Coasts

“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

The ocean disposal of wastewater is an efficient alternative in the sewage system of coastal areas since the urban density of such regions is a barrier to the settlement of conventional sewage treatment plants. In addition, the associated costs of this alternative are significantly lower than the convention in the long term. The degradation of microbiological contaminants strongly depends on solar radiation and the factors that regulate its intensity, such as the depth of the effluent plume, seasons, and cloud cover. The submarine disposal of domestic sewage constitutes a low-sanitation-risk alternative regarding the contamination of bathing areas. The results based on computational modeling corroborate this alternative, showing that the coastal zone is not affected by marine sewage discharges. Full article

Coastal upwelling that cools sea temperatures and nutrifies the euphotic layer is the focus of this research, motivated by how these processes benefit the marine ecosystem. Here, atmosphere–ocean reanalysis fields and satellite radiance data are employed to link South African coastal upwelling with nearshore winds and currents in the 2000–2021 period. Temporal behavior is quantified in three regimes—Benguela, transition, and Agulhas—to distinguish the influence of offshore transport, vertical pumping, and dynamic uplift. These three mechanisms of coastal upwelling are compared to reveal a leading role for cyclonic wind vorticity. Daily time series at west, south, and east coast sites exhibit pulsing of upwelling-favorable winds during summer. Over the western shelf, horizontal transport and vertical motion are in phase. The south and east shelf experience greater cyclonic wind vorticity in late winter, due to land breezes under the Mascarene high. Ekman transport and pumping are out of phase there, but dynamic uplift is sustained by cyclonic shear from the shelf-edge Agulhas current. Temporal analysis of longshore wind stress and cyclonic vorticity determined that vertical motion of ~5 m/day is pulsed at 4- to 11-day intervals due to passing marine high/coastal low-pressure cells. Height sections reveal that 15 m/s low-level wind jets diminish rapidly inshore due to topographic shearing by South Africa’s convex mountainous coastline. Mean maps of potential wind vorticity show a concentration around capes and at nighttime, due to land breezes. Air–land–sea coupling and frequent coastal lows leave a cyclonic footprint on the coast of South Africa that benefits marine productivity, especially during dry spells with a strengthened subtropical atmospheric ridge. This work has, for the first time, revealed that South Africa is uniquely endowed with three overlapping mechanisms that sustain upwelling along the entire coastline. Amongst those, cyclonic potential vorticity prevails due to the frequent passage of coastal lows that initiate downslope airflows. No other coastal upwelling zone exhibits such a persistent feature. Full article

Evaluating the effects of environmental events across both biophysical and social dimensions is important in establishing a holistic view of such events. This study focuses on the impact of a devastating heat stress incident that occurred in many locations across the Caribbean region and South Atlantic during the 2023 summer season. The survey and focus of data collection was within Monroe County, a unique nature-based setting south of Miami, Florida, USA. The impact of the heat wave is still being calculated at the time of submission of this paper, but indications are that there was a major negative impact. The survey and data collection sought to understand recreationists’ perceptions, knowledge, and behavior changes as result of the heat stress impact in the Florida Keys. Respondents were interviewed during community workshops in person and through an online sample of boating/angler license holders. The results indicated a change in behavior by some respondents, which may have a longer-term economic impact, along with trends of satisfaction with outdoor recreation over time. This rapid survey method can be applied to future scenarios where social and economic data are needed to fully contextualize environmental impacts in addition to biological endpoints. Full article

This study examines the frequency of tropical cyclones in the Bay of Bengal and their impact on Bangladesh. The extent of environmental harm led to the selection of two specific areas: the Panpatty Union and Galachipa Upzilla in the Patuakhali district, and the Sariakat Union and Swandip Upzilla in the Chittagong district. The results indicate that cyclonic storms are more common in May and November. The results also demonstrate that the studied regions are vulnerable to the effects of tropical cyclones and suffer significant consequences. The differences in influence between the two locations are statistically significant with a confidence level of 90%. The findings have significant ramifications for policymaking decisions. Full article

The coastal region of the Caribbean is notable for the chemical diversity found in its sponge products, resulting in the biosynthesis of a range of natural marine products, including polyketides. The objective of this manuscript is to summarize the isolated polyketides from sponges of the genus Plakortis located around the Caribbean coasts. This review provides a comprehensive overview of specimen location, isolation procedures, characterization methods, and biological assay studies of about 95 polyketides isolated from 1978 to 2024 in the Caribbean coasts of The Bahamas, Cayman Islands, Belize, Dominica, Jamaica, Martinique, Panamá, Puerto Rico, and Tobago. The Caribbean polyketides have been isolated from different types of Plakortis sp., such as P. simplex, P. halichondroides, P. zyggompha, and P. angulospiculatus, which have demonstrated antimicrobial, anticancer, anti-inflammatory, antiparasitic, and antiviral activities. A variety of linear polyketides with different functionalities have been reported, including endoperoxides (1,2-dioxane), lactones, indane-type bicyclics (spiculane and zyggomphic), alcohols, alkenes, styryl groups, α,β-unsaturated carboxylic acids, and ketones, as well as related natural products of biosynthetic origin. The aim is to encourage further exploration by researchers in the Caribbean’s coastal marine environments, promoting the discovery and investigation of novel polyketide cyclic peroxides and related secondary metabolites to identify additional bioactive medicinal natural products. Full article

