Impacts of a high-discharge submarine sewage outfall on water quality in the coastal zone of Salvador (Bahia, Brazil)

Driving mechanisms for the adaptation and degradation of petroleum hydrocarbons by native microbiota from seas prone to oil spills

Offshore waters have a high incidence of oil pollution, which poses an elevated risk of ecological damage. The microbial community composition and metabolic mechanisms influenced by petroleum hydrocarbons vary across different marine regions. However, research on metabolic strategies for in-situ petroleum degradation and pollution adaptation remains in its nascent stages. This study combines metagenomic techniques with gas chromatography-mass spectrometry (GC-MS) analysis. The data show that the genera Pseudoalteromonas, Hellea, Lentisphaera, and Polaribacter exhibit significant oil-degradation capacity, and that the exertion of their degradation capacity is correlated with nutrient and oil pollution stimuli. Furthermore, tmoA, badA, phdF, nahAc, and fadA were found to be the key genes involved in the degradation of benzene, polycyclic aromatic hydrocarbons, and their intermediates. Key genes (INSR, SLC2A1, and ORC1) regulate microbial adaptation to oil-contaminated seawater, activating oil degradation processes. This process enhances the biological activity of microbial communities and accounts for the geographical variation in their compositional structure. Our results enrich the gene pool for oil pollution adaptation and degradation and provide an application basis for optimizing bioremediation intervention strategies.

Evidence of plastics contamination and sewage-derived residues in a Brazilian Hope Spot for conservation of marine biodiversity - Cagarras Islands and surrounding waters

Cagarras Islands Archipelago, a no-take MPA in Southeast Brazil, was designated as Natural Monument (MONA Cagarras) and, more recently, recognized as Hope Spot for biodiversity conservation. This study aimed to assess plastic contamination by analyzing marine litter and microplastics in MONA Cagarras and surrounding waters. Marine litter (34.12 kg) was caught by artisanal fishermen in MONA Cagarras proximities, and plastics represented ∼79 %. Personal hygiene items and strains of hair were found, suggesting sewage-derived contamination from Ipanema SSO. Microplastics were detected in MONA Cagarras surface waters. Fragments and black particle were the most frequently found microplastic shape and color, respectively. μ-FTIR analysis identified, in descending order of occurrence, polystyrene-PS, polyethylene-PE, polyvinyl chloride-PVC, polypropylene-P, and polyamide-PA. Our integrated results of macro and microplastic contamination highlight an issue of effective conservation and health of marine biodiversity in MONA Cagarras and surrounding waters and a concern for better management of Brazilian MPAs.

Simulations of water pollutants in the Hangzhou Bay, China: Hydrodynamics, characteristics, and sources

China's coastal waters are confronting serious water quality problems, particularly the Hangzhou Bay in the Yangtze River Delta. To find out the underlying cause, we use the Regional Ocean Modeling System (ROMS) to simulate the hydrodynamic characteristics and the evolution of water pollutants. The results show that the hydrodynamic conditions are complicated and the semi-exchange time is 46 days, significantly hindering the dilution and diffusion of water pollutants. Concentrations of each typical pollutant as chemical oxygen demand (COD), dissolved inorganic nitrogen (DIN), and phosphate (PO4) decrease from west to east, showing an obvious enrichment in the coastal region. Source-oriented results show that the inland water pollution of the Yangtze River and the Qiantang River is the key contributor, and the sewage outfalls on the coast near the bay worsen the pollution. This suggests that the government needs to strengthen the management of sources that affect water security.

