The plastic Trojan horse: Biofilms increase microplastic uptake in marine filter feeders impacting microbial transfer and organism health.

Microplastic pollution has become a major source of concern, with a large body of literature surrounding the impacts of microplastic ingestion by biota. However, many of these studies utilise virgin microbeads, which are not reflective of environmental microplastics that are rapidly colonised with microbial communities (plastisphere) in marine ecosystems. It is a concern therefore that current evidence of the impacts of microplastics on biota are unrepresentative of the environmental microplastic pollution. In this study, uptake and bioaccumulation of both virgin and Escherichia coli coated microplastics, by European native oysters (Ostrea edulis) were compared, and the physiological responses of oysters to the exposure were investigated. The uptake of E. coli coated microplastics was found to be significantly higher than the uptake of virgin microplastics, with average concentrations of 42.3 ± 23.5 no. g-1 and 11.4 ± 0.6 no. g-1 microbeads found in oysters exposed to coated and virgin microplastics, respectively. This suggests that environmental microplastic uptake into the marine trophic web by benthic filter feeders may be greater than previously thought. The oxygen consumption and respiration rate of oysters exposed to E. coli coated microplastics increased significantly over time, whilst virgin microplastics did not produce any measurable significant physiological responses. However, less than 0.5% of the total amount of administered microbeads were retained by all oysters, suggesting a limited residence time within the organisms. Although microplastics did not bioaccumulate in oyster tissues in the short-term, microorganisms assimilated by the ingestion of coated microplastics may be transferred to higher trophic levels. This poses a risk, not only for wildlife, but also for food safety and human health. The capacity to carry pathogens and expose a wide range of organisms to them means microplastics may have an important role as vectors for disease.

Optimising sample preparation for FTIR-based microplastic analysis in wastewater and sludge samples: multiple digestions.

The lack of standardised methodologies in microplastic research has been addressed in recent years as it hampers the comparison of results across studies. The quantification of microplastics in the environment is key to the assessment of the potential eco-toxicological impacts that this new category of emerging pollutants could have on terrestrial and aquatic species. Therefore, the need for protocols that are robust, simple and reliable together with their standardisation are of crucial importance. This study has focused on removal of organic matter with Fenton reagent from wastewater and sludge samples. This step of analysis was optimised by implementing a multi-digestion treatment on these samples that have high concentration of complex mixtures of organic matter, which interfere with microplastic enumeration. Moreover, this study targeted the detection of microplastics in the sub-hundred-micron size range due to the potential higher risks associated with smaller-sized particles and the limited data available from previous wastewater research. To show the validity of the method, triplicate samples of raw sewage, final effluent and sludge were independently spiked with two different sizes and types of microplastic polymers. Due to the various analytical stages required for the isolation of microplastics, time is a limiting factor in sample processing. The sequential digestion with Fenton reagent represents an inexpensive and time-efficient procedure for wastewater research providing effective degradation of organic material. These advantages over other currently available methods mean the method is suitable for analysis of large numbers of samples allowing robust monitoring data sets to be generated.

Development and evaluation of a new diffusive gradients in thin-films technique for measuring organotin compounds in coastal sediment pore water.

Organotins present a toxicological risk to biota in the aquatic environment. Understanding the behaviour of these compounds in sediment is challenging, with sophisticated analytical techniques required for their measurement. We investigated the use of silica-bound sorbents for diffusive gradients in thin-films (DGT) adsorption gels to pre-concentrate five organotins (monobutlytin (MBT), dibutyltin (DBT), tributyltin (TBT), diphenyltin (DPhT), triphenyltin (TPhT)) found frequently in coastal sediment. C8 sorbent showed optimum performance in uptake and recovery of organotins for pH and ionic strength ranges typical of coastal waters. Recoveries from adsorption gels deployed in filtered sea water were MBT = 123 ± 20%, DBT = 75 ± 12%, TBT = 81 ± 16%, DPhT = 72 ± 30%, TPhT = 58 ± 10% respectively. Devices were used to investigate DGT fluxes and pore water concentrations of organotins in coastal sediment collected from a contaminated site. DGT fluxes measured in sediment cores for the five organotins ranged between 4.3 × 10-8 and 1.6 ×10-5ngcm2s-1. The depletion of organotin species within pore waters at the interface with DGT devices was measured over a series of deployment times (2, 7, 14, 21 and 28 days) and provided estimates of the concentration of organotins in pore waters at Langstone Harbour, UK, prior to depletion by the DGT device and information on their spatial heterogeneity. The novel in situ DGT device developed can pre-concentrate organotins from pore waters in coastal sediment core samples and allows their detection at low environmental concentrations using conventional gas chromatographic/mass spectrometric instrumentation. Use of the DGT device overcomes many problems associated with the conventional pore water sampling of organotins. Our preliminary data suggests it has potential in the future to be a useful tool in investigating the environmental fate of these pollutants. The use of the C8 gel will also allow for the simultaneous sequestration of other semi- and non-polar analytes present in the pore water.

