Comparison of learning models to predict LDPE, PET, and ABS concentrations in beach sediment based on spectral reflectance.

Microplastic (MP) contamination on land has been estimated to be 32 times higher than in the oceans, and yet there is a distinct lack of research on soil MPs compared to marine MPs. Beaches are bridges between land and ocean and present equally understudied sites of microplastic pollution. Visible-near-infrared (vis-NIR) has been applied successfully for the measurement of reflectance and prediction of low-density polyethylene (LDPE), polyethylene terephthalate (PET), and polyvinyl chloride (PVC) concentrations in soil. The rapidity and precision associated with this method make vis-NIR promising. The present study explores PCA regression and machine learning approaches for developing learning models. First, using a spectroradiometer, the spectral reflectance data was measured from treated beach sediment spiked with virgin microplastic pellets [LDPE, PET, and acrylonitrile butadiene styrene (ABS)]. Using the recorded spectral data, predictive models were developed for each microplastic using both the approaches. Both approaches generated models of good accuracy with R2 values greater than 0.7, root mean squared error (RMSE) values less than 3 and mean absolute error (MAE) < 2.2. Therefore, using this study's method, it is possible to rapidly develop accurate predictive models without the need of comprehensive sample preparation, using the low-cost option ASD HandHeld 2 VNIR Spectroradiometer.

Investigating quorum-quenching marine bacilli as potential biocontrol agents for protection of shrimps against Early Mortality Syndrome (EMS).

Early Mortality Syndrome (EMS) has been a major problem for shrimp aquaculture in Southeast Asia due to its epizootic prevalence within the region since the first reported case in 2009. This study explores the application of halophilic marine bacilli isolated from coral mucus and their quorum-quenching abilities as potential biocontrol agents in aquaculture systems to combat the causative agent of EMS, Vibrio parahaemolyticus. N-acylhomoserine lactone (AHL)-degrading (AiiA) activity was first screened by PCR then confirmed by bio-reporter assay, and a combination of 16S rDNA sequence analysis and quantitative phenotype assays including biofilm-formation and temperature-growth responses were used to demonstrate diversity amongst these quorum-quenching isolates. Three phenotypically distinct strains showing notable potential were chosen to undergo co-cultivation as a method for strain improvement via long term exposure to the pathogenic V. parahaemolyticus. The novel approach taken led to significant improvements in antagonism and quorum quenching activities as compared to the ancestral wild-type strains and offers a potential solution as well as pathway to improve existing beneficial microbes for one of the most pressing issues in shrimp aquacultures worldwide.

Increased transfer of trace metals and Vibrio sp. from biodegradable microplastics to catfish Clarias gariepinus.

Microplastic ingestion has been documented in various aquatic species. This causes physical damage, and additionally contaminated microplastics transfer attached pollutants and microbial pathogens to ingesting organisms. Continued metal accumulation can lead to toxicity and adverse health effects; attached microbial pathogens can cause dysbiosis - which lowers host immunity and promotes infections. Catfish, Clarias gariepinus, are a major food source in Southeast Asia, a hotspot of plastic pollution. This study aimed to quantify the transfer of the trace metals copper (Cu) and lead (Pb) -at environmentally relevant concentrations-from microplastics (polyamide 12, PA12, and polylactic acid, PLA) to catfish. Fish were reared for three months and exposed to seven different combinations of feed, supplemented with plastics and metals. At monthly intervals, fish gills, intestines, liver, and edible muscles were analysed for Cu and Pb concentrations using ICP-OES, and the intestines content assessed for Vibrio sp.. Our results showed that biodegradable PLA transferred higher amounts of metals to catfish than expected and also led to increased Vibrio counts in the intestines compared to PA12. Trace metal accumulation was significantly different in varying tissues, with highest concentrations observed in the gills, followed by liver, intestines, and lastly edible muscles. The results of this study further support the existing evidence that microplastics act as efficient shuttles to concentrate and transfer metals. They also indicate that their uptake can cause dysbiosis (increased numbers of Vibrio sp.). Most importantly, however, our study highlights that biodegradable polymers, such as PLA, could actually pose a greater environmental threat when ingested compared to the more common polymers such as PA12.

A functional gene-array analysis of microbial communities settling on microplastics in a peat-draining environment.

Concerns about microplastic (MP) pollution arise from the rafting potential of these durable particles which potentially propagate harmful chemicals and bacteria across wide spatial gradients. While many studies have been conducted in the marine environment, knowledge of MPs in coastal and freshwater systems is limited. For this study, we exposed two MPs (polyethylene terephthalate and polylactic acid) to the undisturbed peat-draining Maludam River in Malaysia, for 6 months. The microbial communities on these MPs and the surrounding water were sequenced by MiSeq, while the genetic responses of these communities were assessed by GeoChip 5.0S. Microbial communities were dominated by the phyla Proteobacteria, Acidobacteria and Actinobacteria. Metabolic processes involved with carbon, nitrogen, sulfur, metal homeostasis, organic remediation and virulence had significantly different gene expression among the communities on MPs and in the surrounding water. Our study is the first to look at changes in gene expression of whole plastisphere communities.

Chemotactic response of Vibrio coralliilyticus to mucus from various coral species.

