Coastal Research Articles

Ecosystem carbon accumulation of Sonneratia apetala mangroves along an afforestation chronology in Bangladesh

Coastal plantation ecosystems play a vital role in the protection of coastal regions, biodiversity conservation, and the provision of valuable ecosystem services. These ecosystems have been recognized for their capacity to sequester carbon, making them instrumental in mitigating global warming. In this study, we assessed ecosystem carbon (EC) density levels in Sonneratia apetala planted coastal ecosystems in the Char Kukri-Mukri and Montaz mangrove reserves in the south-central Bangladesh. Using 48 representative plots from four stand ages (8-32 years), carbon density changes in trees and soil (0–15 and 15–30 cm) were evaluated. Results showed significant differences in vegetation carbon (VC) density, soil organic carbon (SOC) concentration, SOC density, and EC density among different stand ages, soil depths and mangroves. The increased EC density in Char Kukri Mukri (12.21 t ha-1 yr-1) and in Char Montaj (12.62 t ha-1 yr-1) with advancing stand ages (year-8 to year-32) provides empirical evidence of the effectiveness of afforestation in enhancing EC density in S. apetala planted mangroves. Regardless of stand age, the higher SOC density found in the upper soil layer (51 t ha-1 in year-32 stand) compared to the lower layer (38 t ha-1 in year-32 stand) in both mangroves highlights that the majority of soil carbon is concentrated in the top 15 cm of the forest floor. Within the 0–30 cm soil layer, SOC density demonstrated an increasing trend, with rates of 1.30 t ha-1 yr-1 in Char Montaj, and 1.33 t ha-1 yr-1 in Char Kukri Mukri mangroves between year-8 and year-32 stands. This study provides valuable insights for policymakers, land managers, and conservation practitioners, emphasizing the significance of coastal plantation ecosystems in carbon sequestration and the need for informed management strategies to optimize their climate mitigation potential.

Plastic Litter: A Hidden Reservoir for Antibiotic-Resistant Pathogens in Coastal Ecosystems

Plastic litter carrying pathogenic bacteria pose serious threats to the health of human and aquatic life. We enumerated the abundance of Escherichia coli and Vibrio species in different types of plastic litter (biomedical, food packages, sanitary, fishing material and miscellaneous) collected from the beaches of Agatti and Kavaratti in the Lakshadweep islands of India using quantitative real-time PCR. Further the antimicrobial resistance profile of E. coli and Vibrio species isolated from these samples were also tested. A very high number (more than three thousand gene copies per gram of plastic litter) of Escherichia coli, and Vibrio spp. were detected in the plastic litter. Vibrio spp. in the plastic litter were identified as V. harveyi, V. neocaledonicus, V. japonicus, V. parahaemolyticus and V. campbelli. More than sixty percentage of E. coli and Vibrio spp. isolated from all samples except the E. coli isolated from fishing gear of Kavaratti had multiple antibiotic resistance index of more than 0.25. Most of the bacteria were resistant towards ampicillin, erythromycin, and moxifloxacin, while least resistance was observed against gatifloxacin, gentamicin, imipenem, meropenem, norfloxacin and trimethoprim. These results indicate that plastic litter may act as a conduit for the attachment and transport of multiple antibiotic resistant pathogens, causing severe setbacks to the global efforts on attaining sustainable development goals 3 (health), 6 (clean water) and 14 (life under water). Therefore, strict implementation of plastic waste management rules, awareness campaigns for cleaning beaches and citizen science initiatives to monitor and remove plastics are proposed for protecting the beaches from the deleterious effects of mismanaged plastics.