Endangered sharks and rays usually often lack basic information specific to conservation, such as population size. Previous studies have reconstructed shark and ray catch statistics between 1950 and 2019 for the southeast = south of Brazil, but lacking detail at the species level, because the catches were grouped by family, genus or even common name (e.g., skates and rays, Dasyatidae, Rhinobatos, Sphyrnidae, Squatinidae). In this study, we used proportions between species from scientific observer fishing trips and Dirichlet regression modelling to reclassify these categories. This model is a multivariate extension of beta regression and enables the modeling of asymmetric and heteroscedastic compositional data, allowing multinomial data to be obtained in a more informative way. The reconstruction of catches for unclassified data showed a massive dominance of the Squatinidae family until the late 1970s, when catches showed signs of decline. At the same time, the rays of the “emplastro” family showed a progressive increase from 2006 onwards. However, this scenario changed after the reclassification. The category Squatinidae was maintained almost exclusively by S. guggenheim, while 16 categories of species were observed within “emplastro” rays, many of which fall into “endangered”, “vulnerable” and “critically endangered” criteria. These reconstructed series provide a more reliable scenario of the catches of thirty elasmobranch species in the southeast and south of Brazil and serve as baseline information for understanding the conservation status of these species. Full article

Recreational fishing is practiced by thousands of people in European coastal waters and is steadily gaining popularity. Serving multiple purposes, recreational fishing provides fresh fish for meals, offers leisure, and contributes to traditional ecological knowledge, especially at the local level. Therefore, analyzing its dynamics and catch is a complex task, since they not only depend on the environmental features but also on the behavior of fishers. In coastal areas, however, most recreational fishers remain unmonitored, making it difficult to obtain data on their impact on fish stocks. This is particularly evident in the Venice lagoon, where we conducted a comprehensive study aiming to characterize recreational fishing dynamics. We collected data through interviews, online questionnaires, and remote sensing techniques, including satellite imagery photointerpretation and machine learning algorithms. Our findings reveal spatial and temporal variations in fishing activity, with certain areas and times experiencing higher fishing pressure. This highlights a seasonality in fishing activity and a pattern in fishers’ behaviors that are associated with fish migratory dynamics. Such an association demonstrates the local fishers’ understanding of the fish lifecycle phases and the environmental conditions of the lagoon. Regarding the catch, the most targeted species are seabream (Sparus aurata), seabass (Dicentrarchus labrax), and cuttlefish (Sepia officinalis), with estimated total catches of 18.65 t per year, 15.82 t per year, and 8.36 t per year, respectively. However, our results showed a significant disproportion between the biomass caught by two different groups of fishers that differ in terms of fishing trip frequency, success rate, and catch. While the average catch of the first group, representing most recreational fishers, might be considered of low impact, the catch of the second group, encompassing recreational fishers who fish with very high frequency and efficiency, is substantial in the context of the lagoon ecosystem. Indeed, even considering a conservative estimate, recreational fishing in the Venice lagoon accounted for approximately 2% of the catch of cuttlefish and 17% of the catch of seabream compared to commercial fishing catch, whereas the catch of seabass by recreational fishing approached that of commercial fishing. Therefore, the implementation of a periodic monitoring program utilizing methods such as machine learning algorithms and remote sensing technologies could support the management of recreational fishing dynamics. We also suggest that participatory processes involving both professional and recreational fishers may aid in defining shared approaches and bottom–up initiatives, ensuring enjoyment as well as sustainable uses of coastal areas. Full article

