. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 378 D. PENN AND H. J. Tide time (hrs) Figure 2. The time of maximum horseshoe crab spawning compared with the time of maximum high tide at (a) Seahorse Key. Florida (1989) and (b) Cape Henlopen, Delaware (1991). The bars indicate the mean number of nesting couples over three days and the points indicate the mean tidal distance recorded during three Hood tides. "Tide time" in- dicates the hours before (-) and after ( + ) the maximum high tide (adapted from Burger el ill., 1977). Tidal synchrony was signi
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 378 D. PENN AND H. J. Tide time (hrs) Figure 2. The time of maximum horseshoe crab spawning compared with the time of maximum high tide at (a) Seahorse Key. Florida (1989) and (b) Cape Henlopen, Delaware (1991). The bars indicate the mean number of nesting couples over three days and the points indicate the mean tidal distance recorded during three Hood tides. "Tide time" in- dicates the hours before (-) and after ( + ) the maximum high tide (adapted from Burger el ill., 1977). Tidal synchrony was significantly different between the two populations (X: = 945. df = 4. P < ). intercorrelated with each other (Table III). A stepwise regression analysis found that [O2] was the variable that best predicted the developmental index in FL (r = , F,,22 = , P = ), whereas the best predictor of in DE was %H:O (r2 = , , = P = ). The [O:] in the sediment samples (sediment analysis) increased significantly with beach distance (r2 = , Fi,22 = 18, P = ) in FL. Sand color below the surface was lighter at higher beach distances (ANOVA, F, ,5K = 143, P = ) and was black or grey from 0 to 3 m. indicating anaerobic conditions (Eagle, 1983). Develop- mental rate () of eggs in the incubator increased sig- nificantly with beach distance (r2 = , F\ j4 = , P = ) and eggs that had been buried in the lower beach (below 3 m) never hatched. Unlike FL. the sedi- ments beneath the surface in DE were rarely grey or black, and most eggs in the lower beach showed some signs of development. Egg din' to erosion In FL sand »is eroded from the lower part of the beach and deposited ai higher beach distances (Fig. 5). However, in the artificial experiment, bead loss occurred only at the highest beach distance (ANCOVA, F,.28 = P = ). No significant associations were found between bead loss (P = ) or final bead depth
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