Bacterioplankton Assembly Along a Eutrophication Gradient Is Mainly Structured by Environmental Filtering, Including Indirect Effects of Phytoplankton Composition.

Biotic interactions are suggested to be key factors structuring bacterioplankton community assembly but are rarely included in metacommunity studies. Eutrophication of ponds and lakes provides a useful opportunity to evaluate how bacterioplankton assembly is affected by specific environmental conditions, especially also by biotic interactions with other trophic levels such as phytoplankton and zooplankton. Here, we evaluated the importance of deterministic and stochastic processes on bacterioplankton community assembly in 35 shallow ponds along a eutrophication gradient in Belgium and assessed the direct and indirect effects of phytoplankton and zooplankton community variation on bacterioplankton assembly through a path analysis and network analysis. Environmental filtering by abiotic factors (suspended matter concentration and pH) explained the largest part of the bacterioplankton community variation. Phytoplankton community structure affected bacterioplankton structure through its effect on variation in chlorophyll-a and suspended matter concentration. Bacterioplankton communities were also spatially structured through pH. Overall, our results indicate that environmental variation is a key component driving bacterioplankton assembly along a eutrophication gradient and that indirect biotic interactions can also be important in explaining bacterioplankton community composition. Furthermore, eutrophication led to divergence in community structure and more eutrophic ponds had a higher diversity of bacteria.

Assessment of human exposure to environmental sources of lead arising from the lead battery manufacturing and recycling sector in Europe: demonstration of a tiered approach in a case study.

BACKGROUND: Standard approaches for the assessment of Man via the Environment exposure are designed to be conservative. However, propagating these exposures into health impact assessment might lead to questionable socio-economic costs. OBJECTIVE: The objective of this study was to develop a novel tiered modelling approach to assess human exposure to lead (Pb) via the environment. METHOD: The approach starts in Tier 1 from EUSES modelling approach, modified with metal specific transfer factors. The generic Tier 2 approach uses the higher tier model GPM for air quality, and dietary exposure modelling based on EFSA's Comprehensive Food Database, in combination with crop specific transfer factors. Tier 3 considers additional site-specific information such as proximity of inhabitants and agricultural activities in relation to industrial sites. RESULTS: This tiered modelling approach was applied to a case study of 50 lead battery manufacturing and recycling sites across Europe. Data sets from general population human biomonitoring studies were used to compare the predicted additional bioburden of Pb resulting from lead battery manufacturing and recycling. The higher tier assessments were able to demonstrate a >20-fold reduction in modelled Pb exposure compared to default assumptions made in Tier 1. SIGNIFICANCE: Leading to better estimates for socio-economic costs in health impact assessment.