This study analyses climate variability on the north coast of Peru to understand how the local weather is coupled with anomalous ocean conditions. Using high-resolution satellite reanalysis, statistical outcomes are generated via composite analysis and point-to-field regression. Daily time series data for 1979–2023 for Moche area (8S, 79W) river discharge, rainfall, wind, sea surface temperature (SST) and potential evaporation are evaluated for departures from the average. During dry weather in early summer, the southeast Pacific anticyclone expands, an equatorward longshore wind jet ~10 m/s accelerates off northern Peru, and the equatorial trough retreats to 10N. However, most late summers exhibit increased river discharge as local sea temperatures climb above 27 °C, accompanied by 0.5 m/s poleward currents and low salinity. The wet spell composite featured an atmospheric zonal overturning circulation comprised of lower easterly and upper westerly winds > 3 m/s that bring humid air from the Amazon. Convection is aided by diurnal heating and sea breezes that increase the likelihood of rainfall ~ 1 mm/h near sunset. Wet spells in March 2023 were analyzed for synoptic weather forcing and the advection of warm seawater from Ecuador. Although statistical correlations with Moche River discharge indicate a broad zone of equatorial Pacific ENSO forcing (Nino3 R~0.5), the long-range forecast skill is rather modest for February–March rainfall (R² < 0.2). Full article

This article presents a diachronic study of evolution along the coastline of Noirmoutier Island in France, a sandy shore particularly susceptible to erosion and submersion risks, which are exacerbated by climate change due to two-thirds of its territory being below sea level. The study is based on an analysis of aerial images covering a period of 72 years, divided into five distinct periods: 1950–1974, 1974–1992, 1992–2000, 2000–2010, and 2010–2022. The methodology used combines two complementary approaches: the Digital Shoreline Analysis System (DSAS) for taking linear measurements of the erosion and accretion that have taken place along various shorelines, and the surface method to evaluate the amount of surface lost or gained between different shorelines while calculating the uncertainties associated with the obtained results. The overall trend observed between 1950 and 2022 indicates that the Noirmoutier coastline studied has gained surface area (81 hectares) at an average rate of +0.57 ± 0.06 m per year. The article then presents an application of the method developed by Durand and Heurtefeux in 2006 to estimate the future position of the shoreline. A map of the local area is also provided, identifying the areas susceptible to coastal erosion by 2052 and by 2122, in accordance with the provisions of the Climate and Resilience Law adopted in France on 22 August 2021. The results reveal that there are many sources of uncertainty in predicting the future evolution of the shoreline using this methodology. Therefore, it is crucial to consider these uncertainties when planning future coastal management actions and adopting appropriate adaptation methods to counteract unforeseen developments. Full article

The spatiotemporal distribution of phytoplankton in estuaries is indicative of processes and transport across the land–ocean aquatic continuum (LOAC). Estuaries, as biogeochemically and physically active systems, process large amounts of nutrients and organic matter influencing the transformation of ecological functions. The transformation of the water column drives variation in phytoplankton composition, biomass, and their spatial distribution. Understanding the dynamics of nutrients and organic matter is challenging, yet it provides a comprehensive insight into phytoplankton spatiotemporal distribution across estuaries. Multiple studies have been conducted to understand the spatiotemporal distribution of phytoplankton. Recently, phytoplankton photosynthetic pigments, fatty acids and stable isotopes have been widely used to identify and quantify phytoplankton distribution. This review highlights the use of biogeochemical markers to identify phytoplankton functional groups. It also assesses the current understanding of patterns in the spatiotemporal distribution of phytoplankton and the impact of physical and environmental factors on their distribution in estuaries and coastal oceans. The review will also gather information from in situ sampling studies to evaluate the current state of knowledge and identify gaps. Full article

A day-to-day temperature (DTD) variability metric was used to detect marine coastal climates in the province of Ontario, Canada. Eleven of fourteen climate stations on islands, most in the Great Lakes and two in other large water bodies, displayed marine characteristics using a day-to-day temperature metric threshold developed for ocean coastal locations in China and Canada with values below 2.35 for the daily minimum temperature variability. Detailed comparisons with neighbouring coastal stations were conducted for six focal areas in the Great Lakes and the marine effect on the local climate was unambiguously demonstrated in a statistically significant manner. Those displaying marine characteristics were all island climate stations, usually at an elevation close to the lake level, and the marine influence, as measured by day-to-day temperature variability, dropped off rapidly with distance and elevation from the local water body. The DTD metric was compared to a diurnal temperature range (DTR) metric. While DTR was able to distinguish in a statistically significant manner between islands and inland stations, an unambiguous threshold between the two was not possible, unlike DTD. Full article

Sand nourishments and groynes as coastal protection measures (CPM) address similar challenges on sandy coasts but take different approaches: while groynes are intended to reduce alongshore sediment transport and erosion, nourishments add new sediment to the system to compensate for erosion. The aim of this study is to compare the ecological effects of such measures on the vegetation. To this end, nutrient analysis and botanical mappings were carried out on a site with installed groynes, a site where sand nourishments are regularly carried out, and a control site without any CPM. In addition to an increase in nutrient availability after the sand nourishment, significant changes in plant species diversity and composition were also measured. The number of higher plants, mosses, and lichen species was lower at the nourishment site. The opposite impacts were observed at the groyne site: an increase in sediment cover by higher plants and mosses and a distinct increase in lichen species. The results suggest that groynes lead to a stabilization of the coastal system and enable dense vegetation growth. In contrast, sand nourishments lead to nutrient input and unstable habitat conditions, attracting certain plant communities but preventing the establishment of ground-covering vegetation. Full article

