Coasts

Marine litter (ML), encompassing human-made objects in marine ecosystems, poses significant threats to the coasts of some Adriatic islands, despite their remoteness and sparse populations. These islands, reliant on tourism, are particularly vulnerable to ML pollution. This study hypothesized that the natural features of the islands influence ML distribution. It employes an integrated geographic approach combining the results of field survey (via sea kayaking) with various indicators which include: (1) coastal orientation and number density of bays, (2) vegetation exposure and biomass share, (3) island area and number density of bays, (4) bay openness and ML quantity, and (5) bay openness and plastic prevalence in ML. Focusing on islands of Lošinj, Pašman, Vis, and the Kornati and Elaphiti archipelago, the study analyzed data collected over six years (2018–2023). Results highlighted that NW-SE and W-E coastal orientations are particularly susceptible to ML accumulation, especially in the southern Adriatic. Linear Fitting Regression analyses revealed a stronger correlation between number density of polluted bays and the surface area of smaller islands (<10 km²) compared to larger islands (>10 km²). The following findings underscore the need for international collaboration and stringent policies to mitigate ML pollution, ensuring the protection of Adriatic marine ecosystems and the sustainability of local communities. Full article

This article presents a rock armour stability formula for coastal revetments under depth-limited breaking waves that defines requisite armour mass as a function of incident wave energy. Parameters include wave height, wave period, toe depth, revetment slope, specific gravity of armour and water, percentage damage and the number of waves. The formula has been calibrated empirically based on university research flume test data. It departs from existing approaches by using wave energy in lieu of wave height as the disturbing parameter, but adopts other parameters developed by previous researchers. Results are compared with established formulae and display better coherence with the flume data. Testing constraints including possible scale effects are highlighted. Recommendations are made for further testing including the effects of seabed slope. Full article

It is estimated that around 10% of the world’s population lives in low-lying coastal areas, with an altitude of up to 10 m: considered vulnerable to unequivocal sea level rise, as result of climate change. This study sought to assess the coastal environmental vulnerabilities of the municipality of Niterói, Rio de Janeiro, Brazil, in these lowlands, through of an analysis matrix, considering sea level rise projections for 2100. The matrix was applied to nine areas along the coast and consisted of assigning values from 1 to 4 (4 being the most critical scenario) to four variables: two to natural indicators and two to socio-economic indicators. The index for each area was obtained from the simple average of the values assigned. In general, the areas facing Guanabara Bay were more sensitive in socio-economic terms, due to population densification and lower per capita income. The areas facing the Atlantic Ocean were more vulnerable in natural terms, due to exposure to waves and the presence of the natural systems protected on land located below the 10-m. These issues highlight the importance of using vulnerability analysis tools, which can enable public authorities to plan and organize the actions in each specific situation. Full article

The abnormal proliferation of Ulva in the Yellow Sea has instigated the notorious green tide phenomenon. Mitigating this ecological challenge necessitates a holistic comprehension of Ulva’s nitrogen and phosphorus uptake behaviors. Investigating the mechanisms governing nutrient absorption, encompassing factors like concentration, form, and input dynamics, has unveiled their profound influence on nutrient assimilation rates. The nutrient absorption characteristics of Ulva prolifera, including its preference for abundant nutrients, a high nitrogen-to-phosphorus (N/P) ratio, and its ability to efficiently absorb nutrients during pulse nutrient input events, determine its dominant role in the green tide events in the Yellow Sea. Although source control and preemptive salvaging are effective methods for managing green tides, addressing the root causes of these coastal ecological disasters requires the implementation of long-term pollution control strategies that align with sustainable development goals, with a priority on reducing marine eutrophication. This is crucial for the effective management and restoration of the coastal ecosystem in the Yellow Sea. Full article

