The effect of solar ultraviolet radiation on marine planktonic ciliate survival and the penetration of ultraviolet irradiance on Georges Bank
Abstract
This study is the first to examine the penetration of UV radiation on Georges Bank, investigate the effect of both ultraviolet-B (UVB: 280–320 nm) and ultraviolet-A (UVA: 280–320 nm) on the survival of marine planktonic ciliates, and compare results between estuarine and off-shore populations. Planktonic ciliates play an important functional role in marine and freshwater ecosystems as grazers, nutrient regenerators, and a link between the microbial food-web and higher trophic levels. Global increases in UVB due to stratospheric ozone depletion may impact their survival. ^ Natural assemblages of microplankton on Georges Bank (Spring 1995, 1997) and the Pettaquamscutt Estuary (Summer, 1996) were exposed to ambient solar irradiance with and without UVB and with and without UV (280–380 nm) for two days. UVB (305 nm, 320 nm) and UVA (340 nm, 380 nm) exposure was measured. Water column UV irradiance on Georges Bank and the Pettaquamscutt Estuary was also measured. Wavelength specific diffuse attenuation coefficients (K dλ) were calculated for 305, nm, 320 nm, 340 nm, 380 nm, and PAR. ^ Ciliate abundance and chlorophyll concentration decreased in the presence of UVB and UVA. The greatest losses occurred due to UVB in April on Georges Bank, with a 657o decrease in mean ciliate abundance and a 52% decrease in mean chlorophyll. UVA caused decreases as great as 36% in ciliate abundance and a 32% in chlorophyll. A dose-response threshold appeared to occur between 600 and 800 Joules/m2 of 305 nm UVB. Results suggest that the effect of UVB on ciliate survival may be indirect as well as direct. ^ Kd305 averaged 1.04 m−1 (SD, ±0.14 m−1) on Georges Bank and varied little over space or time. UV attenuation was significantly higher on the Crest region compared to the Southern Flank of Georges Bank, possibly due to phytoplankton-derived DOM. Penetration of UVB relative to mixed depth suggests that ciliates may be impacted by environmental UV on Georges Bank. Kd305 in the Pettaquamscutt Estuary (12.59 m−1) was an order of magnitude greater than on Georges Bank, indicating that near-shore microplankton are exposed to less environmental UV than off-shore communities. ^
Subject Area
Biology, Oceanography|Biophysics, General
Recommended Citation
Elena Berneita Martin-Webb,
"The effect of solar ultraviolet radiation on marine planktonic ciliate survival and the penetration of ultraviolet irradiance on Georges Bank"
(1999).
Dissertations and Master's Theses (Campus Access).
Paper AAI9961436.
http://digitalcommons.uri.edu/dissertations/AAI9961436