Coastal streams and sewage outfalls: Hot spots of mercury discharge, pollution and cycling in nearshore environments

The coastal streams (CSs) and sewage outfalls (SOs) are widely distributed and direct anthropogenic stress on global coastal ecosystems. However, the CS/SO-associated mercury (Hg) discharge, pollution and cycle in nearshore environment are less quantified. Here, we report that total Hg (THg) and methylmercury (MMHg) concentrations in waters of CSs (n = 8) and SOs (n = 15) of the northern China were ∼102 to 103 times of coastal surface waters and 10 to 102 times of major rivers in China and other regions. The CS/SO discharges resulted in the increase of total organic carbon (TOC) contents, THg and MMHg concentrations and TOC-normalized THg and MMHg concentrations in sediments of CS/SO-impacted coasts. The laboratory experiments further illustrated that the CS/SO-impacted sediments characterized with high potentials of dissolved THg and MMHg productions and releases. Our findings indicate that the layout optimization of SOs is able to reduce the Hg risk in coastal environment.

Microbiome and antibiotic resistance profiling in submarine effluent-receiving coastal waters in Croatia

Wastewater treatment plant (WWTP) effluents are pointed as hotspots for the introduction of both commensal and pathogenic bacteria as well as their antibiotic resistance genes (ARGs) in receiving water bodies. For the first time, the effect of partially treated submarine effluents was explored at the bottom and surface of the water column to provide a comprehensive overview of the structure of the microbiome and associated AR, and to assess environmental factors leading to their alteration. Seawater samples were collected over a 5-month period from submarine outfalls in central Adriatic Sea, Croatia. 16S rRNA amplicon sequencing was used to establish taxonomic and resistome profiles of the bacterial communities. The community differences observed between the two discharge areas, especially in the abundance of Proteobacteria and Firmicutes, could be due to the origin of wastewaters treated in WWTPs and the limiting environmental conditions such as temperature and nutrients. PICRUSt2 analysis inferred the total content of ARGs in the studied microbiomes and showed the highest abundance of resistance genes encoding multidrug efflux pumps, such as MexAB-OprM, AcrEF-TolC and MdtEF-TolC, followed by the modified peptidoglycan precursors, transporter genes encoding tetracycline, macrolide and phenicol resistance, and the bla operon conferring β-lactam resistance. A number of pathogenic genera introduced by effluents, including Acinetobacter, Arcobacter, Bacteroides, Escherichia-Shigella, Klebsiella, Pseudomonas, and Salmonella, were predicted to account for the majority of efflux pump-driven multidrug resistance, while Acinetobacter, Salmonella, Bacteroides and Pseudomonas were also shown to be the predominant carriers of non-efflux ARGs conferring resistance to most of nine antibiotic classes. Taken together, we evidenced the negative impact of submarine discharges of treated effluents via alteration of physico-chemical characteristics of the water column and enrichment of bacterial community with nonindigenous taxa carrying an arsenal of ARGs, which could contribute to the further propagation of the AR in the natural environment.

Study on layout optimization of sewage outfalls: a case study of wastewater treatment plants in Xiamen

In order to protect the offshore environment and strengthen the comprehensive rectification of sewage outfalls, an evaluation method of regional sewage outfalls by combining the marine numerical simulation and comprehensive evaluation technology was constructed, considering the marine environmental capacity and the ecological impact of sewage discharge from outfalls on the marine eco-environment sensitive areas. Then the layout rationality of each outfall was evaluated and the discharge scale was optimized with a case study of existing sewage outfalls in Xiamen. The results show that, the comprehensive evaluation score of Yundang outfall was 3 points in 2025, evaluated as the outfall with irrational layout. In 2035, the comprehensive evaluation scores of Fenglin and Dalipu outfalls were 3 and 2 points respectively, evaluated as the outfall with irrational discharge scale. It is suggested to control the scale of expansion or increase the reclaimed water reuse rate in Jimei and Gaoqi Wastewater Treatment Plants. This method has enriched the evaluation system for layout optimization of sewage outfalls, providing scientific supports for comprehensive improvement of sewage outfalls and marine environmental management.