Foam pollution in the tailwater discharge from coastal power plants poses a significant challenge. However, the mechanisms underlying foam formation and stability remain understudied, which hinders the development of effective control strategies. This study investigated the impacts of temperature and algal concentration on foam stability in tailwater discharge from coastal power plants through simulation experiments to elucidate mechanisms of foam stability. A laboratory simulation device was developed to adjust temperature and algal concentration and measure foam layer height, half-life, bubble diameter, surface tension, and viscosity. This device was used to replicate foam scenarios typical of coastal power plant tailwater discharge to analyze the effects of temperature and algal concentration on foam stability through comprehensive data collection and analysis across various operational conditions. The findings revealed that foam stability decreased with increasing temperatures (15–45 °C). However, during hot summer months, higher temperatures (range of 30–40 °C) hindered foam dissipation owing to algal blooms and the release of surface-active substances. The functional relationship between foam stability index (half-life, foam layer height, bubble diameter) and temperature and algae concentration was established, which provides a scientific basis for predicting foam stability under different conditions. This research elucidates the complex dynamics of foam in the tailwater discharge from coastal power plants and provides insights for developing more effective foam control strategies, potentially mitigating adverse impacts on the marine ecosystem. In future research, by adding experimental conditions such as pH, ionic strength, and different types of protein polysaccharides, a more comprehensive understanding of the mechanism of bubble generation can be achieved, providing more accurate foam suppression optimization solutions for future engineering practices. Full article

Since 2011, recurring Sargassum Brown Tides (SBTs), caused by periodic massive influxes of holopelagic Sargassum spp., have impacted seagrass meadows in the 50–200 m wide nearshore fringes of Mexican Caribbean reef lagoons. The present study aimed to assess the cumulative effects of SBTs in 2015 and 2018–2019 through a spatial–temporal analysis of seagrass meadows in the Puerto Morelos reef lagoon. We hypothesized that the impacts of the SBTs likely extended beyond the near-shore fringe and were detectable across the seagrass landscape throughout the entire reef lagoon. Through time, the spatial configuration of the seagrass meadows presented a new self-organized configuration linked to spatial fragmentation, an increase in the number of patches but a decrease in size, and changes in vegetation communities, indicating a shift in ecosystem state. This shift may serve as an early warning signal of reef system deterioration. Monitoring seagrass meadow status using this approach provides a deeper understanding of their dynamics, shifts and resilience, and will facilitate the development of timely management strategies. Full article

A new marine climate metric, marine season, is introduced for Foxe Basin, Nunavut, Canada capturing the time of the year that the Basin is influenced by open water. The metric is developed with a day-to-day temperature variability framework using the Hall Beach (Sanirajak) climate record (1957–2023). Day-to-day minimum temperature variability provides a clear signal of the marine season. The new metric is compared to the more traditional breakup and freeze-up dates of sea ice that uses a 5/10th sea-ice spatial coverage threshold. While the two metrics are in general agreement, some important differences occur related to the time required for the breakup (full ice coverage to 5/10th sea-ice coverage). The timing from onset of the marine season to 5/10th ice coverage has shortened in time in a statistically significant fashion, indicating a more rapid breakup in recent years. In contrast, the freeze-up period, 5/10th to full sea-ice coverage has increased. The longer ice-free season, as determined by sea-ice data, arises primarily from open water changes in the breakup (shorter) and freeze-up (longer) period timing. These are novel insights that suggest that the basic sea-ice regime, oscillating from a full sea-ice platform and ice-free conditions has not changed, but rather the observed changes are in the nature of the transitions between these two states, breakup and freeze-up. Full article

This study addresses the challenge of identifying pollutant sources in aquatic coastal environments using inverse problem techniques hampered by particularities in hydrodynamic and Lagrangian models. An approach is presented employing the General Inverse Problem Platform (GRIPP) coupled with a General Simulated Annealing (GenSA) algorithm for robust backtracking. This methodology was applied to a hypothetical case study in Guanabara Bay, Brazil, using the MOHID Water platform for hydrodynamic and Lagrangian simulations. GRIPP significantly improved emission identification and pathway representativeness compared to traditional backtracking methods by exploring multiple potential particle origins and optimizing seeding parameters. The optimization yielded a solution with a mean error of 0.019 degrees between predicted and observed tracer locations. This demonstrates the potential of GRIPP and GenSA for solving practical environmental problems in coastal regions. The use of GRIPP can bypass eventual numerical errors in cases of long-term pollution source identification when compared to traditional methods. This approach contributes with blended models for the identification of potential sources of Lagrangian tracer emissions, as well as a potential solution to determine the pathways of pollutants. Full article

