Complex Aquatic Environments Research Articles

Heteroaggregation of nanoplastics with oppositely charged minerals in aquatic environment: Experimental and theoretical calculation study

The transport, fate, and toxic effects of nanoplastics (NPs) would be affected by various environmental factors. In this study, the aggregation behaviors of polystyrene nanoplastics (PSNPs) with or without the presence of oppositely charged minerals (Mg/Al layered double hydroxides (LDH) and kaolin) in aqueous phase were investigated through settling experiment, and the influencing factors including pH and ionic strength (IS) were also analyzed systematically. Our results revealed that pH had a negligible effect on the fate of individual PSNPs under natural aquatic conditions, while high IS would cause homoaggregation. The positively charged LDH decreased the stability of PSNPs, while negatively charged kaolin had a weak effect on it, suggesting that electrostatic interaction was directly related to the stability of PSNPs in aquatic environment. Further experiments of PSNPs with other metal oxides with different surface charges (Al2O3 and SiO2) confirmed the importance of electrostatic interaction for PSNPs-minerals heteroaggregation. Transmission electron microscopic (TEM), Derjaguin–Landau–Verwey–Overbeek (DLVO) theory, and Density function theory (DFT) calculations were combined for the first time to explain the heteroaggregation mechanism, demonstrating that there were expected to exist hydrogen bond and van der Waals interaction in addition to the dominant force of electrostatic interaction. Our findings are expected to shed light on the environmental behavior of PSNPs in a complex aquatic environment.

Expansion of C1Q Genes in Zhikong Scallop and Their Expression Profiling After Exposure to the Toxic Dinoflagellates

C1Q (Complement 1Q) is an important recognition molecule in the immunological complement system, which could also be putatively involved in the stress responses induced by endotoxins or exotoxins, potentially through detoxification processes. Marine bivalves are well adapted to highly complex aquatic environments with various stressors. As filter feeders, they have to cope with highly potent microalgae-derived neurotoxins, such as paralytic shellfish toxin (PSTs). Zhikong scallops, Chlamys farreri, are commercially important bivalve with the remarkable ability to accumulate PSTs. Exploring the C1Qs related to PST accumulation in C. farreri could benefit our understanding of the adaptations of bivalve species. In the present study, we systematically analyzed C1Q genes in C. farreri. In total, 97 CfC1Q genes mainly from the expanded C1Q-B subfamily were identified, from which the C1QL, C1QTNF, and C1QDC1 members in C. farreri were revealed to be under positive selection. Spatiotemporal expression analysis revealed that most CfC1QLs and CfC1QDC1s were highly expressed during the post-umbo stage and in hepatopancreas, while most CfC1QTNF members were highly expressed after the creeping larva stage and in mantle. The hepatopancreas and kidney in C. farreri are two toxin-rich organs with the highest concentrations of PSTs, acting as major “centers” for toxin accumulation and transformation, respectively. Therefore, after feeding the scallops with PST-producing dinoflagellates Alexandrium minutum and Alexandrium catenella, we determined the expression patterns of CfC1Qs in these two organs. In kidney, more than 85% of CfC1QLs and CfC1QDC1s showed drastic up-regulation with both diets. However, among these members with significant induction, a different response manner was detected after feeding with A. minutum and A. catenella, respectively as acute and chronic response patterns. In comparison, far fewer CfC1Qs showing significant up-regulation in hepatopancreas with both toxic diets and only mild regulation pattern could be found. This organ-, toxin-, and time-dependent genetic regulation of CfC1Qs may contribute to the virulence difference on account of the tissue-specific or dinoflagellate-specific different toxin analogs composition, implying the possible involvement of CfC1Qs in PST transport and homeostasis. Our findings imply the functional diversity of scallop C1Q genes in coping with PST accumulation, which might be developed as potential molecular indicators for monitoring toxin accumulation in edible mollusks or provide insight into the lineage-specific adaptation of scallops for dealing with microalgal toxin challenges.