Zostera marina is an ecologically valuable species that has been declining due to anthropogenic environmental stressors. In this study, spatial and temporal indicators of eelgrass stress, such as coverage and biomass, were compared with the isotopic composition of C, N, and S to understand the mechanism(s) of plant stress. Eelgrass samples were collected in June, July, and August of 2020 at five stations along an estuary spatial gradient in the southern Gulf of St. Lawrence to measure above- and below-ground biomass and tissue isotopes in eelgrass leaves and roots/rhizomes. Eelgrass biomass was lowest at the innermost sampling station, which coincided with eutrophication-induced hypoxia relative to outer sampling stations. δ¹³C levels at the upstream station were depleted compared to downstream stations. Comparatively, δ¹⁵N and δ³⁴S findings were not correlated with plant biomass. Thus, sulfide intrusion was not a major stressor for eelgrass in this estuary. Between the years 2014 and 2020, eelgrass coverage was found to have increased, which coincided with high and low recorded external nutrient loads from the Wheatley River, respectively. Ultimately, these findings indicate that isotopic composition and biomass can be useful in assessing the health of eelgrass in temperate estuaries. Full article

Some seismo-stratigraphic evidence on the occurrence of wave-cut marine terraces in the Licosa promontory (Southern Tyrrhenian Sea, Italy) based on Sub-bottom Chirp seismic sections is herein presented. Such evidence is provided by marine terraced surfaces situated at various water depths below sea level and etched into the rocky acoustic basement, which are extensively extending in the seaward extension of the Licosa promontory. It is possible that the isotopic stratigraphy and the terraced marine surfaces are connected, so they can be attributed and dated indirectly. The geologic study of seismic profiles has pointed to the prominence of the acoustic basement, extending to the seabed close to the coast and subsiding seawards under the Quaternary marine succession. Ancient remains of marine terraces, found at a range of water depths between 5 m and 50 m, have documented the major morphological changes of the acoustic basement during the Late Quaternary. Full article

Estuaries that become closed from the ocean through the formation of a sand bar are particularly susceptible to degradation and often experience poor water quality and fish kills. Sampling was conducted seasonally for two years in the deeper waters of the Vasse–Wonnerup (southwestern Australia) after a large fish mortality event to identify the fish species present and determine if richness, abundance, diversity and faunal composition differed among regions and over time. Species richness, abundance and diversity were far greater in the downstream regions than in the upstream regions, reflecting patterns in salinity. Catch rates of two marine estuarine-opportunist mugilids (Mugil cephalus and Aldrichetta forsteri) and an estuarine-resident sparid (Acanthopagrus butcheri), which were the species most affected by the mortality event, were relatively stable. It is suggested that before sampling commenced, mugilids had entered the estuary following an artificial sand bar breach, while the loss of 0+ (new recruits) A. butcheri in the mortality event and subsequent recruitment failure prevented stocks from increasing. Temporal shifts in fish composition were driven by less abundant species, which utilized the estuary more opportunistically. Increases in the occurrences and abundances of these species coincided with an open bar and salinities close to those of seawater. The data also show how the estuary responds to differing hydrodynamic phases and artificial breaches. Full article

Remote video imagery using shoreline edge detection is widely used in coastal monitoring in order to acquire measurements of nearshore and swash features. Some of these systems are constrained by their long setup time, positioning requirements and considerable hardware costs. As such, there is a need for an autonomous low-cost system (~EUR 500), such as Timex cameras, that can be rapidly deployed in the field, while still producing the outcomes required for coastal monitoring. This research presents an assessment of the effect of the sampling strategy (time-lapse intervals) on the precision of shoreline detection for two low-cost cameras located in a remote coastal area in western Ireland, overlooking a dissipative beach–dune system. The analysis shows that RMSD in the detected shoreline is similar to other studies for sampling intervals ranging between 1 s and 30 s (i.e., RMSD_mean for Camera 1 = 1.4 m and Camera 2 = 0.9 m), and an increase in the sampling interval from 1 s to 30 s had no significant adverse effect on the precision of shoreline detection. The research shows that depending on the intended use of the detected shorelines, the current standard of 1 s image sampling interval when using Timex cameras can be increased up to 30 s without any significant loss of accuracy. This positively impacts battery life and memory storage, making the systems more autonomous; for example, the battery life increased from ~10 days to ~100 days when the sampling interval was increased from 1 to 5 s. Full article