Spatial and Temporal Vertical Distribution of Chlorophyll in Relation to Submarine Wastewater Effluent Discharges

The vertical distribution of chlorophyll in coastal waters is influenced by a combination of the hydrodynamic environment and different biotic and abiotic processes. The spatial and temporal occurrences of chlorophyll profiles provide a good representation of the changes in the marine environment. The majority of studies in the Adriatic Sea have so far been conducted in areas unaffected by anthropogenic pressure. Our study site is located near two marine outfalls, which are part of the public sewage system. This study aims to characterize the chlorophyll vertical distribution and describe its variability based on the stratification conditions and the presence of a wastewater effluent plume. Based on these conditions, we identified three characteristic scenarios/types of chlorophyll profiles. The first one occurs when the vertical mixing of the water column creates the upwelling of chlorophyll and nutrients to the upper part of the water column. The second and third scenarios occur during stratified conditions and differ by the extent of the effluent plume intrusion. Using modern fluorescence techniques, we identified and described three different vertical chlorophyll profiles, characterizing them according to their physical and biological parameters and processes. For cases with a visible effluent intrusion, we confirmed the importance of the pycnocline formation in keeping the effluent below and maintaining the higher water quality status at the top of the water column.

Anthropogenic impact on the organic carbon sources, transport and distribution in a subtropical semi-enclosed bay

Suspended particulate organic carbon (POC) and sedimentary total organic carbon (TOC) in coastal areas play critical roles in the global carbon cycle, yet sources and dynamics of coastal POC and TOC have been affected by various anthropogenic activities such as aquaculture, sewage discharge, dam construction and land reclamation. To better understand the anthropogenic impacts on coastal organic carbon, this study was carried out in a representative semi-enclosed bay, Dongshan Bay, Southeast China. Through analyses of stable isotopic compositions of both POC (δ¹³C_POC and δ¹⁵N_PN) and TOC (δ¹³C_TOC and δ¹⁵N_TN), the ratio of total organic carbon vs. total nitrogen (C/N), grain size, Chl-a concentrations and hydrological parameters, our study led to the following main findings: 1) During flood season, the distribution of δ¹³C_POC, δ¹³C_TOC, δ¹⁵N_PN and δ¹⁵N_TN values within the bay did not follow the conventional land-sea transition pattern. This distribution pattern indicated more terrestrial organic matter input seaward, which contrasts with the conventional organic matter distribution along the estuarine gradient. 2) Using the organic δ¹³C, δ¹⁵N and C/N signatures of different endmembers, we found that the sources of organic matter deposited in the bay were strongly related to anthropogenic activities, including municipal wastewater discharge, aquaculture, land reclamation and sluice-dyke construction. Furthermore, 3) by applying the Grain Size Trend Analysis Model and the previously-estimated residual current directions, we suggested that human activities have not only altered the sources of organic matter to the semi-enclosed bays, but also significantly modified their transportation and deposition patterns, and might influence the ultimate fate of organic matter into and out of Dongshan Bay. The conclusions of this study should be applicable to similar coastal bays around the world.

Characterization and ecological function of bacterial communities in seabed sediments of the southwestern Yellow Sea and northwestern East China Sea, Western Pacific

The marine ecosystems of the marginal seas of the Western Pacific region are frequently disturbed by terrigenous materials. It is of great significance to investigate the ecological functioning of these marine areas, which can be well understood by exploring the microbial communities of sediments. However, the geographical distribution, composition, and genetic functions of sedimentary bacterial communities of the Yellow Sea and East China Sea (YEC Seas) are poorly understood. In this work, sediment samples were collected from YEC Sea areas to investigate bacterial communities by high-throughput sequencing. A total of 1960 genera were determined, with Proteobacteria being the dominant phylum (45.03%), followed by Planctomycetes, Bacteroidetes, Acidobacteria, and Chloroflexi. Correlation analysis indicates that the bacterial composition is influenced by environmental factors, including pressure, depth, seawater density, salinity, organic matter content, nutrient, and heavy metal. Approximately 178 metabolism pathways annotated in the Kyoto Encyclopedia of Genes and Genomes (KEGG) database were detected in the bacterial communities, including ones for nutrient metabolism (C, 3.04%; S, 0.70%; N, 0.52%; and P, 0.22%) and exogenous pollutant metabolism (e.g., polycyclic aromatic hydrocarbons (PAHs), chlorobenzene, and benzoate; up to 4.97%). The results demonstrate that the abundant bacterial communities in the sediments of the YEC Seas are important for maintaining marine ecological functioning, especially for elemental biogeochemical cycling and exogenous pollutant transformation.

