Penny is an environmental scientist by background who has worked on the biogeochemistry of aquatic systems, and the impacts of food production and environmental change on the quality of inland and coastal waters for the past 30 years. She has provided advice to a range of UK Government, intergovernmental organisations and international agencies on the nature and scale of nutrient enrichment in waters, the consequences of this enrichment for ecosystem health, and the most effective strategies for the control of nutrient flux from land basd sources to waters.  She is currently a member of the UNECE Task Force for Reactive Nitrogen and its Expert Panel on Nitrogen Budgets, advises the Wessex Water Catchment Panel, sat on the Defra Biodiversity Targets Advisory Group and Defra Nutrient Management Expert Group, and was Chair of the Defra Water Expert Advisory Group.  

Penny has particular interests in the role of dissolved organic matter as a driver of biodiversity loss in freshwater ecosystems, the potential to develop holistic management strategies which tackle multiple stressors in freshwaters and their catchments, and in ensuring that environmental management policy is underpinned by robust science evidence. She works with researchers across a range of disciplines to meet these challenges, from chemical to biological, environmental, earth, agricultural, social, economic and political sciences. 

Her research to date has highlighted the quantitative importance of organic and particulate nitrogen and phosphorus fractions in the total nutrient load transported to and within water bodies; the importance of short-term, extreme flow conditions in controlling the nutrient source/sink function in soils, wetlands and freshwaters; and the necessity when upscaling findings from local to national scale, of defining quasi-homogenous geoclimatic units exerting broadly similar controls on nutrient flux from land to water, as the base unit for modelling.  Her work has revealed the finite capacity of both natural and constructed wetlands to store nutrients in transit from land to stream. Her most recent work has revealed the diversity of nutrient, organic, pathogen and ecotoxin contaminants flushed from livestock farming to streams. This research has been critical in helping us to better understand the sources of pollutants within the landscape, the pathways by which material moves from land to stream under differing environmental conditions, the rates at which this material is cycled, transported and transformed instream and the impacts of multiple contaminant stressors on stream ecosystem health. 

Penny's ongoing research focus is on characterising the role of dissolved organic matter (DOM) in freshwater ecosystems. Originally she was funded to study its character and flux to freshwaters in relation to nutrient enrichment and climatic controls under the NERC Large Grant DOMAINE programme (2014-2019). More recently her attention has focused on exploring livestock farming as a source of DOM in UK rivers under her NERC QUANTUM project (2023-2026) as part of the NERC and Defra-funded National Freshwater Quality Programme, and in exploring the processing of DOM, focusing on both carbon and nitrogen, by the riverine bacterioplankton community under the NERC MICRO-CYCLE (2025-2028) programme. Her most recent work is funded under the ERC REFRESH Advanced Grant (2024-2029) where she is combining newly developed field experimental approaches using isotope tracers with environmental genomics approaches to reveal the relative rates and mechanisms governing biotic uptake of DOM as nutrient resource by the freshwater biota, and its food web scale and biodiversity impacts.  These programmes capitalise on recent novel analytical and in situ monitoring technologies to elucidate the fine scale variability in nutrient flux behaviours and source character in catchments, and the ways in which the hydrochemical signature of nutrient flux from catchments, defined at high resolution, may be used to diagnose the stresses on that system and their likely responses to proposed on-farm mitigation efforts.