The popular paradigm in trophic dynamic theory is that contemporary autochthonous organic matter (e.g., phytoplankton) sustains consumer growth, whereas aged allochthonous organic matter is conceptually considered recalcitrant resources that may only be used to support consumer respiration but suppress consumer growth. This resource-age paradigm has been challenged by a growing body of recent evidence that ancient (radiocarbon depleted) organic carbon (OC) released from glaciers and permafrost can be incorporated by consumers in aquatic systems. However, little information is available regarding the food quality of ancient terrestrial OC and how it impacts the growth of consumers in lakes. Here, ancient dissolved organic carbon (DOC) was extracted from frozen soils in an alpine lake catchment. The contents of polyunsaturated fatty acids (PUFAs) in soil DOC increased significantly after bioconversion by heterotrophic bacteria. The utilization of soil DOC by heterotrophic bacteria also increased the total phosphorus concentration in the systems. Gammaproteobacteria and Betaproteobacteria showed a strong negative correlation with the percentage contents of fluorescent components, including humic-like and tyrosine-like components. Daphnia magna were fed Auxenochlorella vulgaris and ancient DOC plus heterotrophic bacteria. The contents of PUFAs and the growth of zooplankton were influenced by the pre-conversion time of ancient DOC by bacteria. When ancient DOC was pre-converted by bacteria for 27 days, D. magna fed on the mixed diets showed the highest body length (3.40 mm) and intrinsic rate of increase in population (0.49 d⁻¹). Our findings provide direct evidence that ancient terrestrial OC can be an important subsidy for lake secondary production, which have important implications for food webs in high-altitude and polar lakes.

Despite growing concern about the occurrence of microplastics in aquatic ecosystems there is only rudimentary understanding of the pathways through which any adverse effects might occur. Here, we assess the effects of polystyrene microplastics (PS-MPs; <70 μm) on a common and widespread algal species, Chlorella sorokiniana. We used laboratory exposure to test the hypothesis that the lipids and fatty acids (FAs) are important molecules in the response reactions of algae to this pollutant. Cultivation with PS-MPs systematically reduced the concentration of essential linoleic acid (ALA, C18:3n-3) in C. sorokiniana, concomitantly increasing oleic acid (C18:1n-9). Among the storage triacylglycerols, palmitoleic and oleic acids increased at the expenses of two essential fatty acids, linoleic (LIN, C18:2n-6) and ALA, while PS-MPs had even more pronounced effects on the fatty acid and hydrocarbon composition of waxes and steryl esters. The FA composition of two major chloroplast galactolipids, monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), were affected implying changes in the conformational structure of photosynthetic complexes in ways that can impair the photosynthesis. These data reveal how exposure to polystyrene microplastics can modify the concentrations of lipid molecules that are important intrinsically in cell membranes, and hence the lipid bilayers that could form an important barrier between algal cellular compartments and plastics in the aquatic environment. Changes in lipid synthesis and fatty acid composition in algae could also have repercussions for food quality, growth and stressor resistance in primary consumers. We advocate further studies of microplastics effects on the lipid composition of primary producers, and of their potential propagation through aquatic food webs.

Persistent organic pollutants (POPs) are believed to alter metabolic homeostasis during fetal development, leading to childhood obesity. However, limited studies have explored how fetal chemical exposures relate to birth and infant weight outcomes in low-income Hispanic families at the highest risk of obesity. Therefore, we sought to determine associations between neonatal POPs exposure measured in newborn dried blood spots (DBS) and prenatal diet quality, birth weight, and overweight status at 18 months old. We conducted a case-control study nested within the Starting Early Program randomized controlled trial comparing POPs concentrations in infants with healthy weight (n = 46) and overweight status (n = 52) at age 18 months. Three categories of POPs, organochlorine pesticides (OCPs), polybrominated diphenyl ethers (PBDEs) and perfluoroalkyl substances (PFASs) were measured in archived newborn DBS. We assessed correlations between prenatal diet quality and neonatal POPs concentrations. Multivariable regression analyses examined associations between POPs (dichotomized at the mean) and birth weight z-score and weight status at 18 months, controlling for confounders. Seven of eight chemicals had detectable levels in greater than 94% of the sample. Higher protein, sodium and refined grain intake during pregnancy were correlated with lower POPs in newborn DBS. We found that high concentrations of perfluorooctanesulfonate (unstandardized coefficient [B]: −0.62, 95% confidence interval [CI]: −0.96 to −0.29) and perfluorohexanesulfate (B: −0.65, 95% CI: −0.99 to −0.31) were related to lower birth weight z-scores compared to those with low concentrations. We did not find associations between PBDEs, OCPs, and the other PFASs with birth weight z-scores, or between any POPs and weight status at 18 months. In conclusion, two PFASs were associated with lower birth weight, an important indicator of child health and growth, although direct associations with infant overweight status were not found. Whether neonatal POPs exposures contribute to economic and ethnic disparities in early obesity remains unclear.

