Environmental observations of antibiotics and other pharmaceuticals have received attention as indicators of an urbanizing global water cycle. When connections between environment and development of antibiotic resistance (ABR) are considered, it is increasingly important to understand the life cycle of antibiotics. Here we examined the global occurrence of erythromycin (ERY) in: 1. wastewater effluent, inland waters, drinking water, groundwater, and estuarine and coastal systems; 2. sewage sludge, biosolids and sediments; and 3. tissues of aquatic organisms. We then performed probabilistic environmental hazard assessments to identify probabilities of exceeding the predicted no-effect concentration (PNEC) of 1.0 μg L−1 for promoting ABR, based on previous modeling of minimum inhibitory concentrations and minimal selective concentrations of ERY, and measured levels from different geographic regions. Marked differences were observed among geographic regions and matrices. For example, more information was available for water matrices (312 publications) than solids (97 publications). ERY has primarily been studied in Asia, North America and Europe with the majority of studies performed in China, USA, Spain and the United Kingdom. In surface waters 72.4% of the Asian studies have been performed in China, while 85.4% of the observations from North America were from the USA; Spain represented 41.9% of the European surface water studies. Remarkably, results from PEHAs indicated that the likelihood of exceeding the ERY PNEC for ABR in effluents was markedly high in Asia (33.3%) followed by Europe (20%) and North America (17.8%). Unfortunately, ERY occurrence data is comparatively limited in coastal and marine systems across large geographic regions including Southwest Asia, Eastern Europe, Africa, and Central and South America. Future studies are needed to understand risks of ERY and other antibiotics to human health and the environment, particularly in developing regions where waste management systems and treatment infrastructure are being implemented slower than access to and consumption of pharmaceuticals is occurring.

One of the fundamentals in the ecotoxicological studies is the need of data comparison, which can be easily reached with the help of a standardized biological model. In this context, any biological model has been still proposed for the biomonitoring and risk evaluation of freshwaters until now. The aim of this review is to illustrate the ecotoxicological studies carried out with the zebra mussel Dreissena polymorpha in order to suggest this bivalve species as possible reference organism for inland waters. In detail, we showed its application in biomonitoring, as well as for the evaluation of adverse effects induced by several pollutants, using both in vitro and in vivo experiments. We discussed the advantages by the use of D. polymorpha for ecotoxicological studies, but also the possible limitations due to its invasive nature.

Polystyrene nanoplastics (PS NPs), which are newly emerging as particulate pollutants, are one of the most abundant plastic types in marine debris. Although there has been extensive research on microplastics, the sorption behavior of PS NPs in surface waters remains unknown. In addition, in the previous joint toxicity studies, the concentration of organic pollutant in the joint system was based on the EC₅₀ of this pollutant, rather than the actually amount of this pollutant adsorbed on nanoplastics (NPs). In this study, the sorption behavior of PS NPs with different surface charges in the surface water of estuaries and joint toxicity of that absorbed tetracycline antibiotic in equilibrium were investigated for the first time. Because of the electrostatic repulsion, salting-out effect, and partition function, the sorption capacity of tetracycline antibiotic by differently charged PS NPs was enhanced with increasing salinity. The biological effects of exposure to tetracycline-saturated PS NPs were complicated, which can be attributed to the surface characteristics of mixtures such as hydrophobicity and charges. Thus, the role of NPs in the natural environment as a carrier of antibiotics may provide an alternative for antibiotic inputs from inland water to coastal marine water, which would not only change the environmental fate and ecotoxicology of antibiotics and NPs, but also pose challenges to the safety of coastal aquaculture and marine ecosystem.

Compared to marine microplastics research, few studies have bio-monitored microplastics in inland waters. It is also important to understand the microplastics’ uptake and their potential risks to freshwater species. The Australian glass shrimp Paratya australiensis (Family: Atyidae) is commonly found in fresh waterbodies in eastern Australia, and are sensitive to anthropogenic stressors but have a wide tolerance range to the natural environmental conditions. This study aimed to understand the microplastics’ occurrence and types in water samples and the shrimp P. australiensis, and identify if the shrimp could be a suitable bioindicator for microplastic pollution. Surface water and P. australiensis across ten urban and rural freshwater sites in Victoria were sampled. In total, 30 water samples and 100 shrimp were analysed for microplastic content, and shrimp body weights and sizes were also recorded. Microplastics were picked, photographed and identified using FT-IR microscopy: in water samples, 57.9% of items including suspect items were selected to identify; all microplastics found in shrimp samples were identified. Microplastics were present in the surface waters of all sites, with an average abundance of 0.40 ± 0.27 items/L. A total of 36% of shrimp contained microplastics with an average of 0.52 ± 0.55 items/ind (24 ± 31 items/g). Fibre was the most common shape, and blue was the most frequent colour in both water and shrimp samples. The dominant plastic types were polyester in water samples, and rayon in shrimp samples. Even though results from this study show a relatively low concentration of microplastics in water samples in comparison with global studies, it is worth noticing that microplastics were regularly detected in fresh waterbodies in Victoria, Australia. Compared with water samples, shrimp contained a wider variety of plastic types, suggesting they may potentially behave as passive samplers of microplastics pollution in freshwater environments.

