Towards an urban marine ecology: characterizing the drivers, patterns and processes of marine ecosystems in coastal cities

Long-Term Demographic Trends of Near Threatened Coastal Dolphins Living in an Urban Estuary

Understanding population demography of threatened species and how they vary in relation to natural and anthropogenic stressors is essential for effective conservation. We used a long-term photographic capture-recapture dataset (1993-2020) of Indo-Pacific bottlenose dolphins (Tursiops aduncus) in the highly urbanised Adelaide Dolphin Sanctuary (ADS), South Australia, to estimate key demographic parameters and their variability over time. These parameters were analysed in relation to environmental variables used as indicators of local and large-scale climatic events. Our findings indicate that apparent survival was high (0.98-0.99) and did not vary seasonally. Estimates of abundance were not directly related to environmental variables but were linked to seasonal temporary emigration. Abundance peaked in summer with an average of 85.37 dolphins (SD = 30.23) and was lowest in winter, with 68.57 (SD = 24.70) individuals. Site fidelity at the population level was low, but lagged identification rates revealed a population of approximately 28 individuals at any one time. Trend analysis suggests an increase in dolphin abundance from 1993 and persistence of the population over decades despite significant urbanisation, although numbers have declined in more recent years. Further research is needed to understand the cumulative impacts leading to this population decline and to assess its future viability under different management scenarios. Conservation strategies aimed at increasing reproductive rates and promoting connectivity to adjacent waters are likely to be more effective in reversing population declines.

Diversity and structure of epibenthic communities across subtidal artificial hard habitats in the Bay of Cherbourg (English Channel)

To inform the performance of ecological engineering designs for artificial structures at sea, it is essential to characterise their impacts on the epibenthic communities colonising them. In this context, the present study aims to compare the community structure among natural and four different artificial hard habitats with different ages and features installed in the Bay of Cherbourg (English Channel): i) cinder blocks and ii) boulders, both installed six years prior to the study, and iii) smooth and iv) rugous concrete dykes, both installed one year prior to this study. Results showed that artificial habitats installed six years ago harboured communities with functional and taxonomic diversity characteristic of mature communities but were still different from those of natural habitat. Conversely, the two dyke habitats installed one year prior to this study presented a poorly diversified community dominated by opportunistic taxa. Furthermore, while the concrete used for the two dyke habitats presented different rugosity properties, both habitats supported similar communities, suggesting that such eco-engineering measures did not affect the settlement of early colonisers. Overall, this study highlights the need for long-term monitoring to comprehensively evaluate epibenthic colonisation of artificial structures.

Potentially toxic elements in urban soils of the coastal city of the Sea of Azov: Levels, sources, pollution and risk assessment

Coastal cities are major centers of economic activity, which at the same time has negative consequences for the environment. The present study aimed to determine the concentrations and sources of PTEs in the urban soils of Taganrog, as well as to assess the ecological and human health risks. A total of 47 urban and 5 background topsoils samples were analyzed by ICP-MS and ICP-AES. A significant excess of Cu, Zn, and Sb was noted in urban soils compared to the upper continental crust and average world-soil (1.7-2.9 times). Statistical analysis showed that the elements in soils were of geogenic, mixed and anthropogenic origin. According to the single pollution index (PI), the greatest danger of soil pollution was represented by anthropogenic elements, namely Cu, W, Pb, Zn, Cd, and Sn, the levels of which were increased in residential and industrial areas. The median contents of As, Mn, Cr, Sr, Mo, Sb, Cu, W, Pb, and Zn were 1.1-2.1 times higher, while Cd and Sn were 2.5 folds higher in the urban soils compared to the background ones. The total pollution index (ZC) showed that only 15% of the soils had high level of pollution, which is typical for the industrial areas. Overall ecological risks were negligible or low in 92% of soils, and were mainly due to elevated levels of Cu, Zn, As, and Pb. Non-carcinogenic risks to humans were mainly related to exposure to La and Pb. The hazard index (HI) values for all PTEs were less than ten, indicating that overall non-carcinogenic risk for adults and children was low-to-moderate and, moderate, respectively. The total carcinogenic risk (TCR) exceeded threshold and corresponded to low risk, with Pb, As, and Co being the most important contributors. Thus, the industrial activities of Taganrog is the main source of priority pollutants.

Morpho-physiological traits and tissue burdens of Ecklonia radiata linked to environmental variation in an urban estuary

Organisms respond to their environment in various ways, including moving, adapting, acclimatising or a combination of responses. Within estuarine habitats, organisms are exposed to naturally variable environmental conditions. In urbanised estuaries, these natural variations can interact with human stressors such as habitat modification and pollution. Here, we investigated trait variation in the golden kelp Ecklonia radiata across an urban estuary - Sydney Harbour, Australia. We found that kelp morphology differed significantly between the more human-modified inner and the less modified outer harbour. Kelp individuals were smaller, had fewer laminae, and lacked spines in the inner harbour where it was warmer, more contaminated and less light was available. Inner harbour populations were characterised by lower tissue nitrogen and higher lead concentrations. These findings provide insights into how environmental variation could affect kelp morphology and physiology, and the high trait variation suggests adaptive capacity in E. radiata.

Environmental Factors Influencing Metal Concentrations in Scomber colias Along the Canary Islands

A total of 140 specimens of Scomber colias were collected from the Canary archipelago waters during the first semester of 2021, with 20 samples from each of the seven main islands. After analyzing the concentrations of metals (Al, Zn, Cd, Pb, Fe, and Cu) with ICP-OES, significant variations were observed among islands, with specimens from Tenerife and Gran Canaria containing higher levels of Al, Cd, and Pb, while those from Lanzarote and Fuerteventura had elevated levels of Zn, Fe, and Cu. These differences are probably related to greater anthropogenic activity around Tenerife and Gran Canaria coasts, leading to higher pollution levels, and the influence of Saharan dust and African upwelling on Lanzarote and Fuerteventura, enriching the waters with nutrients. Specific management strategies to mitigate marine pollution and continuous monitoring are crucial to safeguard marine ecosystems and to ensure food security.

The Tree of Life eDNA metabarcoding reveals a similar taxonomic richness but dissimilar evolutionary lineages between seaports and marine reserves

Coastal areas host a major part of marine biodiversity but are seriously threatened by ever-increasing human pressures. Transforming natural coastlines into urban seascapes through habitat artificialization may result in loss of biodiversity and key ecosystem functions. Yet, the extent to which seaports differ from nearby natural habitats and marine reserves across the whole Tree of Life is still unknown. This study aimed to assess the level of α and β-diversity between seaports and reserves, and whether these biodiversity patterns are conserved across taxa and evolutionary lineages. For that, we used environmental DNA (eDNA) metabarcoding to survey six seaports on the French Mediterranean coast and four strictly no-take marine reserves nearby. By targeting four different groups-prokaryotes, eukaryotes, metazoans and fish-with appropriate markers, we provide a holistic view of biodiversity on contrasted habitats. In the absence of comprehensive reference databases, we used bioinformatic pipelines to gather similar sequences into molecular operational taxonomic units (MOTUs). In contrast to our expectations, we obtained no difference in MOTU richness (α-diversity) between habitats except for prokaryotes and threatened fishes with higher diversity in reserves than in seaports. However, we observed a marked dissimilarity (β-diversity) between seaports and reserves for all taxa. Surprisingly, this biodiversity signature of seaports was preserved across the Tree of Life, up to the order. This result reveals that seaports and nearby marine reserves share few taxa and evolutionary lineages along urbanized coasts and suggests major differences in terms of ecosystem functioning between both habitats.