Mussels get higher: A study on the occurrence of cocaine and benzoylecgonine in seawater, sediment and mussels from a subtropical ecosystem (Santos Bay, Brazil)

Data on the occurrence of cocaine (COC) and benzoylecgonine (BE) in marine environmental compartments are still limited, with few studies reporting superficial water contamination, mainly in tropical zones. In this sense, environmental data of these substances are essential to identify potential polluting sources, as well as their impact in costal ecosystems. The aim of this study was to evaluate the occurrence of COC and BE in seawater, sediment and mussels from a subtropical coastal zone (Santos Bay, São Paulo, Brazil), as well as to determine a field measured Bioaccumulation Factor (BAF). COC and BE were detected in all water samples in concentrations ranging from 1.91 ng·L^-1 to 12.52 ng·L^-1 and 9.88 ng·L^-1 to 28.53 ng·L^-1, respectively. In sediments, only COC was quantified in concentrations ranging from 0.94 ng·g^-1 to 46.85 ng·g^-1. Similarly, only COC was detected in tissues of mussels 0.914 μg·kg^-1 to 4.58 μg·kg^-1 (ww). The field-measured BAF ranged from 163 to 1454 (L·kg^-1). Our results pointed out a widespread contamination by cocaine and its main human metabolite benzoylecgonine in Santos Bay. Mussels were able to accumulate COC in areas used by residents and tourists for bathing, fishing, and harvest, denoting concern to human health. Therefore, our data can be considered a preliminary assessment, which indicates the need to evaluate drugs (including illicit as COC) in environmental and seafood monitoring programs, in order to understand their risks on the ecosystem and human health.

Escherichia coli Capacity to Repopulate Microcosms Under Osmotic/U.V. Synergic Stress in Tropical Waters

In both Brazilian and European regulations, the impact assessment of sewage discharges into coastal waters is based on microbiological analyses of fecal indicators such as Escherichia coli, frequently used in prevision hydrodynamic models. However, the decay rates of E. coli vary depending on environmental conditions, and analysis may lead to inaccurate conclusions. This study aimed to analyze the decay of culturable and viable (but not culturable) E. coli in outdoor conditions, by creating microcosms inoculated with pre-treated sewage. The microcosms were filled with 9.88 L of filtered water (0.22 μm membrane), 3.5% salt, 0.1-0.2% BHI, and 1% bacterial suspension obtained by reverse filtration. PMA-qPCR of E. coli uidA gene and Colilert measurements were applied to evaluate population counts after 2 h, 4 h, and 26 h. After nine hours of exposure to solar radiation, the viable cells decreased to 2.76% (interpolated value) of the initial population, and the cultivable fraction of the viable population accounted for 0.50%. In the dark period, the bacteria grew again, and viable cells reached 8.54%, while cultivable cells grew to 48.14% of initial population. This behavior is possibly due to the use of nutrients recycled from dead cells. Likewise, populations of E. coli in sewage outfalls remain viable in the sediments, where resuspension can renew blooming.

Using stable isotopes to discriminate anthropogenic impacts of the sedimentary organic matter pollution in the Rodrigo de Freitas Lagoon (RJ, Brazil)

