Bedford Institute of Oceanography

Two different oils, a Bunker C heavy fuel oil and a marine diesel-type oil, were recovered from the M/V Schiedyk 53years after sinking. Microcosm experiments to quantify their degradation potential, potential toxicity and the microbial response to oiling were conducted in 4 seasons. Incubations lasted 21 or 28 d without additional nutrients and with low (<200ppm) oil concentrations. The recovered oils showed no indication of prior weathering. Abiotic degradation rate constants indicate faster removal of polycyclic aromatic compounds (PACs) (0.037 d-1±0.024 (n=237)) compared to n-alkanes (0.006 d-1±0.002 (n=60)). Biodegradation rate constants could rarely be calculated (n=53 total). Abiotic losses of n-alkanes from marine diesel were 15× higher than with Bunker C. Losses of parent PACs (0.64%±1.70) were lower than losses of alkylated PACs (10.85%±19.51), which had lowest losses in winter. Potential toxicity of the oils remained high throughout the incubations, with higher toxicity associated with marine diesel (76.9%±3.2) compared to Bunker C (65.7%±4.3). Although little biodegradation was observed and no bloom of prokaryotes occurred, taxa associated with aerobic degradation of both n-alkanes and PACs increased. The identity of the taxa varied with season, reflecting differences in temperature and nutrient status. The lack of detectable biodegradation is likely associated with nutrient limitation. Overall, the results suggest oil recovered from shipwrecks after half a century may have limited weathering and some susceptibility to abiotic degradation with biodegradation depending on the local temperature and nutrient concentrations.

When oil reaches shorelines during a marine oil spill, it can persist in the sediment for decades, extending well beyond on-water operations and can become a significant expense to the overall response. Oil's persistence on beaches is initially driven by its ability to penetrate sediment, a process heavily influenced by a suite of in situ shoreline conditions as well as the oil's properties. One property of note is viscosity, which undergoes non-linear changes under the influence of temperature and influences oil's ability to penetrate shoreline sediments. Through 435 column experiments, this study systematically examines the penetration behaviour of diluted bitumen (dilbit) and a distillate very low-sulphur fuel oil (VLSFO) in unsaturated, coarse-grained, inorganic beach sediments under seven temperature regimes (Polar to Equatorial), five sediment types and two oil types. Results indicate that the sediment's temperature significantly influences oil penetration, while the presence of temperature gradients within the sediments exerts minimal influence on its penetration. Low temperatures limited oil penetration, concentrating oil near the sediment's surface. In contrast, higher temperatures in those same sediments resulted in deeper penetration and increased the net volume of oil-contaminated sediment. These findings confirm the temperature-viscosity feedback as a key control on oil migration in marine beach sediments and provide new empirical insights that directly inform shoreline response strategies and waste management planning across diverse climatic regions.

There is widespread recognition that existing regulatory and advisory systems for fisheries management in Canada influence our ability to address ecosystem-level objectives, particularly relative to bycatch mitigation. However, the monitoring programs, information storage systems (i.e. databases) and data extraction workflows used for fisheries analyses have rarely been considered in this context. Management goals for bycatch mitigation represent a substantial departure from the original objectives used to structure monitoring programs and their associated databases. Using a detailed example from multispecies groundfish fleets in Atlantic Canada, we demonstrate that the way information from fisheries is stored, as well as the analytical workflows used to identify and summarize information from commercial fishing trips, complicate research on bycatch. Employing the same workflow and data extraction process to answer all types of fisheries management questions is fraught with pitfalls. We hope this perspective will inform the way in which bycatch analyses are incorporated into Canadian fisheries management, and provide the impetus to redesign current data management systems to meet emerging fisheries challenges in Canada.

The Canadian Arctic Archipelago (CAA) lies within Inuit Nunangat, the homeland of the Inuit, and encompasses extensive coasts of Nunavut. These shorelines are continuously changing, shaped by sea ice, glaciers, icebergs, permafrost, and oceanographic dynamics during the open-water season. Inuit knowledge offers profound insights into coastal change; however, systematic measurements of ocean waves and water levels remain scarce, which limits our ability to model nearshore processes and anticipate shoreline responses, both critical for adaptation. We present a dataset of water levels and wave statistics collected between 2021 and 2023 in partnership with three communities: Ausuittuq (Jones Sound), Canada’s northernmost community; Ikaluktutiak and Kugluktuk (both in Coronation Gulf). The dataset includes 19 calibrated pressure sensors in the nearshore zone and 6 offshore wave buoys deployed with Inuit boat operators, capturing more than 427 days of hourly observations. Observed conditions include significant wave heights up to 1.7 m and peak wave periods up to 6.0 s. All files are published in open formats with structured documentation to ensure transparency, accessibility, and reuse.