Life goes on: Spatial heterogeneity promotes biodiversity in an urbanized coastal marine ecosystem

Both human populations and marine biodiversity are concentrated along coastlines, with growing conservation interest in how these ecosystems can survive intense anthropogenic impacts. Tropical urban centres provide valuable research opportunities because these megacities are often adjacent to mega-diverse coral reef systems. The Pearl River Delta is a prime exemplar, as it encompasses one of the most densely populated and impacted regions in the world and is located just northwest of the Coral Triangle. However, the spatial and taxonomic complexity of this biodiversity, most of which is small, cryptic in habitat and poorly known, make comparative analyses challenging. We deployed standardized settlement structures at seven sites differing in the intensity of human impacts and used COI metabarcoding to characterize benthic biodiversity, with a focus on metazoans. We found a total of 7184 OTUs, with an average of 665 OTUs per sampling unit; these numbers exceed those observed in many previous studies using comparable methods, despite the location of our study in an urbanized environment. Beta diversity was also high, with 52% of the OTUs found at just one site. As expected, we found that the sites close to point sources of pollution had substantially lower diversity (44% less) relative to sites bathed in less polluted oceanic waters. However, the polluted sites contributed substantially to the total animal diversity of the region, with 25% of all OTUs occurring only within polluted sites. Further analysis of Arthropoda, Annelida and Mollusca showed that phylogenetic clustering within a site was common, suggesting that environmental filtering reduced biodiversity to a subset of lineages present within the region, a pattern that was most pronounced in polluted sites and for the Arthropoda. The water quality gradients surrounding the PRD highlight the unique role of in situ studies for understanding the impacts of complex urbanization pressures on biodiversity.

A reciprocal transplant approach to predation in fouling communities found in natural and artificial habitats

Human influence along the coastline is a significant threat to biodiversity and includes the alteration or replacement of natural habitat with artificial structures. Infrastructure such as docks and marinas are common throughout the world and typically have negative impacts on coastal flora and fauna. Impacts include the reduction of native biodiversity, the increase of introduced species, and the alteration of biotic interactions (e.g., predation). Many studies examine human disturbance on biotic interactions within a single habitat (i.e., docks or marinas) but what lacks are paired comparisons using standardized methods of biotic interactions between artificial and nearby natural habitats. In the current study, benthic fouling communities were allowed to develop, with and without predator access, in artificial and seagrass habitats. Cages were used to reduce predation and removed to expose communities to fish predators. Prior to exposure, communities were either left at their original site or transplanted to the opposite habitat and changes in the percent cover of species found were compared. Initially, community composition differed between habitats and when predation was reduced (caged vs. open). When developed communities within cages were exposed to predators, predation was strong but only in artificial habitats and regardless of where communities originated. In contrast, little predation occurred at seagrass sites on previously caged communities developed within seagrass beds or that were transplanted from artificial habitat. Taken together, results indicate that the strength of biotic interactions can differ depending on habitat, leading to changes in community composition. With the continuous expansion of artificial structures world-wide, it is becoming increasingly important to understand not only their effects on biotic interactions and biodiversity but also how these effects extend and compare to adjacent natural habitats.

A new sampling device for metabarcoding surveillance of port communities and detection of non-indigenous species

Metabarcoding techniques are revolutionizing studies of marine biodiversity. They can be used for monitoring non-indigenous species (NIS) in ports and harbors. However, they are often biased by inconsistent sampling methods and incomplete reference databases. Logistic constraints in ports prompt the development of simple, easy-to-deploy samplers. We tested a new device called polyamide mesh for ports organismal monitoring (POMPOM) with a high surface-to-volume ratio. POMPOMS were deployed inside a fishing and recreational port in the Mediterranean alongside conventional settlement plates. We also compiled a curated database with cytochrome oxidase (COI) sequences of Mediterranean NIS. COI metabarcoding of the communities settled in the POMPOMs captured a similar biodiversity than settlement plates, with shared molecular operational units (MOTUs) representing ca. 99% of reads. 38 NIS were detected in the port accounting for ca. 26% of reads. POMPOMs were easy to deploy and handle and provide an efficient method for NIS surveillance.

Early detection of emerging persistent perfluorinated alkyl substances (PFAS) along the east coast of India

Perfluorooctanoic acid (PFOA) and Perfluorooctane sulfonate (PFOS) are resistant to breakdown and are now considered global contaminants. However, interest in these recalcitrant compounds among scientists and legislators has grown significantly in recent years. In the present study, we analyzed the level of PFOA and PFOS contamination in surface water from the coastal regions of Tamil Nadu and West Bengal. After solid phase extraction, 49 samples were analyzed by liquid chromatography coupled with mass spectrometry (LOD ≤ 1.5 ng L-1). The PFOA and PFOS present in all samples at the highest concentration were found in the Ennore coastal region (reaching a maximum of 24.8 ng L-1 and 13.9 ng L-1 in CH-6 and CH-14 respectively). Similarly, on the West Bengal coast, concentrations of PFOA ranged from <1.5 to 14.0 ng L-1 and <1.3 to 8.2 ng g-1 in water and sediment respectively. PFOS concentrations in water and sediment ranged from <1.2 to 9.0 ng L-1 and <1.2 to 7.9 ng g-1, respectively. According to the principal component analysis, the majority of the variances (65.04 %) show a positive association, which points to industrial and domestic discharges as significant point sources of these compounds. The results from this study could be used to determine and understand the levels of PFOA and PFOS contamination along the Indian Coast as well as provide baseline information for imminent monitoring investigations. The environmental occurrences of PFOA and PFOS reported in the current study would allow policymakers to take appropriate measures to safeguard coastal ecosystems or reduce the likelihood of contamination, creating a sustainable and healthy environment.

Terrestrial inputs and physical processes control the distributions of potentially toxic elements (PTEs) in the seawater of the large-range Beibu Gulf, the northern South China Sea

The potentially toxic elements (PTEs), Cu, Pb, Zn, Cd, Cr, Hg and As in the water from the Beibu Gulf, were investigated to reveal the contaminant characteristics and assess the risks to human health. The results showed that the concentration of PTEs in the Beibu Gulf varies significantly both seasonally and spatially, with higher concentrations in summer and in the northern and southern gulf. Terrestrial inputs and local anthropogenic discharge are responsible for the higher level in the northern gulf, and the transportation of water masses is also an important factor for the higher concentrations in the southern gulf. Ecological risk assessment suggested that Hg is the main ecological risk factor. The health risk assessment revealed that dermal exposure to PTEs in the gulf presents potentially carcinogenic health effects for humans. This study provides new insight into the transport of PTEs over a large area of the Beibu Gulf.

Citizen scientists study beach litter along 12,000 km of the East Pacific coast: A baseline for the International Plastic Treaty

Anthropogenic Marine Litter (AML) accumulating on beaches causes damage to coastal ecosystems and high costs to local communities. Volunteers sampled AML on 130 beaches along the central and southern East Pacific coasts, with AML densities ranging from 0.46 to 2.26 items m-2 in the different countries. AML composition was dominated by plastics and cigarette butts, the latter especially in Mexico and Chile. The accumulation of AML in the upper zones of the beaches and substantial proportions of cigarette butts, glass and metal pointed mainly to local sources. Statistical modelling of litter sources on continental beaches revealed that tourism, access and related infrastructure (e.g. parking lots) best explained AML densities, while plastic densities were also influenced by the distance from river mouths and national Gross Domestic Product. Large-scale monitoring can be a useful tool to evaluate the effectiveness of public policies that should primarily focus on land sources.

