Temperature-dependent effects of microplastics on sediment bacteriome and metabolome.

The increasing prevalence of microplastics in the environment has become a concern for various ecosystems, including wetland ecosystems. Here, we investigated the effects of three popular microplastic types: polyethylene, polylactic acid, and tire particles at 5 °C and 25 °C on the sediment microbiome and metabolome at the 3% (w/w) level. Results indicated that temperature greatly influenced catalase and neutral phosphatase activities, whereas the type of microplastic had a more significant impact on urease and dehydrogenase activities. The addition of microplastic, especially tire particles, increased microbial diversity and significantly altered the microbial community structure and metabolic profile, leading to the formation of different clusters of microbial communities depending on the temperature. Nonetheless, the effect of temperature on the metabolite composition was less significant. Functional prediction showed that the abundance of functional genes related to metabolism and biogeochemical cycling increased with increasing temperature, especially the tire particles treatment group affected the nitrogen cycling by inhibiting ureolysis and nitrogen fixation. These observations emphasize the need to consider microplastic type and ambient temperature to fully understand the ecological impact of microplastics on microbial ecosystems.

Superoxide-imbalance Pharmacologically Induced by Rotenone Triggers Behavioral, Neural, and Inflammatory Alterations in the Eisenia fetida Earthworm.

BACKGROUND: Some studies have suggested that mitochondrial dysfunction and a superoxide imbalance could increase susceptibility to chronic stressful events, contributing to the establishment of chronic inflammation and the development of mood disorders. The mitochondrial superoxide imbalance induced by some molecules, such as rotenone, could be evolutionarily conserved, causing behavioral, immune, and neurological alterations in animals with a primitive central nervous system. OBJECTIVE: Behavioral, immune, and histological markers were analyzed in Eisenia fetida earthworms chronically exposed to rotenone for 14 days. METHODS: Earthworms were placed in artificial soil containing 30 nM of rotenone distributed into a plastic cup that allowed the earthworms to leave and return freely into the ground. Since these organisms prefer to be buried, the model predicted that the earthworms would necessarily have to return to the rotenone-contaminated medium, creating a stressful condition. The effect on survival behavior in the immune and histological body wall and ventral nervous ganglia (VNG) structures, as well as gene expression related to inflammation and mitochondrial and neuromuscular changes. RESULTS: Rotenone-induced loss of earthworm escape behavior and immune alterations indicated a chronic inflammatory state. Some histological changes in the body wall and VNG indicated a possible earthworm reaction aimed at protecting against rotenone. Overexpression of the nicotinic acetylcholine receptor gene (nAChR α5) in neural tissues could also help earthworms reduce the degenerative effects of rotenone on dopaminergic neurons. CONCLUSION: These data suggest that mitochondrial dysfunction could be an evolutionarily conserved element that induces inflammatory and behavioral changes related to chronic stress.

The synergistic effect of microplastic and malathion exposure on fiddler crab Minuca ecuadoriensis microplastic bioaccumulation and survival.

We assessed the combined effects of polyethylene microplastic (MP) and malathion (MLT) on the survival of the fiddler crab Minuca ecuadoriensis, and MP tissue bioaccumulation in four treatments following 120 h exposure: T1) Control; T2) MLT 50 mg L-1; T3) MP 200 mg L-1; and T4) MLT (50 mg L-1) + MP (200 mg L-1). The highest mortality (80%) was in T4, followed by T2 (28%) and no mortality was in T3. Higher MP bioaccumulation was observed in T4 (572 items g tissue-1) followed by T3 (70 items g tissue-1). Our findings indicate that the synergistic effect of MLT and MP increased M. ecuadoriensis bioaccumulative capacity and decreases survival. Thus, as MP contamination in aquatic environments is ubiquitous, our study raises a warning on the synergistic effects of MP with other environmental contaminants and serves as a baseline for further studies.

The influence of microplastics pollution on the feeding behavior of a prominent sandy beach amphipod, Orchestoidea tuberculata (Nicolet, 1849).

Pollution by microplastics has become a global threat affecting coastal habitats such as sandy beaches and their resident macrofauna. The goal of this study was to assess the influence of microplastics on the feeding behavior and growth rate of a widespread sandy beach amphipod, Orchestoidea tuberculata. These organisms were exposed to artificial food prepared with Poly(styrene-co-divinylbenzene) microspheres (8 µm particle size) at 3 different concentrations (0%, 5% and 10%). The amphipods consumed significantly more food when the concentration of microplastics was 0% and significantly less when the concentration was 10%, both in trials in which they had a choice (preference experiments) and those in which they did not have a food choice. In contrast to this, the amphipod's absorption efficiency and estimated growth rates were not significantly affected by the concentration of microplastics. Combined, these results indicate that high microplastics concentrations (e.g. 10%) cause a reduction in the amphipod's consumption rates and, indirectly, may affect the role of this species as a main consumer of stranded seaweeds in sandy beaches ecosystems.

Can the Atlantic ghost crab be a potential biomonitor of microplastic pollution of sandy beaches sediment?

The objective of the present study was to test whether the Atlantic ghost crab Ocypode quadrata is a reliable biomonitor of microplastic (MP) pollution of beach sediments. To test the hypothesis (H1) that the sediment is the main source of MP ingestion, the proportion of MP types (hard plastic, microfibers, pellet, soft plastic, and extruded polystyrene foam) in the gut content was compared with that on the strandline. The types of MPs in the gut content and sediment had similar proportions; black (~49%) and blue (~45%) microfibers were responsible for this similarity (55%), hence confirming H1. However, the second hypothesis (H2) that prevalence of MP in the gut content is related to its density on beach with distinct urbanization degree was not accepted. These results indicate that high trophic plasticity of the ghost crab and, consequently, multiple-sources of contamination may interfere with its use as a biomonitor of MP pollution.

Effect of container, vitrification volume and warming solution on cryosurvival of in vitro-produced bovine embryos.

The aim of the present research was to develop a low cost and easy to perform vitrification method for in vitro-produced cattle embryos. Effect of container material was evaluated (plastic straw compared to glass capillary, experiment 1), two volume sample (1 compared to 0.5 microL, experiment 2) and warming solution composition medium (Tissue Culture Medium 199 (TCM-199) compared to phosphate buffered saline (PBS), experiment 3) as modifications of the open pulled straw (OPS) system in order to reduce embryo damage caused by exposure to cold. In all experiments, day 7 and expanded blastocysts of cattle were exposed to the vitrification solution 1 for 3 min and 30s in solution 2. After this, embryos were placed in a droplet and loaded in a narrow end container, and immediately submerged into liquid nitrogen. For warming, vitrified embryos were plunged into warming solution 1 for 3 min, and transferred into warming solution 2 for 1 min. Fresh embryos kept in culture were used as control group. Hatching rates were recorded in all cases at day 13. In experiment 1 there was no significant effect of container material on hatching rates. Postwarming survival rate of vitrified embryos was lower than control (27.5% plastic straws, 18.9% glass capillary and 80.5% control, P<0.05). In experiment 2, there was no significant effect of volume in hatching rates (58.3% 1 microL, 61.3% 0.5 microL and 80.5% control, P<0.05). In experiment 3, the composition of the holding medium of warming solution influenced hatching rates (84.1% TCM-199, 74.8% PBS and 91.1% control P<0.05). These data suggest that neither glass capillaries nor reduced sample volume could improve hatching rates after vitrification-warming with open pulled straw (OPS) procedure, and that PBS can replace TCM-199 in warming solutions, but lesser hatching rates should be expected.