Abstract. Surface ocean alkalinity enhancement (OAE), through the release of alkaline materials, is an emerging marine carbon dioxide removal technology that could increase the storage of anthropogenic carbon in the ocean. Observations collected during recent and on-going field trials will provide important information on the feasibility and effects of alkalinity additions on carbon cycling and study ecological responses. However, given the scales involved (24/7 continuous addition, meters to hundreds/thousands of kilometers and minutes to months for alkalinity dispersion) observations, even with the use of autonomous platforms, will remain inherently sparse and limited. Alone, they cannot provide a comprehensive quantification of the effects of OAE on the carbonate system, and ultimately of the net air-sea CO2 fluxes. Numerical models, informed and validated by field observations, are therefore essential to OAE deployments and the measurement, reporting, and verification (MRV) of any resulting carbon uptake. They can help guide fieldwork design, including optimal design of measurement monitoring networks, provide forecasts of the ocean state, simulate the effects of alkalinity additions on the seawater carbonate system, and allow one to quantify net CO2 uptake. Here we describe a coupled physical-biogeochemical model that is specifically designed for coastal OAE. The model is an implementation of the Regional Ocean Modelling System (ROMS) in a nested grid configuration with increasing spatial resolution from the Scotian Shelf to Halifax Harbour (coastal fjord, eastern Canada), a current test site for operational alkalinity addition. The biogeochemical model simulates oxygen dynamics, carbonate system processes (including air-sea gas exchange), and feedstock properties (dissolution, sinking). We present a multi-year hindcast validated against the long-term weekly time series available for a long-term monitoring station at the deepest part of Halifax Harbour, as well as alkalinity addition simulations at various locations inside and outside the harbour to show the model's capabilities for assessing the effects of OAE at this coastal site. We found that release locations had a strong effect on the outcome of the addition, whereas feedstock types influenced the distribution of the signal. Up to 69 % of the net CO2 uptake was realized within the model domain, most of it inside the harbour. These results stress the importance of operational design, as well as the use of high-resolution regional models when quantifying additionality.

Microorganisms regulate key biogeochemical processes and ecosystem feedbacks to climate change, yet they remain underrepresented in global environmental policy and implementation frameworks. The World Microbiome Project (WMP) Environment and Climate Change Roadmap sets out a coordinated agenda to embed microbial science into climate mitigation, adaptation, and nature-based solutions. It identifies three scientific priority actions: (1) microbial process accounting, (2) global integration of microbiome data, and (3) the deployment of microbiomes for ecological resilience. These priorities define the core knowledge and governance gaps that currently limit the effectiveness of climate mitigation, adaptation, and nature-based solutions. To operationalise these priorities, the Roadmap establishes interoperable microbiome data infrastructures linking distributed observations across biomes, a federated governance model combining regional stewardship with global standards, and measurable microbial indicators translated into policy-relevant targets for climate, biodiversity, and ecosystem rehabilitation. The roadmap proposes alignment with existing climate and biodiversity agreements to avoid duplication and maximise impact. By articulating concrete near-term priorities and cross-sector partnerships, this Comment aims to catalyse coordinated investment and action so that microbial systems are recognised, protected, and harnessed as essential components of a stable and just climate future.

This study evaluates monthly sea levels during 1993–2023 from four ocean models using tide gauge and altimeter data in the Northwest Atlantic with its shelf seas, including the Gulf of Maine, Scotian Shelf, Gulf of St. Lawrence, and the Newfoundland and Labrador Shelf. The evaluation is carried out for four different aspects: the multi-decadal mean and linear trend, seasonal cycle, and the de-trended and de-seasonalized anomalies. Overall, the high-resolution model with advanced data assimilation (GLORYS12v1) possesses skills in all four aspects. The other three models show different discrepancies in reproducing the observed sea level variations relative to GLORYS12v1. They possess low or no skills for the timing (despite reasonable standard deviations) of sea level anomalies at time scales longer than 20 months along the coast, and at all time scales on the shelf, over the shelf break, and in the deep ocean. Without data assimilation, the models with high and medium resolutions show biases in the time-mean sea levels in the Labrador Sea that can be attributed to the simulated stronger and weaker deep convection (deeper and shallower mixed layer depth), respectively. The medium-resolution model, using a different data assimilation approach than GLORYS12v1, shows biases in the seasonal amplitude and multi-decadal trends.

Abstract Automated sampling enables the collection and analysis of eDNA from regions that are limited by site access, sampling times, and operator safety. eDNA sampling devices must be rigorously tested against existing technologies to demonstrate fitness across different operational settings and sample quality. The Dartmouth Ocean Technologies, Inc. (DOT) automated eDNA sampler preserves samples and can be deployed at a range of temperatures and depths. The DOT sampler has previously been tested in marine environments for up to three months, with validation against manual protocols. In this study we tested the DOT sampler in four water bodies in Nova Scotia, Canada, with an expanded set of genetic analyses. We successfully profiled prokaryotes, eukaryotes, and fish using the 16S, 18S, and 12S ribosomal RNA genes respectively, in a brackish pond, a freshwater lake, and two marine harbours. eDNA samples collected by the DOT sampler were statistically concordant with manual Niskin-bottle samples in a range of aqueous habitats. We detected taxonomic groups consistent with the salinity level of each sampled habitat, including invasive species such as smallmouth bass and chain pickerel in the freshwater lake. One marine harbour was sampled at pre-defined time intervals in the days following a significant rainfall event during which site access was limited. We detected ten times as many probable fecal-associated bacteria by proportion at this site relative to the other marine harbour. Onboard preservation of samples in RNAlater allowed the identification of groups with different levels of metabolic activity, and shotgun metagenomic analysis identified key metabolic pathways and a small number of sequences with homology to known antimicrobial-resistance genes.