title: Additive effects of enhanced ambient ultraviolet B radiation and increased temperature on immune function, growth and physiological condition of juvenile (parr) Atlantic Salmon, Salmo salar.
abstract: Climate change models predict increased ultraviolet B (UVB) radiation levels due to stratospheric ozone depletion and global warming. In order to study the impact of these two environmental stressors acting simultaneously on the physiology of fish, Atlantic salmon parr were exposed, for 8 weeks in outdoor tanks, to different combinations of UVB radiation (depleted and enhanced) and temperature (standard rearing temperature of 14 °C or 19 °C). The immune function (plasma IgM, lysozyme activity and complement bacteriolytic activity), growth (body weight) and physiological condition (haematocrit and plasma protein concentration) of the fish were determined. Increased UVB level, regardless of water temperature, had a negative effect on immune function parameters, growth and physiological condition. Higher temperature increased plasma IgM concentration but had a negative effect on complement bacteriolytic activity under both spectral treatments. Increased temperature, irrespective of UVB level, increased fish growth but negatively affected haematocrit and plasma protein. Exposing the fish to enhanced UVB at elevated temperature increased plasma IgM concentration and slightly improved growth. However, complement activity and physiological condition parameters decreased more than when the fish were exposed to each stressor separately. The changes were mainly additive; no interactive or synergistic effects were observed. The negative impact of multiple stressors on immune function, together with predicted increases in pathogen load in warmer waters resulting from global climate change, suggest an increased risk to diseases in fishes.
authors.affiliation: Department of Biological and Environmental Science, University of Jyväskylä, PO Box 35, Ambiotica, FI-40014 Jyväskylä, Finland. ilmari.e.jokinen@jyu.fi
authors.forename: Ilmari E
authors.initials: IE
authors.lastname: Jokinen
authors.forename: Harri M
authors.initials: HM
authors.lastname: Salo
authors.forename: Eveliina
authors.initials: E
authors.lastname: Markkula
authors.forename: Kaisa
authors.initials: K
authors.lastname: Rikalainen
authors.forename: Michael T
authors.initials: MT
authors.lastname: Arts
authors.forename: Howard I
authors.initials: HI
authors.lastname: Browman
mesh_terms: D000822:Animal Husbandry; D000818:Animals; D001835:Body Weight / Q000528:radiation effects*; D057231:Climate Change; D003165:Complement System Proteins / Q000378:metabolism; D006358:Hot Temperature; D007075:Immunoglobulin M / Q000378:metabolism; D009113:Muramidase / Q000097:blood; D020317:Salmo salar / Q000254:growth & development* / Q000276:immunology*; D014466:Ultraviolet Rays
chemical_list: D007075:Immunoglobulin M; D003165:Complement System Proteins; D009113:Muramidase