Influence of dissolved black carbon on the aggregation and deposition of polystyrene nanoplastics: Comparison with dissolved humic acid

Dissolved black carbon (DBC), widely found in soil and water environments is likely to affect the transport of nanoplastics in aquatic environments. The aggregation and deposition behaviors of fresh and aged polystyrene nanoplastics (PSs) with and without DBC in NaCl solution were investigated by time-resolved dynamic light scattering (DLS) and quartz crystal microbalance with dissipation monitoring equipment (QCM-D) techniques. The results suggest that DBC can screen the surface charges of PSs by interacting with PSs through hydrogen bonding, hydrophobic interactions and π-π interactions, although they were negatively charged. DBC promoted the aggregation of PSs under relatively low ionic strengths, and it minimally affected the stability of PSs under high ionic strength. Deposition experiments showed that both DBC in salt solution and DBC adsorption on silica surface facilitated the deposition of fresh PSs while HA inhibited both deposition processes. After aging, PSs were more stable, and the effects of DBC and HA were weakened. This study investigated the influence mechanism of DBC on the aggregation and deposition behaviors, which provides new insights into the stability and transport of PSs in complex aquatic environments.

Efficient Cooperative Structured Control for a Multijoint Biomimetic Robotic Fish

In this article, we propose an efficient locomotion control method for a two-dimensional tracking task of a biomimetic four-joint robotic fish. Regarding this issue as a comprehensive optimization procedure, we propose an optimization-based cooperative structured control framework, in which the combination of evolutionary strategy and deep deterministic policy gradient is employed to optimize the same objective function. An inconsistent optimization method is presented to further enhance the effect of parameter optimization on central pattern generator model. Moreover, for the sake of a higher reward and better robustness of controllers governed by deep reinforcement learning, we propose a linear weighted controller trained with periodic method. Extensive simulation and experimental results verify the significant energy saving of the proposed method in tracking tasks. Noticeably, the cooperative structured control can save <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{23.97}\%$</tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{22.13}\%$</tex-math></inline-formula> , and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{38.72}\%$</tex-math></inline-formula> energy compared with sliding mode control, active disturbance rejection control, and proportional-integral-differential control in experiments, respectively, holding a great promise for the long-term intelligent work of the biomimetic robotic fish in complex aquatic environments.

Toward a Novel Robotic Manta With Unique Pectoral Fins

This article proposes the mechanical design and dynamic model of an innovative manta-inspired robot system for both efficient fast swimming and high spatial maneuverability. Inspired by some biological studies, a pair of unique pectoral fins with six separate degrees of freedoms (DOFs) are developed. The novel design is characterized by an improved crank-rocker mechanism and a distinctive horizontal DOF. The former not only endows the robot with high swimming speed, but also guarantees efficient flapping patterns which are close to manta rays. The latter is employed to coordinate with the flapping movement, allowing remarkable pitch adjustment. Further, the basic motion strategy is presented by detailed analyses to the pectoral fins. Besides, based on the Morrison equation and infinitesimal method, a complete dynamic model for robotic manta with flexible pectoral fins is established, whose parameters are determined through experimental data. Moreover, the linear swimming and pitching experiments are conducted, demonstrating the prominent movement performance of the presented design and the effectiveness of the dynamic model. The obtained results shed light on updated design and control of next-generation agile underwater vehicles and robots capable of multimodal motions in dynamic and complex aquatic environments.

The environmental fate of graphene oxide in aquatic environment—Complete mitigation of its acute toxicity to planktonic and benthic crustaceans by algae

Graphene oxide (GO) as the most studied hydrophilic graphene derivative can be deployed in a broad spectrum of environmental technologies opening the issue of its ecotoxicity. Nevertheless, the information about its behavior in complex aquatic environment is still not sufficient. Here, we studied the interaction of three differently oxidized GO systems with planktonic and benthic crustaceans. By standard toxicity tests, we observed the importance of feeding strategy as well as the surface oxidation of GO with respect to GO’s ecotoxicity. However, to gain a clearer insight into GO’s environmental fate, we introduced a pre-treatment with algae as the most common source of food for crustaceans. Such an adjustment mimicking the conditions in real aquatic ecosystems resulted in complete mitigation of acute toxicity of GOs to all organisms and, more importantly, to the eradication of oxidative stress caused by GOs. We argue, that the pre-exposition of food is a crucial factor in GO’s overall environmental fate, even though this fact has been completely neglected in recent studies. These experiments proved that GO is not a hazardous material in complex aquatic environments because its acute toxicity can be successfully mitigated through the interaction with algae even at very high concentrations (25 mg/L).

