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The Mar Menor is a hypersaline coastal lagoon with high environmental value and a characteristic example of a highly anthropized hydro-ecosystem located in the southeast of Spain. An unprecedented eutrophication crisis in 2016 and 2019 with abrupt changes in the quality of its waters caused a great social alarm. Understanding and modeling the level of a eutrophication indicator, such as chlorophyll-a (Chl-a), benefits the management of this complex system. In this study, we investigate the potential machine learning (ML) methods to predict the level of Chl-a. Particularly, Multilayer Neural Networks (MLNNs) and Support Vector Regressions (SVRs) are evaluated using as a target dataset information of up to nine different water quality parameters. The most relevant input combinations were extracted using wrapper feature selection methods which simplified the structure of the model, resulting in a more accurate and efficient procedure. Although the performance in the validation phase showed that SVR models obtained better results than MLNNs, experimental results indicated that both ML algorithms provide satisfactory results in the prediction of Chl-a concentration, reaching up to 0.7 R2CV (cross-validated coefficient of determination) for the best-fit models.

Coastal lagoons are among the marine habitats with the highest biological productivity, and supports a great variety of human activities and pressures that makes them especially vulnerable to trophic imbalances. While dystrophic crises are common in many lagoons, others like the Mar Menor show homeostatic mechanisms, high resilience and clear waters. This paper analyses the water column descriptors dynamic during the last 22 years in this lagoon, in the context of a eutrophication process produced by an increase in nutrient inputs, mainly derived from agriculture. Despite the increase in nitrate loads, the lagoon maintained two decades of homeostatic regulation, keeping the water transparency and relatively low levels of nutrients and chlorophyll a (Prebreak phase), followed by a sudden change of state in 2016 with an abrupt increase in nutrients and chlorophyll a concentration and loss of water transparency (Break phase), and a relatively rapid recovery after the reduction of nutrient discharges (Recovery phase). The activation of the regulation mechanisms is manifested by an ammonium production, as a consequence of the trophic web activity. The low relationship between chlorophyll and nutrients, mainly at small spatio-temporal scales, disagrees with the eutrophication traditional models, suggesting a rapid response of primary producers to nutrient inputs and a zooplankton control in the short-term, which in turn is controlled by the rest of the trophic web components. Homeostatic properties that provide resistance to the Mar Menor lagoon to deal with eutrophication are based on several mechanisms: channelling its production towards the benthic system (maintaining high biomasses of primary producers, filter feeders and detritivores), a top-down control of the pelagic trophic web exerted by ichthyoplankton and jellyfish, and exporting surplus production outside the system. Resilience of the system would be based on the high turnover in the species composition related to the restricted connectivity with the sea, the spatio-temporal variability of the environmental conditions, and the multiplicity of spatial-temporal scales involved in lagoon processes. TRIX index was sensitive to the water quality changes. However, in our study, its current score does not allow to anticipate or alert the eutrophication risk and the trophic breakpoint of the system.

In this paper I explore societal polarization as a challenge to environmental governance and sustainability transformations. I focus on how processes of knowledge co-production can be used as transformative avenues in highly polarized environmental disputes. I investigate the case of nonpoint driven eutrophication in the Mar Menor Lagoon, Spain, where the interplay of divergent epistemic, political, and affective processes exacerbates societal divisions around environmental degradation. Drawing on process-relational and affect theory, I argue that co-production within polarized contexts might focus on relational transformation by placing attention on how differences emerge from and are transformed within affective relations in knowledge encounters. Through a diffractive reading of a co-production experience with actors holding polarized positions in relation to the Mar Menor, the paper sheds light on the affective patterns underpinning polarization by framing, blaming, and eluding responsibility, which is termed the “responsibility trap.” It suggests that transcending “us vs them” dichotomies in environmental disputes calls for an affective engagement that shifts the responsibility trap to matters of co-response-ability. In our co-production experience, a partial relational transformation in this direction was achieved recognizing the lagoon as a shared matter of care, foregrounding how knowledge affects, embodying polarized narratives, exposing uncertainties in contested facts, and demonstrating that action can be taken even under uncertain conditions. Such a relational shift enabled a preliminary weaving of ways of knowing-feeling-becoming with the social-ecological transformation of the Mar Menor.

