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THE EFFECTS OF HIGH IRRADIANCE ON THE SETTLEMENT COMPETENCY AND VIABILITY OF KELP ZOOSPORES1
Article first published online: 29 FEB 2008
© 2008 Phycological Society of America
Journal of Phycology
Volume 44, Issue 2, pages 495–500, April 2008
How to Cite
Cie, D. K. and Edwards, M. S. (2008), THE EFFECTS OF HIGH IRRADIANCE ON THE SETTLEMENT COMPETENCY AND VIABILITY OF KELP ZOOSPORES. Journal of Phycology, 44: 495–500. doi: 10.1111/j.1529-8817.2008.00464.x
Received 14 March 2007. Accepted 26 June 2007.
- Issue published online: 29 FEB 2008
- Article first published online: 29 FEB 2008
Elevated irradiance has a profound effect on the successful dispersal and establishment of kelp zoospores, affecting their physiology and viability. The research to date, however, has been on zoospores localized near the benthos, with little attention on the importance of vertical transportation and subsequent exposure to increased irradiance. Therefore, we wanted to investigate the effects of exposure to high irradiance on the reproductive planktonic life-history stages of kelps Macrocystis pyrifera (L.) C. Agardh and Pterygophora californica Rupr. Zoospores of both species were exposed to different irradiances (75, 275, 575, 1,025 μmol photons · m−2 · s−1) over varying durations (1, 2, 4, 8, 12 h) and subsequently monitored for settlement competency, gametophyte development, and reproductive viability. Settlement success for M. pyrifera was uniform throughout all irradiance × time treatments, while settlement for P. californica decreased with increasing exposure time but not irradiance, although settlement was generally reduced at the highest irradiance level. Following zoospore settlement, germ tube development was visible in the gametophytes of both species within 1 week, although a significant decline of germ tube density in P. californica was observed with increasing irradiance. Similarly, a decrease in germ tube development with increasing exposure was observed across all irradiance levels for M. pyrifera, but irradiance itself was not significant. Further development into embryonic sporophytes was remarkably similar to gametophyte development, suggesting that the effect of exposure of kelp zoospores to high irradiance on subsequent sporophyte production is mediated through gametophyte development as well as zoospore survival.