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Title: Deoxygenated groundwater upwelling in the Atlantic salmon incubation zone : implications for embryonic survival and an opportunity for adaptation
Author: Bloomer, Jack
ISNI:       0000 0004 6422 2817
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2016
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There is increased recognition that groundwater upwelling causes low oxygen in Atlantic salmon nests (redds), and reduces incubation success. Field data suggest patterns of groundwater upwelling are driven by seasonal hydrological variation. However, these data are currently limited to a small number of sites and are predominantly descriptive. Consequently, wavelet analysis was performed on a range of published and unpublished datasets that monitored oxygen concentration in the incubation zone of Atlantic salmon spawning rivers throughout the UK. This analysis demonstrated episodes of groundwater induced oxygen depletion in all locations and that groundwater upwelling was linked to antecedent and prevailing weather conditions. To test the possible effects of episodic periods of hypoxia on Atlantic salmon eggs, such as those caused by groundwater upwelling, an incubation facility was designed that enabled fine-scale control of oxygen depletion. Hypoxia in the earlier stages of development did not affect survival but caused alevin to hatch later in an underdeveloped state. Low oxygen conditions at the later stages of development reduced survival by 15% and caused premature hatching of severely underdeveloped alevin. Therefore, effective management of factors that influence groundwater upwelling is important to limit effects on incubating salmonids The membrane surrounding the Atlantic salmon egg is a barrier to oxygen diffusion, so its permeability influences oxygen supply to the embryo. Due to factors such as deoxygenated groundwater upwelling, oxygen supply varies among spawning locations and could drive inter-population membrane architecture variation. Electron microscopy egg membrane permeability of five UK Atlantic salmon populations varied substantially, and eggs with the lowest permeability were most susceptible to hypoxia-induced mortality. Therefore, variation in egg membrane structure could represent adaptation to oxygen stress, such as that caused by deoxygenated groundwater upwelling, and reinforces the importance of maintaining genetic integrity of distinct populations.
Supervisor: Sear, David ; Kemp, Paul Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available