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Highlights • PAH, PCB and PBDE sediment concentrations were studied in Chapala Lake, Mexico. • POP sediment concentrations were indicative of moderate to intense contamination. • POP sediment concentrations can be harmful for human through fish consumption. • Despite the banning of POP use, sediment concentrations are still growing since 1990s. • Long-range atmospheric transport has been the main source of POPs to the sediments. Abstract 210Pb-dated sediment cores and surface sediments from Lake Chapala (LC), Mexico, were analyzed to assess the temporal trends in concentrations and fluxes of persistent organic pollutants (POPs: PAHs, PCBs and PBDEs). Total sediment concentrations of PAHs (95-1,482 ng g−1), PCBs (9-27 ng g−1) and PBDEs (0.2-2.5 ng g−1) were indicative of moderate to intense contamination. The POP concentrations have progressively increased since the 1990s. The light molecular weight PAHs, and the prevalence of PCB congeners with low-chlorination levels (e.g., di- to tri-CB) and low-to medium-brominated (tri- to penta-BDE) PBDEs in most sections of the sediment profiles, suggested that these POPs have most likely reached these sediments by long-range atmospheric transport from distant sources; although the significant presence of heavier PAH, PCB and PBDE congeners in the topmost sediments, indicate that other nearby and local sources (soil erosion from the catchment, urban and industrial wastewaters discharges, as well as navigation) might have also contributed to the recent input of POPs to LC. Taking into account the relevance of LC as regional freshwater supply and commercial fishing ground, the potential risk posed by the organic contaminated sediments to the biota and human population should not be underestimated. [ABSTRACT FROM AUTHOR]

Abstract This study investigated acute arsenic toxicity and bioconcentration capacity in Litopenaeus vannamei because it has been frequently exposed to lower salinities than its isosmotic point (25 g L−1). Juveniles (9.9 ± 0.4 g) were exposed to low (5–10 g L−1) and isosmotic salinity (25 g L−1) levels; As values were 30.8, 20.2, 16.8 and 13.9 mg L−1 at 5 g L−1; 30.4, 19.1, 16.8 and 14.8 mg L−1 at 10 g L−1; 31.5, 19.0, 15.0 and 11.9 mg L−1 at 25 g L−1 at 24, 48, 72 and 96 h LC 50 , respectively. No significant differences were found among As LC 50 values calculated for different salinity levels and same exposure times, concluding that low salinity did not affect shrimp sensitivity to As. Likewise, no significant differences were observed in As bioconcentration in shrimp exposed to the same waterborne As and distinct salinity, supporting the results of acute toxicity. Bioconcentration factors of As maintained a relatively stable tendency where all values (0.8 ± 0.2 to 1.7 ± 0.4) were statistically comparable to 1, indicating that As was accumulated in a similar proportion to waterborne As concentration at three salinity levels. This study proposed 135.3 ± 12.1 μg L−1 for salinities from 5 to 25 g L−1 as provisional safe As concentration. According to these results, the hypothesis that sustains an effect of low salinity on As acute toxicity and its bioconcentration capacity cannot be acceptable. Therefore, the information provided allows knowing the threshold levels of As in water to avoid ecological and economic losses. Graphical abstract Unlabelled Image Highlights • Acute toxicity and bioconcentration of As were determined in shrimp juveniles. • LC 50 -96 h were 13.9, 14.8 and 11.9 mg L−1 for 5, 10 and 25 g L−1. • Significant differences were not found between LC 50 for different salinities examined. • As bioconcentration was not affected by the low-salinities examined. • It is proposed as safe As level 135.3 ± 12.1 μg L−1 for salinities from 5 to 25 g L−1. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the production of an aquaponic culture of white shrimp (Penaeus vannamei) and basil (Ocimum basilicum) using two sources of low-salinity water (1.7 g L-1): diluted seawater (DSW) and groundwater (GW) with zero water exchange at a stocking ratio of 4.9 shrimp per basil plant. Six aquaponic treatment systems were constructed: three individual aquaponic systems for DSW-basil, three for GW-basil, and a control (per triplicate) of basil with a hydroponic solution. Stock densities for shrimp were 75 post-larvae m-2 and 16 plants m-2 for basil. With the exception of the yield in the shrimp culture (kg m-2 or ton ha-1), no significant differences (P > 0.05) were found for the final individual weight, survival, growth rate and feed conversion ratio between DSW and GW, whereas for basil, lower yields were found with DSW. No significant differences in the basil production between the control and the treatment GW were found. Feed consumption per kg of total harvested basil was significantly lower (P < 0.05) in GW treatment, while for feed intake in the shrimp farming, where no significant differences were found (P > 0.05). The aquaponic culture of shrimp and basil using these two types of low-salinity water sources showed promising results. The estimates of both crop yields were compared with those recorded in the literature and for commercial field crops from northwest Mexico. [ABSTRACT FROM AUTHOR]

