Mobile Field Respirometry System for Evaluating Effects of Environmental Stressors on Fish Performance

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Biodiversity loss in response to human activities is a critical and compelling scientific issue. It has thus become increasingly important to advance our ability to understand and predict effects of environmental stressors on performance and fitness traits. Hypoxia (low dissolved oxygen, DO) is one of the most serious manifestations of anthropogenic stress to fresh and coastal waters driven by influxes of wastes and fertilizers that accelerate eutrophication. And, for fish, severe hypoxia can be a powerful limiting factor on fitness-related performance (e.g., swimming). Climate warming may exacerbate hypoxia, because the solubility of oxygen in water decreases with rising temperature, while the metabolism of ectotherms (cold-blooded organisms) like fish increases. Hypoxia may also exacerbate effects of thermal stress by limiting aerobic performance of fish at higher temperatures. Given that hypoxia and global warming are both pervasive aquatic stressors, it is critical to address their interactive effects. This is particularly important in tropical fishes, many of which are critical to food security in the developing world, and may be particularly sensitive to climate warming given narrow thermal windows. The Mobile Respirometry Lab (MRL) offers a unique opportunity to carry out standardized “on-site” measures of fish performance and thermal tolerance across multiple species and multiple locations identified from our long-term (24-yr) data base of DO and temperature for aquatic sites in Uganda, East Africa. The MRL will move our research programs to the next level by allowing us to look for parallel (and unique) patterns of response to two pervasive stressors across multiple fish lineages. The MRL is a field-compatible system that integrates respirometry equipment and software provided by Loligo Systems (http://www.loligosystems.com) housed in a 4-wheel drive pick-up with a hardened (secure) canopy cover and an accompanying portable outdoor enclosure. This system, run using portable solar panels, a field generator, and battery-operated pumps will allow us to assay fish at remote sites, opening the door for a more widespread and representative analysis of fish response to environmental stressors. Experiments will quantify temperature sensitivity and short-term acclimation capacity of standard and resting metabolic rate, critical oxygen tension, and critical thermal maximum using a combination of acute exposures and thermal acclimations. We will target a suite of phylogenetically distant fish species across broad environmental gradients including fishes critical to food security in the region. The MRL will facilitate collaboration and training both nationally and internationally; and we estimate that each year this system will be used by 1 PDF, 1-2 graduate students, and 1-2 undergraduates, and a research assistant, thus contributing to the training of up to 6 HQP per year.