Occurrence, distribution and sources of petroleum contamination in reef-associated sediments of the Gulf of Mannar, India

The distribution of saturated hydrocarbons and polycyclic aromatic hydrocarbons (PAHs) was assessed in superficial sediment samples collected from Mandapam island groups, Gulf of Mannar, India. The hydrocarbon distribution pattern and the n-alkane indices (e.g., carbon preference index (CPI) and natural n-alkanes ratio (NAR)) were deployed to differentiate between the biogenic and anthropogenic sources. Petroleum pollution was indicated by the pristane/phytane ratio close to 1. Presence of a prominent unresolved complex mixture (UCM) as well as hopane concentrations further supported this assertion. The evaluation of petrogenic sources of contamination were also comprehended by various diagnostic ratios of PAHs. The sites associated with shipping activities, tourism, and located near the mainland and accessible portions of the islands exhibited high petroleum contamination. Correlation analysis underlines the significance of combining petroleum-specific marker compounds and diagnostic ratios to improve the assessment of human influence on marine ecosystems.

Macroecology of rocky intertidal benthic communities along the southwestern Atlantic: Patterns of spatial variation and associations with natural and anthropogenic variables

Assessing spatial variability in biodiversity and its relationships with potential drivers is necessary for understanding and predicting changes in ecosystems. Here, we evaluated spatial patterns in sessile macrobenthic communities in rocky intertidal habitats along the southwestern Atlantic (SE Brazil), spanning over 500 km of coastline. We applied a rapid-survey approach focusing on the main space occupiers and habitat-forming taxa. We partitioned community variance into spatial scales ranging from metres to hundreds of kilometres and assessed whether community patterns were associated with variation in shore topography, nearshore ocean, and human influence. The communities from the mid-midlittoral level exhibited equivalent variation (31-35%) at the scales of quadrats (metres), sites (kilometres), and sub-regions (tens of kilometres). For the communities from the low-midlittoral and infralittoral fringe levels, most variability occurred at the scales of quadrats and sites (30-42%), followed by sub-regions (22%). Wave fetch, sea surface temperature (SST), and shore inclination were the variables that best explained community structure at the mid-midlittoral. At the low-midlittoral and infralittoral fringe, the most influential variables were related to oceanic forcing (SST, total suspended solids, particulate organic carbon, chlorophyll-a concentration) and human influence. Univariate analyses also revealed strong associations between the abundance of the main components of the communities and the predictor variables evaluated. Our results suggest that urbanised estuarine bays and coastal upwelling regimes have a strong influence on adjacent benthic communities, driving macroecological patterns in the study area. This study advances the knowledge in macroecology and biogeography of rocky shores in an understudied coastline and globally and provides valuable insights for future assessments of ecological changes resulting from unfolding human impacts.

Confirmation of significant sea turtle nesting activity on a remote island chain in the Gulf of Mexico

Globally, six of the seven sea turtle species are threatened or endangered and as such, monitoring reproductive activity for these species is necessary for effective population recovery. Remote beaches provide a challenge to conducting these surveys, which often results in data gaps that can hamper management planning. Throughout the summer of 2022, aerial surveys were conducted over the Chandeleur Islands in the Gulf of Mexico. Turtle crawls were photographed for subsequent review by 10 expert observers. Whenever possible, ground surveys were conducted, and samples of unhatched eggs or dead hatchlings were collected. A summary of historic reports of sea turtle nesting activity at this site was also compiled. On 11 days between May 4, 2022, and July 30, 2022, photographs of 55 potential sea turtle crawls were taken. Observers identified 54 of those as being made by a sea turtle. There was high-to-moderate certainty that 16 of those crawls were nests, that 14 were made by loggerheads, and that two were made by Kemp's ridleys. Observers were least certain of species identification when surveys were conducted during rainy weather. Genetic analyses based on mitochondrial and nuclear DNA were conducted on samples from five nests and those analyses confirmed that three nests were laid by Kemp's ridleys and two were laid by loggerheads. Historic records from the Chandeleur Islands substantiate claims that the Chandeleurs have supported sea turtle nesting activity for decades; however, the consistency of this activity remains unknown. Our aerial surveys, particularly when coupled with imaging, were a useful tool for documenting nesting activity on these remote islands. Future monitoring programs at this site could benefit from a standardized aerial survey program with a seaplane so trends in nesting activity could be determined particularly as the beach undergoes restoration.

Cut the rope: Short-term colonization of mooring lines by fouling community within the port of Livorno (Northern Tyrrhenian Sea, Western Mediterranean), focusing on alien species recruitment

The early stages of fouling development on artificial substrates were examined for spatial-temporal variation in the commercial and touristic harbours (use destinations) of the port of Livorno (Tuscany, Italy). The experiment was carried out by submerging two types of experimental ropes with different surface textures, considering three times of submersion. Particular attention was paid to the colonization dynamics of non-indigenous species (NIS). The type of rope did not significantly affect fouling development. However, when the NIS assemblage and the whole community were taken into account, the colonization of ropes varied depending on the use destination. The touristic harbour exhibited a degree of fouling colonization higher than the commercial one. NIS were observed in both harbours since the beginning of colonization, eventually achieving higher population densities in the touristic harbour. The use of experimental ropes represents a promising quick cost-effective tool for monitoring of NIS presence in port environments.

Distribution, sources and risk assessment of polycyclic aromatic hydrocarbons in surface sediments from the Yellow Sea coast, China

To study the distribution, sources, ecological/health risks, and the impact of regional economic variations on polycyclic aromatic hydrocarbons (PAHs) contaminations along the coast of the Yellow Sea in China, sediments from a broad coastal coverage were collected and analyzed. The total contents of 16 priority PAHs varied between 1.4 and 1675.9 ng/g except in the site of H18 (3191.4 ng/g) adjacent to Qingdao City, with an average value of 295.7 ng/g. PAH pollution along the coast presented a distinctive geographical feature, which was closely linked to local human activities, such as Rongcheng with industrial zones and aquacultural areas, and Yancheng Wetland with developed aquaculture. The source analysis results indicated that PAHs were mainly from pyrolytic sources, with smaller contributions from petroleum spills and combustion. Risk assessment suggested that PAH pollution along the Yellow Sea coast showed negligible biological risks and health risks in most areas.

Reintroducing a keystone bioturbator can facilitate microbial bioremediation in urban polluted sediments

Anthropogenic environmental stressors have significantly reduced biodiversity and the capacity of remnant natural habitats to deliver ecosystem functions and services in urban areas. To mitigate these impacts and recover biodiversity and function, ecological restoration strategies are needed. While habitat restoration is proliferating in rural and peri-urban areas, strategies purposely designed to succeed under the environmental, social and political pressures of urban areas are lacking. Here, we propose that ecosystem health in marine urban areas can be improved by restoring biodiversity to the most dominant habitat, unvegetated sediments. We reintroduced a native ecosystem engineer, the sediment bioturbating worm Diopatra aciculata, and assessed their effects on microbial biodiversity and function. Results showed that worms can affect the diversity of microbes, but effects varied between locations. Worms caused shifts in microbial community composition and function at all locations. Specifically, the abundance of microbes capable of chlorophyll production (i.e. benthic microalgae) increased and the abundance of microbes capable of methane production decreased. Moreover, worms increased the abundances of microbes capable of denitrification in the site with lowest sediment oxygenation. Worms also affected microbes capable of degrading the polycyclic aromatic hydrocarbon toluene, although the direction of that effect was site-specific. This study provides evidence that a simple intervention such as the reintroduction of a single species can enhance sediment functions important for the amelioration of contamination and eutrophication, although further studies are needed to understand the variation in outcomes between sites. Nevertheless, restoration strategies targeting unvegetated sediments provide an opportunity to combat anthropogenic stressors in urban ecosystems and may be used for precondition before more traditional forms of habitat restoration such as seagrass, mangrove and shellfish restoration.