Structural and functional parameters of the Black Sea phytoplankton during the summer bloom of the coccolithophore Emiliania huxleyi

The aim of the study was to examine the main primary production indicators, describe the controlling factors and identify the conditions for the weak bloom of Emiliania huxleyi in the Crimea coast of the Black Sea during June – July 2022. The surface chlorophyll a (Chl a) varied between 0.3 to 1.5mgm-3 and primary production (PP) within 12–174mgC m-3 day-1. The integrated concentration of Chl a in the euphotic layer was 4–29mgm-2, and that of PP - 240–835mgC m-3 day-1. On average, 49% of Chl a was located bellow the photosynthetic zone. The relationship between integral PP and the total Chl a, nitrogen (nitrates and ammonium), phosphates and silicates in the euphotic layer, analyzed by a multiple regression, showed that 70% of the PP variability was accounted for by the first three variables. While the significance of total Chl a was the highest, followed by phosphates, nitrogen had a negligible effect and that of silicates was not detected. In the surface layer (0–1m), the total phytoplankton biomass was co-dominated by dinoflagellates, the large cell diatom Pseudosolenia calcar-avis and the coccolithophore E. huxleyi. A weak bloom of E. huxleyi (cell abundance 1.0–1.8·106 cells L-1) was detected at 11 out of the 23 sampling stations. The relatively large thickness of the upper mixed layer (about 10m on average) and phosphorus deficiency were the main factors limiting the bloom of this coccolithophore.

Characterising intertidal sediment temperature gradients in estuarine systems

Coastal marine ecosystems are under increasing threat from environmental shifts associated with climate change, particularly increasing temperatures, as temperature influences the physiology, distribution, and abundance of marine organisms. Sediment temperatures on soft sediment intertidal flats are highly variable in space and time due to intermittent exposure to air and seawater. Surface sediment layers may have greater temperature variation relative to deeper layers, and local physical and biological characteristics as well as oceanic and atmospheric temperature conditions are expected to influence the temperatures experienced by sediment dwelling fauna. However, there is little reporting of the dynamics of sediment temperatures in these ecosystems and the local conditions that drive them. We focused on measuring estuarine intertidal sediment temperatures to describe the conditions that resident intertidal macroinvertebrates, including infauna, are being exposed to. Monitoring of sediment temperatures in intertidal ecosystems during summer revealed that sandy intertidal flats had greater temperature fluctuations than muddy intertidal flats. Local weather conditions were important drivers of both low and high tide sediment temperatures, and satellite derived sea surface temperature (SST) data for the study area were sparse and poorly matched sediment temperatures, revealing limitations of satellite SST for predicting site-specific intertidal sediment temperatures in nearshore areas. This study demonstrates the need for long term monitoring of intertidal sediment temperatures across large spatial scales and environmental gradients to understand and predict the potential impacts of climate change.

Refining submarine groundwater discharge analysis through nonlinear quantile regression of geochemical time series

A reliable quantification of fresh submarine groundwater discharge (SGD) is key to understanding and managing water quality and habitat of coastal ecosystems. However, current radon tracer-based SGD quantifications suffer greatly from uncertainty and subjectivity in tracer signal processing and the indirect estimation of non-SGD related tracer sources and sinks. This study provides a new procedure and models SGD rates as upper envelopes in radon and inverted salinity vs water depth regressions over tidal cycles. We use non-linear quantile regression to model these envelopes and account for signal lag correction and noise suppression via optimization towards matched radon and inverted salinity envelope data, and a monotonic (i.e., non-oscillating) trend for the water depth. We then quantify the SGD rate based on the temporal change of the modeled radon envelope inventory and define the radon signature of the fresh groundwater endmember (which is critically important for the calculation of volumetric discharge rates) as the zero-salinity intercept in the envelope regression. Our results indicate that the traditional radon mass balance, if applied at a data aggregation interval of < 1 h and if based on a subjective mixing loss estimation, may lead to a substantial overestimate of SGD. This limitation should be carefully considered in the calibration of lager scale, model-based SGD analyses.

