1).

Discussion
Sargassum overgrowth and atypical influxes in the western tropical Atlantic and Caribbean coasts poses a challenge for the ecosystem (marine and terrestrial), the economy, the society, and the politics of affected countries [106]. Public and private initiatives in all sectors have evolved to understand, address and provide solutions to this complex problem. These initiatives in Mexico are numerous and valuable, as described here. However, several issues preclude effective advancements in reaching an integral management of the At least one national or international collaboration was identified in 87 of the projects. The average number of collaborations was three within each project. From these, 76% were national academic, private, civil or governmental collaborations, while 24% were international academic and private collaborations (Supplementary File S1). The academic institutions with more established collaborations were UNAM and CINVESTAV, while the government agencies that collaborated the most were CONACYT, SEMAR and CONABIO (Supplementary File S1).

Discussion
Sargassum overgrowth and atypical influxes in the western tropical Atlantic and Caribbean coasts poses a challenge for the ecosystem (marine and terrestrial), the economy, the society, and the politics of affected countries [106]. Public and private initiatives in all sectors have evolved to understand, address and provide solutions to this complex problem. These initiatives in Mexico are numerous and valuable, as described here. However, several issues preclude effective advancements in reaching an integral management of the macroalgae.
We found limited peer-reviewed research publications and open-access databases compared with the number of conducted projects. The latter is critical because it prevents repetition of research efforts over time [107]. Most projects that did not develop publications had an estimated duration of less than two years (Supplementary File S1). Funding duration may not be optimal and multiple-year projects should be prioritized, and especially so along strategic lines that require longer periods to obtain results with meaningful implications in decision-making processes (e.g., monitoring, restoration) [108].
Another important issue is that the research funding seems to respond to atypical influxes events, without continuity or long-term planning (Supplementary File S1). This makes it difficult to understand the cause of the phenomenon, generate adequate predictions or consolidate industries around the resource, especially since efforts continue to focus mainly on mitigation (containment and cleanup) [22] and not on generating a foundation for a robust monitoring and early warning system.
We also found a cluster of research and experts in a few institutions. We think it is important to push more institutions towards innovative excellence across all aspects of this complex topic, without compromising the expertise already achieved. National cooperation between different institutions should be a criterion for future call for proposals and funding [22]. Projects in co-design, co-development and co-delivery are needed, expanding and strengthening existing channels of multisectoral collaboration.
The geographical representation of initiatives and projects addressing the Sargassum phenomenon across the Mexican coasts is imbalanced. The attention of academic and other sectors has focused primarily on areas of touristic importance, neglecting rural areas, protected natural areas, fishing zones, etc., where atypical Sargassum influxes and their impacts have not been assessed and hence not understood nor quantified [22]. This imbalance needs to be addressed by prioritizing initiatives and research that involve local communities and study sites outside highly developed areas [109]. This will be more feasible when infrastructure in the field allows researchers to reach these sometimes isolated, difficult to reach locations [52].
There is a disparity of efforts between the different strategic lines, which hampers a comprehensive understanding and management of the phenomenon [22]. This disparity responds to the temporal and spatial scales required to generate the knowledge, and should be reduced by emphasizing efforts on those lines with more gaps. Development of capacities and experts within these lines are also required. Communication strategies, international cooperation and paths towards a legal regulatory framework establishing an adequate Sargassum management and use are all issues that should be promoted and improved by the governmental sector [80].
Within all strategic lines, there exist significant obstacles to advancing their consolidation. There are logistical and financial limitations, especially to conducting research in the open ocean [110]. For example, in the line of origin and ecological importance, the limited research on the origin of the phenomenon or the role of Sargassum rafts as an essential habitat may be related to limited financial resources to conduct research cruises. Another limitation is the inherent long project extension within some strategic lines. For example, in the line of monitoring, data availability, model validation, technology development, etc., require multi-year research funding to achieve a level where the resulting tools can have practical applications. Finally, there is a lack of a comprehensive regulatory framework in Mexico, hindering advancements towards the establishment of value chains (Ministry of Foreign Affairs [111]) and a Sargassum-based circular economy. The SEMARNAT guidelines are a first step to fixing regulation voids; however, these are not compulsory.
This state of the art addresses the advances and needs of each of the strategic lines and provides a road map for future research and actions. By having a clear picture of the existing knowledge, it is possible to coordinate more effectively the interinstitutional, multisectoral and multidisciplinary efforts. Based on the identified needs, we determined ten major challenges that need to be addressed at different temporal scales and with different complexity levels (i.e., where major needs and limitations are and where the resources to overcome those needs and limitations are higher) to achieve measurable impacts on the integrated Sargassum management, with national level implications ( Figure 10).
Phycology 2022, 2, FOR PEER REVIEW 20 sources to overcome those needs and limitations are higher) to achieve measurable impacts on the integrated Sargassum management, with national level implications ( Figure  10). To overcome these challenges, it is crucial to change the perspective that Sargassum is a waste and that it should be managed as such. Instead, we should embrace Sargassum as a national resource. Sargassum is not only a golden pelagic forest of great ecological and environmental value (e.g., CO2 sequestration capacity) [2,28,29], but it also has an undeniable economic potential for society [80]. Atypical Sargassum influxes will continue to occur [12], so it is necessary to establish a mechanism that facilitate biomass harvest at sea with a robust early warning system that will allow timely actions. The negative impacts of Sargassum on coasts and beaches will be minimized once it is properly valued as is any other fishery resource. To achieve this status, it is necessary to diminish existing knowledge gaps by means of research and tangible coordinated actions.
The Sargassum topic is complex and extends beyond a single country's problem. One of the main goals of this research was to facilitate the transfer of knowledge of successful Sargassum actions conducted by different Mexican sectors and stakeholders. Some of these actions can be scaled up regionally and promote the development of joint regional solutions to understand the long-term multifactorial effects on ocean and human health of the massive Sargassum standings at a regional scale [112]. Without appropriate management, beached Sargassum will keep resulting in ecological, environmental and public health problems including the high costs of biodiversity and ecosystem resilience loss.

Supplementary Materials:
The following supporting information can be downloaded at: www.mdpi.com/xxx/s1. References [113][114][115][116][117][118][119][120][121] are cited in the supplementary materials.  To overcome these challenges, it is crucial to change the perspective that Sargassum is a waste and that it should be managed as such. Instead, we should embrace Sargassum as a national resource. Sargassum is not only a golden pelagic forest of great ecological and environmental value (e.g., CO 2 sequestration capacity) [2,28,29], but it also has an undeniable economic potential for society [80]. Atypical Sargassum influxes will continue to occur [12], so it is necessary to establish a mechanism that facilitate biomass harvest at sea with a robust early warning system that will allow timely actions. The negative impacts of Sargassum on coasts and beaches will be minimized once it is properly valued as is any other fishery resource. To achieve this status, it is necessary to diminish existing knowledge gaps by means of research and tangible coordinated actions.
The Sargassum topic is complex and extends beyond a single country's problem. One of the main goals of this research was to facilitate the transfer of knowledge of successful Sargassum actions conducted by different Mexican sectors and stakeholders. Some of these actions can be scaled up regionally and promote the development of joint regional solutions to understand the long-term multifactorial effects on ocean and human health of the massive Sargassum standings at a regional scale [112]. Without appropriate management, beached Sargassum will keep resulting in ecological, environmental and public health problems including the high costs of biodiversity and ecosystem resilience loss.