A modified YOLOv3 detection method for vision-based water surface garbage capture robot

To tackle the water surface pollution problem, a vision-based water surface garbage capture robot has been developed in our lab. In this article, we present a modified you only look once v3-based garbage detection method, allowing real-time and high-precision object detection in dynamic aquatic environments. More specifically, to improve the real-time detection performance, the detection scales of you only look once v3 are simplified from 3 to 2. Besides, to guarantee the accuracy of detection, the anchor boxes of our training data set are reclustered for replacing some of the original you only look once v3 prior anchor boxes that are not appropriate to our data set. By virtue of the proposed detection method, the capture robot has the capability of cleaning floating garbage in the field. Experimental results demonstrate that both detection speed and accuracy of the modified you only look once v3 are better than those of other object detection algorithms. The obtained results provide valuable insight into the high-speed detection and grasping of dynamic objects in complex aquatic environments autonomously and intelligently.

UV-C-activated persulfate oxidation of a commercially important fungicide: case study with iprodione in pure water and simulated tertiary treated urban wastewater.

Recently, the European Food Safety Authority (EFSA) has banned the use of iprodione (IPR), a common hydantoin fungicide and nematicide that was frequently used for the protective treatment of crops and vegetables. In the present study, the treatment of 2mg/L (6.06μM) aqueous IPR solution through ultraviolet-C (UV-C)-activated persulfate (PS) advanced oxidation process (UV-C/PS) was investigated. Baseline experiments conducted in distilled water (DW) indicated that complete IPR removal was achieved in 20min with UV-C/PS treatment at an initial PS concentration of 0.03mM at pH = 6.2. IPR degradation was accompanied with rapid dechlorination (followed as Cl- release) and PS consumption. UV-C/PS treatment was also effective in IPR mineralization; 78% dissolved organic carbon (DOC) was removed after 120-min UV-C/PS treatment (PS = 0.30mM) compared with UV-C at 0.5W/L photolysis where no DOC removal occurred. LC analysis confirmed the formation of dichloroaniline, hydroquinone, and acetic and formic acids as the major aromatic and aliphatic degradation products of IPR during UV-C/PS treatment whereas only dichloroaniline was observed for UV-C photolysis under the same reaction conditions. IPR was also subjected to UV-C/PS treatment in simulated tertiary treated urban wastewater (SWW) to examine its oxidation performance and ecotoxicological behavior in a more complex aquatic environment. In SWW, IPR and DOC removal rates were inhibited and PS consumption rates decreased. The originally low acute toxicity (9% relative inhibition towards the photobacterium Vibrio fischeri) decreased to practically non-detectable levels (4%) during UV-C/PS treatment of IPR in SWW.

Distinguishing and mapping of aquatic vegetations and yellow algae bloom with Landsat satellite data in a complex shallow Lake, China during 1986–2018

• The spectral characteristics of aquatic vegetations and yellow algae were analyzed. • Several spectral indices were proposed to distinguish aquatic vegetations and yellow algae. • Seasonal and inter annual dynamics of aquatic vegetations and yellow algae were investigated. • The responses of aquatic vegetations and yellow algae to air temperature were discussed. • The MAI concept is considered to be extendable and applicable. Global lakes have suffered from algae blooms and loss or expansion of aquatic vegetations in recent decades. Remote sensing is considered as an effective approach to monitor aquatic vegetations and algae blooms. However, individual spectral index is unable to separate them due to the similarity in spectral features. In this paper, spectral characteristics analyses were conducted to find suitable spectral indices for distinguishing emergent vegetation, submerged aquatic vegetation and floating yellow algae in a complex aquatic environment, Ulansuhai Lake, China. It was found that near infrared band was appropriate to extract open water, and short-wave infrared band was suitable for extracting emergent vegetation, whereas the green and red bands were the characteristic spectra for distinguishing submerged aquatic vegetation and yellow algae. Hence, we firstly used the normalized difference vegetation index (NDVI) to extract open water, and the emergent vegetation spectral index (EVSI) to extract emergent vegetation. Then, a new developed macroalgae index (MAI) was used for distinguishing submerged aquatic vegetation and yellow algae. The applicability of the spectral indices was tested against both in situ measurements and Landsat-8 Operational Land Imager (OLI) data. The results indicated that the combination of these spectral indices was an effective method to separate aquatic vegetations and yellow algae. The proposed method was then applied to time-series Landsat images for investigating the seasonal and inter annual dynamics of aquatic vegetations and yellow algae and their responses to air temperature in the Ulansuhai Lake. The results show that emergent vegetation area increased from May to its maximum in July. The submerged aquatic vegetation area gradually increased from May to its maximum coverage in August, and decreased from late September. The yellow algae appeared in late May, and reached its maximum area in June or July, and disappeared in October. The long-term variation analyses showed that emergent vegetation area increased from 1986 to 2014, and was decreasing from 2014. The area of submerged aquatic vegetation increased during 1986–2008, and sharply decreased from 2009 to 2013, followed by a significant increasing from 2014. The yellow algae bloom mainly outbroke during the period of 1998 to 2010. We also found that the yellow algae area was more sensitive to short term mean temperature, while the area of emergent vegetation was sensitive to longer timescale of temperature. The submerged aquatic vegetation area had no significant correlation with air temperature. Besides, our study also indicated that the MAI concept can be extendable and applicable to other high-resolution satellite sensors (e.g., GF-2 PMS) and other regions with different algae blooms (e.g., Yellow Sea).