This work explores the role of knowledge claims and uncertainty in the public dispute over the causes and solutions to nonpoint-driven overfertilization of the Mar Menor lagoon (Spain). Drawing on relational uncertainty theory, we combine the analysis of narratives and of uncertainty. Our results show two increasingly polarized narratives that deviate in the causes for nutrient enrichment and the type of solutions seen as effective, all of which relate to contested visions on agricultural sustainability. Several interconnected uncertainties are mobilized to dispute the centrality of agriculture as a driver for eutrophication and to confront strategies that may hamper productivity. Yet, both narratives rest on a logic of dissent that strongly relies on divergent knowledge to provide legitimacy, ultimately reinforcing contestation. Transforming the ongoing polarization dynamics may require different inter- and transdisciplinary approaches that focus on sharing rather than assigning responsibility and that unpack rather than disregard existing uncertainties.

The potential threat posed by the invasive species Atlantic blue crab ( Callinectes sapidus ), through the foraging strategy based on stomach contents and reproductive ecology analysis, was investigated in the hypersaline Mar Menor lagoon (SE Spain). The main groups preyed upon by blue crab were mostly Penaeus kerathurus and Palaemon spp., accounting for 43.3% of their total weight (gravimetric index, %W), teleosts (19.7%W), brachyurans (14.7%W, mostly Carcinus aestuarii ), and bivalves (9.9%W, mostly Ruditapes decussatus and Cerastoderma edule ). Significant differences were found in feeding habits related to size but not sex. Size at first maturity (L 50 ) was 92 mm for males and 96 mm carapace width (CW) for females. Females showed a seasonal trend in the gonadosomatic index (GSI), which remained high between May and September and peaked in August. Ovigerous females appeared from May until October, peaking in September. The smallest ovigerous specimen found in the lagoon measured 73 mm CW. The number of eggs produced per individual ranged from 284 thousand to 2.2 million, showing a direct correlation with total length. Our results highlight that the blue crab constitutes a threat to the Mar Menor ecosystem, from both the economic and ecological points of view. The blue crab causes major economic damage to local fisheries shortening the average life of fishing gear. It also competes with the fishermen for economically valuable species such as striped prawn, rockpool shrimp, or Mediterranean green crab. We conclude that the blue crab behaves like a dangerous invasive species in the Mar Menor lagoon and further studies are required to design a proper management plan.

This paper presents the results on the presence and characterization of microplastics (MP) in the gastrointestinal tract of gilthead seabream (Sparus aurata L.), a species of commercial interest from the Mar Menor coastal lagoon in Southeast Spain. This is the first time that microplastic ingestion is recorded in any species from this semi-enclosed bay. Stomach and intestine from a total of 17 specimens captured by local fishermen were processed, and microplastic particles and fibers found in all of them were displayed. Overall, 40.32% (279/692) of total isolated microparticles proved to be microplastics; i.e., <5 mm, as identified by FTIR spectroscopy. The average value by fish was 20.11 ± 2.94 MP kg−1, corresponding to average concentrations of 3912.06 ± 791.24 and 1562.17 ± 402.04 MP by kg stomach and intestine, respectively. Four MP forms were isolated: fiber (71.68%), fragment (21.15%), film (6.81%), and microbead (0.36%), with sizes ranging from 91 µm to 5 mm, an average of 0.83 ± 0.04 mm, and no statistically significant differences between mean sizes in stomach and intestine samples (F-test = 0.004; p = 0.936). Nine polymer types were detected, although most of fibers remained unidentified because of their small size, the presence of polymer additives, or closely adhered pollutants despite the oxidizing digestion carried out to eliminate organic matter. No significant correlation was found between main biological parameters and ingested microplastics, and high-density polyethylene (HDPE), low-density polyethylene (LDPE), polyethylene polypropylene (PEP), and polyvinyl (PV) were identified as the most abundant polymers. The average microplastic ingestion in this study area was higher than those reported in most studies within the Mediterranean Sea, and closely related to microplastic pollution in the surrounding area, although with a predominance of fiber form mainly due to fishery activities.

Eutrophication is a significant threat to aquatic ecosystems worldwide, and the Mar Menor hypersaline lagoon exemplifies a coastal lagoon at risk of algal blooms due to excessive nutrient loads, nitrogen, and phosphorus. These nutrients originate from various sources within the lagoon’s catchment area, including urban, agricultural, and livestock activities. Regular and occasional loads—during flood events—produce algal blooms that can significantly reduce the water oxygen content and cause massive mortalities, as observed in recent years. A daily algal growth model (Mmag) was developed to better understand the processes and determine key elements such as the phosphorus water–sediment interchange and deep water plants that effect the entire ecosystem and algal growth. The analysis developed can be applied in other wetlands around the world facing similar challenges. In the Mar Menor, both nitrogen and phosphorus have high relevance depending on the period of the year and the phosphorus legacy in the sediments. Floods are the main phosphorus input to the lagoon (80–90%), which goes to the sediment and is released after during the warm months in the following years. At the end of summer, phosphorus released from the sediment and the regular nitrate inputs to the lagoon increase the algal bloom risk. The good status of deep water plants, which reduces the phosphorus release in summer, is a key element to reduce the algal bloom risk. An integrated set of measures is required to reduce the mean chlorophyll to levels under 1 or 0.5 µgChla/L that can make the Mar Menor more robust and resilient.