Background: By 2050, most of the global human population will live in coastal regions, and the climatic impacts on these areas represent a significant concern for governments, private sector companies, and societies. Thus, environmental management of coastal regions plays a central role in the global climate agenda. Methods: The study employed a mixed-methods approach, integrating quantitative and qualitative techniques to conduct a systematic literature review (SLR). This included the construction of networks of related topics, time series analysis, literature mapping, and the identification of research gaps. The databases used were Web of Science, Science Direct, and Scopus. The inclusion and exclusion criteria encompassed articles published between 2014 and 2023, off-topic articles, unavailable articles, or paid access articles. At the end, 96 studies were included in this RSL. Results: The results revealed a predominance of studies addressing climate management in coastal regions, primarily focused on adaptation strategies. However, there is a notable deficiency in studies that address integrated mitigation and adaptation strategies. Time series analysis predicted an increase in the focus on coastal management and climate change in the coming years. Conclusion: The research underscores the central role of coastal management in addressing climate change and achieving the Sustainable Development Goals (SDGs). It encourages multi-level management, integrating government officials, business leaders, and civil society in the development of more effective practices for climate change adaptation and mitigation. Full article

Microplastics (MPs) are polymeric particles, mainly fossil-based, widely found in marine ecosystems, linked to environmental and public health impacts due to their persistence and ability to carry pollutants. In São Paulo’s northern coast, geomorphological factors and anthropogenic activities intensify the deposition of these pollutants. Through multivariate techniques, this study aims to investigate the role of the morphometrical parameters as independent variables in quantifying the distribution of MPs on the region’s sandy beaches. Using beach face slope (tanβ) and orientation (Aspect) derived from remote sensing images, calibrated by in situ topographic profiles collected through GNSS positioning, and laboratory analyses, six machine learning models Random Forest, Gradient Boosting, Lasso and Ridge regression, Support Vector Regression, and Partial Least Squares regression were tested and evaluated for performance. The Gradient Boosting model demonstrated the best performance, indicating its superior capacity to capture complex relationships between predictor variables and MPs deposition, followed by Random Forest model. Morphometric analysis revealed, once again, that in this coastal section of São Paulo, beaches with Sloping profiles oriented toward the SSW are more susceptible to MPs accumulation, especially near urban centers. Ultimately, incorporating geomorphological variables into predictive models enhances understanding of MPs deposition, providing a foundation for environmental policies focused on marine pollution mitigation and coastal ecosystem conservation while also contributing to achieve SDG 14. Full article

The River Ter is one of the axes which, in a west-east direction, has historically articulated the population of the extreme north-east of the Iberian Peninsula. Although its upper, middle and part of the lower courses do not present any problems in its course, its mouth in the Mediterrane-an Sea has raised many questions due to the existence of two potential branches, one to the north that would flow into the Gulf of Roses and another to the south that would flow into the Bay of Pals. In 2016, an exhaustive documentary study on the potential southern branch provided exhaustive information on the existence of lake areas and their relationship with the settlement between the 9th and 11th centuries, but raised doubts about the existence of the river in the bay from Pals. Subsequently, between 2020 and 2022, geological studies have been carried out in this area which demonstrate the existence of the river in this area but with a variable course, with changes in the river channel (meandering, diffuse and braided), and with notable changes that conditioned the settlement of this sector of the coast and as was recorded in written documentation between the 9th and 11th centuries. Full article

Shoreline measurement techniques using satellite-derived imagery can provide decades of observations of shoreline change. Here we apply these techniques to the western south shore of Long Island, New York, which has three distinct beaches, Rockaway Peninsula, Long Beach, and Jones Beach Island, which are 18, 15, and 24 km in length, respectively. These beaches are recreation areas for millions of regional residents and include several groin fields, sediment dredging and nourishment operations, and a coastal wave climate that includes winter northeasterly storms and summer hurricanes. The shorelines along the western ends of these three beaches have been accreting at ~4 m/yr during the observation record (1984–2022) resulting from net westward longshore drift. The central 10–12 km of the beaches have lower shoreline change rates, and these rates are generally lowest within the groin fields (0.5–1.5 m/yr). Shoreline change observations also provide evidence for westward propagating accretion and erosion sediment waves that have durations of several years. Beach nourishment projects are shown to significantly influence rates of shoreline accretion, and this is commonly followed by significant shoreline retreat during the subsequent years. Full article