Over the last decades, the Rodrigo de Freitas Lagoon (RFL), Rio de Janeiro, Brazil, has been impacted by the release of untreated domestic sewage, causing eutrophication processes with negative effects on its biota. Recently, the RFL underwent urban interventions to fulfill the demands of the 2016 Olympic Games, which included building the waist gallery and monitoring clandestine waste discharges into the underground drainage network. Organic-source tracing methods can be successfully used to characterize the organic matter transported from the urbanized areas to the RLF. The application of the elemental (C, N) and stable isotope (δ¹⁵N and δ¹³C) fingerprint methods in sediments from the RLF indicated a reduction in the domestic sewage inputs from 32 ± 16 to 12 ± 13% between 2015 and 2017. However, the sewage inputs continue being worrying. Our results also suggest that the main source of organic matter pollution in the lagoon comes from indiscriminate domestic sewage release from river channels. Secondary pollution sources are associated with the underground drainage network that still shows punctual and irregular releases of domestic sewage. Petroleum products, mainly from sewers, also show as possible organic pollution sources. Finally, the findings indicate that the interventions carried out in the RFL are promising. However, they were insufficient to cease the pollutant inputs and mitigate the negative impacts of eutrophication.

Benefits and Detriments of Gadolinium from Medical Advances to Health and Ecological Risks

Gadolinium (Gd)-containing chelates have been established as diagnostics tools. However, extensive use in magnetic resonance imaging has led to increased Gd levels in industrialized parts of the world, adding to natural occurrence and causing environmental and health concerns. A vast amount of data shows that metal may accumulate in the human body and its deposition has been detected in organs such as brain and liver. Moreover, the disease nephrogenic systemic fibrosis has been linked to increased Gd³⁺ levels. Investigation of Gd³⁺ effects at the cellular and molecular levels mostly revolves around calcium-dependent proteins, since Gd³⁺ competes with calcium due to their similar size; other reports focus on interaction of Gd³⁺ with nucleic acids and carbohydrates. However, little is known about Gd³⁺ effects on membranes; yet some results suggest that Gd³⁺ interacts strongly with biologically-relevant lipids (e.g., brain membrane constituents) and causes serious structural changes including enhanced membrane rigidity and propensity for lipid fusion and aggregation at much lower concentrations than other ions, both toxic and essential. This review surveys the impact of the anthropogenic use of Gd emphasizing health risks and discussing debilitating effects of Gd³⁺ on cell membrane organization that may lead to deleterious health consequences.

Ecotoxicological assessment of chemotherapeutic agents using toxicity tests with embryos of Mellita quinquiesperforata

The consumption of anticancer agents has increased in the recent decades, and these substances may be present in sewage. Consequently, they may reach the environment when sanitation infrastructure is ineffective. This study evaluated the toxicity of three anticancer agents-Tamoxifen (TAM), Cisplatin (CisPt), and Cyclophosphamide (CP)-on the development of embryos of the sand-dollar Mellita quinquiesperforata. Adult individuals were collected in sandy beaches, and gametes were obtained. Freshly-fertilized eggs were exposed to increasing sets of concentrations of each compound, and the effective concentrations needed to cause a 50% effect in the organisms (EC50) were calculated. The three compounds were toxic, and their EC50 values were 16.78 ± 2.42 ng·L^-1 (TAM), 27.20 ± 38.26 ng·L^-1 (CisPt), and 101.82 ± 70.96 ng·L^-1 (CP). There is no information on the environmental levels of these compounds in Brazil, but as they were already detected in ng·L^-1 levels worldwide, it can be expected that these substances pose environmental risks to the marine biota.

Can Palythoa cf. variabilis biochemical patterns be used to predict coral reef conservation state in Todos Os Santos Bay?

