Sunlight surveillance: improved monitoring of harmful UV radiation in freshwater ecosystems

Abstract 1) Ultraviolet radiation (UVR) has a range of strong effects on freshwater ecosystems, and changing UVR is implicated in global amphibian declines. The link between UVR and amphibian declines is not well understood, largely due to limited understanding of actual UVR exposure regimes in freshwater ecosystems. Logistical challenges in measuring aquatic UVR regimes in situ have impeded progress, including the design of cost-effective radiometric monitoring tools and the measurement of UVR at ecologically relevant scales. 2) We designed novel underwater UVR loggers and deployed them in southeast Queensland creeks to log near-continuous underwater UV Index (UVI) for 11 days across 4 sampling events within the peak amphibian breeding season. We compared these data with solar modelling, dosimetric and handheld radiometric techniques. 3) The dataset (2616 hours from 39 UV sensors) revealed a highly heterogenous daily UVR microenvironment that showed capacity for harmful UVI exposures at both sites. Traditional UVR monitoring techniques often missed these high UVR exposures. 4) Fine scale UVR data logging was proven to be a gold standard of monitoring the UVR microenvironment in freshwater systems. This is important for understanding the relevance of laboratory-based studies investigating how freshwater organisms respond to UVR, monitoring changing UVR in aquatic systems and ultimately predicting how aquatic systems will respond to changes in UVR levels associated with global climate change.