Effects of different routes of exposure to metals on bioaccumulation and population growth of the cyclopoid copepod Paracyclopina nana

We examined effects of the three metals cadmium (Cd), copper (Cu), and nickel (Ni) on two subpopulations of the cyclopoid copepod Paracyclopina nana. We sought to investigate the effects of metal exposure on population growth and structure of P. nana and to understand the parameters affecting the metal bioaccumulation in copepods. A first experiment tested the hypothesis of competition between these metals in a mixture using a P. nana mass culture in 10 L beakers with the sublethal concentrations (1/3 of LC50) as determined for E. affinis. A second experiment pursued the same with a P. nana population which was adapted to a higher Cu concentration for several generations (226.9 ± 15.9 μg g−1 dw Cu in copepods) and using the proper sublethal concentrations for P. nana. After 96 h of exposure, results from the first experiment showed a decreasing population growth and instead of an increasing metal accumulation in copepods. Cd also appeared to be more accumulated when it was alone, confirming the hypothesis of metal competition in mixture. Results from the second experiment revealed less marked effects. When metal concentrations increased in the treatment it decreased in copepods, indicating depuration activity in the population already adapted to metal exposure. This paper is the first one investigating the parameters affecting the bioaccumulation capacity of P. nana in response to metals. It offers a better understanding of copepod responses to metal contamination in a complex aquatic environment.

Historical Occurrence of Algal Blooms in the Northern Beibu Gulf of China and Implications for Future Trends.

Large-scale harmful algal blooms (HABs) occur in the coastal waters of the northern Beibu Gulf, China, and have deleterious effects on the marine ecosystem. The frequency, duration, and extent of HAB events in this region have increased over the last 30 years. However, the underlying causes of HABs and their likely future trends are unclear. To investigate, we evaluated historical data for temporal trends of HABs in the Beibu Gulf, and association with environmental factors as possible drivers. The results confirmed that HAB events had increased in frequency, from 6 reported events during the period 1985–2000, to 13 during 2001–2010, and 20 during 2011–2017. We also found that the geographic scale of algal blooms had increased from tens of km2 to hundreds of km2. There were temporal changes in HAB trigger species: prior to 2000, the cyanobacteria Microcystis aeruginosa was the dominant species, while during the period 2001–2010, blooms of cyanobacteria, dinoflagellates, and diatoms co-occurred, and during 2011–2017, the haptophyte Phaeocystis globosa became the dominant algal bloom species. Principal component analysis and variation partitioning analysis indicated that nutrient discharge, industrial development, and human activities were the key drivers of HAB events, and redundancy analysis showed that variation in the algal community tended to be driven by nutrient structure. Other factors, such as shipping activities and mariculture, also contributed to HAB events and algal succession, especially to P. globosa blooms. We speculated that the increasing severity of algal blooms in the northern Beibu Gulf reflects a more complex aquatic environment and highlights the damaging effects of anthropogenic inputs, urbanization development, and an expanding industrial marine-economy on the marine ecosystem. This research provides more insight into the increase of HABs and will aid their management in the Beibu Gulf.