The Rising Tide of Antimicrobial Resistance in Aquaculture: Sources, Sinks and Solutions.

As the human population increases there is an increasing reliance on aquaculture to supply a safe, reliable, and economic supply of food. Although food production is essential for a healthy population, an increasing threat to global human health is antimicrobial resistance. Extensive antibiotic resistant strains are now being detected; the spread of these strains could greatly reduce medical treatment options available and increase deaths from previously curable infections. Antibiotic resistance is widespread due in part to clinical overuse and misuse; however, the natural processes of horizontal gene transfer and mutation events that allow genetic exchange within microbial populations have been ongoing since ancient times. By their nature, aquaculture systems contain high numbers of diverse bacteria, which exist in combination with the current and past use of antibiotics, probiotics, prebiotics, and other treatment regimens-singularly or in combination. These systems have been designated as "genetic hotspots" for gene transfer. As our reliance on aquaculture grows, it is essential that we identify the sources and sinks of antimicrobial resistance, and monitor and analyse the transfer of antimicrobial resistance between the microbial community, the environment, and the farmed product, in order to better understand the implications to human and environmental health.

Comment on "Nature of phosphorus limitation in the ultraoligotrophic eastern Mediterranean".

Thingstad et al. (Reports, 12 August 2005, p. 1068) reported that in situ mesoscale phosphorus enrichment of the eastern Mediterranean Sea altered selected biological parameters and concluded that the added phosphorus was rapidly transferred from bacteria to mesozooplankton. However, because of a lack of replication and a misinterpretation of their statistical analyses, that conclusion is not supported by the data.

Peer reviewed publication rates. An indication of research output.

BACKGROUND: The General Practice Evaluation Program (GPEP) funded general practice research between 1990-1999. We were interested in the publication rate of GPEP funded research as a measure of its research productivity. METHODS: A literature search and an email survey of GPEP researchers. We compared publication rates between the types of grants, types of institutions, and academic status of the authors. RESULTS: By June 2002, there were 201 peer reviewed articles in a range of 64 Australian and international peer reviewed journals from 99 projects (41% of completed or in progress projects, mean 2.3 per project), ranging from 0-22 per project. Forty-one investigators indicated they were in the process of writing for publication or plan to publish. They were more likely to publish with the support of a university. DISCUSSION: GPEP has achieved one of its major objectives--to contribute to evidence and knowledge about general practice. The publication rate indicates that Australian general practice research should still improve.

The decline and fate of an iron-induced subarctic phytoplankton bloom.

Iron supply has a key role in stimulating phytoplankton blooms in high-nitrate low-chlorophyll oceanic waters. However, the fate of the carbon fixed by these blooms, and how efficiently it is exported into the ocean's interior, remains largely unknown. Here we report on the decline and fate of an iron-stimulated diatom bloom in the Gulf of Alaska. The bloom terminated on day 18, following the depletion of iron and then silicic acid, after which mixed-layer particulate organic carbon (POC) concentrations declined over six days. Increased particulate silica export via sinking diatoms was recorded in sediment traps at depths between 50 and 125 m from day 21, yet increased POC export was not evident until day 24. Only a small proportion of the mixed-layer POC was intercepted by the traps, with more than half of the mixed-layer POC deficit attributable to bacterial remineralization and mesozooplankton grazing. The depletion of silicic acid and the inefficient transfer of iron-increased POC below the permanent thermocline have major implications both for the biogeochemical interpretation of times of greater iron supply in the geological past, and also for proposed geo-engineering schemes to increase oceanic carbon sequestration.