Waterborne exposure towards fungicides is known to trigger negative effects in aquatic leaf-associated microbial decomposers and leaf-shredding macroinvertebrates. We expected similar effects when these organisms use leaf material from terrestrial plants that were treated with systemic fungicides as a food source since the fungicides may remain within the leaves when entering aquatic systems. To test this hypothesis, we treated black alder (Alnus glutinosa) trees with a tap water control or a systemic fungicide mixture (azoxystrobin, cyprodinil, quinoxyfen, and tebuconazole) at two worst-case application rates. Leaves of these trees were used in an experiment targeting alterations in two functions provided by leaf-associated microorganisms, namely the decomposition and conditioning of leaf material. The latter was addressed via the food-choice response of the amphipod shredder Gammarus fossarum. During a second experiment, the potential impact of long-term consumption of leaves from trees treated with systemic fungicides on G. fossarum was assessed. Systemic fungicide treatment altered the resource quality of the leaf material resulting in trends of increased fungal spore production and an altered community composition of leaf-associated fungi. These changes in turn caused a significant preference of Gammarus for microbially conditioned leaves that had received the highest fungicide treatment over control leaves. This higher food quality ultimately resulted in a higher gammarid growth (up to 300% increase) during the long-term feeding assay. Although the underlying mechanisms still need to be addressed, the present study demonstrates a positive indirect response in aquatic organisms due to systemic pesticide application in a terrestrial system. As the effects from the introduction of plant material treated with systemic fungicides strongly differ from those mediated via other pathways (e.g., waterborne exposure), our study provides a novel perspective of fungicide-triggered effects in aquatic detritus-based food webs.

The Qinling subspecies of giant panda (Ailuropoda melanoleuca qinlingensis), is highly endangered; fewer than 350 individuals still inhabit Qinling Mountains. Previous research revealed captive pandas were exposed to bromine, so we hypothesized that captive pandas were exposed to and affected by polybrominated diphenyl ethers (PBDEs). To test this hypothesis, we tested blood and feces of captive and wild pandas, their drinking water, food (bamboo leaves) from SWARC (Shaanxi Wild Animal Research Center)and FNNR (Foping National Nature Reserve) and supplemental feedstuff given to captive panda at SWARC. We found 13 congeners of PBDEs in fecal samples, of which BDE47, BDE66, BDE71, BDE99, and BDE154 were the dominant, total PBDE concentration in feces of captive pandas was 255% higher than in wild pandas. We found nine PBDEs congeners in blood samples: BDE153 and BDE183 were the predominant congers. PBDEs in blood from captive pandas were significantly higher than in wild pandas. The total concentration of PBDEs were 5473 and 4835 (pg.g) in Fargesia qinlingensis, were 2192 and 1414 (pg.g) in Bashannia fargesii (2192, 1414 pg g), 0.066, 0.038 (pg/ml) in drinking water, and 28.8 (pg.g) in supplemental feedstuff for captive and wild pandas, which indicate that the PBDEs came from its bamboo feed, especially from Bashannia fargesii. Our results demonstrate that BDE99 and BDE47 could be threatening the pandas’ health especially for captive panda and there are potential health risks from PBDEs for pandas. In the short term, this risk may be ameliorated by strict control of food quality. In the long term, however, reducing air, water and soil contamination so as to improve environmental quality can best reduce these risks to meet the international standard such as Stockholm Convention.

The innovative and sustainable technologies are highly needed to decrease serious environmental problems from current agriculture. Herein, the green and biosafe copper-based nano-agriculture was described for tomato production. Prepared Cu nanoclusters (NCs) showed small size (3.0 ± 0.5 nm) and high bioavailability. At low concentration (1 mg kg⁻¹) in soil, Cu NCs improved the activities of antioxidant enzymes (superoxide dismutase, catalase and peroxidase) in the tomato plants, which could help to slow down leaf aging, increase photosynthesis and carbohydrates content by 19.4 % and 14.9 %, respectively. Cu NCs promoted the roots' growth, especially increasing the root tip’ number, which might contribute to the increase in absorption of macronutrients (K, Mg and P) and micronutrients (B, Mn, Cu and Zn). The Cu NCs (1 mg kg⁻¹) promoted tomato growth and increased the tomato fruit yields by 12.2 % compared to the control. Moreover, the tomato fruit qualities had been improved meanwhile the accumulation of Cu in fruits was not observed. These findings indicate that the Cu NCs have potential to be safely applied for tomato production.