Ecological condition of seagrass meadows around sea-based tin mining activities in the waters of Bangka Belitung Islands, Indonesia

Bangka Belitung islands have long been major tin producers, impacting the environment, including coastal ecosystems. Tin extraction from the seabed increases water turbidity and alters chemical composition, adversely affecting seagrass meadows. This study investigated the ecological condition of seagrass meadows around sea-based tin mining activities on the islands. We mapped seagrass habitat extent and calculated the Seagrass Ecological Quality Index (SEQI) at five locations reflecting varying environmental impacts of tin mining. Satellite imagery from Landsat 7 ETM+ (2000) and Sentinel L2A (2022) was used, showing higher mapping accuracy during low tide. Our analysis revealed that seagrass meadows near mining sites had low species diversity and significant habitat decline over the past two decades (82.79 %). SEQI values were lower, and Total Suspended Solid (TSS) levels were higher near mining operations. This study underscores the detrimental effects of tin mining on seagrass meadows, urging stringent regulations, rehabilitation, and continuous monitoring for sustainability.

Contrasting pollution responses of native and non-native fish communities in anthropogenically disturbed estuaries unveiled by eDNA metabarcoding

Understanding the influence of environmental pollutants on the assembly mechanisms of estuarine fish communities is vital for addressing conservation challenges in these biodiverse ecosystems. Although significant research has explored the toxic impacts of pollutants such as petroleum, heavy metals, and eutrophication on individual species and populations, their effects on community assembly processes and the differential responses of native versus non-native fish at the meta-community level remain inadequately understood. This study utilized environmental DNA (eDNA) metabarcoding to analyze fish community diversity across 28 subtropical estuaries in China, assessing how these pollutants affect community composition and assembly mechanisms. Results indicated that eDNA was 2.54 times more effective than traditional methods in species identification, while also enabling the detection of a higher number of non-native fish species and more diverse functional guilds within estuarine ecosystems. A significant distance decay pattern (p < 0.05) was observed among native fish, whereas non-native species exhibited non-significant patterns. Neutral and null models showed that non-native species had significantly higher migration rates (0.005939 vs 0.001757) and a greater contribution of stochastic processes (82.38% vs 70.59%) compared to native species. Additionally, distance-based redundancy analysis (db-RDA), variance partitioning analysis (VPA), and correlation analyses revealed that native species were strongly constrained by environmental factors, particularly oil, Hg, Zn, Pb, Cr6+, and NH4+, while non-native species displayed notable resilience to these pollutants. These findings highlight the potential for non-native species to disproportionately influence community dynamics and assembly through unrestricted random dispersal amid environmental disturbances. This research clarifies the contrasting ecological responses of native and non-native fish communities to anthropogenic pressures in estuarine environments, offering essential insights into ecosystem resilience and informing biodiversity conservation strategies in rapidly changing coastal ecosystems.

Statistical Analysis of Extreme Sea Levels in the Red Sea

Coastal areas frequently experience high-sea-level events that can cause property damage and loss of life. From a coastal engineering perspective, accurately estimating the probability of extreme sea levels is crucial for designing robust coastal structures. While these estimates are typically based on long-term tide-gauge observations, sea-level hindcasts are also used when available data are limited. This study obtained estimates of extreme sea-level probabilities for the Red Sea, utilizing a 30-year dataset (1993–2022) containing hourly sea level records reconstructed using a surge model (MOG2D), a global tide model (FES2014), and sea-level anomaly data from satellite altimeters. The reconstructed sea-level data were validated against measurements from six tide gauges along the eastern Red Sea and demonstrated good agreement. Spatial maps of extreme sea levels indicated values ranging from approximately 0.4 to 1.8 m. The highest estimates for the 100-year return level were found in the northern Gulf of Suez, with elevated values also observed in the northern and southern Red Sea. Furthermore, we assessed the impact of sea-level rise on extreme sea-level probabilities. Our results revealed that even small increments in the mean sea level could lead to considerable changes in extreme sea-level probabilities across most of the Red Sea. Overall, our findings are valuable for various coastal development projects along the Red Sea coast and for improving coastal vulnerability assessments.

