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Indirect, passive approaches for monitoring coarse bedload transport could allow cheaper, safer, higher‐resolution, longer‐term data that revolutionises bedload understanding and informs river management. Here, insights provided by seismic impact plates in a downstream reach of a flashy gravel‐bed river (River Avon, Devon, UK) are explored in the context of plate performance. Monitoring of a centrally‐situated plate (IP1) during an extremely wet 12‐month period demonstrated that impacts were related to discharge as a measure of transport potential (R2 = 0.38) but that factors other than transport limitations are important. Analysis of discrete flow events revealed consistent rising‐limb and falling‐limb impact spikes biased toward the latter for larger events. Such patterns may result from disruption of the upstream armour layer (rising limb) and supply enhancements related to both upstream mass bank failures and/or flood routing of non‐local sediment sources (falling limb). Installation of additional impact plates indicated that plate IP1 was indeed dominantly related to instantaneous discharge, that a three‐plate lateral array somewhat better explained impact variability (R2 = 0.49), and that the bedload track shifts laterally with discharge. Aggregating event‐total IP1 impacts against volumetric discharge further increases explanation as intra‐event and stochastic bedload factors are subsumed but left 26% unexplained variance related to the unsampled bedload mass, inter‐event supply differences, and attributes of plate performance. Annualising the data created an impact‐based 'effective discharge’ for this extremely wet year that was closer to morphological bar‐full in magnitude than bankfull, but the preceding results imply this outcome is related as much to supply limitations as transport limitations. Overall, passive approaches offer a liberating prospect for bedload monitoring, capable of producing insights only achievable through high resolution, extended time periods. Such results could potentially inform threshold conditions and geomorphological effectiveness of flows for future river management strategies. Copyright © 2015 John Wiley & Sons, Ltd.

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Fresh and freeze-dried sample sections of the coastal macroalgae, Fucus serratus and F. vesiculosus, and the brackish water macroalga, F. ceranoides, have been analysed for trace elements by field-portable-X-ray fluorescence (FP-XRF) spectrometry using a Niton XL3t in a low density mode with thickness correction. When analysed fresh in a laboratory accessory stand for a period of 200 seconds, As, Br, Fe and Zn were registered in the apex, mid-frond and lower stipe of all species, with detection limits of a few μg g (As) or a few tens of μg g (Br, Fe, Zn); when analysed dry under the same conditions, concentrations returned were systematically higher and Cu and Pb were detected in a number of F. ceranoides sections. Concentrations arising from both approaches on a dry weight basis were highly correlated, with deviations from unit slope attributed to the absorption of fluorescent X-rays by internal and surficial water when analysed fresh. With algorithms correcting for the effects of water on mass and X-ray absorption, sections of F. vesiculosus and F. ceranoides were analysed in situ with the XRF connected to a mobile stand and laptop. Dry weight concentrations returned for As and Zn were significantly correlated with respective concentrations subsequently determined by ICP-MS following acid digestion and with a slope close to unity; lower concentrations of Fe returned by ICP were attributed to the incomplete acid digestion of silt particles that evaded an initial cleaning step, while Br concentrations could not be verified independently because of loss of volatile forms during digestion. The in situ determination of trace elements in fucoids by FP-XRF provides a rapid and non-destructive means of monitoring environmental quality and identifying hot-spots of contamination, and enables a research strategy to be developed iteratively that is informed by immediate results.

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