A chemical contaminant of growing concern to freshwater aquatic organisms, including many amphibians, is chloride ion. The salinization of freshwater ecosystems is likely caused, in part, by the application of massive amounts of road de-icing salts to roadways during winter months. The issue of freshwater salinization has become the subject of many toxicity studies and is often investigated in conjunction with other chemical stressors. However, few published studies attempt to investigate the interactions of elevated chloride concentration and increased temperature. Further, no studies have investigated the gap between the recommended feeding conditions typically used in standard toxicity tests and those that may exist in natural amphibian habitats. This study addressed the critical issues of elevated chloride, increased temperature, and variation in food quality. We conducted a 96-h acute toxicity test to investigate acute chloride toxicity as impacted by different diets, as well as a chronic toxicity test to investigate the impacts of chloride, temperature, and resource quality on the survival and development of larval Lithobates sylvaticus (wood frogs). Chloride LC₅₀s ± 1 SE were 3769.22 ± 589.05, 2133.00 ± 185.95, and 2644.69 ± 209.73 mg Cl⁻/L were for non-fed, low-protein diet, and high-protein diet, respectively. For the chronic toxicity study, elevated chloride decreased tadpole survival. Increased temperature, and lower resource quality, were found negatively impacted survival of tadpoles and altered time-to-metamorphosis. This study shows that environmentally relevant concentrations of chloride, temperatures, and the protein content of the diet all exert critical effects on larval wood frogs.

Mercury (Hg) is a global toxic pollutant and has raised the world's attention for decades. In this study, we reviewed the fish mercury levels in China (both marine and freshwater, as well as wild and farmed) documented over the past decade and their controlling environmental and biological factors. China is the largest contributor of global Hg cycling and the largest nation for the consumption and export of fish and fish product, thus Hg level in fish becomes a critical issue for food safety and public health. In China, Hg in fish is generally accumulated at a low level, but significant geographical differences were evident and formed the “hot spots” from the north to the south. For marine fish, the east (median: 70 ng g−1 ww, range: 5.0–330 ng g−1 ww) and southeast (median: 72 ng g−1 ww, range: 0.3–329 ng g−1 ww) of China have higher total Hg concentrations than the other coastal areas. For freshwater fish, Tibetan Plateau exhibited the highest total Hg levels (median: 104 ng g−1 ww, range: 5.0–868 ng g−1 ww). Risk assessment of the exposure of low-Hg-level fish to China's population deserves more attention and detailed fish consumption advisories to specific populations are urgently needed. The biokinetic model is a useful tool to characterize the underlying processes involved in Hg accumulation by fish. The diet (Hg concentration, speciation, food quality and quantity) and growth appear to be the important factors affecting the Hg levels of fish in China. The Hg biotransformation can also make contributions to Hg speciation and overall accumulation in fish. The intestinal microbes play an important role in Hg biotransformation and the potential for minimizing Hg contamination in fish deserves further investigation.

Increasing applications of titanium dioxide nanoparticles (nano-TiO2) have intensified the risk of environmental contamination. Since nano-TiO2 can absorb metals and be consumed as ‘food’ by zooplankton but also can interact with phytoplankton, they could significantly disturb the existing metal assimilation patterns. In the present study, we quantified the dietary assimilation of Cd and Zn from nano-TiO2 and algae (Chlamydomonas reinhardtii) at comparable particle concentrations as well as in complex food environment (variable food quality and quantity) in a freshwater zooplankton Daphnia magna using the radiotracer technique. For both nano-TiO2 and algae as food, the feeding food quality and depuration food quantity significantly affected the assimilation efficiencies (AEs) of Cd and Zn. At feeding food quantity of 1 mg/L to 10 mg/L without food in depuration, the AEs of Cd and Zn from nano-TiO2 were lower than those from algae. When food was added during depuration, the influences of nano-TiO2 on metal AEs were variable due to the differential effects of food quantity on the gut passage of nano-TiO2 and algae. Furthermore, mixed nano-TiO2 and algae had the lowest metal AEs compared to sole nano-TiO2 or algae as a result of interaction between nano-TiO2 and algae during feeding. Overall, this study showed the distinguishing metal AEs between nano-TiO2 and algae, and that nano-TiO2 could significantly reduce the existing metal AEs from algae. More attention should be paid to the potential roles of nano-TiO2 in disturbing metal assimilation in the environmental risk assessments of nanoparticles.

Food quality affects the food consumption rate, flux through the gut, and exposure to contaminants in animals. This study evaluated the effects of food quality on cadmium exposure in the soil collembolan Folsomia candida. Animals were exposed to constant concentrations of cadmium for 38 h via artificial food consisting of an agar medium with various concentrations of sugar (glucose), total nutrients (baker's yeast), or fungal odour (1-octen-3-ol). The expression of the gene encoding a deduced metallothionein-like motif containing protein was used as a biomarker of cadmium exposure. Glucose concentrations of 2% or higher reduced the expression levels of the biomarker. Within the range of 0.1–8% yeast, medium concentrations led to higher biomarker levels. At high concentrations of 1-octen-3-ol (2000 mg/l), feeding and the biomarker response were reduced. These results suggest that even at equivalent cadmium concentrations, food quality affects cadmium exposure by altering food consumption rates.