The seasonal variation and distribution among different matrices of endocrine-disrupting chemicals (EDCs) were investigated in the eutrophic water ecosystem of the Pearl River Delta, Guangdong, China. The chlorophyll a (Chl a) levels were generally higher in summer than in spring; however, the concentrations of 4-tert-octylphenol (OP), 4-nonylphenol (NP), and bisphenol A (BPA) in surface water were generally higher in spring (oligotrophic) than in summer (eutrophic). The levels of EDCs in SPM were lower in spring than in summer, a pattern seen in the seasonal variation of Chl a and particulate organic carbon (POC). The seasonal variations of EDCs in water bodies with different levels of eutrophication were analyzed in several dimensions including sediment, POC, algae and fish bile. The log Kₒc for SPM/water was higher in summer than in spring. The log Kₒc values for NP, OP, and BPA exhibited the following trends between matrices: colloid/water > sediment/water > SPM/water > algae/water, colloid/water > sediment/water > algae/water > SPM/water, and colloid/water > algae/water > sediment/water > SPM/water. The EDCs levels were different in fish tissues with the order bile > liver > muscle, with the concentrations being an order of magnitude higher in bile than in liver and an order of magnitude higher in liver than in muscle. The sequence of the bioconcentration factor (log BCF) for bile/water and liver/water was NP < OP < BPA in eutrophic conditions, but NP > OP > BPA in oligotrophic conditions. The order in eutrophic conditions was the same as the log BCF and log Kₒc for algae/water, indicating that the accumulation of EDCs in water bodies could be affected by algae, which could be one of the reasons of the seasonal variation of EDCs in water.

The dispersants Corexit 9527 and Corexit 9500 were extensively used during the response to the Deepwater Horizon accident in 2010. In addition to the monitoring programs established by federal and state governments, local communities also conducted studies to determine if chemical constituents from these dispersants impacted nearshore and inland waters. One community (the City of Orange Beach, Alabama) collected water samples between September, 2010 and January, 2011, and found the dispersant-related chemicals propylene glycol, 2-butoxyethanol, and dioctyl sodium sulfosuccinate at nearshore and inland water sampling sites. In this paper, we examine their dataset in an attempt to discern the origin of these chemicals. Our assessment indicates that these compounds are unlikely to be present as a result of the use of Corexit dispersants; rather, they are likely related to point and non-point source stormwater discharge.

Satellite images were used to assess surface water quality based on the concentration of chlorophyll a (chla), light penetration measured by the Secchi disk method (SD), and the Cyanobacteria cells number per mL (cyano). For this case study, six reservoirs interconnected were evaluated, comprising the Cantareira System (CS) in São Paulo State (Brazil). The work employed Sentinel-2 images from 2015 to 2018, SNAP image processing software, and the native products conc_chl and kd_z90max, treated using Case 2 Regional Coast Color (C2RCC) atmospheric correction. The database was obtained from CETESB, the agency legally responsible for operation of the Inland Water Quality Monitoring Network in São Paulo State. The results demonstrated robustness in the estimates of chla (RMSE = 3.73; NRMSE% = 19%) and SD (RMSE = 2,26; NRMSE% = 14%). Due to the strong relationship between cyano and chla (r² = 0.84, p < 0.01, n = 90), both obtained from field measurements, there was also robustness in cyano estimates based on the estimates of chla from the satellite images. The data revealed a clear pattern, with the upstream reservoirs being more eutrophic, compared to those downstream. There were evident concerns, about water quality, particularly due to the high numbers of Cyanobacteria cells, especially in the upstream reservoirs.

The connection between nutrient input and algal blooms for inland water productivity is well known but not the spatial pattern of water nutrient loading and algae concentration. Remote sensing provides an effective tool to monitor nutrient abundances via the association with algae concentration. Twenty-one field campaigns have been conducted with samples collected under a diverse range of algal bloom conditions for three central Indiana drinking water bodies, e.g., Eagle Creek Reservoir (ECR), Geist Reservoir (GR), and Morse Reservoir (MR) in 2005, 2006, and 2008, which are strongly influenced anthropogenic activities. Total phosphorus (TP) was estimated through hyperspectral remote sensing due to its close association with chlorophyll a (Chl-a), total suspended matter, Secchi disk transparency (SDT), and turbidity. Correlation analysis was performed to determine sensitive spectral variables for TP, Chl-a, and SDT. A hybrid model combining genetic algorithms and partial least square (GA-PLS) was established for remote estimation of TP, Chl-a, and SDT with selected sensitive spectral variables. The result indicates that TP has close association with diagnostic spectral variables with R 2 ranging from 0.55 to 0.72. However, GA-PLS has better performance with an average R 2 of 0.87 for aggregated dataset. GA-PLS was applied to the airborne imaging data (AISA) to map spatial distribution of TP, Chl-a, and SDT for MR and GR. The eutrophic status was evaluated with Carlson trophic state index using TP, Chl-a, and SDT maps derived from AISA images. Mapping results indicated that most MR belongs to mesotrophic (48.6%) and eutrophic (32.7%), while the situation was more severe for GR with 57.8% belongs to eutrophic class, and more than 40% to hypereutrophic class due to the high turbidity resulting from dredging practices.