Implementing a novel biomonitoring tool to detect the biodiversity impacts of fine sediment stress in streams and rivers

The transport of fine sediments by rivers to the oceans, represents (i) an important part of the global denudation system, (ii) an important component of global biogeochemical cycles, and (iii) an essential constituent of freshwater ecosystems, critical to habitat heterogeneity and ecological functioning (Turley et al., 2014). However, when human activities cause a significant deviation in the dynamics of fine sediment from 'natural' or 'reference' conditions, this can cause ecological degradation. It is therefore essential that fine sediment, which is one of the most commonly attributed causes of water quality impairment globally (Richter et al., 1997), is managed in order to minimise these impacts.

Increasingly, freshwater managers and policy-makers require conservation measures that will protect and improve biodiversity, whilst minimising the costs and societal impacts on users and inhabitants of catchments (Turak & Linke, 2011). This includes minimising the costs associated with conventional monitoring of water quality parameters such as suspended and deposited sediment. Conventional monitoring of physicochemical water quality parameters can be relatively expensive and time-consuming; there are tens of parameters that could be analysed, and sampling must be frequent enough to ensure that the values obtained are representative of long-term exposure. Recently, there has been a shift away from these conventional monitoring methods, towards approaches that focus on low-frequency (lower-cost) biomonitoring techniques, defined broadly as 'the use of biota to gauge and track changes in the environment' (Friberg et al., 2011). This type of approach relies on being able to predict the expected fauna and/or flora for a site if it were in, or close to reference condition (with minimal anthropogenic disturbance). Where the observed community composition does not deviate significantly from the expected community, no major monitoring or mitigation programmes are required. Where the biological community composition does deviate significantly from that expected, then the presence or abundance of certain species or assemblages of species can provide information on the likely causes of the deviation from the reference condition, allowing for monitoring and management resources to be targeted.

The Empirically-weighted Proportion of Sediment-sensitive Invertebrate (E-PSI) index is a biomonitoring tool that was developed, through a NERC CASE Studentship supervised by Dr Gary Bilotta, to detect the biodiversity impacts of fine sediments in streams and rivers (Turley et al., 2016). This biomonitoring tool has been selected by the UK's Technical Advisory Group for the Water Framework Directive, for use by UK environment agencies to assess the degree to which stream and river sites are affected by sediment stress. The aim of this NERC Innovation Internship is to integrate this new biomonitoring tool into agency modelling and reporting systems, ensuring and demonstrating the tool's applicability. The E-PSI tool, once integrated into agency systems, will improve the efficiency and effectiveness of ecological status assessments and stressor-identification as part of national and international water resource legislation, for a stressor (sediment) which is estimated to contribute towards the failure to achieve good ecological status in ~25% of UK waterbodies.

References:
Friberg et al. (2011) Advances in Ecological Research 44, 1-68.
Richter et al. (1997) Conservation Biology 11, 1081-1093.
Turak & Linke (2011) Freshwater Biology 56, 1-5.
Turley et al. (2014) Freshwater Biology 59(11), 2268-2277.
Turley et al. (2016) Ecological Indicators 70, 151-165.