Agenda item

The committee received a presentation from Professor Darren Grocke, Professor of Stable Isotope Geochemistry, University of Durham.

Professor Darren Grocke addressed the committee to present the findings of a two‑year scientific study using nitrogen stable isotope analysis of seaweed to identify sources of nutrient pollution affecting Scarborough’s bathing waters. He explained that analysis of over 3,400 samples of Fucus and Ulva collected from 18 sites between September 2023 and October 2025 demonstrated that nitrogen signals recorded in the seaweed were consistent with pollution from animal manure and human sewage, rather than seabird guano or routine agricultural fertilisers. The results consistently identified Scalby Beck as a dominant source of nitrogen pollution, with ocean currents transporting this pollution from the North Bay into the South Bay, particularly during summer months when pollution levels intensified. Seasonal comparisons showed relatively cleaner conditions in winter and significant deterioration in summer, including a pronounced pollution event in July 2025 affecting much of the coastline. Professor Grocke highlighted the advantage of using seaweed as an integrative monitoring tool, capturing average pollution over several weeks rather than short‑term snapshots, and noted that visible increases in seaweed growth were often indicative of nutrient enrichment rather than good environmental health. He also raised concerns that beach sand movement could remobilise stored nutrients and contaminants, potentially exacerbating pollution as material was redistributed along the bay. He concluded that the evidence strongly pointed to nutrient inputs via Scalby Beck as a priority area for targeted investment and remediation, and that improved scientific understanding was essential to inform effective long‑term solutions.

Members’ discussion

Following Professor Darren Grocke’s presentation, councillors commended the robustness of his scientific analysis, focusing discussion on the finding that animal manure and human sewage were the dominant contributors rather than fertiliser runoff or seabird guano. Members questioned what practical systems and regulatory changes were needed to address pollution from Scalby Beck, including stronger controls on CSOs, greater oversight of agricultural and groundwater inputs, and clearer accountability given the absence of a single authority with overall responsibility. Councillors raised concerns about historic planning decisions, overdevelopment and infrastructure capacity, and emphasised the importance of continued monitoring to assess whether remedial actions delivered real improvement, noting with concern that funding for Professor Grocke’s work had ceased and advocating for further commissioning of similar studies as quality assurance alongside future Yorkshire Water investment. There was strong interest in expanding the approach beyond traditional bacterial indicators to a broader assessment of water quality, including routine testing of beach sand before relocation, consideration of nature‑based solutions such as seaweed, mussel and aquatic planting to absorb excess nutrients, and complementary monitoring techniques. Members also explored how improvements at identified source areas would translate into public confidence about swimming safety, acknowledged uncertainties around wider climatic factors, and stressed the value of extending investigations further inland to understand how catchment‑wide processes influencing coastal water quality, concluding that Professor Grocke’s work provided a critical evidence base to guide sustained action.