Hopkins Marine Station Student Paper

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(full paper is archived in the Miller Library)

Title: Factors affecting changes in the community structure of the macrofauna of beach wrack
Student Author(s): Frantz, Robert K.
Faculty Advisor(s): Lee, Welton
Pages: 41
Location: Final Papers Biology 175H
Date: June 1972
Keywords: sandy beaches
Abstract: Wrack macrofauna on North Moss Beach, Monterey County, California, were studied in an attempt to determine if a faunal succession occurs in aging wrack. Samples of naturally occuring wrack and of wrack artifically placed on the beach were collected and studied. An attempt was made to establish the relative age of wrack by determining its moisture content, assuming that wrack loses moisture gradually and steadily as it ages. Hwever, wrack at different stages of decan can have same moisture content. Therefore, no definite conclusions could be made in regard to succession in naturally occuring wrack. Yet, it was found tha among wrack banks seemingly in the same general state of decay, great variation in species composition and species abundance may take place. This was also demonstrated in samples of artificial wrack over both short and long periods of time. The evidence suggests that typical terrestrial succession does not occur in wrack. Sporadic and sudden changes in species composition and species population sizes seem to be the rule. In an atttempt to explain more clearly how such changes in the community of wrack macrofauna may take place with time, an hypothesis has been formulated which takes into account the spatial and temporal variability in the state of beach wrack and the mechanism by which typical wrack fauna may respond relative to possible pre-adaptations to similar kinds of environmental situations.