This study investigated the thermo-hydrodynamic groundwater environment of a sandy beach where a unique sand bathing method attracts many visitors. The discussed temperatures covered a wide range, from the normal to the boiling temperature of water. We, at first, examined the feasible conditions for sand bathing and found that the volumetric water content was the crucial factor. Comprehensive field observations were implemented to elucidate two physical quantities: the groundwater flow and the temperature in the sand layer. The latter one was found to be governed by the groundwater level and tidal fluctuations. The characteristics obtained were found to be consistent with the feasible conditions in the landward area. While in the offshore area, the temperature was proved to have suddenly dropped. These results strongly suggest that the underground heat source is distributed in specific spots. A numerical model to describe the groundwater flows and the heat transfer mechanism was developed based on a saturated/unsaturated seepage flow model. The computational results were found to adequately reproduce the observed spatial temperature distribution. The reproduction ability of the model was found to be limited in terms of temporal variations; it was good for the groundwater level, but not for the temperature in the sand. Full article

Salt marshes are vital coastal ecosystems, increasingly threatened by rising sea level and human pressures, that provide essential services, including coastal protection, habitat support, and carbon sequestration. This study examines the effectiveness of different eco-engineering structures in restoring salt marshes in the Mondego Estuary, Portugal, by assessing their impacts on benthic macroinvertebrate communities as bioindicators of ecosystem health. The experimental design included five experimental cells: wood palisade (Fence), geotextile fabric (Geotextile), geotextile bags filled with sand (Bags), a cell with autochthonous vegetation (Plants), and a Control cell with bare soil. Monitoring took place from 2019 to 2021, with both before and after intervention sampling to evaluate species composition, biomass, and density. Key ecological indices, such as the AZTI’s Marine Biotic Index (AMBI), Shannon-Wiener Diversity, and Pielou’s Evenness, were calculated alongside measurements of environmental variables. The results indicated minimal impacts on biodiversity, with observed variations primarily attributed to seasonal dynamics. While the wood palisade enhanced species richness and density, geotextile provided better community stability. The findings emphasize the importance of long-term monitoring, stakeholder engagement, and sustainable use of materials to optimize restoration efforts and better inform coastal management strategies in the face of climate change. Full article

This paper presents a meta-analysis of mangrove area in Mexico, using linear mixed models to assess trends from 1970 to 2020. The objective is to highlight the changes in the extent of these vital ecosystems over the past five decades. The analysis reveals a concerning decline of approximately 163.33 hectares per year from 1970 to 2005. Although a rebound was observed starting in 2016—likely due to effective conservation efforts—these ecosystems continue to decline overall. The states that have shown a consistent decline in mangrove area include Campeche, Sinaloa, Nayarit, Chiapas, Veracruz, Oaxaca, Guerrero, Colima, and Jalisco. Threats to mangroves vary significantly by region. In the North Pacific, the expansion of aquaculture farms has contributed to over 60% of mangrove loss. In contrast, the Yucatán Peninsula faces challenges from urban development, oil exploitation, and road expansion. Additionally, tourism activities have severely impacted the states of Colima, Jalisco, Guerrero, and Quintana Roo. In the Gulf of Mexico, the primary threats include aquaculture, transportation routes, and hydraulic infrastructure. Based on these findings, seven action strategies for the ecological restoration of mangroves are proposed. These strategies, drawn from successful case studies and existing literature, include: comprehensive restoration initiatives, expansion of research and data sources, updates to current regulations, regulation of anthropogenic activities, inter-institutional coordination, education and awareness-raising efforts, and continuous monitoring and evaluation. Full article

This study investigated the shoreline evolution of the Tuscany coast (Italy) from 1878–1883 to 2019. The 205 km sandy coastline, divided into 821 sectors, each one 250 m long, was analyzed to understand how human activities have altered this once-pristine coast. Sub-period analyses highlighted the impacts, both positive and negative, of various shore-protection projects. Initially, regional beaches were undeveloped and accreting, except for a few river deltas where alternating phases of erosion and accretion were observed. Coastal erosion began at deltas’ areas due to the reduction in sediment inputs and, at other areas, enhanced by the development of human settlements and tourism activities. This triggered the construction of protection structures that shifted erosion processes downdrift, a process that induced the downdrift extension of the structures (according to the “domino” effect), determining the transformation of a completely natural and resilient environment into a largely rigid one. Beach nourishment projects, mostly using inland quarries, added about 1 million cubic meters of sediment from the 1980s to 2019. Currently, 57.8% of beaches are larger than in the 1880s, 9.4% did not change and 32.8% are narrower. Overall, the Tuscan coast gained 6.5 km² of beach surface with an average shoreline advancement of 32 m. Recent trends (2005–2019) show that 37.7% of the coast is eroding, 21.1% is stable, and 41.2% is accreting, with a total surface area increase of about 200,000 m². The beach surface area is still increasing despite the existing reduced sediment input due to the limited sediment loss resulting from the presence of morphological cells enclosed by very prominent headlands and the absence of submarine canyons that would otherwise direct sediments to the continental shelf. Full article

