Abstract
Improving stream water quality in agricultural landscapes is an ecological priority and a legislative duty for many governments. Ecosystem health can be effectively characterised by organisms sensitive to water quality changes such as diatoms, single-celled algae that are a ubiquitous component of stream benthos. Diatoms respond within daily timescales to variables including light, temperature, nutrient availability and flow conditions that result from weather and land use characteristics. However, little consideration has been given to the ecological dynamics of diatoms through repeated seasonal cycles when assessing trajectories of stream function, even in catchments actively managed to reduce human pressures. Here, six years of monthly diatom samples from three independent streams, each receiving differing levels of diffuse agricultural pollution, reveal robust and repeated seasonal variation. Predicted seasonal changes in climate-related variables and anticipated ecological impacts must be fully captured in future ecological and water quality assessments, if the apparent resistance of stream ecosystems to pollution mitigation measures is to be better understood.
Highlights
In the context of a changing climate and agricultural intensification, it is recognised that freshwater ecosystems are vulnerable to multiple anthropogenic stressors, including excess sediment and nutrient delivery, whilst being modulated by climate-dependent flow, water temperature and event-driven transfers from catchments[1,2,3]
An Ordnance Survey/EDINA supplied service; 1.2) Images of the diatom biofilm assemblages in situ at Newby Beck November 2015; 1.3) (a) Monthly Ecological Quality Ratio (EQR: a diatom-based Water Framework Directive (WFD) community metric which measures ecological status) for Pow Beck and ratio of Achnanthidium minutissimum to Amphora pediculus (b) Monthly EQR for Newby Beck and ratio of Achnanthidium minutissimum to Amphora pediculus and (c) Monthly EQR for Thackthwaite Beck and ratio of Gomphonema parvulum and Navicula lanceolata from March 2011 to August 2016
The greatest range in ecological status was observed within Newby Beck where EQR values varied between those indicative of ‘high’ to ‘bad’ water quality
Summary
In the context of a changing climate and agricultural intensification, it is recognised that freshwater ecosystems are vulnerable to multiple anthropogenic stressors, including excess sediment and nutrient delivery, whilst being modulated by climate-dependent flow, water temperature and event-driven transfers from catchments[1,2,3]. Full consideration of organism colonisation, resilience to high-energy events and seasonal controls is needed to produce robust biological datasets that capture ecosystem function and variability Failure to consider this temporal dynamic could bias inferences drawn from ecological assessment and contribute to poorly-targeted mitigation within catchments, potentially incurring significant economic cost. The relative contribution of weather, catchment land use and reach-scale processes on benthic stream ecology has not been rigorously assessed to date via multi-annual, high-resolution in situ environmental monitoring programmes. This is true within highly dynamic low-order streams. These diatom data are evaluated alongside high-resolution environmental monitoring data to determine the relative discrete and combined contributions of land use, the seasonality of precipitation, temperature and light, and in-stream environmental variables that combine to define the niche experienced by benthic diatoms
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