Coral persistence despite marginal conditions in the Port of Miami

Coral cover has declined worldwide due to anthropogenic stressors that manifest on both global and local scales. Coral communities that exist in extreme conditions can provide information on how these stressors influence ecosystem structure, with implications for their persistence under future conditions. The Port of Miami is located within an urbanized environment, with active coastal development, as well as commercial shipping and recreational boating activity. Monitoring of sites throughout the Port since 2018 has revealed periodic extremes in temperature, seawater pH, and salinity, far in excess of what have been measured in most coral reef environments. Despite conditions that would kill many reef species, we have documented diverse coral communities growing on artificial substrates at these sites-reflecting remarkable tolerance to environmental stressors. Furthermore, many of the more prevalent species within these communities are now conspicuously absent or in low abundance on nearby reefs, owing to their susceptibility and exposure to stony coral tissue loss disease. Natural reef frameworks, however, are largely absent at the urban sites and while diverse fish communities are documented, it is unlikely that these communities provide the same goods and services as natural reef habitats. Regardless, the existence of these communities indicates unlikely persistence and highlights the potential for coexistence of threatened species in anthropogenic environments, provided that suitable stewardship strategies are in place.

Environmental DNA metabarcoding reveals the influence of human activities on microeukaryotic plankton along the Chinese coastline

Microeukaryotic plankton, with its extremely diverse taxa, is a key component in both the marine food web and biogeochemical cycling. Coastal seas, which are home to the numerous microeukaryotic plankton that underpin the functions of these aquatic ecosystems, are often impacted by human activities. However, understanding the biogeographical patterns of diversity and community structure of microeukaryotic plankton and the role that major shaping factors play at the continent scale is still a challenge in coastal ecology. Here, the biogeographic patterns of biodiversity, community structure, and co-occurrence patterns were investigated by environmental DNA (eDNA) based approaches. Unlike most eDNA studies, we combined several methods (in silico PCR, mock and environmental communities) to systematically evaluate the specificity and coverage of primers to overcome the limitation of marker selection on biodiversity recovery. The 1380F/1510R primer set showed the best performance for the amplification of coastal plankton with the highest coverage, sensitivity, and resolution. We showed a unimodal pattern for planktonic alpha diversity with latitude (P < 0.001), and nutrient-related factors (NO₃N, NO₂N, and NH₄N) were the leading predictors for spatial patterning. Significant regional biogeographic patterns and potential drivers for planktonic communities were found across coastal regions. All communities generally fitted the regional distance-decay relationship (DDR) model with the strongest spatial turnover rate was found in the Yalujiang (YLJ) estuary (P < 0.001). The environmental factors, especially inorganic nitrogen and heavy metals (HMs), had the greatest impact on planktonic community similarity in the Beibu Bay (BB) and East China Sea (ECS). Furthermore, we observed spatial plankton co-occurrence patterns, and the networked topology and structure were strongly driven by potential anthropogenic activity factors (nutrients and HMs). Overall, our study provided a systematic approach for metabarcode primer selection in eDNA-based biodiversity monitoring and revealed that the spatial pattern of the microeukaryotic plankton community was mainly controlled by regional human activity-related factors.

Quantitative spatial assessment of the impact of urban growth on the landscape network of Türkiye's coastal cities

This study aims to evaluate the impact of urban spatial expansion on the landscape patterns of coastal cities in Türkiye through the use of spatio-temporal indices. To this end, temporal samples covering a period of approximately 30 years (1986-2000 and 2000-2015) were analyzed for six selected coastal cities in Türkiye. The urban spatial growth patterns in these cities were characterized using 17 geospatial indices, and Pearson's correlation coefficient and principal component analysis were employed to assess the quantitative relationships between urban spatial development and the fragmentation of landscape networks. The results of the study demonstrated that the patterns of landscape fragmentation caused by the spatial growth patterns of the selected coastal cities can be divided into two categories: disconnected landscape connections and perforated landscape patterns. Leapfrog development was identified as a major factor in the fragmentation of landscape continuity, leading to the formation of perforated green structures. The findings of this research can serve as spatial guidelines for addressing disconnected landscapes, a crucial factor in enhancing urban sustainability in Türkiye's coastal cities. Furthermore, the outcomes of this study may be useful for informing the national well-being strategy for urban planning and natural mitigating policies in Türkiye's coastal regions.

Fast accumulation of anthropogenic litter on upgraded breakwaters: A persistent and hidden threat to coastal habitats

Breakwater construction is common on different coasts, and by means of their structural complexity these built infrastructures can trap anthropogenic litter. We investigated the temporal persistence of anthropogenic litter in breakwaters, and how fast litter accumulates on them. We sampled anthropogenic litter in old (>10 years since construction) breakwaters and in a recently upgraded one (5 months) and on rocky shores located in a coastal conurbation, in central Chile (33°S). We found breakwaters had much higher litter densities than rocky habitats, and this pattern was persistent through time (~5 years). Also, a recently upgraded breakwater had similar composition and densities of litter items as older breakwaters. Therefore, litter accumulation on breakwaters is a very fast process related to their topographic structure and to the willingness of people to dispose of anthropogenic litter in the infrastructure. Redesigning the breakwater structure is required to reduce litter accumulation on the coast and their impacts.

Breakwaters as habitats for synanthropes: Spatial associations of vertebrates and vegetation with anthropogenic litter

Urban infrastructures can provide 'novel' habitats for marine and terrestrial animals and plants, enhancing their ability to adapt to urban environments. In particular, coastal infrastructures characterized by a complex three-dimensional morphology, such as breakwaters, could provide species refuges and food. We investigated the role of breakwaters in providing habitat for vertebrates and plants, and the influence of anthropogenic litter in regulating the value of these structures as habitat. We sampled vertebrate and plant species and quantified the amount of anthropogenic litter on breakwaters and adjacent rocky habitats at several sites in three different countries (Italy, Spain and Chile). We found breakwaters to accumulate more litter items (e.g. especially plastics) than adjacent rocky habitats by means of their large-scale (i.e., 1 m) structural complexity. Birds, which used the artificial infrastructure as transitory habitat, reached similar abundances in breakwaters compared with adjacent rocky platforms. In contrast, synanthropic mammal species, such as Rattus norvegicus and feral cats, were slightly more frequent on breakwaters and appeared to use them as permanent habitat. Plants were frequent in the upper zone of breakwaters and, even though many macrophyte species can trap litter, their cover correlated negatively with anthropogenic litter density. Therefore, breakwaters provide either transitory or permanent habitats for different species, despite functioning as a sink for anthropogenic litter. Thus, new infrastructure should be designed with lower structural complexity in their supralittoral zone limiting the proliferation of synanthropic species. In addition, restricting public access to sensitive areas and enforcing littering fines could enhance the ecological value of these novel habitats by reducing the benefits to pest species.

Ecological disturbances and abundance of anthropogenic pollutants in the aquatic ecosystem: Critical review of impact assessment on the aquatic animals

Anthropogenic toxins are discharged into the environment and distributed through a variety of environmental matrices. Trace contaminant detection and analysis has advanced dramatically in recent decades, necessitating further specialized technique development. These pollutants can be mobile and persistent in small amounts in the environment, and ecological receptors will interact with it. Despite the fact that few researches have been undertaken on invertebrate exposure, accumulation, and biological implications, it is apparent that a wide range of pollutants can accumulate in the tissues of aquatic insects, earthworms, amphipod crustaceans, and mollusks. Due to long-term stability during long-distance transit, a number of chemical and microbiological agents that were not previously deemed pollutants have been found in various environmental compartments. The uptake of such pollutants by the aquatic organism is done through the process of bioaccumulation when dangerous compounds accumulate in living beings while biomagnification is the process of a pollutant becoming more hazardous as it moves up the trophic chain. Organic and metal pollution harms animals of every species studied so far, from bacteria to phyla in between. The environmental protection agency says these poisons harm humans as well as a variety of aquatic organisms when the water quality is sacrificed in typical wastewater treatment systems. Contrary to popular belief, treated effluents discharged into aquatic bodies contain considerable levels of Anthropogenic contaminants. This evolution necessitates a more robust and recent advancement in the field of remediation and their techniques to completely discharge the various organic and inorganic contaminants.