The accumulation, mass balances, and potential health risks associated with the presence of Hg were evaluated in basil cultivated simultaneously with shrimp by aquaponics (∼1.7 g L−1). Two aquaponic (well water (WW) and diluted seawater (DSW)) treatments and one hydroponic control (hydroponic solution (HS)) were examined. The trend of Hg accumulated in basil tissues was roots > leaves > stems. No significant differences (p > 0.05) were found between aquaponic treatments. Mercury concentrations in the edible basil tissues were below the maximum allowable levels (0.2 mg kg−1) for vegetables established by international guidelines (WHO, 2007; CREU, 2018). The mass balances evidenced that most Hg (> 99%) entered the aquaponic system through the input water, while the main output route (> 90%) was through the zeolite used in plants. Mercury inorganic speciation in water was similar between WW and DSW treatments. The dominating speciation was HgCl 2 (50%), which is a bioavailable form that biota can use. In the HS treatment, the chemical speciation was different as it formed complexes mainly with ammonia. The health risk index for Hg was < 1.0, which indicates that the population exposed to the consumption of basil grown with shrimp would not be at risk. [Display omitted] • It is feasible to use low-salinity shrimp culture effluents for basil production. • Basil production in descending order was well water > control > diluted seawater. • Hg concentration in basil tissues in descending order was roots > leaves > stems. • Most Hg (>99%) entered via input water and the main output (>90%) was via zeolite. • Mercury levels found in basil did not exceed the safe limits and HRIs were < 1. [ABSTRACT FROM AUTHOR]

The omnipresence of microplastics (MPs) in marine and coastal environments has attracted attention owing to their effects on various organisms, including humans. We present the first study of MPs in the gastrointestinal tract (GT), gills (GI), and exoskeleton (EX) of the farmed whiteleg shrimp Litopenaeus vannamei from commercial aquaculture facilities in northwestern Mexico that have operated semi-intensively for the last two decades. We found that the number of MP items per tissue was 7.6 ± 0.6 in the GT, 6.3 ± 0.9 in the GI, and 4.3 ± 0.9 in the EX, with an average of 18.5 ± 1.2 MP items per shrimp (1.06 items/g, wet weight [ww]). MP concentrations were 261.7 ± 84.5, 13.1 ± 1.8, and 2.6 ± 0.6 items/g (ww) in the GT, GI, and EX, respectively. Microplastics ranged from 30 to 2800 μm in size (360 ± 39 μm) with fibers (∼90.8%), filament-shape (∼93.4%), and transparent (∼47.7%) being the most common ones. Polyethylene (∼54.5%) and polyamide (∼24.2%) were the most commonly identified polymers, although polyesters (∼12.1%), polystyrene (∼6.1%), and nylon (∼3.0%) were also found. The abundance of MPs in farmed L. vannamei may be related to their feeding habits and the availability of MP sources in aquaculture facilities. [Display omitted] • Farmed shrimp contained 18.5 ± 1.2 microplastics (MPs)/shrimp (1.1 MP/g shrimp). • The number of MPs in the gastrointestinal tract was 261.7 ± 84.5 items/g. • MPs were predominantly fibers (91%) in the gastrointestinal tract of shrimp. • The most common size interval of MPs was 101–600 μm. • MPs in farmed shrimp were mainly polyethylene and polyamide. [ABSTRACT FROM AUTHOR]