The relationship between tourism and the environment is often studied through tourism’s impact on destinations, with limited focus on how eco-degradation affects tourism, including residential tourism, which remains the most loyal to specific destinations. This study examines whether a destination’s eco-degradation impacts the residential tourists’ satisfaction and their intention to revisit. Two studies were conducted on the Mar Menor destination (Spain) using two online questionnaires administered through social media. Study 1 (from October 2020 to December 2021, n = 822) explored tourists’ perceptions of the destination’s ecological situation. Study 2 (November 2022 and March 2023, n = 453) examined how the destination’s eco-degradation influences residential tourists’ intention to revisit, considering the mediating role of destination attachment and perceived value. We found that residential tourists’ perceptions and revisit intentions vary with accommodation type. Eco-degradation impacts holiday satisfaction but not revisit intentions. Second-home ownership compels visits despite dissatisfaction or a preference for alternative destinations. This research contributes to the scarce literature on residential tourism by showing that place attachment and the perceived value, satisfaction, and behavioural intentions can explain revisit intention even in contexts of eco-degradation of the destination.

The objective of this study was to evaluate the level of pollution, sources and potential risk of heavy metals (Zn, Cu, Mn, Cd, Cr, Ni, Fe and Pb) and arsenic (As) in four dry riverbeds affected by mine tailing, which drain into one of the biggest coastal lagoon of Europe (Mar Menor). El Beal, La Carrasquilla, Las Matildes and Ponce dry riverbeds sediments were sampled along its course (20, 18, 13, 19 samples were collected, respectively), and total/soluble metal(loid)s, water soluble ions, nitrogen, and organic/inorganic carbon contents were analyzed. Spatial distribution, principal component analysis (PCA), hierarchical cluster analysis (HCA), contamination factor (Cf), pollution load index (PLI) and potential ecological risk index (RI) were used to identify the possible sources of metal(loid)s and to assess the sediment pollution status. The results showed that the mean total concentrations of As, Cu, Cd, Mn, Zn and Pb exceeded the natural background levels of the study area, with the highest values located close to the mining areas. Correlation and cluster analysis identified that Cd and Zn were associated mainly with anthropogenic activities for all riverbeds, while Cr and Ni come from parent. PLI graded the four riverbeds as contaminated by heavy metals, while RI manifested that 100% of samples located in El Beal, La Carrasquilla and Las Matildes had a significantly high ecological risk. Therefore, this study suggests that mine wastes are the main source of metal(loids) contamination in the dry riverbeds, which results can be used to design actions and measures to reduce the environmental impact of metal(loid)s in the Mar Menor coastal lagoon.

The Mar Menor is a hypersaline coastal lagoon located in the southeast of Spain. This fragile ecosystem is suffering several human pressures, such as nutrient and sediment inputs from agriculture and other activities and decreases in salinity. Therefore, the development of an operational system to monitor its evolution is crucial to know the cause-effect relationships and preserve the natural system. The evolution and variability of the turbidity and chlorophyll-a levels in the Mar Menor water body were studied here through the joint use of remote sensing techniques and in situ data. The research was undertaken using Operational Land Imager (OLI) images on Landsat 8 and two SPOT images, because cloudy weather prevented the use of OLI images alone. This provided the information needed to perform a time series analysis of the lagoon. We also analyzed the processes that occur in the salt lagoon, characterizing the different spatio-temporal patterns of biophysical parameters. Special attention was given to the role of turbidity and chlorophyll-a levels in the Mar Menor ecosystem with regard to the programs of integral management of this natural space that receives maximum environmental protection. The objective of the work has been fulfilled by answering the questions of the managers: when did the water quality in the Mar Menor begin to change? What is happening in the lagoon? Is remote sensing useful for monitoring the water quality in the Mar Menor? The answers to these questions have allowed the generation of a methodology and monitoring system to track the water quality in the Mar Menor in real-time and space. The tracking system using satellite images is open to the incorporation of images provided by new multispectral sensors.