Characterization of grass carp (Ctenopharyngodon idella) beta-defensin 1: implications for its role in inflammation control.

Considering that fish grows in a complex aquatic environment, there is an increasing interest in fish β-defensins, which is an important group of antimicrobial peptides (AMPs). In this study, grass carp (Ctenopharyngodon idella) β-defensin 1 (gcdefb1) was isolated using homology cloning technology. Tissue distribution assay showed that gcdefb1 transcripts were expressed with the highest levels in brain and liver, followed by some mucous tissues. To examine gcDefb1 bioactivities, the recombinant gcDefb1 proteins fused with thioredoxin tag protein (Trx) (Trx-Defb1) were induced for production in Escherichia coli Rosetta-gami2(DE3)pLysS under optimal expression conditions. The antibacterial activity of Trx-Defb1 against Aeromonas hydrophila was assessed and its minimum inhibitory concentration (MIC) was 36μM. Interestingly, Trx-Defb1 significantly inhibited LPS-induced Tnf-α (gcTnf-α) secretion and nitric oxide production in grass carp head kidney monocytes/macrophages (HKM), although Trx-Defb1 alone had no effect. Our studies provide the first evidence of fish β-defensin 1 engaging in both antimicrobial and inflammation suppression process.

Subpixel Surface Water Extraction (SSWE) Using Landsat 8 OLI Data

Surface water extraction from remote sensing imagery has been a very active research topic in recent years, as this problem is essential for monitoring the environment, ecosystems, climate, and so on. In order to extract surface water accurately, we developed a new subpixel surface water extraction (SSWE) method, which includes three steps. Firstly, a new all bands water index (ABWI) was developed for pure water pixel extraction. Secondly, the mixed water–land pixels were extracted by a morphological dilation operation. Thirdly, the water fractions within the mixed water–land pixels were estimated by local multiple endmember spectral mixture analysis (MESMA). The proposed ABWI and SSWE have been evaluated by using three data sets collected by the Landsat 8 Operational Land Imager (OLI). Results show that the accuracy of ABWI is higher than that of the normalized difference water index (NDWI). According to the obtained surface water maps, the proposed SSWE shows better performance than the automated subpixel water mapping method (ASWM). Specifically, the root-mean-square error (RMSE) obtained by our SSWE for the data sets considered in experiments is 0.117, which is better than that obtained by ASWM (0.143). In conclusion, the SSWE can be used to extract surface water with high accuracy, especially in areas with optically complex aquatic environments.

Machine Learning Automatic Model Selection Algorithm for Oceanic Chlorophyll-a Content Retrieval

Ocean Color remote sensing has a great importance in monitoring of aquatic environments. The number of optical imaging sensors onboard satellites has been increasing in the past decades, allowing to retrieve information about various water quality parameters of the world’s oceans and inland waters. This is done by using various regression algorithms to retrieve water quality parameters from remotely sensed multi-spectral data for the given sensor and environment. There is a great number of such algorithms for estimating water quality parameters with different performances. Hence, choosing the most suitable model for a given purpose can be challenging. This is especially the fact for optically complex aquatic environments. In this paper, we present a concept to an Automatic Model Selection Algorithm (AMSA) aiming at determining the best model for a given matchup dataset. AMSA automatically chooses between regression models to estimate the parameter in interest. AMSA also determines the number and combination of features to use in order to obtain the best model. We show how AMSA can be built for a certain application. The example AMSA we present here is designed to estimate oceanic Chlorophyll-a for global and optically complex waters by using four Machine Learning (ML) feature ranking methods and three ML regression models. We use a synthetic and two real matchup datasets to find the best models. Finally, we use two images from optically complex waters to illustrate the predictive power of the best models. Our results indicate that AMSA has a great potential to be used for operational purposes. It can be a useful objective tool for finding the most suitable model for a given sensor, water quality parameter and environment.

