Locomotor behavior of Neocaridina palmata: a study with leachates from UV-weathered microplastics

Weathering of plastics leads to the formation of increasingly smaller particles with the release of chemical compounds. The latter occurs with currently unknown environmental impacts. Leachate-induced effects of weathered microplastics (MPs) are therefore of increasing concern. To investigate the toxicity of the chemical mixtures from such plastics, we exposed the freshwater shrimp Neocaridina palmata to enriched leachates from unweathered and artificially weathered (UV-A/B light) MPs (≤1 mm) from recycled low-density polyethylene (LDPE-R) pellets and from a biodegradable, not fully bio-based starch blend (SB) foil. We analyzed the individual locomotor activity (moved distance and frozen events) on day 1, 3, 7 and 14 of exposure to five leachate concentrations equivalent to 0.40–15.6 g MPs L−1, representing the upper scale of MPs that have been found in the environment. The median moved distance did not change as a function of concentration, except for the unweathered SB treatment on day 14 that indicated hyperactivity with increasing concentrations. Significant impacts were solely detected for few concentrations and exposure days. Generally, no consistent trend was observed across the experiments. We further assessed the baseline toxicity of the samples in the Microtox assay and detected high bioluminescence inhibitions of the bacterium Aliivibrio fischeri. This study demonstrates that neither the recycled nor the biodegradable material are without impacts on test parameters and therefore cannot be seen as safe alternative for conventional plastics regarding the toxicity. However, the observed in vitro toxicity did not result in substantial effects on the behavior of shrimps. Overall, we assume that the two endpoints examined in the atyid shrimp N. palmata were not sensitive to chemicals leaching from plastics or that effects on the in vivo level affect other toxic endpoints which were not considered in this study.

Preliminary ecotoxicity assessment of selected flavour and fragrance compounds using Microtox assay

The bioluminescence inhibition bioassay using marine bacteria Vibrio fischeri is widely used as a tool to assess the toxicity of chemical compounds, because of the many benefits comprising cost and time effectiveness, rapidness, sensitivity, and ease of operation. In addition, the test is used for various types of organic and inorganic compounds. Due to the insolubility of organic compounds in water, a suitable solubilizer should be applied. The ecotoxicity of the solvent should be negligible in relation to marine bacteria. On account of superior human activities the synthesis of new chemical substances is inextricably linked to the emergence of chemical compounds that are a potential threat on environment. A Microtox system utilizing the 81.9% Basic Test with 14 dilutions was applied to pre-evaluate the ecotoxicity of β-cyclocitral oxime, citronellal oxime and perillaldehyde oxime. Substances solutions with an initial concentration of 0.036% in DMSO were prepared. The preliminary results show that the studied scent compounds are characterized by quite high toxicity. In order to confirm the received ecotoxicity values, it is necessary to carry out additional surveys using another range of concentrations and biotests on organisms at each trophic level.

Toxicity evaluation of ballast water discharged at The Onne Port complex using the microtox assay

Ballast water from ninety-six (96) International vessels calling the Onne Port complex were analyzed for physicochemical and acute toxicity test using the bioluminescence bacteria (Vibrio fisheri) from October 2015 to September 2016. The result of the microtox assay showed that the ballast water were generally toxic in the months under review. The Tanker vessels were generally more toxic than the RoRo/Container carriers. For the RoRo/Container carriers, the EC50 values for the 5 minutes and 15 minutes microtox assay ranged from 7.99± 2.45% in November, 2015 to 44.04±1.70% in June 2016 and 8.97±1.07% in November 2015 to 44.98±11.13% in June 2016. Similarly, for the tanker vessels, the EC50 values ranged from 5.63±1.97% in June 2016 to 28.17±1.71% in January 2016. In comparison to the reference chemical (Zinc sulphate) for the 5 minutes and 15 minutes microtox assay test, the EC50 values ranged from 1.00 ± 0.24% to 3.49±0.61% and 2.03±1.15% to 5.16±2.99% respectively. The seawater which served as controls were generally not toxic as the EC50 values was 100% from October 2015 to September 2016. The discharge of these ballast water poses a major environmental threat to the water quality and Port infrastructures at the Onne Port complex as contaminants may find their way into the food chain/food web and bioaccumulate in the tissues of indigenous biota (microorganisms, crabs, mangrove oysters and fin-fishes). This research work flags off the need for the regulators of Maritime Safety and Administration in Nigeria to monitor closely International vessels calling at major ports in Nigeria and the need to begin to domesticate some of the IMO guidelines on Ballast water management and ensure strict compliance.Key words: Ballast water, Toxicity, Vibrio fischeri, International Maritime Organization

