Ultraviolet radiation and photosynthesis by Georgian Bay phytoplankton of varying nutrient and photoadaptive status
1997
Furgal, J A | Smith, REH
The photosynthesis-irradiance responses of phytoplankton from Georgian Bay (Laurentian Great Lakes) were measured in 1993 to determine the influence of ultraviolet-B (UV-B, 290-320 nm) radiation and the interacting effects of natural changes in nutrient status and photoadaptive state. Silicate concentrations and phosphorus availability (inferred from ³²P incorporation) varied widely but had little direct influence on photosynthetic performance. UV-B caused up to 80% loss of photosynthetic capacity in 1-day simulated surface exposures (artificial light) and up to 40% loss in half-day exposures (natural light), quantitatively consistent with reported responses of marine phytoplankton. The widely varying nutrient status and photoadaptive state (as inferred from photosynthetic light responses) of the phytoplankton had no significant influence on their sensitivity to UV-B radiation, and midsummer communities were as sensitive as spring or fall communities. To a first approximation, the impact of UV-B was proportional to the seasonal variation in surface UV-B irradiance being maximal near the summer solstice.
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