Greater macroinvertebrate diversity and freshwater mussel density in meander margins of an Amazon river

AbstractMeanders are complex aquatic environments exhibiting different flow and sediment characteristics that influence macroinvertebrate distribution. Differences in macroinvertebrate composition, freshwater mussel density (mainly Castalia ambigua Lamarck, 1819) and habitat variables were investigated, using uni‐ and multivariate analyses, in two zones, the margin and thalweg, of the meanders of a 7‐km stretch of a morphologically unaltered tropical alluvial lowland river. Clear differences were found between meander zones, with greater taxonomic and functional diversity of macroinvertebrates and greater freshwater mussel densities in the meander margin. A total of 12 families of macroinvertebrates were exclusive to the meander margin, and macroinvertebrate indicators of zones were Philopotamidae and Leptoceridae (meander margin) and Chironomidae and Elmidae (meander thalweg). In the meander margin, there were no differences in macroinvertebrate abundance, and taxonomic and functional group diversity among areas with low, medium and high mussel density. Macroinvertebrate abundance did not vary between zones, but in both, abundance was associated with lower pH and higher electrical conductivity. Low shear velocity, which stabilises the river bed, high organic matter content and percentage silt in the meander margin were associated with higher taxonomic and functional macroinvertebrate diversity, as well as the presence of freshwater mussels. Natural unaltered meanders are spatially heterogeneous in both habitat and biodiversity and, similar to restored meanders, support greater macroinvertebrate taxonomic and functional diversity, as well as maintain freshwater mussel beds, mainly by stabilising the river bed. The meander margin may also be important for attracting mussel host fish that feed on macroinvertebrates and aid mussel dispersal. Thus, the meander margins, and other similar riparian habitats with low shear velocity, for example, side channels and pools, have potentially high conservation value and should be afforded due protection.

Heat Shock Protein 70 Gene of Ya-Fish (Schizothorax Prenanti) Responses to Thermal Stress and Bacterial Challenges

The homeostasis of Ya-fish (Schizothorax prenanti) health may be affected by a wide variety of stressful stimuli from the complex aquatic environment. Heat shock proteins are extensively distributed and highly conserved in various animals, particularly Hsp70 which is a novel and potential biomarker for stressful environmental factors and disease conditions. The expression of SpHsp70 was detected to evaluate the potential use of SpHsp70 as a warning signal for some stimuli. In this study, freshwater Schizothorax prenanti were exposed to thermal stress and pathogenic bacteria in the aquatic environment. Results showed that SpHsp70 were ubiquitously and differentially expressed in nine examined organs/tissues. In Ya-fish, stessorspecific reactions were observed after different bacterial challenges. At the acute stage, SpHsp70 expression was significantly up-regulated in the kidney after Streptococcus agalactiae challenge, however SpHsp70 expression significantly increased in the spleen after Aeromonas hydrophila challenge. These reactions suggest that the response of SpHsp70 to bacterial stimuli depends on different stressors. Hence, thermal sensitivity and stressorspecificity precluded the simple use of SpHsp70 as warning information in S. prenanti.

Influence of substrate orientation on tadpoles' feeding efficiency.

ABSTRACTIn nature, tadpoles encounter food on substrates oriented at different angles (e.g. vertically along stems, horizontally on the bottom of the pond). We manipulated the orientation of food-covered surfaces to test how different orientations of surfaces affect tadpoles' feeding efficiency. We studied taxa that differed in the oral morphology of their larvae and position in the water column. We hypothesized that species would differ in their ability to graze upon surfaces at different orientations and that differences in the tadpoles' feeding ability would result in different growth rates. The orientation of food-covered surfaces did not affect the growth rate of bottom-dwelling tadpoles (whose growth rate varied only between species). Among midwater tadpoles, some species appear to have a generalist strategy and experienced a high relative growth rate on numerous substrate orientations, whereas others achieved high growth rates only on flat substrates (i.e. at 0° and 180°). We conclude that oral morphology constrains tadpoles' ability to feed at different substrate orientations, and this could lead to niche partitioning in structurally complex aquatic environments. Because physical parameters of the environment can affect tadpoles' growth rate, characterizing these features might help us better understand how competition structures tadpole assemblages.