Vibrio coralliilyticus, a prominent pathogenic bacteria, is known to cause tissue damage in the coral Pocillopora damicornis and is attracted towards the coral via chemotaxis. However, the potential of V. coralliilyticus to infect most of the other coral hosts via chemotaxis is unknown. In this study, we used capillary assays to quantify the chemotactic response of V. coralliilyticus to the mucus of four tank-cultivated coral species (Cataphyllia jardine, Mussidae sp., Nemenzophyllia turbida, and Euphyllia ancora), and mucus from three wild coral species (Acropora sp., Porites sp., and Montipora sp.). The bacteria showed a positive chemotactic response to each coral mucus tested, with the highest response recorded to the mucus of Acropora sp. and the lowest response to the mucus of Montipora sp. A microfluidic chip was then used to assess the chemotactic preference of V. coralliilyticus to the mucus of the tank cultivated corals. Here too, the bacterium showed positive response, but with a slightly different ranking order. The strong chemotactic response of V. coralliilyticus towards the mucus tested could indicate a broader host range of V. coralliilyticus, and by extension, indicate a threat to weakened coral reefs worldwide.

A comparative UHPLC-Q/TOF-MS-based eco-metabolomics approach reveals temperature adaptation of four Nepenthes species.

Nepenthes, as the largest family of carnivorous plants, is found with an extensive geographical distribution throughout the Malay Archipelago, specifically in Borneo, Philippines, and Sumatra. Highland species are able to tolerate cold stress and lowland species heat stress. Our current understanding on the adaptation or survival mechanisms acquired by the different Nepenthes species to their climatic conditions at the phytochemical level is, however, limited. In this study, we applied an eco-metabolomics approach to identify temperature stressed individual metabolic fingerprints of four Nepenthes species: the lowlanders N. ampullaria, N. rafflesiana and N. northiana, and the highlander N. minima. We hypothesized that distinct metabolite regulation patterns exist between the Nepenthes species due to their adaptation towards different geographical and altitudinal distribution. Our results revealed not only distinct temperature stress induced metabolite fingerprints for each Nepenthes species, but also shared metabolic response and adaptation strategies. The interspecific responses and adaptation of N. rafflesiana and N. northiana likely reflected their natural habitat niches. Moreover, our study also indicates the potential of lowlanders, especially N. ampullaria and N. rafflesiana, to produce metabolites needed to deal with increased temperatures, offering hope for the plant genus and future adaption in times of changing climate.

Spatial-temporal variations in surface ozone over Ushuaia and the Antarctic region: observations from in situ measurements, satellite data, and global models.

The Antarctic continent is known to be an unpopulated region due to its extreme weather and climate conditions. However, the air quality over this continent can be affected by long-lived anthropogenic pollutants from the mainland. The Argentinian region of Ushuaia is often the main source area of accumulated hazardous gases over the Antarctic Peninsula. The main objective of this study is to report the first in situ observations yet known of surface ozone (O3) over Ushuaia, the Drake Passage, and Coastal Antarctic Peninsula (CAP) on board the RV Australis during the Malaysian Antarctic Scientific Expedition Cruise 2016 (MASEC'16). Hourly O3 data was measured continuously for 23 days using an EcoTech O3 analyzer. To understand more about the distribution of surface O3 over the Antarctic, we present the spatial and temporal of surface O3 of long-term data (2009-2015) obtained online from the World Meteorology Organization of World Data Centre for greenhouse gases (WMO WDCGG). Furthermore, surface O3 satellite data from the free online NOAA-Atmospheric Infrared Sounder (AIRS) database and online data assimilation from the European Centre for Medium-Range Weather Forecasts (ECMWF)-Monitoring Atmospheric Composition and Climate (MACC) were used. The data from both online products are compared to document the data sets and to give an indication of its quality towards in situ data. Finally, we used past carbon monoxide (CO) data as a proxy of surface O3 formation over Ushuaia and the Antarctic region. Our key findings were that the surface O3 mixing ratio during MASEC'16 increased from a minimum of 5 ppb to ~ 10-13 ppb approaching the Drake Passage and the Coastal Antarctic Peninsula (CAP) region. The anthropogenic and biogenic O3 precursors from Ushuaia and the marine region influenced the mixing ratio of surface O3 over the Drake Passage and CAP region. The past data from WDCGG showed that the annual O3 cycle has a maximum during the winter of 30 to 35 ppb between June and August and a minimum during the summer (January to February) of 10 to 20 ppb. The surface O3 mixing ratio during the summer was controlled by photochemical processes in the presence of sunlight, leading to the depletion process. During the winter, the photochemical production of surface O3 was more dominant. The NOAA-AIRS and ECMWF-MACC analysis agreed well with the MASEC'16 data but twice were higher during the expedition period. Finally, the CO past data showed the surface O3 mixing ratio was influenced by the CO mixing ratio over both the Ushuaia and Antarctic regions. Peak surface O3 and CO hourly mixing ratios reached up to ~ 38 ppb (O3) and ~ 500 ppb (CO) over Ushuaia. High CO over Ushuaia led to the depletion process of surface O3 over the region. Monthly CO mixing ratio over Antarctic (South Pole) were low, leading to the production of surface O3 over the Antarctic region.