Urban rendezvous along the seashore: Ports as Darwinian field labs for studying marine evolution in the Anthropocene

Humans have built ports on all the coasts of the world, allowing people to travel, exploit the sea, and develop trade. The proliferation of these artificial habitats and the associated maritime traffic is not predicted to fade in the coming decades. Ports share common characteristics: Species find themselves in novel singular environments, with particular abiotic properties-e.g., pollutants, shading, protection from wave action-within novel communities in a melting pot of invasive and native taxa. Here, we discuss how this drives evolution, including setting up of new connectivity hubs and gateways, adaptive responses to exposure to new chemicals or new biotic communities, and hybridization between lineages that would have never come into contact naturally. There are still important knowledge gaps, however, such as the lack of experimental tests to distinguish adaptation from acclimation processes, the lack of studies to understand the putative threats of port lineages to natural populations or to better understand the outcomes and fitness effects of anthropogenic hybridization. We thus call for further research examining "biological portuarization," defined as the repeated evolution of marine species in port ecosystems under human-altered selective pressures. Furthermore, we argue that ports act as giant mesocosms often isolated from the open sea by seawalls and locks and so provide replicated life-size evolutionary experiments essential to support predictive evolutionary sciences.

Living and dead bivalves are congruent surrogates for whole benthic macroinvertebrate communities in Puget Sound

To integrate paleoecological data with the “whole fauna” data used in biological monitoring, analyses usually must focus on the subset of taxa that are inherently preservable, for example by virtue of biomineralized hardparts, and those skeletal remains must also be identifiable in fragmentary or otherwise imperfect condition, thus perhaps coarsening analytical resolution to the genus or family level. Here we evaluate the ability of readily preserved bivalves to reflect patterns of compositional variation from the entire infaunal macroinvertebrate fauna as typically sampled by agencies in ocean monitoring, using data from ten long-established subtidal stations in Puget Sound, Washington State. Similarity in compositional variation among these stations was assessed for five taxonomic subsets (the whole fauna, polychaetes, malacostracans, living bivalves, dead bivalves) at four levels of taxonomic resolution (species, genera, families, orders) evaluated under four numerical transformations of the original count data (proportional abundance, square root- and fourth root-transformation, presence-absence). Using the original matrix of species-level proportional abundances of the whole fauna as a benchmark of “compositional variation,” we find that living and dead bivalves had nearly identical potential to serve as surrogates of the whole fauna; they were further offset from the whole fauna than was the polychaete subset (which dominates the whole fauna), but were far superior as surrogates than malacostracans. Genus- and family-level data were consistently strong surrogates of species-level data for most taxonomic subsets, and correlations declined for all subsets with increasing severity of data transformation, although this effect lessened for subsets with high community evenness. The strong congruence of death assemblages with living bivalves, which are themselves effective surrogates of compositional variation in the whole fauna, is encouraging for using bivalve dead-shell assemblages to complement conventional monitoring data, notwithstanding strong natural environmental gradients with potential to bias shell preservation.

Equivocal associations between small-scale shoreline restoration and subtidal fishes in an urban estuary

Restoration of degraded coastal and estuarine habitats owing to human activities is a major global concern. In Puget Sound, Washington, U.S.A., removal of hard armor from beaches and intertidal zones has become a priority for state and local agencies. However, the effectiveness of these shoreline restoration programs for subtidal habitats and fish is unknown. We surveyed six restoration sites in Puget Sound over 2 years to evaluate associations between shoreline restoration and subtidal fish abundance. We measured the abundance of juvenile salmonids and forage fishes along armored, restored, and reference shorelines. Bayesian generalized linear models showed limited support for associations between shoreline restoration and these fishes in the 3-7 years since armor removal. Pacific herring were more abundant at reference shorelines; the shoreline effect for surf smelt varied by survey site. Shoreline restoration was not an important predictor of salmonid abundance; the best models for Chinook and chum salmon included predictors for survey site and eelgrass, respectively. The retention of survey site in several species' top models reveals the influence of the broader landscape context. We also found seasonal variation in abundance for chum salmon and surf smelt. Our results suggest that juvenile forage fish and salmonids in estuaries likely have unique responses to shoreline features, and that the positive effects of armor removal either do not extend into subtidal areas or are not detectable at local scales. To be most effective, coastal restoration programs should consider broader landscape patterns as well as species-specific habitat needs when prioritizing investments.

Projecting Future Climate Change-Mediated Impacts in Three Paralytic Shellfish Toxins-Producing Dinoflagellate Species

Toxin-producing microalgae present a significant environmental risk for ecosystems and human societies when they reach concentrations that affect other aquatic organisms or human health. Harmful algal blooms (HAB) have been linked to mass wildlife die-offs and human food poisoning episodes, and climate change has the potential to alter the frequency, magnitude, and geographical extent of such events. Thus, a framework of species distribution models (SDMs), employing MaxEnt modeling, was used to project changes in habitat suitability and distribution of three key paralytic shellfish toxin (PST)-producing dinoflagellate species (i.e., Alexandrium catenella, A. minutum, and Gymnodinium catenatum), up to 2050 and 2100, across four representative concentration pathway scenarios (RCP-2.6, 4.5, 6.0, and 8.5; CMIP5). Despite slightly different responses at the regional level, the global habitat suitability has decreased for all the species, leading to an overall contraction in their tropical and sub-tropical ranges, while considerable expansions are projected in higher latitudes, particularly in the Northern Hemisphere, suggesting poleward distributional shifts. Such trends were exacerbated with increasing RCP severity. Yet, further research is required, with a greater assemblage of environmental predictors and improved occurrence datasets, to gain a more holistic understanding of the potential impacts of climate change on PST-producing species.

Impact of in Situ Simulated Climate Change on Communities and Non-Indigenous Species: Two Climates, Two Responses

Climate change constitutes a major challenge for marine urban ecosystems and ocean warming will likely strongly affect local communities. Non-Indigenous Species (NIS) have been shown to often have higher heat resistance than natives, but studies investigating how forthcoming global warming might affect them in marine urban environments remain scarce, especially in Situ studies. Here we used an in Situ warming experiment in a NW Mediterranean (warm temperate) and a NE Atlantic (cold temperate) marina to see how global warming might affect recruited communities in the near future. In both marinas, warming resulted in significantly different community structure, lower biomass, and more empty space compared to control. However, while in the warm temperate marina, NIS showed an increased surface cover, it was reduced in the cold temperate one. Metabolomic analyses on Bugula neritina in the Atlantic marina revealed potential heat stress experienced by this introduced bryozoan and a potential link between heat stress and the expression of a halogenated alkaloid, Caelestine A. The present results might indicate that the effects of global warming on the prevalence of NIS may differ between geographical provinces, which could be investigated by larger scale studies.

Improving City Water Quality through Pollution Reduction with Urban Floodgate Infrastructure and Design Solutions: A Case Study in Wuxi, China

Floodgate operation is one of the main forms of river regulation in the development and utilization of river basins. It changes the natural structure, flow process, and correlative environment of rivers. However, there is little analysis of the multiple impacts of small floodgate operation on the water environment in river networks and of the regulation patterns of urban floodgate infrastructure on pollution. In this paper, a one-dimensional hydrodynamic-water quality model, MIKE 11, was used, taking Wuxi's two main pollutant indicators-the permanganate index (COD_Mn) and ammonia nitrogen (NH₃-N)-to simulate the water quality response of Wuxi's river network based on different design solutions of urban floodgate infrastructure. The results show that among the three design scenarios, the order of the decreasing amplitude of the COD_Mn and NH₃-N concentrations was as follows: 1.4 m design solution scenario > 2.1 m design solution scenario > 0.7 m design solution scenario. Meanwhile, under the 1.4 m scenario, the maximum decrease in the COD_Mn concentration reached 37.57%, and the maximum decrease in the NH₃-N concentration reached 206%. In the entire river network system, the improvement in the water quality in the downstream area was significantly better than that in the upstream area. In addition, under the three scenarios of floodgate operation, the changes in pollutant concentrations during the flood season (June-September) were significantly lower than those during the dry season (October-February) and the flat water season (March-May). The research results can provide theoretical support and new ideas for future research on the ecological operation of small floodgates and related research on the water environment effect.