Ecophysiological adaptation and potential of energy production of two halophytes grown in the Red Sea coast of Egypt

Ecophysiological adaptation and potential of energy production of two halophytes grown in the Red Sea coast of Egypt

High microplastic pollution in marine sediments associated with urbanised areas along the SW Bulgarian Black Sea coast

This study aims to provide baseline data on microplastic (MP) concentrations in beach and seabed sediments of the SW Black Sea coast, and to identify possible sources of MP pollution in the area. MP concentrations in beach sediments in urbanised coastal areas, as well as in all seabed sediments, were on average higher than in other parts of the Black Sea and most other European seas. Urban coastal areas showed the highest average MP concentrations (mean ± SD): 464.44 ± 272.50 MP·kg−1 dry sediment in beach samples, 825.93 ± 396.30 MP·kg−1 dry sediment in seabed samples, while coastal sediments in an area with no local anthropogenic activities had significantly lower average MP concentrations: 84.44 ± 147.57 MP·kg−1 in beach samples, and 550.62 ± 245.71 MP·kg−1 in seabed samples. Possible identified sources of MPs include sewage water discharges, urban waste, coastal fisheries and aquaculture, as well as accumulation of marine litter on beaches and in adjacent offshore areas, serving as sources of secondary MP pollution.

Towards optimizing conservation planning: A performance evaluation of modeling techniques for predicting Mediterranean native species distribution

Understanding the intricate relationships between environmental conditions and key variables influencing species distribution is critical for ecology and conservation, especially in the face of escalating environmental challenges intensified by climate change. Species Distribution Models (SDMs) are valuable tools for predicting current and future habitat suitability, aiding in conservation planning. This study specifically sought to evaluate the predictive performance of different modeling techniques in determining the geographical distribution of three Mediterranean native species with different ecological flexibility in the western Mediterranean coastal land of Egypt namely Thymelaea hirsuta (L.) Endl., Ononis vaginalis Vahl, and Limoniastrum monopetalum (L.) Boiss. An ensemble model incorporating three modeling algorithms -the generalized linear model, boosted regression trees, and random forests- was juxtaposed against the Maxent non-parametric machine-learning modeling technique. The models integrated diverse variables, encompassing climatic, edaphic, habitat, and topographic factors. The results unveiled a high degree of similarity and agreement between the Maxent and ensemble models, both exhibiting outstanding fits and performance metrics. The ensemble model demonstrated remarkable accuracy across various measures evaluating model performance. However, Maxent showcased a comparatively strong performance, particularly in identifying critical areas for the distribution of the studied Mediterranean species. These findings emphasize the importance of employing a suite of modeling techniques to refine conservation planning and management strategies. At the local scale, the outcomes can guide targeted actions such as habitat restoration and species monitoring programs. Regionally, and globally it can inform policy development and cross-border conservation initiatives that address shared environmental challenges and contribute to frameworks for studies of similar ecosystems worldwide. Such a comprehensive approach ensures more effective safeguarding of Mediterranean native species under changing environmental conditions.

Socio-economic risk assessment of the setback zone in beaches threatened by sea level rise induced retreat (Peloponnese coast- Eastern Mediterranean)

Abstract Beaches play a pivotal role in supporting the socio-economic sector, particularly within the 'Sun, Sea, and Sand' (3S) tourism model. Valued for their ecosystem services, these coastal landforms are among the most dynamic and vulnerable environments, facing significant pressure from various climate challenges, which is further intensified by extensive anthropic exploitation. Their sustainable use is intrinsically linked to balancing the 3Ps: Planet, People, and Profit. To address the need for protection and sustainable utilization of coastal areas, the European Union has introduced the Protocol on Integrated Coastal Zone Management (ICZM) in the Mediterranean, specifically recommending in Article 8(2) the establishment of a setback buffer zone where permanent constructions are prohibited. This paper explores the application of risk mapping in the context of coastal setback policies, focusing on their effectiveness in managing beach retreat and adapting to climate change, particularly rising sea levels. The study examines selected beach areas in Peloponnese, Greece, influenced by various socio-economic factors. Through this analysis, the paper aims to contribute to the discourse on coastal management strategies that balance environmental sustainability with socio-economic benefits.