Unraveling the dispersion and environmental impact of anthropogenic discharges in transitional water ecosystems

Transitional waters are characterized by spatial and temporal environmental gradients that make it difficult to discern between anthropogenic and natural stressors on ecosystem functioning. Here, we explored a combination of sampling surveys, analytical techniques focusing on fluorescent dissolved organic matter (FDOM) and remote-sensed products to evaluate the extension and impact of anthropogenic discharges into a Mediterranean coastal lagoon (Mesologgi, Greece). Surface water samples were collected from 20 to 25 sampling points covering the entire surface area of the lagoon during four sampling campaigns. Additional water samples were collected from the adjacent coastal ocean and the main freshwater tributaries to the lagoon, including two Pumping Stations (PS) draining an intensively farmed area, and the emissary of a Wastewater Treatment Plant (WWTP). Remote-sensed products validated the ability of our sampling strategy to capture the temporal and spatial variability of biogeochemical properties within the lagoon. Results showed the PSs and WWTP to be significant sources of nutrients to the lagoon. Parallel factor analysis identified one tryptophan-like, one microbial humic-like and three terrestrial humic-like FDOM components. Principal component analysis identified humic-like FDOM components as potential tracers of anthropogenic inputs into the lagoon. The distributions of the tryptophan-like FDOM component and remote-sensed chlorophyll a were strongly correlated and appeared associated with the location and dispersal of local anthropogenic stressors. Our results showed that the joint analysis of FDOM composition and remote-sensed biogeochemical properties permit to track anthropogenic inputs into complex aquatic environments inclusive of transitional waters, elucidating their impact over the biogeochemistry of the receptor ecosystems.

Removal of novel antiandrogens identified in biological effluents of domestic wastewater by activated carbon

Environmental antiandrogenic (AA) contaminants in effluents from wastewater treatment plants have the potential for negative impacts on wildlife and human health. The aim of our study was to identify chemical contaminants with likely AA activity in the biological effluents and evaluate the removal of these antiandrogens (AAs) during advanced treatment comprising adsorption onto granular activated carbon (GAC). In this study, profiling of AA contaminants in biological effluents and tertiary effluents was conducted using effect-directed analysis (EDA) including high performance liquid chromatography (HPLC) fractionation, a recombinant yeast screen containing androgen receptor (YAS), in combination with mass spectrometry analyses. Analysis of a wastewater secondary effluent from a membrane bioreactor revealed complex profiles of AA activity comprising 14 HPLC fractions and simpler profiles of GAC effluents with only 2 to 4 moderately polar HPLC fractions depending on GAC treatment conditions. Gas chromatography–mass spectrometry and ultra-high performance liquid chromatography-nanospray mass spectrometry analyses of AA fractions in the secondary effluent resulted in detection of over 10 chemical contaminants, which showed inhibition of YAS activity and were potential AAs. The putative AAs included biocides, food additives, flame retardants, pharmaceuticals and industrial contaminants. To our knowledge, it is the first time that the AA properties of N-ethyl-2-isopropyl-5-methylcyclohexanecarboxamide (WS3), cetirizine, and oxcarbazepine are reported. The EDA used in this study was proven to be a powerful tool to identify novel chemical structures with AA activity in the complex aquatic environment. The adsorption process to GAC of all the identified antiandrogens, except WS3 and triclosan, fit well with the pseudo-second order kinetics models. Adsorption to GAC could further remove most of the AAs identified in the biological effluents with high efficiencies.

Effects of water chemistry and surface contact on the toxicity of silver nanoparticles to Bacillus subtilis.

The growing use of silver nanoparticles (AgNPs) has created concerns about its potential impacts on natural microbial communities. In this study, the physicochemical properties of AgNPs and its toxicity on natural bacteria Bacillus subtilis (B. subtilis) were investigated in aqueous conditions. The characterization data showed that AgNPs highly aggregated in aqueous conditions, and the hydrodynamic diameter of AgNPs in aqueous conditions was larger than its primary size. The studied AgNPs was less toxic to B. subtilis in estuarine water as compared to that in Milli-Q water and artificial seawater, which might be due to the observed enhanced aggregation of AgNPs in estuarine water. The toxicity of AgNPs to B. subtilis was greatly reduced when their surface contact was blocked by a dialysis membrane. Scanning electron microscope images showed that exposure contact to AgNPs resulted in damage of the microbial cell wall and enhanced formation of fibrillar structures. These results suggest that particle-cell contact is largely responsible for the observed toxicity of AgNPs in B. subtilis. This study can help to understand the potential impacts of AgNPs to natural microbes, especially in the complex aquatic environments.