Evaluation of the effects of urbanization and environmental features on sandy beach macrobenthos highlights the importance of submerged zones

To assess how sandy beach biodiversity is influenced by the effects of environmental features and urbanization, we sampled the macrofauna in the whole across-shore gradient of 90 beach sites in Southeast Brazil. We found that morphodynamic features were the main drivers of macrobenthos, but urbanization-related variables, such as number of beachgoers and number of constructions on the upper shore, decreased species richness and biomass. We also found that submerged zones sustained the highest number of species and biomass in the across-shore gradient, but were the most impacted by human activities. By demonstrating the ecological importance of submerged zones, our results show that beach management practices, which are mainly focused on the upper shore, are missing important components of beach biodiversity. To secure the sustainability of beach ecosystems, management initiatives should include both their social and ecological components and consider the entire Littoral Active Zone as the proper management unit.

Muddy (silty-sand) beaches in semi-arid regions attenuate the contaminants flowing into the sea as a submarine groundwater discharge

Urbanized coastal areas are well-recognized hotspots for the contaminant-enriched groundwater discharge, influencing sensitive coastal ecosystems. The present study investigates how muddy beaches in the semi-arid region alter the contaminant flux flowing into the sea using submarine groundwater discharge (SGD) estimation and hydrogeochemical analysis of coastal waters (groundwater, porewater, and seawater). Fresh SGD carries contaminants such as nutrients and trace metals in the coastal ecosystem, causing increased vulnerability towards eutrophication, harmful algal blooms, and human health. We found that SGD reaching the coast carries immense nutrient flux (155.6 mmol NO₃^- · day^-1; 35 mmol P · day^-1 and 12.4 mmol DSi · day^-1) and trace metal load ranging from 0.1 to 14.9 mmol · day^-1. The nutrient fluxes were higher in the upper saline plume compared to the lower plume. The muddy beach attenuates the nutrients in varying percentages of 9.7 to 22% of NO₃^-, 1.9 to 25.5% of P due to denitrification and phosphorus absorption, and also caused 19.6% reduction of SO₄^2-. The reduction in SO₄^2- leads to the formation of sulfide (HS^-) that promotes the metal precipitation, resulting in the removal of Pb and Cu. This attenuation of nutrients leads to a change in the nutrient ratio (N/P = 7-11) approaching the Redfield ratio, implying the vulnerability of algal bloom at the Dehri beach. Overall, the muddy beach can serve as a natural biogeochemical reactor as it attenuates the nutrient and serves as a source for certain trace metals (Fe, Mn, Zn, and Ni), altering the composition of SGD. Probably this is the first study that emphasizes the attenuation of trace metals in the muddy beaches of a semi-arid region.

Bacterial biofilm colonization and succession in tropical marine waters are similar across different types of stone materials used in seawall construction

Seawalls are important in protecting coastlines from currents, erosion, sea-level rise, and flooding. They are, however, associated with reduced biodiversity, due to their steep orientation, lack of microhabitats, and the materials used in their construction. Hence, there is considerable interest in modifying seawalls to enhance the settlement and diversity of marine organisms, as microbial biofilms play a critical role facilitating algal and invertebrate colonization. We assessed how different stone materials, ranging from aluminosilicates to limestone and concrete, affect biofilm formation. Metagenomic assessment of marine microbial communities indicated no significant impact of material on microbial diversity, irrespective of the diverse surface chemistry and topography. Based on KEGG pathway analysis, surface properties appeared to influence the community composition and function during the initial stages of biofilm development, but this effect disappeared by Day 31. We conclude that marine biofilms converged over time to a generic marine biofilm, rather than the underlying stone substrata type playing a significant role in driving community composition.

Dredging transforms the seafloor and enhances functional diversity in urban seascapes

Landscape modification alters the condition of ecosystems and the complexity of terrain, with consequences for animal assemblages and ecosystem functioning. In coastal seascapes, dredging is routine practice for extracting sediments and maintaining navigation channels worldwide. Dredging modifies processes and assemblages by favouring species with wide trophic niches, diverse habitat requirements and tolerances to dredge-related eutrophication and sedimentation. Dredging also transforms the three-dimensional features of the seafloor, but the functional consequences of these terrain changes remain unclear. We investigated the effects of terrain modification on the functional diversity of fish assemblages in natural and dredged estuaries to examine whether dredging programs could be optimised to minimise impacts on ecological functioning. Fish assemblages were surveyed with baited remote underwater video stations and variation in functional niche space was described using species traits to calculate metrics that index functional diversity. Terrain variation was quantified with nine complementary surface metrics including depth, aspect, curvature, slope and roughness extracted from sonar-derived bathymetry maps. Functional diversity was, surprisingly, higher in dredged estuaries, which supported more generalist species with wider functional niches, and from lower trophic levels, than natural estuaries. These positive effects of dredging on functional diversity were, however, spatially restricted and were linked to both the area and orientation of terrain modification. Functional diversity was highest in urban estuaries where dredged channels were small (i.e. <1% of the estuary), and where channel slopes were orientated towards the poles (i.e. 171-189°), promoting both terrain variation and light penetration in urban estuaries. Our findings highlight previously unrecognised functional consequences of terrain modification that can easily be incorporated into dredging programs. We demonstrate that restricting the spatial extent of dredging operations and the orientation of dredged channel slopes, wherever this is practical, could help to limit impacts on ecosystem functioning and productivity in urban seascapes.

Conceptualisation of multiple impacts interacting in the marine environment using marine infrastructure as an example

The human population is increasingly reliant on the marine environment for food, trade, tourism, transport, communication and other vital ecosystem services. These services require extensive marine infrastructure, all of which have direct or indirect ecological impacts on marine environments. The rise in global marine infrastructure has led to light, noise and chemical pollution, as well as facilitation of biological invasions. As a result, marine systems and associated species are under increased pressure from habitat loss and degradation, formation of ecological traps and increased mortality, all of which can lead to reduced resilience and consequently increased invasive species establishment. Whereas the cumulative bearings of collective human impacts on marine populations have previously been demonstrated, the multiple impacts associated with marine infrastructure have not been well explored. Here, building on ecological literature, we explore the impacts that are associated with marine infrastructure, conceptualising the notion of correlative, interactive and cumulative effects of anthropogenic activities on the marine environment. By reviewing the range of mitigation approaches that are currently available, we consider the role that eco-engineering, marine spatial planning and agent-based modelling plays in complementing the design and placement of marine structures to incorporate the existing connectivity pathways, ecological principles and complexity of the environment. Because the effect of human-induced, rapid environmental change is predicted to increase in response to the growth of the human population, this study demonstrates that the development and implementation of legislative framework, innovative technologies and nature-informed solutions are vital, preventative measures to mitigate the multiple impacts associated with marine infrastructure.