Correction: Strategic environmental assessment for sustainable coastal zone management in Saudi Arabia, aligning with vision 2030

Correction: Strategic environmental assessment for sustainable coastal zone management in Saudi Arabia, aligning with vision 2030

A Model of Microwave Emission from Mouth Regions of Arctic Rivers Providing for Radiometer Pixel Land Contamination

The paper presents a model of microwave emission from mouth regions of Arctic rivers taking into account radiometer pixel contamination by land. Modeling of seasonal and interannual dynamics of brightness temperature of different regions of the Yenisei Bay is performed on the example of MIRAS radiometer data from the SMOS satellite. The necessity of considering the coastal zone in brightness temperature modeling in the studied regions is shown. Comparison of the model calculations with SMOS L1C data has shown a good agreement. Analysis of model calculations and satellite data has allowed us to determine the location of the fresh and salt water mixing zone in the Yenisei Bay during the ice period, provided that the model takes into account the coastal zone captured by the radiometer pixel.

Long-term Coastline Monitoring in the Thanh Hoa Province (Vietnam) Using Landsat 5 and Landsat 8 Data

In recent years, extensive human activities have had a profound impact on the estuaries and coastal areas of Vietnam, most notably in coastal erosion and accretion. This paper used the Landsat multi-temporal data for the period 1988–2022 to assess coastline change in Thanh Hoa province (North Central Vietnam). Water indices calculated from Landsat imagery data, including NDWI, ANDWI, MNDWI, AWEInsh, AWEIsh, and BandWet, are used to extract surface water areas and then vectorize and overlay to estimate shoreline variability. The Otsu thresholding method is used to classify “water surface” and “land objects” and then evaluate the accuracy using the Kappa coefficient. The obtained results show that the ANDWI index has the highest accuracy in extracting the water body of the study area, in which the value of the Kappa coefficient reaches 0.95 compared to 0.91, 0.92, 0.93, 0.92 and 0.92 at using NDWI, MNDWI, AWEInsh, AWEIsh and BandWet indicies. Boundary vectorization and vector image overlays were performed to assess shoreline variability and map shoreline dynamics. The results obtained show that in the northern part of the coastal zone of Thanh Hoa province there is active accretion (increment) of the coastline. The average accretion rate was 150 m/year, the maximum rate was 457 m/year. In contrast, on the southern coast of Thanh Hoa province, coastline erosion predominates with a maximum rate of 38 m/year and an average rate of about 10 m/year.

Hydroacoustic Observations Reveal Drivers of Mixing and Salinization of a Karst Subterranean Estuary During Intense Precipitation

AbstractKarst subterranean estuaries within globally ubiquitous carbonate aquifers are coastal groundwater ecosystems that provide an essential water resource for human populations. To understand the drivers of salinization within a coastal aquifer in the Yucatan Peninsula (Mexico), we employed hydroacoustics in flooded caves to observe how oceanic and atmospheric events facilitate mixing between the meteoric lens (fresh‐brackish groundwater) and the saline groundwater on tidal and episodic timescales. Precipitation during Tropical Storm Carlotta increased the flow and salinity of the meteoric lens without evidence for vertical mixing across the halocline. We postulate that vertical migration of haloclines in the conduit relative to those within the rock matrix during precipitation creates lateral density gradients that drive mixing, and ultimately creates a brackish layer within the meteoric lens. These results provide a mechanistic explanation for vertical and lateral exchange in a coastal carbonate aquifer, which has implications for groundwater response to future climatic change.

