NWRT - Llyn Cwellyn Paleo Study

Description

Background The North Wales Rivers Trust (NWRT) is a river restoration charity covering the rivers of Gwynedd, Anglesey, Conwy, and Denbighshire. The Trust has recently received Heritage Lottery funding for ‘Prosiect Torgoch’ which aims to conserve Arctic charr in North Wales. Llyn Cwellyn (SH 56179 54889) supports one of only three natural Arctic charr populations in Wales. Analysis of WFD monitoring data indicate there has been an increase in nutrients entering the lake, which is driving a decline in deep-water dissolved oxygen. As part of Prosiect Torgoch, NWRT are commissioning a paleoecology study at Llyn Cwellyn to further understand historic trends in nutrients. Work required The aim of this project is to sample a lake sediment core from Llyn Cwellyn and analyse nutrient, sedimentation, and diatom changes over time. Palaeolimnological methods offer a means of reconstructing the environmental history of standing waters by studying subfossil fragments of the biota preserved in the lake sediments. The project aims to reconstruct the decadal environmental history of Llyn Cwellyn over approximately the last century, with particular attention to the eutrophication history of the site. The work to be commissioned will involve: • Collecting an open water core from the deep basin (~38 m depth); • Sub-sampling the core and performing lithostratigraphic analyses; • Dating the core using radiometric dating methods (210Pb and 137Cs); • Analysing ~twelve core samples at decadal time intervals for diatom remains; • Analysing the core using X-Ray Fluorescence (XRF) to track changes phosphorous (P). Please see the CCW report attached with this ITT for further information on the methods. NWRT will arrange all necessary permissions and lake access. Boat access to the lake is at SH 56438 54259. Deliverables • A document describing the methods used, including any limitations or difficulties encountered • Raw data, which should include percentage abundance of diatom species, sedimentation rates, and the distribution of phosphorous (each at ~decadal time intervals between 1920 and 2023). Data should be in csv format or similar. Other than the methods, there are no reporting requirements for this project. Assessment of quotes NWRT procurement policy requires three quotes for projects exceeding £5,500. Quotes will be evaluated according to price and the quality of the proposal. Please provide CVS for the consultants who will be assigned to the project and examples of similar projects your organisation has delivered. Your fee breakdown should include: • Travel • Reporting (methods and delivery of raw data) • Field work • Laboratory analysis • Project Management (include one startup meeting of 1 hour)