Effects of urbanization on the nutritional ecology of a highly active coastal shark: Preliminary insights from trophic markers and body condition

The synergistic effects of coastal urbanization have dramatically impacted biological communities. Yet, few studies have investigated how urbanization can influence the diet quality and trophic ecology of coastal sharks. In a preliminary study, we examined for spatial variation in the nutritional ecology of a highly active marine predator, the blacktip (Carcharhinus limbatus) exposed to regional differences in coastal urbanization in southeast Florida. We used medium-term nutritional indicators (i.e., body condition and whole blood stable isotopes [δ¹⁵N and δ¹³C]) and short-term dietary markers (i.e., plasma fatty acid profiles) to test the hypothesis that blacktip sharks sampled within highly urbanized areas (hereafter, 'urban sharks') would exhibit higher body condition, but lower diet quality, compared to conspecifics sampled in areas exposed to relatively low levels of urbanization (hereafter, 'urban sharks'). Our initial results showed that urban blacktip sharks exhibited relatively higher body condition, blood δ¹⁵N levels, and percentages of saturated fatty acids compared to non-urban sharks. Collectively, these results suggest a possible positive alteration in the amount of food consumed by blacktip sharks in the study region and/or in the caloric value of their prey. We also found lower percentages of bacterial markers and higher values of dinoflagellate markers in urban sharks. Accordingly, we did not detect an expected reduction in diet quality (in terms of essential fatty acids) in this highly active species exposed to urbanization, as has been previously reported in a resident shark species (Ginglymostoma cirratum). Therefore, it is possible that lifestyle and feeding behavior influence the quality of food consumed by urban sharks. We suspect that impacts of urbanization are more pronounced in resident, sedentary and benthic species.

Holistic Impact Evaluation of Human Activities on the Coastal Fish Biodiversity in the Chinese Coastal Environment

Ecological qualities and resources in coasts are threatened by various human activities, such as pollution and fishery. Impact evaluation of environmental stressors over a wide coastal stretch has been limited due to lack of efficient and standardizable biodiversity monitoring and assessment tools. Integrating environmental DNA (eDNA) and ecological traits, a holistic approach was developed to assess the impact of pollution and aquaculture on fish biodiversity in Chinese coastal areas. Taking the Yalujiang Estuary (YLJK) from the Yellow Sea and the Nan'ao Island Area (NAO) from the South China Sea as cases, the performance of the eDNA biomonitoring workflow was validated. First, the eDNA results of 22 sampling sites reached more than 85% of the asymptotes of species or ASVs in each area. A total of 115 fish species in both areas were detected and NAO was 1.8 times richer than YLJK using eDNA and the fish eDNA composition was consistent with the historical data. eDNA recovered distinct variations of fish sequence, taxonomic and functional diversity, and the corresponding trends following the offshore distance between the two areas. Fish sequence diversity was decreased primarily by estuarine pollution factors (chemical oxygen demand and zinc) in the YLJK. Compared with no breeding areas, lower fish sequence diversity was in breeding areas in the NAO. By integrating ecological traits, the eDNA approach offers promising opportunities for future fish biodiversity monitoring and assessment in national and global coastal environments.

A review of methods and indicators used to evaluate the ecological modifications generated by artificial structures on marine ecosystems

The current development of human activities at sea (e.g. land reclamation, maritime activity and marine renewable energy) is leading to a significant increase in the number of infrastructures installed in marine settings. These artificial structures provide new hard-bottom habitats for many marine organisms and can thus modify the structure and functioning of coastal ecosystems. In order to better evaluate the nature of these modifications as well as the potential benefits and/or impacts generated, it becomes essential to develop assessment methods that can be applied to a wide variety of study sites from harbours to coastal offshore environments. In this context, our study aims to review the different methods and indicators available which are used to measure the modifications of biodiversity and ecological functioning generated by such structures. Among the methods reviewed, we highlight some that were developed specifically for artificial structures, and others intended for various primary uses but which have been successfully transposed to artificial structures. Nevertheless, we also point out the lack of reliable methods concerning some biological ecosystem components impacted by artificial structures. In this context, we require the adaptation or creation of brand-new indicators to achieve a better characterisation of the ecological impacts generated by these structures. Overall, this study highlights a very high number of existing methods, which provide stakeholders with useful tools to study the impacts of artificial structures, and identifies the need to develop integrative indicators to enhance the deployment of new artificial structures.

Influence of Urbanization on Patterns of Variability of Mytilus galloprovincialis Populations

Urbanization is currently one of the most widespread disturbances urgently requiring empirical data regarding its effects on coastal ecosystems. The aim of this study was to compare patterns of variability in populations of the Mediterranean mussel, Mytilus galloprovincialis, between urban and non-urban intertidal rocky shores, over a temporal scale of 12 months and multiple spatial scales (from cm to 10 s of km). For this, variance components associated with percentage cover, spat and total density, condition index, shell length and clump thickness of mussels were compared. Different patterns emerged depending on the response variable and the spatial and temporal scale. There was in general, a higher variability in urban than in non-urban shores, particularly for shell length, spat and total density that can be interpretated as a first stage of degradation, before noticing changes in mean values of these variables. Moreover, the most relevant scales of variability of total and spat density changed with urbanization (10 s of km in urban; 10 s of cm/m in non-urban). Results highlight the need for adopting proper management plans that should include the relevant spatial and temporal scales of variability; otherwise, they will fail in ameliorating urbanization effects on intertidal ecosystems.

Behaviour broadens thermal safety margins on artificial coastal defences in the tropics

Tropical species are predicted to be among the most vulnerable to climate change as they often live close to their upper limits to thermal tolerance and in many cases, behavioural thermoregulation is required to persist in the thermal extremes of tropical latitudes. In concert with warming temperatures, near-shore species are faced with the additional threat of shoreline hardening, leading to a reduction in microhabitats that can provide thermal refuges. This situation is exemplified in Singapore, which lies almost on the equator and so experiences year-round hot temperatures, and much of its coastline is now seawall. To investigate the thermal ecology of a common intertidal gastropod, Nerita undata, on these artificial structures, we measured thermal conditions on two seawalls, the temperatures of habitats occupied by the snail, and compared these with the snail's thermal tolerance by measuring heart rate and behavioural thermoregulation (as preferred temperature, Tpref). At one of the two seawalls (Tanjong Rimau), temperatures experienced by N. undata exceeded all measures of thermal tolerance in the sun, while at the other (Palawan Beach), they did not. Temperatures in habitats occupied by the snails on the seawalls were similar to their measured Tpref in the laboratory and were lower than all measures of thermal tolerance. Behavioural thermoregulation by the snails, therefore, significantly increased the thermal safety margins of N. undata on the relatively homogenous seawalls in Singapore, and at one of the two seawalls were necessary to allow snails to survive. Accordingly, to facilitate motile species to maintain broad thermal safety margins through behavioural regulation, the provision of additional refuges from thermal stress is recommended on artificial coastal defences such as seawalls.

Variations in benthic fluxes of sediments near pier pilings and natural rocky reefs

Marine artificial structures such as pilings are replacing natural habitats, and modifying surrounding areas, often resulting in local decreases in species diversity and facilitation of bioinvasion. Most research on the impacts of artificial structures in marine ecosystems has primarily focused on rocky bottom habitats and biodiversity, overlooking the effects of these structures on the functioning of nearby sedimentary habitats. Here we compared, for the first time, benthic metabolism (O₂ fluxes) and sediment-water nutrient (inorganic nitrogen, phosphate, and dissolved organic nitrogen) fluxes in shallow water sediments adjacent to pilings and natural reefs. We also measured sediment properties (grain size, total organic carbon, total nitrogen, C:N ratio and chlorophyll-a content). We found that sediments near pilings were generally finer with greater C:N ratios than those near reefs, while differences in other sediment properties between types of habitats were dependent on the site. We found significant differences in the oxygen consumption, primary productivity, and net ecosystem metabolism in sediments around pilings compared to sediments near natural reefs, but these patterns differed by site. Net nutrient fluxes were similar in sediments near pilings and reefs at both sites. This study showed that although pilings can be associated with changes in the functioning of sedimentary habitats, patterns and the direction of change seem to vary depending on local conditions.

