Effects of flow reduction and artificial light at night (ALAN) on litter decomposition and invertebrate communities in streams: A flume experiment

River ecosystems are heavily impacted by multiple stressors, where effects can cascade downstream of point sources. However, a spatial approach to assess the effects of multiple stressors is missing. We assessed the local and downstream effects on litter decomposition, and associated invertebrate communities of two stressors: flow reduction and artificial light at night (ALAN). We used an 18-flow-through mesocosm system consisting of two tributaries, where we applied the stressors, merging in a downstream section. We assessed the changes in decomposition rate and invertebrate community structure in leaf bags. We found no effect of ALAN or its interaction with flow reduction on the litter decomposition or the invertebrate community in the tributaries. Flow reduction alone led to a 14.8 % reduction in decomposition rate in the tributaries. We recorded no effect of flow reduction on the macroinvertebrates community composition in the litter bags. We also observed no effects of the spatial arrangement of the stressors on the litter decomposition and macroinvertebrate community structure downstream. Overall, our results suggest the impact of stressors on litter decomposition and macroinvertebrate communities remained local in our experiment. Our work thus calls for further studies to identify the mechanisms and the conditions under which spatial effects dominate over local processes.

Perceived multiple stressor effects depend on sample size and stressor gradient length

Multiple stressors are continuously deteriorating surface waters worldwide, posing many challenges for their conservation and restoration. Combined effect types of multiple stressors range from single-stressor dominance to complex interactions. Identifying prevalent combined effect types is critical for environmental management, as it helps to prioritise key stressors for mitigation. However, it remains unclear whether observed single and combined stressor effects reflect true ecological processes unbiased by sample size and length of stressor gradients. Therefore, we examined the role of sample size and stressor gradient lengths in 158 paired-stressor response cases with over 120,000 samples from rivers, lakes, transitional and marine ecosystems around the world. For each case, we split the overall stressor gradient into two partial gradients (lower and upper) and investigated associated changes in single and combined stressor effects. Sample size influenced the identified combined effect types, and stressor interactions were less likely for cases with fewer samples. After splitting gradients, 40 % of cases showed a change in combined effect type, 30 % no change, and 31 % showed a loss in stressor effects. These findings suggest that identified combined effect types may often be statistical artefacts rather than representing ecological processes. In 58 % of cases, we observed changes in stressor effect directions after the gradient split, suggesting unimodal stressor effects. In general, such non-linear responses were more pronounced for organisms at higher trophic levels. We conclude that observed multiple stressor effects are not solely determined by ecological processes, but also strongly depend on sampling design. Observed effects are likely to change when sample size and/or gradient length are modified. Our study highlights the need for improved monitoring programmes with sufficient sample size and stressor gradient coverage. Our findings emphasize the importance of adaptive management, as stress reduction measures or further ecosystem degradation may change multiple stressor-effect relationships, which will then require associated changes in management strategies.

Managing the small stream network for improved water quality, biodiversity and ecosystem services protection (SSNet)

This paper outlines the research being undertaken by the recently-initiated four-year (to March 2022) project on the small stream network in Ireland (SSNet) funded by the Irish Environmental Protection Agency (EPA). The overarching objective of SSNet is to advance knowledge on the role of small streams in water quality, biodiversity and ecosystem services protection that will inform policy, measures and management options to meet water quality and other resources protection targets. The project will start with a synthesis of available information on the importance of small streams to initiate communication with stakeholders and introduce the project. This will be followed by a compilation and analysis of existing data on small streams in Ireland to inform the selection of sites for the proposed research. Three work packages will collect new data on hydrochemistry with a focus on the nutrient retention potential of headwater streams, hydromorphology and biodiversity. All three investigations will share common sites to enable interconnections between the three elements to be explored and provide an integrated approach to the research. Modelling based on the results from each of the aforementioned tasks will be used to estimate the level of intervention in the small stream network required to have measurable effects throughout a catchment on both water quality (N, P & sediment) and flows, and overall delivery/maintenance of ecosystem services. We will also engage volunteers in both biological water quality and hydromorphological assessments and evaluate the potential of citizen science in facilitating greater monitoring coverage of the small stream network.

The development of novel flexible electrode arrays for the electrochemotherapy of solid tumour tissue. (Potential for endoscopic treatment of inaccessible cancers)

Therapeutic "electroporation" involves application of electric fields to target cells/tissues, thereby rendering their cell membranes transiently porous, thus making feasible the cellular uptake and efficacy of previously impermeant and ineffective therapeutic agents. The objectives of this research are a) the development of flexible electrode arrays for incorporation into microsystem endoscopic devices, and b) the assessment of their efficacy in delivering selected genetic and pharmaceutical anticancer therapies. Gold electrodes were fabricated on flexible polyimide substrates following predictive modeling and simulation of electric fields using FEMLAB software. Subsequent assessment of electroporation efficiency in-vitro involved 1) enumeration of viable tumour cells after delivery of electric pulses and exposure to low concentrations of bleomycin, otherwise known as electrochemotherapy 2) Efficacy of gene delivery by detection of emitted green fluorescence by cells after electroporation with the pEGFP plasmid and 3) In-vivo efficacy of electrochemotherapy in a variety of human solid tumour masses in nude mouse models (xenografts). The flexible electrode system was found to be successful for electrical delivery of plasmids and drugs in-vitro and in-vivo. We found in-vivo complete regression of prostate, colon, oesophageal, and renal cancers with reduced growth rates for fibrosarcoma and breast cell lines. These flexible electrodes are suitable for electrochemotherapy or gene therapy to solid tumours masses and may be fabricated for application to the treatment of some cancers in humans by transcutaneous or endoscopic delivery systems.

Chemometric modeling to relate antioxidants, neutral lipid fatty acids, and flavor components in chicken breasts

Relationships among quality factors in retailed free-range, corn-fed, organic, and conventional chicken breasts (9) were modeled using chemometric approaches. Use of principal component analysis (PCA) to neutral lipid composition data explained the majority (93%) of variability (variance) in fatty acid contents in 2 significant multivariate factors. PCA explained 88 and 75% variance in 3 factors for, respectively, flame ionization detection (FID) and nitrogen phosphorus (NPD) components in chromatographic flavor data from cooked chicken after simultaneous distillation extraction. Relationships to tissue antioxidant contents were modeled. Partial least square regression (PLS2), interrelating total data matrices, provided no useful models. By using single antioxidants as Y variables in PLS (1), good models (r2 values > 0.9) were obtained for alpha-tocopherol, glutathione, catalase, glutathione peroxidase, and reductase and FID flavor components and among the variables total mono and polyunsaturated fatty acids and subsets of FID, and saturated fatty acid and NPD components. Alpha-tocopherol had a modest (r2 = 0.63) relationship with neutral lipid n-3 fatty acid content. Such factors thus relate to flavor development and quality in chicken breast meat.

ZG-1494 alpha, a novel platelet-activating factor acetyltransferase inhibitor from Penicillium rubrum, isolation, structure elucidation andbiological activity

A novel inhibitor of platelet-activating factor (PAF) acetyltransferase, an essential enzyme in the remodeling pathway of platelet-activating factor synthesis, was identified by a high throughout screen of natural product extracts of microbial origin. The compound, ZG-1494 alpha, was isolated from an ethyl acetate extract of a culture broth of Penicillium rubrum through bioassay guided fractionation. The structure of ZG-1494 alpha was determined by spectroscopic methods. A key feature of the structure, which is relatively rare among natural products, is the 5-hydroxy-3-pyrrolin-2-one moiety. A 13C-13C INADEQUATE was utilized to unambiguously determine the regiochemistry of this molecule.