Hopkins Marine Station Student Paper

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Title: Spatial patterns between the Hewatt transect and adjacent intertidal areas
Student Author(s): Davy, Jessica
Faculty Advisor(s): Watanabe, James
Pages: 26
Location: Final Papers Biology 175H
Date: June 1999
Abstract: The Hewatt transect is a permanently marked area perpendicular to shore running through the protected rocky intertidal zone at Hopkins Marine Station. Species abundance data collected in 1933-37 and 1993-95 showed a significant difference for many species during the intervening years. In order to determine how representative the Hewatt transect is of the protected rocky intertidal zone at Hopkins, a 90 x 15 m area surrounding the Hewatt transect was compared to three adjacent areas of the same size. Three organisms were sampled in two or three 15-m transects within each of the four areas. Ten quadrats were counted in each transect. Additionally, the substrate rugosity for each area was measured. For Anthopleura sola, a solitary anemone, there were significant differences among areas (P=.02), but not among transects-within-areas (P=.16). For Serpulorbis squamigerus, a tube dwelling gastropod, there were no significant differences at either level (P=.15 and .15). For the alga Endocladia muricata, there were no significant differences among areas (P=.23), but highly significant differences among transects-within-areas (P<<.001). Substrate rugosity showed no significance between areas (P=.72). These data indicate that while there are some differences between the Hewatt area and adjacent areas, there is no evidence that the Hewatt area is non-representative of the HMS intertidal. While the intertidal zone is certainly not homogeneous, it is possible to conclude that the changes seen in the 60 year interval were due to significant species abundance change and not stochastic variation. Additionally, the environmental processes that caused these changes are likely to have influenced the distribution of organisms across the intertidal zone.