Metabolic rate depression (MRD) has long been proposed as the key metabolic strategy of hypoxic survival, but surprisingly, the effects of changes in hypoxic O 2 tensions (Pw O2 ) on MRD are largely unexplored. We simultaneously measured the O 2 consumption rate (Ṁ O2 ) and metabolic heat of goldfish using calorespirometry to test the hypothesis that MRD is employed at hypoxic Pw O2 values and initiated just below P crit , the Pw O2 below which Ṁ O2 is forced to progressively decline as the fish oxyconforms to decreasing Pw O2 . Specifically, we used closed-chamber and flow-through calorespirometry together with terminal sampling experiments to examine the effects of Pw O2 and time on Ṁ O2 , metabolic heat and anaerobic metabolism (lactate and ethanol production). The closedchamber and flow-through experiments yielded slightly different results. Under closed-chamber conditions with a continually decreasing Pw O2 , goldfish showed a P crit of 3.0±0.3 kPa and metabolic heat production was only depressed at Pw O2 between 0 and 0.67 kPa. Under flow-through conditions with Pw O2 held at a variety of oxygen tensions for 1 and 4 h, goldfish also initiated MRD between 0 and 0.67 kPa but maintained Ṁ O2 to 0.67 kPa, indicating that P crit is at or below this Pw O2 . Anaerobic metabolism was strongly activated at Pw O2 ≤1.3 kPa, but only used within the first hour at 1.3 and 0.67 kPa, as anaerobic end-products did not accumulate between 1 and 4 h exposure. Taken together, it appears that goldfish reserve MRD for near-anoxia, supporting routine metabolic rate at sub-P crit Pw O2 values with the help of anaerobic glycolysis in the closed-chamber experiments, and aerobically after an initial (<1 h) activation of anaerobic metabolism in the flow-through experiments, even at 0.67 kPa Pw O2 .

Anthropogenic increases in global temperature and agricultural runoff are increasing the prevalence of aquatic hypoxia throughout the world. We investigated the potential for a relatively rapid evolution of hypoxia tolerance using two isolated (for less than 11 000 years) populations of threespine stickleback: one from a lake that experiences long-term hypoxia (Alta Lake, British Columbia) and one from a lake that does not (Trout Lake, British Columbia). Loss-of-equilibrium (LOE) experiments revealed that the Alta Lake stickleback were significantly more tolerant of hypoxia than the Trout Lake stickleback, and calorimetry experiments revealed that the enhanced tolerance of Alta Lake stickleback may be associated with their ability to depress metabolic rate (as indicated by metabolic heat production) by 33% in hypoxia. The two populations showed little variation in their capacities for O extraction and anaerobic metabolism. These results reveal that intraspecific variation in hypoxia tolerance can develop over relatively short geological timescales, as can metabolic rate depression, a complex biochemical response that may be favoured in long-term hypoxic environments.

Pathogen genomics is a critical tool for public health surveillance, infection control, outbreak investigations as well as research. In order to make use of pathogen genomics data, they must be interpreted using contextual data (metadata). Contextual data include sample metadata, laboratory methods, patient demographics, clinical outcomes and epidemiological information. However, the variability in how contextual information is captured by different authorities and how it is encoded in different databases poses challenges for data interpretation, integration and their use/re-use. The DataHarmonizer is a template-driven spreadsheet application for harmonizing, validating and transforming genomics contextual data into submission-ready formats for public or private repositories. The tool’s web browser-based JavaScript environment enables validation and its offline functionality and local installation increases data security. The DataHarmonizer was developed to address the data sharing needs that arose during the COVID-19 pandemic, and was used by members of the Canadian COVID Genomics Network (CanCOGeN) to harmonize SARS-CoV-2 contextual data for national surveillance and for public repository submission. In order to support coordination of international surveillance efforts, we have partnered with the Public Health Alliance for Genomic Epidemiology to also provide a template conforming to its SARS-CoV-2 contextual data specification for use worldwide. Templates are also being developed for One Health and foodborne pathogens. Overall, the DataHarmonizer tool improves the effectiveness and fidelity of contextual data capture as well as its subsequent usability. Harmonization of contextual information across authorities, platforms and systems globally improves interoperability and reusability of data for concerted public health and research initiatives to fight the current pandemic and future public health emergencies. While initially developed for the COVID-19 pandemic, its expansion to other data management applications and pathogens is already underway.

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