“Blue carbon” refers to the carbon sequestered by the world’s oceanic and coastal ecosystems, particularly through coastal vegetation such as mangroves, salt marshes, seagrasses, and marine macroalgae. These ecosystems play a crucial role in the global carbon cycle by serving as significant carbon sinks, absorbing carbon dioxide from the atmosphere and storing it in biomass and sediments over long periods. This study explores the use of environmental DNA (eDNA) to detect marine macrophytes and microalgae assemblages contributing to blue carbon in sediments across various coastal ecosystems. The research addresses the challenges of traditional monitoring methods by utilizing high-throughput sequencing of the 18S-V9 region amplified using eDNA from sediment samples collected at eight locations in the United States and South Korea. The results reveal a diverse array of taxa, underscoring the variability in community composition across different conditions. Notably, sites with seagrass beds and Ulva blooms showed distinct patterns in microalgal community structure. This study underscores the potential of eDNA analysis in providing comprehensive insights into the biodiversity of marine macrophyte ecosystems, thus informing conservation efforts and enhancing the understanding of marine ecological dynamics. Full article

For almost all the Sicilian islands, there are no faunistic data concerning marine Heterobranchia, which is one of the most sought-after groups of marine critters by photographers and diving enthusiasts all over the world. With the present study, carried out through underwater photography at various dive sites and stretches of coastline in the island of Marettimo, we made the first contribution to the knowledge of the marine Heterobranchia fauna present on this island of the Egadi archipelago. Through data collection, it was possible to document the presence of 43 species of marine Heterobranchia. Data analysis showed a remarkable homogeneity in the number of species between the examined sites. This is probably due to the peculiar environmental homogeneity present in the sites of this island, which are almost all rich in the presence of both benthic suspension feeders (the favorite prey of many groups of marine Heterobranchia) and environments full of crevices, grottos, and vertical walls, which are the preferred habitats of the majority of these mollusks. The higher number of marine heterobranch species found in Marettimo compared to the smaller number of species found on the other recently examined Sicilian islands (Pantelleria, Lipari, and Vulcano) is probably due to the massive presence of rich coralligenous biocoenoses and the particular hydrodynamic regime to which Marettimo is subject. Full article

Emerging pollutants, like phytoestrogens, are gaining attention in the scientific community for their impact on aquatic organisms. Nevertheless, there is a paucity of studies examining their effects on tropical aquatic species. In this context, the objective of this study was to (i) conduct chronic ecotoxicological assays with the sea urchin Echinometra lucunter with two phytoestrogens, namely genistein and daidzein (both derived from soy plant), and compare the results to the synthetic estrogen ‘estradiol valerate’; (ii) predict the potential risks of these phytoestrogens through an ecological risk assessment; and (iii) create a prioritization list of the most hazardous phytoestrogens using environmental persistence, bioaccumulation, and toxicity (PBT criteria). The results of chronic exposure demonstrated the following order of toxicity: daidzein (IC₅₀ = 2.60 mg/L); genistein (IC₅₀ = 3.37 mg/L); and estradiol valerate (IC₅₀ = 28.40 mg/L). The results classify genistein and daidzein as “toxic” and estradiol valerate as “harmful” to the sea urchin. The final ranking of the PBT approach in coastal waters was as follows: biochanin A (the highest priority), followed by formononetin, genistein, enterolactone, daidzein, estradiol valerate, coumestrol, and 8-prenylnaringenin. The dataset highlights the importance of environmental monitoring to track phytoestrogens in Latin American coastal areas, particularly in developing countries. Full article