Abstract: Concentrations of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) were measured in a sediment core from the tropical freshwater inner lagoon of Las Matas, near the petroleum industrial area of Minatitlán-Coatzacoalcos, in the Gulf of Mexico. A 210Pb-derived chronology was used to reconstruct the historical PAH and PCB accumulation in the site during one century (1906–2005). Both geochemical and sedimentological data indicated that a major change occurred in 1947±4, including a shift to coarser sediments and a significant decrease of Al, Li, Fe, organic C and total N contents. This was likely due to the changes in hydrology caused by the confinement of Las Matas Lagoon due to the construction of the Trans-Isthmus road in 1946. PAHs in these samples show relatively low concentrations (259–1176ngg−1), and the congener relative abundances indicate the influence of pyrogenic (petroleum combustion) sources. Total PCB concentrations in the sediments ranged from 24 to 77ngg−1, and are composed by low chlorinated PCBs, with 3- and 4-CB as the prevalent species (51–65% and 29–40%, respectively). PAHs and PCBs were detected at depths corresponding to the early 1900s, when Minatitlán refinery started operations, although their time evolution appears to be influenced by different accumulation processes. The PCB background is most likely produced by the combustion of natural organic matter, and an industrial contribution can be recognized when normalizing with OC contents. We concluded that atmospheric deposition is the most significant source of PAHs and PCBs for this water body. This study also provided evidence of the alteration of the wetlands surrounding this industrial area due to urbanization; the fragmentation and alteration of Las Matas Lagoon hydrology contributes to the gradual loss of the wetlands in the zone. [Copyright &y& Elsevier]

• Metals redox-active and non redox-active cause oxidative stress. • Antioxidant enzymes are induced or inhibited by metals depending on decapod species. • Antioxidant defense strategies vary among decapod crustaceans. The objective of this review is to synthetize knowledge of the relationship between metals and oxidative stress in aquatic crustaceans (mainly shrimp and crabs) to analyze antioxidant responses when organisms are exposed to metals because the direct metal binding to the active site of enzymes inactivates most of the antioxidant systems. This study reviewed over 150 works, which evidenced that: (i) antioxidant defense strategies used by aquatic decapod crustaceans vary among species; (ii) antioxidant enzymes could be induced or inhibited by metals depending on species, concentration, and exposure time; and (iii) some antioxidant enzymes, as superoxide dismutase increase their activity in low metal levels and time exposures, but their activities are inhibited with higher metal concentrations and exposure time. [ABSTRACT FROM AUTHOR]

Abstract: Exposure to different levels of a mixture in equitoxic concentrations of Cd, Cu, Fe, Hg, Mn, Pb and Zn, equivalent to between 5 and 0.5% the individual respective 96-h median lethal concentrations (0.05–0.005AF: application factors) caused dose- and time-dependent damages to the hepatopancreas, gills, epipodites and midgut tissues of Litopenaeus vannamei juveniles. After between 1 and 3–4 weeks, there was between 50 and 100% loss of the hepatopancreas R cells and of the tubules regular structure. Gill alterations were observed between 2 and 3 weeks with 0.05–0.025 and 0.005AF, respectively. Epipodites showed time- and dose-dependent increasing degrees of melanization, and hemocytic enteritis was observed with 0.025 and 0.01AF. Exposure to 0.05 and 0.025AF caused also 50 and 12% mortalities after 2 and 3 weeks respectively, showing that even at these low levels the mixture of these metals may have a mid-term lethal effect. For this reason, the assessment of risk and of safe levels of toxic substances added to any natural environment through human or natural sources, should not neglect the effects on biological systems caused by the interaction of minute amounts of toxicants, which would be harmless unless present in combination. [Copyright &y& Elsevier]