. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. EFFECTS OF LUNAR INCLINATION 109. 150 1930 1940 1950 1960 1970 1980 1990 2000 Year Figure 1. Variation in lunar orbual (A) and seasonal vanation m the average time for which mtertldal organisms are exposed to air (B) calculated for a 2' above MLLW at Pacfic Grove. Cahfonua. The hexes fn (A, enclose the data corresponding to the penods during the transect was censused Ist by Hewatt ,1931-1933 [23, 24, and agatn by Barry ., ''Vr^'ri 0177T36T2 trc Iculat (Walner E P Nautical Shareware. 32 Barney Hill
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. EFFECTS OF LUNAR INCLINATION 109. 150 1930 1940 1950 1960 1970 1980 1990 2000 Year Figure 1. Variation in lunar orbual (A) and seasonal vanation m the average time for which mtertldal organisms are exposed to air (B) calculated for a 2' above MLLW at Pacfic Grove. Cahfonua. The hexes fn (A, enclose the data corresponding to the penods during the transect was censused Ist by Hewatt ,1931-1933 [23, 24, and agatn by Barry ., ''Vr^'ri 0177T36T2 trc Iculat (Walner E P Nautical Shareware. 32 Barney Hill Wayland, Massachusetts 01778-3602) to calculate he tides' at Pacihc Grove for the period 1 Oct. 1924 through 30 Sep,. 2000. From these data we measured to the nearest minute, each penod that an organism would be exposed to air dunng daytime hours 0600- 1800 Pacific Standard Time), assuming that the organism was a, a known height on the sW ,- to 6 relative to MLLW). The average penod of exposure was then calculated for the winter , I Oct. to 31 Mar.) Ind summer months ,1 Apr. to 30 Sept., of each year. Winter of a particular year was assumed to extend from 1 Oct. of the previous year to 31 Mar. of the given year. which are sessile as adults and thus incapable of adjusting their spatial position to counter the whims of nature. Of particular importance is the average time of emergence— the time during which intertidal organisms are exposed to a desiccating atmosphere, extremes in temperature, hypo- osmotic stress during heavy rains, or other terrestrial in- sults. Time of aerial exposure is controlled primarily by two factors: the vertical level of the organism on the shore (a factor under biological control) and the fluctuation of the tides (a matter of physics). The level of the tides is governed by the action of gravitational attractions and centripetal accelerations act- ing on the water in the ocean, and may be modified by the topography of the local ocean basin, barometric
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