Coral reefs are one of the most diverse, complex and productive marine ecosystems on the planet. Global climate change and other anthropogenic impacts have had a strong impact on the equilibrium of these ecosystems and causing the denominated "coral reef crisis". One consequence of coral reef crisis is the phase shift in reef communities, where scleractinian corals responsible for the bioconstruction of the coralline building are replaced by macroalgae or soft corals. In Todos os Santos Bay (TSB) there is a rare case of phase shift caused by the soft coral Palythoa cf. variabilis. When in population outbreak, this coral species becomes dominant and leads to loss of scleractinian coral cover. Palythoa genus establishes a symbiotic relationship with dinoflagellate algae of the genus Symbiodinium, that is changed in phase shift coral reefs, but other alterations remain unknown. In this study, the metabolism (oxidative damage, antioxidant and biotransformation enzymes, electron transport chain activity and photosynthetic pigments) of P. cf. variabilis from reefs in different conservation states was studied to identify and relate if changes that may occur in the biochemical and metabolism of the coral might trigger the population outbreak, identify parameters recognizing if corals are in stress and assess if one or more parameters can reflect the level of stress organisms are experiencing. The results obtained evidenced a clear distinction in the biochemistry and metabolism of corals from conserved sites and sites in phase shift, and these changes may be the trigger for population outbreak. Some of the parameters were able to discriminate the level of stress corals are experiencing and may allow to recognize the most at-risk coral reefs that need immediate intervention and prevent the entry into or revert P. cf. variabilis outbreak and phase shift in coral reefs. Actions like these can be of vital importance for the preservation of TSB coral reefs and possibly for other threatened reefs worldwide.

Dynamics of coastal bacterial community average ribosomal RNA operon copy number reflect its response and sensitivity to ammonium and phosphate

The nutrient-rich effluent from wastewater treatment plants (WWTPs) constitutes a significant disturbance to coastal microbial communities, which in turn affect ecosystem functioning. However, little is known about how such disturbance could affect the community's stability, an important knowledge gap for predicting community response to future disturbances. Here, we examined dynamics of coastal sediment microbial communities with and without a history of WWTP's disturbances (named H1 and H0 hereafter) after simulated nutrient input loading at the low level (5 mg L^-1 NH₄⁺-N and 0.5 mg L^-1 PO₄^3--P) or high level (50 mg L^-1 NH₄⁺-N and 5.0 mg L^-1 PO₄^3--P) for 28 days. H0 community was highly sensitive to both low and high nutrient loading, showing a faster community turnover than H1 community. In contrast, H1 community was more efficient in nutrient removal. To explain it, we found that H1 community constituted more abundant and diversified r-strategists, known to be copiotrophic and fast in growth and reproduction, than H0 community. As nutrient was gradually consumed, both communities showed a succession of decreasing r-strategists. Accordingly, there was a decrease in community average ribosomal RNA operon (rrn) copy number, a recently established functional trait of r-strategists. Remarkably, the average rrn copy number of H0 communities was strongly correlated with NH₄⁺-N (R² = 0.515, P = 0.009 for low nutrient loading; R² = 0.749, P = 0.001 for high nutrient loading) and PO₄^3--P (R² = 0.378, P = 0.034 for low nutrient loading; R² = 0.772, P = 0.001 for high nutrient loading) concentrations, while that of H1 communities was only correlated with NH₄⁺-N at high nutrient loading (R² = 0.864, P = 0.001). Our results reveal the potential of using rrn copy number to evaluate the community sensitivity to nutrient disturbances, but community's historical contingency need to be taken in account.

Contribution of fluorite mining waste to mercury contamination in coastal systems

Samples from 13 beaches along the northern Spanish coast, a region with a history of heavy industries, were first screened to identify signs of pollution. High concentrations of Hg and Ba on Vega beach were found, both elements belong to the fluorite ore paragenesis, mined in the surroundings. Samples of beach and fluvial sediments, and nearby soils were collected in Vega beach area to address potential Hg pollution, fate and sources. Most samples showed a similar pollutants fingerprint to that of beach samples, especially those taken from white dunes, registering notable Hg concentrations. Hg was enriched in the finer fractions, and overall the main input was attributed to the mining waste discharged along the coast in the past. Although a specific risk assessment and study of the submerged sediments are advisable for this area, Hg bioavailability and methylation were low, thus indicating that this metal poses a reduced environmental risk.

