Impacts of UV radiation on respiration, ammonia excretion, and survival of copepods with different feeding habits

Solar ultraviolet radiation (UVR) is known to harm aquatic organisms by damaging key molecules. Here, we showed that UV-A as well as UV-B affected differentially the respiration, ammonia excretion, and mortality of the copepods Pseudodiaptomus marinus (herbivorous) and Labidocera bipinnata (omnivorous). Adding UV-A (320–400 nm, 62.4 W m −2 ) to PAR (400–700 nm, 278 W m −2 ) decreased respiration by 10.2% in P. marinus and 46.1% in L. bipinnata , and additionally, the presence of UV-B (280–320 nm, 2.63 W m −2 ) further decreased it by 8.1 and 18.8%, respectively. The ammonia excretion of P. marinus was suppressed by 13.9% in 30 min exposures to PAR + UV-A compared with those receiving PAR only; however, in the presence of UV-B, it decreased by 13.8% compared to the control. In L. bipinnata , exposure to PAR decreased the ammonia excretion by 33.4%, while the presence of UV-B caused additional suppression by 15.8%. The mortalities of both copepod species increased with prolonged duration under all radiation treatments. More carotenoids and UV-absorbing compounds were found in P. marinus than in L. bipinnata , which could have been responsible for the higher resistance of the former to solar UVR.