Place-Based Conservation in Coastal and Marine Ecosystems: The Importance of Engagement with Underrepresented Communities

Through the years, research has described the importance of community-based approaches in the management of coastal and marine ecosystems. Coastal and marine issues are multifaceted and require place-specific approaches developed in partnership with vulnerable communities who are impacted by environmental stressors. Place-based conservation, a management approach that focuses on unique, place-specific characteristics, and other similar methods. It considers the need to integrate human dimensions and location-centered approaches, which are often lacking in typical natural resource management. Meaningful engagement with underrepresented communities can holistically account for socioeconomic factors and cultural knowledge that inform best management practices. As the health of marine and coastal ecosystems is linked with environmental quality and local livelihoods, engaging practitioners with knowledge of these systems can support science and trust in environmental management. This article discusses the importance of community-based research, local insight, various examples of successful management, and culturally relevant knowledge to advance sustainable place-based conservation.

The Optimal Arrangement of Boats in a Coastal Maritime Passenger Lines System Using Graph Theory

This paper presents research in the field of optimization in maritime passenger traffic that can ensure the long-term sustainability of coastal maritime passenger lines system. For the purpose of the research contained in this paper, it has been hypothesized that the optimal arrangement of boats within a coastal maritime passenger lines system will reduce the consumption of propulsion energy, the emission of harmful gasses and operating costs. The aim of this paper is to present an efficient algorithm for a reduction in propulsion energy consumption in coastal maritime passenger lines systems by reassigning boats to lines that they service. The problem is modeled using a bipartite graph and the solution is obtained by searching for optimal matching using Edmonds’ algorithm. The authors apply, for the first time, Edmonds’ algorithm to the problems of the optimization of assignments of boats to lines. The research results were confirmed by tests on a representative example. The optimization results on only 10 ships in the given example show yearly savings of 91,097.30 L of fuel (lowering costs by EUR 69,233.95) and reducing CO2 by 243.59 tons, which proves that this algorithm found a much more efficient arrangement that could result in a significant reduction in propulsion energy consumption, thus providing economic and ecological benefits.

Carbon Sequestration Potential of Rhizophora mucronata in Tongke-Tongke Mangrove Forest, Sinjai Regency, Indonesia

Mangroves play a crucial role in coastal ecosystems, offering significant ecological benefits and acting as important carbon sinks. This study focuses on the carbon sequestration potential of Rhizophora mucronata in the Tongke-Tongke mangrove forest, Sinjai Regency, Indonesia. By measuring the carbon content in leaves, roots, and sediments, the study found carbon content ranges from 0.09 to 0.11 tons/ha in leaves with a carbon absorption capacity ranging from 0.33–0.42 tonnes/ha and 0.44 to 0.72 tons/ha in roots with absorption capacity reaching 1.60–2.64 tonnes/ha, with sediment carbon content varying significantly ranges from 8.66–156.83 tons/ha with an absorption capacity of 31.79–575.55 tons/ha. The carbon content in mangrove stands reaches 109.23–180.87 tonnes/ha, with carbon uptake reaching 400.89–663.80 tonnes/ha. Results indicate that R. mucronata has a substantial carbon absorption capacity, underscoring the importance of these ecosystems in climate change mitigation. The findings aim to inform conservation strategies and potential carbon trading initiatives, contributing to global climate resilience.

Application of Remote Sensing in Analyzing Mangrove Forest Changes and Drivers in Mui Ca Mau National Park, Vietnam

Mangroves are vital in coastal ecology and for sustaining and securing coastal communities. However, several factors such as human activities and climate change have changed mangroves' quantity and quality. This research analyses land-use/land cover (LULC) changes focusing on mangroves in Mui Ca Mau National Park (MCMNP) from 1995-2022. Collected Landsat imagery in 1995, 2003, and 2022 were applied to perform this research. Overall accuracy and Kappa of land cover classification were 88.5% and 0.86 in 2003, and 87.6% and 0.85 in 2022, respectively. The classified results showed that the mangrove area had increased significantly from 4,316.1 hectares in 1995 to 8,741.3 and 10,764.1 hectares in 2003 and 2022, respectively. In addition, the drivers of mangrove change were identified and analyzed. This study showed the important role of policy in mangrove conservation and the sustainable use of natural resources. The study provided useful information for policy-making in terms of forest conservation and management.