Abstract
UVB alters photosynthetic rate, fatty acid profiles and morphological characteristics of phytoplankton. Copepods, important grazers of primary production, select algal cells based upon their size, morphological traits, nutritional status, and motility. We investigated the grazing rates of the copepod Calanus finmarchicus on the diatom Thalassiosira weissflogii cultured under 3 levels of ultraviolet radiation (UVR): photosynthetically active radiation (PAR) only (4 kJ-m−2/day), and PAR supplemented with UVR radiation at two intensities (24 kJ-m−2/day and 48 kJ-m−2/day). There was no significant difference in grazing rates between the PAR only treatment and the lower UVR treatment. However, grazing rates were significantly (∼66%) higher for copepods feeding on cells treated with the higher level of UVR. These results suggest that a short-term increase in UVR exposure results in a significant increase in the grazing rate of copepods and, thereby, potentially alters the flow rate of organic matter through this component of the ecosystem.
Highlights
Reduction in stratospheric ozone is linked to increases in ultraviolet radiation (280–400 nm), e.g. [1,2], and damaging UVB (280–320 nm) levels
Grazing rates of copepods feeding on laboratory-reared algae are used to estimate egg production, trophic transfer rates and to parameterize models of food web structure
Most of our laboratory-based knowledge of the grazing rates of copepods is based on algae cultured under photosynthetically active radiation (PAR), devoid of any ultraviolet radiation (UVR)
Summary
Reduction in stratospheric ozone is linked to increases in ultraviolet radiation (280–400 nm), e.g. [1,2], and damaging UVB (280–320 nm) levels. Reduction in stratospheric ozone is linked to increases in ultraviolet radiation (280–400 nm), e.g. [1,2], and damaging UVB (280–320 nm) levels. Extended daily exposures, superimposed upon increases related to ozone depletion, likely induce UVB damage to susceptible aquatic organisms. Ultraviolet radiation, even at its current level, is harmful to aquatic organisms and reduces the net productivity of many marine ecosystems UVB can have a range of inhibitory effects on algae (see [10]), including changes in morphology and nutrient uptake [11,12], damage to DNA and to light transduction and carbon assimilation mechanisms [13,14,15], as well as alterations in fatty acid composition and other nutritional components of cells [16,17]
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