Effects of long-term kelp canopy exclusion on the abundance of the annual alga Desmarestia ligulata (Light F)
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- 作者：Edwards ; Matthew S.
- 关键词：Desmarestia ligulata ; Disturbance ; Kelp canopy exclusion ; Kelp forest ; Macrocystis pyrifera ; Pterygophora californica ; Recruitment ; Seaweed ; Storm ; Turf algae
- 刊名：Journal of Experimental Marine Biology and Ecology
- 出版年：1998
- 出版时间：October 15, 1998
- 年：1998
- 卷：228
- 期：2
- 页码：309-326
- 全文大小：483 K
文摘
Experiments in a central California Macrocystis pyrifera (L.) C.A. Agardh forest examined the effects of long-term (six year) kelp canopy exclusion on the abundance of the annual brown alga Desmarestia ligulata (Light F). Exclusion of both surface and subsurface kelp canopies from replicate clearings within Stillwater Cove, CA, USA showed that D. ligulata sporophyte recruitment is opportunistic, with more sporophytes occurring in areas where canopies were excluded than under control canopies. Kelp canopy exclusion also increased spring and summer bottom irradiances, and resulted in a steady increase of perennial turf algae over the six-year study. This, in turn, led to a decrease in the availability of nongeniculate coralline algae (the primary substratum on which D. ligulata recruits). Subsequently, the annual maximum abundance of D. ligulata sporophytes decreased in the canopy clearings, but did not change under control canopies. Removal of turf algae from experimental plots further increased bottom irradiances and significantly enhanced D. ligulata recruitment. When released from apparent competition for light and space, D. ligulata sporophytes exhibited an annual life history, with recruitment occurring during a two-week period (April 4–April 17) in the spring, and maximum bottom cover occurring in the summer (July). The onset of Desmarestia sporophyte recruitment was closely associated with seasonal increases in daylength and rapid decreases in ocean temperature. These results indicate that the Desmarestia sporophyte life history is both annual and opportunistic, with the onset of recruitment stimulated by predictable, seasonal changes in environmental conditions, and the magnitude of recruitment modified by stochastic processes that affect the availability of light and space. Comparison of these results with those from similar studies indicate that they are robust and suggest that they may be generalized over broad temporal and spatial scales.