Effects of Water Motion on Propagule Release from Algae with Complex Life Histories

Gordon, R.; Brawley, S.

'This study demonstrates that water motion has strong effects upon algal reproduction, but Communicated by J.P. Grassle, New Brunswick R. Gordon' S. H. Brawley ([g]) School of Marine Sciences, University of Maine, Orono, ME, 04469-5722, USA E-mail: Brawley@maine.edu Fax: + 1-207-5812969 Present address: R. Gordon Saigene Corporation, 220 W. Harrison St., Seattle, WA 98119, USA that the effects may vary between species, possibly due to their different life histories.' 'Reproductive marine algae with complex life histories may respond differently to water motion depending upon whether the spore-producing or gamete-producing phase is considered. Two such species, the kelp Alaria esulenta (L.) Greville (Phaeophycaea) and Ulva lactuca L. (Chlorophyta), were examined experimentally in the laboratory. The Kelp was collected in April-June 2000 and U Lactuca was collected in July-August 2000, from four intertidal habitats at Schoodic Point, Maine, USA. Orbital shakers were used to generate water motion. Sporophylls of A. esculenta released more zoospores under shaken versus calm conditions, whereas fewer antheridia on the microscopic male gameophytes released sperm under shaken versus calm conditions when male and female gameophytes were placed together. However, antheridial sperm release was equivalent when male gameophytes were exposed to undiluted media from dense cultures of mature female gameophytes under shaken versus calm conditions. These data suggest that water motion inhibited sperm release by diluting the sperm-releasing pheromone produced by ripe eggs below a threshold required to cause sperm release. Water motion stimulated both gamete and zoospore release from U. lactuca. This is the first report in an alga of stimulation of gamete release by increased water motion, but it is notable that parthenogenesis occurs in Ulva spp.; thus, gametes may develop into gametophytes (1 N) or parthenosporophytes (2 N). This study demonstrates that water motion has strong effects upon algal reproduction, but that the effects may vary between species, possibly due to their different life histories.' /STUDY LOCATIONS:/ /ACADIA NATIONAL PARK/SCHOODIC POINT/

Effects of Water Motion on Propagule Release from Algae with Complex Life Histories

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