The introduction of non-indigenous species (NIS) is one of the top drivers of global biodiversity loss, with ballast water discharge from ships being the primary source of aquatic NIS introductions around the world [1]. Shipping activity has dramatically increased in the Canadian Arctic due to climate change and increased resource extraction [2] with Milne Inlet having the largest increase in shipping traffic due to raw iron exports [3,4]. Ballast water discharge in this previously undeveloped inlet brings NIS introduction risks with potential impacts to sensitive Arctic marine species/habitats (e.g. areas important for feeding/breeding of narwhal/bowhead, bird colonies and Arctic char), consequences for food security/ local community well-being, and more widespread effects if NIS become established and spread to other Arctic regions. Recent updates in regulations have led to the requirement for ballast water management systems (e.g. chlorination or UV) onboard vessels, to treat ballast water before discharge, although there is uncertainty about their efficacy in Arctic environments. Southern ballast water studies found approximately half of sampled vessels exceeded international treatment standards (Regulation D2 [5]) with 10 to 1000s of organisms/m3 of ballast water [6,7,8], including NIS to Canada [7,8]. Colder temperatures often lead to slower chemical reactions, suggesting treatment efficacy to ballast water treatment systems may be lower on Arctic voyages [8] than voyages to southern Canadian ports. In addition, organisms that survive treatment may be hardy, and may be more likely to establish in Arctic environments [9]. This project will assess the number and types of organisms in ballast water discharged, as well as efficacy of ballast water treatment systems on-board ships travelling to the arctic to better understand the potential risk of NIS under Arctic conditions. Further, it will assess the feasibility of ballast water sampling and analysis methods for future use by community members/organizations for future ballast water monitoring. In 2026 and 2027, we propose to sample for up to 8 weeks (length of sampling will be dependant on resources and capacity at Milne Inlet) during the shipping season to sample a total of up to ~64-80 vessels over the duration of the trial monitoring program. Sampling will require a team of 4-5 people who will work with ship’s staff to connect sampling equipment to the appropriate sample port on-board. Sampling would include the use of the Ballast Catch tool to filter at least 1000-L of ballast water and collect large size class (≥50 m) organisms samples as well as the collection of raw (unfiltered) water samples for the small size class (≥10 m and ≤10m) organisms. In addition to large and small size class samples, water quality parameters (water temperature, pH, and salinity) will be measured, residual chlorine levels will be assessed (i.e. to assess if the chlorine used to kill living organisms in ballast water neutralized properly) and environment DNA/RNA (eDNA/eRNA) will be collected for later individual- and meta-barcoding to determine the types of organisms present in ballast water samples. Sample processing will happen on-site at Milne Inlet port where an indicative tool (SATAKE Ballast eye) will be used to count the number of live organisms in ballast water samples, and assess levels of compliance with the D-2 ballast management standards. A portion of all ballast water samples collected will be preserved for later taxonomic assignment using morphological and genomic methods. Each year, we will host a training workshop where Inuit youth from Pond Inlet, Igloolik and Sanirajak (Hall Beach) involved in the project will learn how to use sampling equipment, and essential safety measures for sampling ships at industrial port sites. A second workshop will take place in the fall where involved Inuit youth will provide feedback on the sampling season and do outreach in each of their communities with support from DFO to share knowledge of the project and discuss questions and concerns will community members. A third workshop will be hosted in the winter where Inuit youth with support from DFO, will analyze data from each field season using mapping and data analysis platforms.