Transport of biodeposits and benthic footprint around an oyster farm, Damariscotta Estuary, Maine.

The benthic impact of aquaculture waste depends on the area and extent of waste accumulation on the sediment surface below and around the farm. In this study we investigated the effect of flow on biodeposit transport and initial deposition by calculating a rough aquaculture "footprint" around an oyster aquaculture farm in the Damariscotta River, ME. We also compared a site under the farm to a downstream "away" site calculated to be within the footprint of the farm. We found similar sediment biogeochemical fluxes, geochemical properties and macrofaunal communities at the site under the farm and the away site, as well as low organic enrichment at both sites, indicating that biodeposition in this environment likely does not have a major influence on the benthos. To predict accumulation of biodeposits, we measured sediment erodibility under a range of shear stresses and found slightly higher erosion rates at the farm than at the away site. A microalgal mat was observed at the sediment surface in many sediment cores. Partial failure of the microalgal mat was observed at high shear velocity, suggesting that the mat may fail and surface sediment erode at shear velocities comparable to or greater than those calculated fromin situ flow measurements. However, this study took place during neap tide, and it is likely that peak bottom velocities during spring tides are high enough to periodically "clear" under-farm sediment of recent deposits.

Chemical assessment state of the science: Evaluation of 32 decision-support tools used to screen and prioritize chemicals.

The last decade has seen an increased focus on evaluating the safety and sustainability of chemicals in consumer and industrial products. In order to effectively and accurately evaluate safety and sustainability, tools are needed to characterize hazard, exposure, and risk pertaining to products and processes. Because many of these tools will be used to identify problematic chemistries, and because many have potential applications in various steps of an alternatives analysis, the limitations and capabilities of available tools should be understood by users so that, ultimately, potential chemical risk is accurately reflected. In our study, we examined 32 chemical characterization tools from government, industry, academia, and non-governmental organizations (NGOs). The tools we studied were diverse, and varied widely in their scope and assessment. As such, they were separated into five categories for comparison: 1) Screening and Prioritization; 2) Database Utilization; 3) Hazard Assessment; 4) Exposure and Risk Assessment; and 5) Certification and Labeling. Each tool was scored based on our weighted set of criteria, and then compared to other tools in the same category. Ten tools received a high score in one or more categories; 24 tools received a medium score in one or more categories, and five tools received a low score in one or more categories. Although some tools were placed into more than one category, no tool encompassed all five of the assessment categories. Though many of the tools evaluated may be useful for providing guidance for hazards - and, in some cases, exposure - few tools characterize risk. To our knowledge, this study is the first to critically evaluate a large set of chemical assessment tools and provide an understanding of their strengths and limitations.

Field evaluation of a PCR test for Schistosoma japonicum egg detection in low-prevalence regions of China.

Sensitive Schistosoma japonicum detection methods are needed to progress from schistosomiasis control to elimination. The sensitivity of the Kato-Katz thick smear and miracidium hatching tests decrease with infection intensity and serological tests cannot always identify current infections. We evaluated a fecal polymerase chain reaction (PCR) assay to detect S. japonicum infection in 106 humans and 8 bovines in China. PCR was highly sensitive, detecting S. japonicum DNA at 0.5 eggs/g of stool. Comparing PCR examination of a single stool sample to the miracidium hatching test using three consecutive stool samples, more humans were hatching test positive (20%) than PCR positive (15%). However, two individuals were PCR positive in a village where no infections were detected by coprological methods. The sensitivity of PCR makes it a promising tool for schistosomiasis diagnostics and screening, although egg shedding variability and stool sample size present challenges for any detection method in low-transmission areas.