Supplementary file 3_Application of stable isotopes in freshwater nutrient management: opportunities and challenges.docx

Stable isotope approaches can provide empirical diagnostic information across four policy-relevant domains, including: supporting nutrient source apportionment for constraining catchment models, identifying internal loading and legacy nutrient sources, assessing nutrient attenuation zones, and evaluating the effectiveness of management actions. Multi-isotope frameworks can often reduce ambiguity in source identification where the selected tracers provide independent and complementary information on sources or processes.

Stable isotope methods are currently absent from regulatory and management frameworks examined here; viable integration options are identified and assessed, from near-term deployment as supplementary investigative tools in persistently failing water bodies, through development of shared protocols and guidance, to longer-term contribution to management and investment frameworks. Current legislative reform provides a relevant, if uncertain, window for incorporating these methods more systematically within routine environmental governance.</p>