The effect of irradiance on the short-term growth rates of two strains of Griffithsia pacifica Kylin
Madden, Matilda L.
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The growth of the warm-water, Mexican strain of the giant-celled marine red alga Griffithsia pacifica Kylin has been studied in great detail. However, a comparison of the growth rates of this strain to the local strains located in Friday Harbor, Washington has not been conducted. This study compared the short-term growth rates of the two strains of Griffithsia under varying light intensities. Stock cultures from the Botany Department at the University of Washington, Seattle and wild samples collected from the dock at Friday Harbor Laboratories in Friday Harbor, Washington were examined. Wild samples were collected from coordinates at N 48° 32.723’ W 123° 00.729’. Prior to cell excision, wild samples were cleaned using sterile razor blades and agar to remove epiphytes and contaminants. All cells were excised and grown in f/2 media for 6 days under LED lights at three intensities: 25, 16 and 8 μmol/m2/s. Morphological difference between stock and wild cultures were observed. Half the stock culture subjects and one third the wild culture subjects died. However, others experienced growth, with the lowest light intensity cultures having a higher growth rate than the higher intensities. The low light stock (8 μmol/m2/s) cultures had significantly higher growth rates than both the low light wild and ambient light (25 μmol/m2/s) stock. The increased growth rate is likely a result of the stock cultures being acclimated to irradiances between 5-10 μmol/m2/s. Future studies of longer time periods and with varying light intensities and temperatures are proposed to further investigate perceived differences.