| Changes in the rocky intertidal flora from 1950 to 2000 were studied at five Palos Verdes Peninsula sites (Los Angeles County, California). Of 74 conspicuous taxa, only 9 were found at all sites and 12 were warm-water species; 25 were classified as ephemeral and 49 as persistent members of the flora. Western-facing Peninsula sites were more diverse than southern-facing sites, averaging 44 versus 26 taxa. Cover averaged 69.8% for the five sites and was much greater for western-facing sites (109.3% versus 44.0%). Fleshy branched, turf-forming (FB-T), jointed calcareous (JC), and crustose (C) macrophytes accounted for 53.2% of the relative floral cover for the Peninsula; these groups made up 76.1% of floral cover at the southern-facing sites but only 39.7% at the western-facing sites. MDS and ANOSIM analyses, based on my data and results from earlier surveys, revealed significant differences in macrophyte community structures over the 50-year period. Increases in FB-T, JC, and C macrophytes have occurred on the Peninsula since the 1950s together with decreases in larger, fleshy algal species, including Silvetia compressa and several species of mid-sized, fleshy red algae. The red alga Caulacanthus ustulatus, possibly an introduced species, is recorded for the Peninsula for the first time. |
