Water bodies including oceans, lakes, and rivers across the world are warming due to climate change and anthropogenic heat emission. This has a variety of impacts such as a reduction in fresh water supply, a reduction in dissolved oxygen content, and an increase in harmful algal blooms. Warming has also been found to alter the metabolic balance of ecosystems; for example, increasing ecosystem respiration at a faster rate than primary production which is predicted to reduce carbon sequestration significantly by the end of the century.

Increasing temperatures also affect metabolism, the chemical reactions within an organism that transform food into usable energy.


Metabolic rate is the rate at which organisms take up, transform, and expend energy and materials. This typically scales with temperature and body size. However, it is unclear how global warming will affect the metabolic rate of species, as most research has focused on acute (short-term) rather than chronic (long-term) thermal exposure.


In a soon to be published paper, Dr Eoin O’Gorman and his research group at the University of Essex conducted respirometry experiments in situ and after placing salmonid fish in different streams to understand the effects of chronic versus acute thermal exposure. They found that it may not all be doom and gloom in a warming world: chronic exposure to warming may reduce the thermal sensitivity of metabolic rate in salmonids, meaning they have a lower than expected energy demand. This was because the fish were able to acclimate or adapt to the warmer environment, potentially giving them a better outlook when forecasting the consequences of global warming on ecosystems.


Over twenty PME miniDOT loggers were used to measure dissolved oxygen concentrations and water temperatures every minute throughout the experiments. Measurements were taken inside chambers secured in shallow water for 1.5-3 hours. Each chamber contained a miniDOT logger and a single fish, with one chamber only containing the miniDOT as a control.

These experiments took place across the UK, Iceland, and Spain, making the miniDOT Loggers an ideal choice due to their compact size. As well as being easy to travel with, the units also fitted easily into small chambers for the experiments.


Dr Eoin O’Gorman and his students are planning further experiments in additional locations including areas of Scotland, the west of Ireland, and France. They are also interested in tagging the fish to understand more about the effects of metabolism and growth on fish life history.

For more information on the PME miniDOT loggers, please click here.

Image credit: Gabriella Lawrie and Alexia Gonzalez Ferreras

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