FVCOM-plume - A three-dimensional Lagrangian outfall plume dilution and transport model for dynamic tidal environments: Model development

Although numerous steady-state effluent plume dilution models are in use, their application in tidal environments remains a challenge. Three-dimensional dynamic circulation models are also inadequate, often due to the lack of required resolution and simplifying assumptions. To overcome these limitations, we present FVCOM-plume-an outfall plume dilution and transport model that operates within the Finite Volume Coastal Ocean Model (FVCOM) framework. It provides simultaneous inclusion of near-field dilution and far-field plume transport processes. The near-field is based on UM3 model using Lagrangian Control Volume approach to compute buoyant plume trajectory and dilution from multiport diffusers. The far-field uses neutrally buoyant particles with point masses and the random walk method to solve unsteady advection-diffusion processes. A density kernel approach is used to compute concentrations at point locations and analyze far-field plume characteristics. The results demonstrate the ability of FVCOM-plume to simultaneously capture near-field and far-field effluent plume dynamics in tidal environments.

Geochemical discrimination of bulk organic matter in surface sediments of the Cross River estuary system and adjacent shelf, South East Nigeria (West Africa)

Knowledge of the sources, distribution and fate of organic matter (OM) in estuarine and adjacent shelf sediments are important for the understanding of the global biogeochemical cycles. Bulk organic carbon (C-org), total nitrogen (TN), biogenic silica (BSi), stable carbon (δ¹³C-org) and nitrogen (δ¹⁵N) isotopes, and sediment grain sizes were measured to study the spatial distributions and sources of sediment OM in the Cross River estuary system (CRES) and adjacent shelf. Surface sediments in the CRES were composed of clayey silt and sandy silt, while the adjacent shelf sediments were mainly silty sand. The range of the studied parameters was -28.79‰ to -22.20‰ for δ¹³C-org, -1.32‰-6.31‰ for δ¹⁵N, 6.7-29.2 for C-org/N ratios, 0.08%-0.33% for TN, 0.24‰-0.74‰ for BSi, and 0.47%-5.28% for C-org, and their spatial distributions showed a general decreasing trend in both the terrestrial and estuarine OM from the riverine regions to the adjacent shelf. Based on the three-end-member mixing model using the δ¹³C and δ¹⁵N isotopic values, ~58.01 ± 15.32% of sediment OM are derived from terrestrial sources dominated by C₃ vascular plants, while ~26.34 ± 9.71% are attributed to estuarine sources dominated by aquatic macrophytes, and ~15.65 ± 12.37% for marine plankton source. Other sources of OM identified included soils underlain C₃ vascular plants and agricultural farms enriched with N, sewage, and petroleum hydrocarbons. The relationship between C-org vs. BSi, and the atomic BSi/Corg ratios suggested that diatoms also play an important role in OM sequestration in surface sediments of the CRES and adjacent shelf. The correlations of the δ¹³C-org and δ¹⁵N isotopic values vs. C-org/N ratios resulted in scatter plots, indicating that the distributions of sediment OM in the CRES and adjacent shelf are influenced by post depositional processes, fixed inorganic N adsorbed on fine-grained sediments, microbial degradation, as well as sediment grain size.

Stable isotopes and geochemical indicators in marine sediments as proxies for anthropogenic impact: A baseline for coastal environments of central Chile (33°S)

Stable isotopes and geochemical proxies (TOC/TN and Chla/TOC) in sediments can be used to distinguish organic matter sources (anthropogenic, terrestrial, or marine). This study aims to characterize organic matter (OM) in superficial sediments from three sectors of central Chile (33°S) that are highly influenced by urban and industrial development. Our results show that a substantial fraction of these OM in Quintero Bay is anthropogenic, from industrial and domestic wastewater sources. In contrast, a mixture of terrestrial and anthropogenic OM dominates the isotopic signal of surface sediments from Concón, derived from non-point industrial and agriculture sources associated with the Aconcagua River basin, while Ritoque exhibited a mixture of different OM sources. However, deposition of allochthonous OM in our study area depends on coastal topography, which influences the local currents and well-ventilated waters, promoting the dispersion and assimilation of OM and thus providing an environment with a high capacity for natural remediation.