Landward zones of mangroves are sinks for both land and water borne anthropogenic debris

The hotspots for mangrove diversity and plastic emissions from rivers overlap in Asia, however very few studies have investigated anthropogenic marine debris (AMD) pollution in these threatened coastal ecosystems. Despite Hong Kong's position at the mouth of the Pearl River, a major source of mismanaged waste in Asia, the mangroves in Hong Kong have never been extensively surveyed for AMD. Here we assessed the patterns of AMD abundance within 18 mangrove forests across Hong Kong surveying both their landward and seaward zones. We recorded and categorised, according to their material and potential uses, both the amount of debris items and area they covered, to better quantify its potential impact on the mangroves. Across Hong Kong mangroves, the average abundance of debris was 1.45 ± 0.38 (SE) items m^-2, with an average coverage of 6.05 ± 1.59%. Plastic formed a high proportion of AMD accounting for 70.31% by number of items and 49.71% by area covered, followed by glass/ceramics and wood/bamboo. Disposable food packaging, fishing gear and industrial and construction related waste were the major sources of AMD we documented. On average, we recorded about six times more debris items m^-2 at the landward sites than at the seaward one, but these abundances varied between the East and the West coastlines of Hong Kong. Our data confirms the hypothesis that landward areas of mangrove forests act as traps and retain marine borne debris, but they also suggest that direct dumping of waste from the land could represent a serious impact for these forests placed in between the land and the sea. More research is needed to ascertain the impact of land disposed debris on mangrove degradation, and this study strongly advocates for a cultural shift about the perception of these forests by the public.

Environmental Impacts of Thermal and Brine Dispersion Using Hydrodynamic Modelling for Yanbu Desalination Plant, on the Eastern Coast of the Red Sea

For any coastal desalination plant, the most effective and practical way to dispose of their brine is to thermally discharge it into the sea via outfalls at some distance from the coast. This study focused on the environmental impacts associated with brine and thermal discharge arising from seawater desalination plants at Yanbu, Saudi Arabia, on the southeastern coast of the Red Sea. The impacts associated with recirculation patterns and dispersions were investigated with the calibrated three-dimensional numerical model Delft3d. The environmental impact assessment and the process of identification and characterisation could help improve strategies for better planning and management of the technological solutions related to desalination. Analysis of the model simulations for the different seasons also suggested that around the outfall location, the magnitude of the flow was always high when considered together with the presence of seasonal eddy circulations. Although the tidal flow is lower, the ambient current and wind cause the far-field discharge to spread along the north–south direction during the winter and summer. The thermal and brine dispersion and environmental compliance were assessed in terms of the extent of dispersion. The well-mixed environment caused more rapid dispersion. From the impact level assessment perspective, the study indicated rapid dilution and dispersion of the wastewater at the study region. The present offshore outfall and further offshore locations were far enough to ensure quick dispersion.

Food web restructuring across an urban estuarine gradient

Food webs in urban estuaries support valuable ecosystem services that are subject to a wide range of stressors that can degrade the structure of trophic networks. Multiple trophic pathways stabilize food webs by providing complementary diet resources for consumers but the consequences of urbanization on estuarine food webs are relatively unknown. In estuarine creeks across an urban-to-suburban gradient, we demonstrate trophic decoupling of benthic and pelagic pathways, trophic niche contraction, and increasing human health risk arising with the same factors that are associated with ecological degradation. This suggests an urban estuarine paradox-human activities often create larger volumes of deep water habitat, yet human activities also render much of this area unproductive with measurable opportunity costs to food webs. Our findings emphasize the shared consequences of environmental degradation for the ecological integrity of urban estuaries and the health of urban communities that rely on estuaries for sustenance.

Differences in the Structure and Diversity of Invertebrate Assemblages Harbored by an Intertidal Ecosystem Engineer between Urban and Non-Urban Shores

Nowadays, coastal urbanization is one of the most serious and prevalent pressures on marine ecosystems, impacting their biodiversity. The objective of this study was to explore differences in attributes and biodiversity associated with an intertidal ecosystem engineer, the mussel Mytilus galloprovincialis Lamarck, 1819 between urban and non-urban shores. For this, mussel attributes and their associated macrofauna were compared between urban and non-urban rocky shores in the north of Portugal. Results showed that the largest sized mussels were more frequent on urban shores, whereas the smallest size class was only present in non-urban shores. Regarding macrofauna associated with mussels, the number of taxa was significantly higher on non-urban shores. Moreover, the structure of the macrobenhic assemblages was significantly different between urban and non-urban shores. Most important taxa responsible for differences were more abundant on non-urban shores except for Nucella lapillus, Idotea pelagica and Oligochaeta that were more abundant on urban shores. Therefore, our results showed that the mussel size frequency and the structure of the associated macrobenthic assemblages changed in urban shores. Considering the relevance of mussel beds for biodiversity and human well-being, our results indicate the need of adopting proper management plans to minimize these effects on urban intertidal ecosystems.

Scrutinizing surficial sediment along a 600-km-long urban coastal zone: Occurrence and risk assessment of fipronil and its three degradates

Contamination in the coastal zone is closely linked to urbanization and has become a global issue. The coastal aquatic environment is the terminal sink for many chemicals; however, little is known about the occurrence and variation among habitats as well as integrative toxicity for pesticides, i.e., fipronil, and its three major degradates (-desulfinyl, -sulfide, and -sulfone, fiproles hereafter) in sediments in urban coastlines. In the present study, we report results of a random stratified survey for fiproles in surficial sediments in five embayment habitats (strata) along the Southern California Bight (SCB), USA coastline. Fiproles were present in a small areal extent (6.8%) of the SCB embayment, and detected in 14 out of 174 stations with a total concentration of the four analytes ranging from 0.50 to 17.5 μg/kg dry weight. The area-weighted mean concentrations were 3.16 ± 3.37, 0.584 ± 0.558, 0.071 ± 0.103, and 0.005 ± 0.009 μg/kg in brackish estuaries, estuaries, bays, and marinas, respectively, with the results below the detection limits in ports. Fipronil sulfone had the greatest detection frequency (8.05%) and highest mean concentration (3.24 ± 3.36 μg/kg) among the four compounds. A screening-level deterministic risk assessment for invertebrates found that, region-wide, fiproles generally posed an insignificant to low acute risk to the amphipod Eohaustorius estuarius in 7.36% of the SCB embayment area. In addition, high risk to the midge Chironomus dilutus was found in 77.5% of the fiproles-detectable area in the brackish estuary stratum that is a part of the Los Angeles River. Fipronil sulfone was identified as the major contributor of these effects. The results of this study establish a baseline of occurrence and toxicity potential for fiproles in coastal sediments of southern California.

Seasonal variations and co-occurrence networks of bacterial communities in the water and sediment of artificial habitat in Laoshan Bay, China

Marine bacteria in the seawater and seafloor are essential parts of Earth’s biodiversity, as they are critical participants of the global energy flow and the material cycles. However, their spatial-temporal variations and potential interactions among varied biotopes in artificial habitat are poorly understood. In this study, we profiled the variations of bacterial communities among seasons and areas in the water and sediment of artificial reefs using 16S rRNA gene sequencing, and analyzed the potential interaction patterns among microorganisms. Distinct bacterial community structures in the two biotopes were exhibited. The Shannon diversity and the richness of phyla in the sediment were higher, while the differences among the four seasons were more evident in the water samples. The seasonal variations of bacterial communities in the water were more distinct, while significant variations among four areas were only observed in the sediment. Correlation analysis revealed that nitrite and mud content were the most important factors influencing the abundant OTUs in the water and sediment, respectively. Potential interactions and keystone species were identified based on the three co-occurrence networks. Results showed that the correlations among bacterial communities in the sediment were lower than in the water. Besides, the abundance of the top five abundant species and five keystone species had different changing patterns among four seasons and four areas. These results enriched our understanding of the microbial structures, dynamics, and interactions of microbial communities in artificial habitats, which could provide new insights into planning, constructing and managing these special habitats in the future.