Ecotoxicity assessment of camphor oxime using Microtox assay – preliminary research

The ecotoxicity assessment of new substances is crucial for their considered launch on the market. Due to various properties of chemical compounds, however, the application of biotests can be challenging. In the case of insoluble compounds, a proper, non-toxic solvent must be applied. The presented preliminary results demonstrate the extremely high ecotoxicity of camphor and camphor oxime, assessed by means of the Microtox system. A 81.9% Basic Test with 14 dilutions was applied. The ecotoxicity of a solvent (i.e. DMSO) was also assessed. The initial concentration of substances was 5%. EC50 values reached 0.00023% and 0.00007% for camphor and camphor oxime, respectively, after 15 min. of incubation of the samples with bioluminescent bacteria. The ecotoxicity of the solvent remained negligible. Due to the extremely high ecotoxicity values of the tested substances, another range of concentrations needs to be applied in future tests to confirm the results.

General baseline toxicity QSAR for nonpolar, polar and ionisable chemicals and their mixtures in the bioluminescence inhibition assay with Aliivibrio fischeri

A general QSAR model for the Microtox assay with the ionisation-corrected liposome–water distribution ratio is applicable to diverse chemicals including acids and bases.

Comparison of Microtox and Xenoassay Light as a Near Real Time River Monitoring Assay for Heavy Metals

Luminescence-based assays for toxicants such as Microtox, ToxAlert, and Biotox have been used extensively worldwide. However, the use of these assays in near real time conditions is limited due to nonoptimal assay temperature for the tropical climate. An isolate that exhibits a high luminescence activity in a broad range of temperatures was successfully isolated from the mackerel,Rastrelliger kanagurta. This isolate was tentatively identified asPhotobacteriumsp. strain MIE, based on partial 16S rDNA molecular phylogeny. Optimum conditions that support high bioluminescence activity occurred between 24 and 30°C, with pH 5.5 to 7.5, 10 to 20 g/L of sodium chloride, 30 to 50 g/L of tryptone, and 4 g/L of glycerol as the carbon source. Assessment of near real time capability of this bacterial system, Xenoassay light to monitor heavy metals from a contaminated river running through the Juru River Basin shows near real time capability with assaying time of less than 30 minutes per samples. Samples returned to the lab were tested with a standard Microtox assay usingVibrio fishceri. Similar results were obtained to Xenoassay light that show temporal variation of copper concentration. Thus, this strain is suitable for near real time river monitoring of toxicants especially in the tropics.

Treatment of Log Yard Runoff in an Aerobic Trickling Filter

Contaminated stormwater runoff from log yards is generated when precipitation comes into contact with wood, woody debris and equipment at outdoor wood sorting, processing and storage facilities. Nine runoff samples collected at a sawmill had biochemical oxygen demand (BOD), chemical oxygen demand (COD), tannins and lignin (T+L), and total suspended solids (TSS) levels ranging from 25 to 745 mg/L, 125 to 4610 mg/L, 10 to 1505 mg/L, and 65 to 2205 mg/L, respectively. Six samples were acutely toxic (EC50 <100%) based on the Microtox assay. The samples were effectively treated using a laboratory-scale, attached microbial growth reactor. Treatment for 24 hours at 34°C resulted in substantial reductions in BOD (94–100%), COD (86–93%) and T+L (91–97%). Near complete removal of acute toxicity and colour were also observed. Twenty-four-hour treatment at lower temperatures, 24 and 5 C, reduced BOD concentrations by 97 and 76%, COD by 91 and 64%, and T+L by 95 and 67%, respectively.