. Bulletin. Science; Natural history; Natural history. 16 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES. TIME (days) Fig. 8. Mean densities of combined resident species per '4,4 m^ from sand (S) and wrack (W) sampling positions throughout the sampling period for each cohort. The pattern of succession described by this study for high beach wrack (subzone three) may be quite different for lower intertidal wrack since each subzone supports characteristic macroinvertebrates (Moore and Legner 1974b). Tidal submergence of wrack may prolong island life by adding moisture and perhaps replenishing nutrients
. Bulletin. Science; Natural history; Natural history. 16 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES. TIME (days) Fig. 8. Mean densities of combined resident species per '4,4 m^ from sand (S) and wrack (W) sampling positions throughout the sampling period for each cohort. The pattern of succession described by this study for high beach wrack (subzone three) may be quite different for lower intertidal wrack since each subzone supports characteristic macroinvertebrates (Moore and Legner 1974b). Tidal submergence of wrack may prolong island life by adding moisture and perhaps replenishing nutrients (, bacteria, surf plankton) needed for faunal growth and reproduction. However, it may push back the successional cycle by driving out several vulnerable wrack residents. Parenthetically, an island may be washed back out to sea, re- positioned on the beach, or further buried by sand following inundation. It is plausible that the original island deposition site is quite stable. Yaninek and Pitelka (1979) found some wrack islands remained in their originally deposited positions for up to 140 days, and Lavoie (1982) determined the location of reinundated islands to be relatively unaffected by rising tides. Undoubtedly, wave action and wind intersperses sand between the stipes of the kelps to establish an effective anchor for the entire island. Sun and wind dry out the wrack, reduce its suitability as a resource, and thereby stunt the successional cycle. The desiccation sequence, which followed moisture loss from the outside toward the wrack's interior, could largely account for in- creasing densities and diversities of sand positions towards later succession (Figs. 7 and 8). I suspect moisture is an essential requirement for a majority of the wrack constituents. The fact that the larger volume cohorts supported a progressively greater variety. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration
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