Graduate Thesis Or Dissertation
 

Exposure to ultraviolet-B radiation : sensitivity evaluation of an important ecological parameter of the marine copepod Acartia clausi

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/kh04dt02r

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  • The ozone present in the atmosphere filters incident solar ultraviolet (UV) radiation such that only the longer wavelengths of the total UV spectrum emitted by the sun reach the earth's surface. Atmospheric increases in nitrogen oxides and chlorofluoromethanes represent a threat to the existence of this protective screen. As the ozone concentration is decreased, there will be a concomitant increase in the mid-wavelength (UV-B) ultraviolet radiation penetrating the atmosphere. The UV-B waveband (286-320 nm) is detrimental to most biological systems. Acartia clausi was observed to be the most common zooplanktonic organism encountered in Yaquina and Netarts Bays, Oregon. It is an herbivorous, calanoid copepod important in coastal and estuarine zooplankton communities throughout the northern hemisphere. Determination of the sensitivity of A. clausi to UV-B radiation was the focus of this investigation. Organisms collected from Yaquiha Bay were maintained in laboratory cultures. Life stages were subjected to varying degrees of UV-B radiation. Irradiation took place on a rotating turntable beneath equal numbers of FS40 sunlamps and "deluxe white" fluorescent lamps. UV-B and visible fluence rates were determined with a Gamma Scientific 2900 SR Spectroradiometer System. Prior to irradiation copepods were randomly assigned to treatments (dosages) utilizing a randomized complete block design. Analysis of variance indicated lack of significant difference between replications permitting their combination and a more accurate estimate of surviving fractions. Least squares regression analysis was performed between surviving fraction and total dose for all treatments administered to each age group, and between the offspring/ survivor ratio and total dose for treatments administered to the oldest age group composed of equal numbers of males and females. Survival was not consistent throughout the age groups, the younger organisms being the more sensitive. Approximate weighting values determined from analytical representations of two generalized action spectra permitted calculation of biologically effective surface irradiances for both laboratory and natural conditions. The effective (i.e., weighted) irradiances could then be compared between these conditions. Results indicate possible sensitivity of some age groups to present levels of UV-B, suggesting it as an important environmental parameter limiting natural populations. Reproductive capability of the surviving organism was also negatively affected.
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