Physiological mechanisms of tolerance to warming and hypoxia in fish under global climate change
MoRE2020 Fellow Tristan Mcarley incoming mobility from the University of Auckland, New Zeeland to the University of Gothenburg
Global climate change is currently on eof humanities greatest challenges, resulting in warming and oxygen depletion (hypoxia) of aquatic ecosystems. Such stressors are challenging for fish, yet the negative effects may be counteracted by physiological plasticity (acclimation) to these environmental stressors. Even so, according to UN's IPCC panels, little is knowns about mechanisms of physiological plasticity and how acclimation to one stressor alters the sensitivity and response to another. This knowledge gap prevents accurate models of climate change effects on biodiversity in aquatic ecosystems.
Here, we will determine how previously observed physiological temperature plasticity in perch from the artificially heated Biotest enclosure at the Forsmark nuclear power plant affects sensitivity to interacting hypoxia stress. Moreover, by analyzing behavioural and physiological responses of fish to experimentally elevated oxygen leveles (hyperoxia) in combination with changes in temperature at our University of Gothenburg lab, we will test the central hypothesis in fish ecophysiology that impaired perfromance and survival of fishes at elevated temperature is due to insufficient body oxygen supply.
The project is a collaboration between the University of Gothenburg and University of Auckland, which bridges two strong academic milieus in New Zeeland and Västra Götaland. Two end-users receive direct benefits of the project; Plant and Food Research New Zeeland who manage natural fisheries and fish farming systems in the face of global warming, and the Swedish Agency for Marine and Water Management (Havs- och vattenmyndigheten) managing aquatic biodiversity and fisheries, as well as forecasting the effects of global change on fish populations and marine ecosystems.
Collaborating end-user: Plant and Food Research New Zeeland and the Swedish Agency for Marine and Water Management (Havs- och vattenmyndigheten)
Summary of Project Results
This project resulted in the completion of four experiments examining the physiological responses of fish to different environmental factors including chronic and acute warming, hypoxia (reduced oxygen levels), hyperoxia (higher than normal oxygen levels) and low salinity. The influence of chronic environmental warming associated with climate change on the ability of fish to tolerate hypoxia (reduced oxygen availability) was examined in European perch. This aspect of the project utilised the Biotest facility: a man-made enclosure located in the Baltic Sea that has been artificially warmed for the past 35 years. Biotest perch, a population which has been exposed to prolonged warming over decades, are better able to tolerate hypoxia than perch from the Baltic population tested at either present day environmental temperatures or following an acute increase to a predicted future temperature. These results present strong evidence European perch have the physiological and/or adaptive capacity to retain normal levels of hypoxia tolerance in a warmer future due to climate change. The influence of hyperoxia on aerobic and cardiovascular performance was examined in rainbow trout. Hyperoxia increased aerobic scope - a key metric of aerobic performance in fish - and the maximum capacity of the heart to pump blood around the fish's circulatory system and deliver oxygen to tissues. Alongside improved aerobic and cardiovascular performance, the ability of rainbow trout to tolerate acutely high temperature also increased with hypoeroxia. These findings show hyperoxia, which may occur naturally due to photosynthetic activity, can provide a metabolic refuge for fish and increase their ability to withstand higher temperatures as the climate warms.
An international research collaboration was completed as part of this project. The collaboration involved MoRE fellow Dr Tristan McArley, Professor Erik Sandblom, and PhD student Daniel Morgenroth from The University of Gothenburg travelling to New Zealand to be hosted by Dr Javed Khan at the National Institute of Water and Atmosphere (NIWA) Bream Bay Aquaculture Park in Ruakaka. Associate Professor Anthony Hickey, who specialises in assessing mitochondrial function in fish, also joined the research team. Prior to arriving, the staff at NIWA set-up rearing tanks where New Zealand kingfish, a high value aquaculture species, could be acclimated to hyperoxia or low salinity conditions for four weeks. The reseach team then compared aerobic performance, cardiovascular performance and mitochondrial function in kingfish acclimated to each condition for four weeks, fish exposed to each condition acutely and control groups. Although the analysis of the data collected in these experiments is still being completed, the results are expected to generate several novel findings regarding the effects of chronic exposure to hyperoxia and low salinity on cardiorespiratory physiology in aquaculture reared fish. The project has established a strong connection between senior researchers at the University of Auckland and the University of Gothenburg, and future plans are being developed to perform research collaborations.