Seasonal Structure of a Central California Rocky Intertidal Community in Relation to Environmental Variations by Michael H. Horn. Steven N. Murray, and Roger R. Seapy, Bull. Southern California Acad. Sci., 82(2). 79-94, 1983. The overall abundance (% cover) of macrophyte populations from a central California rocky intertidal habitat near Piedras Blancas was greatest during summer and fall and least during winter. As with the macrophytes. total macroinvertebrate abundance (% cover and density) was lowest in winter. However, unlike the macrophyte pattern, macroinvertebrate abundance was highest in spring. Summer macrophyte standing stocks were characterized by increased abundances of the more delicate, rapidly growing and spatially unpredictable annual seaweeds. In contrast, the reduced winter macrophyte flora was dominated by populations of structurally tougher, slower growing and spatially predictable perennial species. High macrophyte standing stocks were associated with increased day length, reduced periods of aerial exposure due to daytime minus tides, low rainfall, and periods of infrequent storms. Conversely, low macrophyte standing stocks were associated with decreased day length, longer periods of aerial exposure, relatively high rainfall, and periods of frequent storms. The seasonal pattern of high summer fall and low winter macrophyte standing stocks parallels that recently described for southern California rocky intertidal communities. However, the less complex, more uniform, and predictable environment of the central California coast appears to lead to more consistent and sharply defined patterns of biotic seasonality.