Rate My Professor Penny Johnes

Professor Penny Johnes is Professor of Biogeochemistry in the School of Geographical Sciences at the University of Bristol, where she holds appointments in Hydrology and the Cabot Institute for the Environment. She earned her BSc and DPhil from the University of Oxford. With over 30 years of experience as an environmental scientist, her research centers on the biogeochemistry of aquatic systems, examining the impacts of food production and environmental change on inland and coastal water quality. Johnes provides expert advice to the UK Government and international agencies on nutrient enrichment in waters, its effects on ecosystem health, and strategies for controlling nutrient fluxes from land-based sources to aquatic environments. Her work emphasizes the role of dissolved organic matter in biodiversity loss in freshwater ecosystems, holistic management of multiple stressors in catchments, and evidence-based environmental policy. Key contributions include quantifying the importance of organic and particulate nitrogen and phosphorus fractions in nutrient loads, elucidating the influence of short-term extreme flow conditions on nutrient source-sink functions in soils, wetlands, and freshwaters, and developing approaches to upscale nutrient flux models using quasi-homogenous geoclimatic units.

Johnes serves on the UNECE Task Force for Reactive Nitrogen and its Expert Panel on Nitrogen Budgets, the IAHS International Commission on Water Quality, the Natural England Science Advisory Committee, the Wessex Water Catchment Panel, the Defra Biodiversity Targets Advisory Group, and the Defra Nutrient Management Expert Group; she chairs the Defra Water Expert Advisory Group. She became a Fellow of the Royal Society of Biology in 2020. Notable publications include 'Exploring the nature, origins and ecological significance of dissolved organic matter in freshwaters: state of the science and new directions' (Biogeochemistry, 2023), 'Microbial uptake kinetics of dissolved organic carbon (DOC) compound groups from river water and sediments' (Scientific Reports, 2019), and 'Dissolved organic nutrient uptake by riverine phytoplankton varies along a gradient of nutrient enrichment' (Science of the Total Environment, 2020). Current projects encompass REFRESH on dissolved organic matter as a nutrient resource in freshwater ecosystems, SMARTWATER on pollution hotspots, and QUANTUM quantifying nutrient enrichment from livestock farming, alongside NERC-funded DOMAINE on dissolved organic matter fluxes and Defra-supported Demonstration Test Catchments for agricultural pollution mitigation.