Gadolinium as an Emerging Microcontaminant in Water Resources: Threats and Opportunities

As a result of high doses of paramagnetic gadolinium (Gd) chelates administered in magnetic resonance imaging (MRI) exams, their unmetabolized excretion, and insufficient removal in wastewater treatment plants (WWTPs), large amounts of anthropogenic Gd (Gdanth) are released into surface water. The upward trend of gadolinium-based contrast agent (Gd-CA) administrations is expected to continue growing and consequently higher and higher anthropogenic Gd concentrations are annually recorded in water resources, which can pose a great threat to aquatic organisms and human beings. In addition, the feasibility of Gd retention in patients administered with Gd-CAs repeatedly, and even potentially fatal diseases, including nephrogenic systemic fibrosis (NSF), due to trace amounts of Gd have recently arisen severe health concerns. Thus, there is a need to investigate probable adverse health effects of currently marketed Gd-CAs meticulously and to modify the actual approach in using Gd contrast media in daily practice in order to minimize unknown possible health risks. Furthermore, the employment of enhanced wastewater treatment processes that are capable of removing the stable contrast agents, and the evaluation of the ecotoxicity of Gd chelates and human exposure to these emerging contaminants through dermal and ingestion pathways deserve more attention. On the other hand, point source releases of anthropogenic Gd into the aquatic environment presents the opportunity to assess surface water—groundwater interactions and trace the fate of wastewater plume as a proxy for the potential presence of other microcontaminants associated with treated wastewater in freshwater and marine systems.

Tracking hospital effluent-derived gadolinium in Atlantic coastal waters off Brazil

The use of gadolinium (Gd) complexes as contrast agents in magnetic resonance imaging (MRI) has resulted in point source releases of anthropogenic Gd into the environment and presents the opportunity to trace the fate of wastewater plumes. Here we collected seawater samples along the coast of Northeast Brazil to investigate the influence of two submarine sewage outfalls on the distribution of Gd and other rare earth elements (REE) in the coastal waters. The shale-normalized REEs only show a small light over heavy REE enrichment and negative Ce anomalies, likely reflecting the influence of freshwater inputs. Positive Gd anomalies are observed at most of the sampling sites, indicating the ubiquitous presence of anthropogenic Gd in coastal waters. The highest Gd anomalies are found in the vicinity of the submarine sewage outfalls and decrease with increasing distance from point source. The total daily discharge of 216 ± 82 g Gd and 92.0 ± 19.3 g Gd was calculated for the Rio Vermelho (ERV) and Boca do Rio (EBR) submarine outfalls, respectively, which on population bases equates to 11.5 ± 4.3 g Gd d^-1 for ERV and 15.5 ± 3.3 g Gd d^-1 for EBR per 100 000 persons. It is estimated that in 2016 the annual emission of anthropogenic Gd by hospitals and clinics in Brazil varied between 527 kg and 5.3 tons. It was roughly estimated that between 698 and 2021 g Gd d^-1 are discharged into the Tropical and South Atlantic waters due to submarine outfall sewage along the coast of Brazil.

Plastic debris collars: An underreported stressor in tropical reef fishes

Plastic debris collar wrappings (PDCW) are involved in the frequent entanglement of several groups of marine animals. In fishes, however aside from 'ghost fishing', PDCW events are rarely documented, and no record of this occurrence exists in tropical reef fishes. Here, we present records for four species afflicted by plastic debris collars. Observations occurred during snorkeling, and included the silver mojarra Eucinostomus argenteus, Atlantic thread herring Ophistonema oglinum, tomtate grunt Haemulon aurolineatum and gray parrotfish Sparisoma axillare. While PDCW may not create an instantaneous source of mortality, our observations suggest that debilitating stress, created by reduced swimming performances, feeding and/or antipredator behavior are likely consequences for afflicted individuals. Given the importance of these performances on survival, reduction in fitness is expected. This note aims to report cases of PDCW and underscore that such interactions between fishes and plastic pollution may be more prevalent than previously expected in coastal reef habitats.