The Effect of Temperature on the Absorption and Fluorescence Spectra of Impurity Crystals

A meta-analysis approach was used to assess the effect of dredging induced changes in sediment composition, under different conditions of natural physical disturbance, for the structure and function of marine benthic macrofaunal communities. Results showed the sensitivity of macrofaunal communities increased as both the proportion of gravel increased and the level of natural physical disturbance decreased. These findings may be explained by the close association of certain taxa with the gravel fraction, and the influence of natural physical disturbance which, as it increases, tends to restrict the colonisation by these species. We conclude that maintaining the gravel content of surface sediments after dredging and, where practicable, locating extraction sites in areas of higher natural disturbance will minimise the potential for long-term negative impacts on the macrofauna

Assessing Risk of E. coli Resuspension from Intertidal Estuarine Sediments:Implications for Water Quality

Estuarine sediments are a reservoir for faecal bacteria, such as E. coli, where they reside at greater concentrations and for longer periods than in the overlying water. Faecal bacteria in sediments do not usually pose significant risk to human health until resuspended into the water column, where transmission routes to humans are facilitated. The erosion resistance and corresponding E. coli loading of intertidal estuarine sediments was monitored in two Scottish estuaries to identify sediments that posed a risk of resuspending large amounts of E. coli. In addition, models were constructed in an attempt to identify sediment characteristics leading to higher erosion resistance. Sediments that exhibited low erosion resistance and a high E. coli loading occurred in the upper- and mid-reaches of the estuaries where sediments had higher organic content and smaller particle sizes, and arose predominantly during winter and autumn, with some incidences during summer. Models using sediment characteristics explained 57.2% and 35.7% of sediment shear strength and surface stability variance respectively, with organic matter content and season being important factors for both. However large proportions of the variance remained unexplained. Sediments that posed a risk of resuspending high amounts of faecal bacteria could be characterised by season and sediment type, and this should be considered in the future modelling of bathing water quality

The effects of tidally driven temporal variation on measuring intertidal cohesive sediment erosion threshold

Accurate measurement of intertidal sediment erodibility is essential for the development of meaningful and accurate models of sediment dynamics. Despite considerable advances in technology and methodology, the measurement of cohesive intertidal sediment erosion remains problematic. Sediment erodibility varies according to both physical and biological properties and processes. These cannot be considered in isolation, as they can interact to create both positive and negative feedbacks, resulting in seemingly idiosyncratic responses in the system. If working models of estuarine sediment dynamics are to be made, it is essential that the influence of these processes on both the measurements and the system itself be considered. Recent developments in measurement technology enable rapid measurement of sediment stability allowing temporal and spatial variability to be measured on a time scale of minutes. This paper reports temporal variability in cohesive intertidal sediment erosion threshold related to immersion and emersion, and the concomitant responses in selected sediment properties (carbohydrates, water content and chlorophyll). Erosion threshold tended to increase over emersion and decrease over immersion, although the patterns of change varied depending upon local conditions, and in one case there was no temporal trend. Temporal changes resulted in a range of measured erosion threshold, dependant upon the erosion device used. Modifications to existing methodology, in order to account for this variation, are proposed and implications for modelling erosion processes are considered.</p

Coastal Biodiversity and Ecosystem Service Sustainability (CBESS) sediment stability by Cohesive Strength Meter (CSM) in salt marsh and mud flat habitats

The dataset comprises the surface stability of sediments as determined by a Cohesive Strength Meter (CSM). Between 3 and 5 replicate measurements were taken from each of the 22 designated experiment quadrats at each of the Coastal Biodiversity and Ecosystem Service Sustainability (CBESS) sites. At each CBESS site, a salt marsh site and a mud flat site was examined and three locations were selected in Morecambe Bay, North West England and three locations in Essex, South East England. The Morecambe Bay samples were taken during the winter and summer of 2013. The Essex samples were taken during the winter, early spring and summer of 2013. This data were collected as part of Coastal Biodiversity and Ecosystem Service Sustainability (CBESS): NE/J015644/1. The project was funded with support from the Biodiversity and Ecosystem Service Sustainability (BESS) programme. BESS is a six-year programme (2011-2017) funded by the UK Natural Environment Research Council (NERC) and the Biotechnology and Biological Sciences Research Council (BBSRC) as part of the UK's Living with Environmental Change (LWEC) programme.,Each site consisted of a polygon of roughly 400 x 500 m to 1000 x 1000 m in size, dependent upon site length (parallel to shore) and width (perpendicular to shore). Twenty two 1 x 1 m quadrats were randomly placed within to each site polygon using R (R Development Core Team, 2014) to specify placement at four different spatial scales (A = 1 quadrat only, B = 3 quadrats at 1 m to 10 m apart, C = 6 quadrats at 10 m to 100 m apart, D = 12 quadrats at 100 m to 1000 m or site maximum). In each quadrat, the CSM was deployed and the erosion threshold of the sediment determined. 3- 5 replicates measurement stations were randomly placed within the quadrat, according to the quadrat-sampling plan.

The effects of rain on the erosion threshold of intertidal cohesive sediments

Intertidal sedimentary environments are complex systems governed by interactions between physical, chemical and biological processes and parameters. Tidally induced flow and wave action are known to be an integral driving force behind the erosion, transport, deposition and consolidation cycle (ETDC) of intertidal sediments. Whilst considerable advances have been made in understanding both the physical and biological processes and their interactions in these systems, it is clear that there are gaps in our understanding. One factor that has been largely ignored to date is that of rain. Visual observations in the field and associated data indicated that rain showers during low tide are correlated with a reduction in the erosion threshold of intertidal cohesive sediments. This paper presents preliminary field and laboratory data showing the importance of rain in reducing the erosion threshold of cohesive intertidal sediments. The implications for our knowledge of, and modelling of the ETDC cycle of cohesive intertidal sediments are discussed