Bull kelp, Nereocystis luetkeana, abundance in Van Damme Bay, Mendocino County, California

Abstract

Size and density data were collected for Nereocystis luetkeana sporophytes from kelp beds in Van Damme Bay, Mendocino County during May, June and July 1990. Length and weight measurements were made on individual plants from representative size groups collected from depths of 6.1 m and 12.2 m. Mean sporophyte weight was 268 g (SD 393 g), while mean stipe length was 214 cm (SD 275 cm). Densities were determined separately for those plants which had reached the surface and for all plants within the water column. Sixty-five 12.7 m2 surface quadrats yielded mean surface densities of 2.2 (SD 1.5) and 2.7 plants/m2 (SD 1.3) in June and July, respectively. Individual plants were counted within 42 1x5 m plots along benthic transect lines yielding average densities of 2.7 (SD 4.5) and 5.2 plants/m2 (SD 3.0) in May and July, respectively. Combined density and size data from July 1990 and kelp bed area estimates from fall 1988 for Van Damme Bay yielded a biomass estimate of 640 metric tons distributed over 45.7 hectares. (15pp.)