Characteristics of the population of the brown algae, Ecklonia cava and Eisenia bicyclis growing in different depths off Touji, Shimoda, Shizuoka prefecture, Japan

Serisawa, Y.; Murakami, H.; Tanaka, J.; Aoki, M.; Sakanishi, Y.; Hirata, T.; Misonou, T.; Yokohama, Y.

Characteristics of the population of the brown algae, Ecklonia cava and Eisenia bicyclis growing in different depths off Touji, Shimoda, Shizuoka prefecture, Japan

2003

Abstract: In April 2001, sporophytes of Ecklonia cava and Eisenia bicyclis (Laminariales, Phaeophyta) were collected from within two haphazardly-placed 1 square m quadrats at each depth of O, 2.5, 5, 10, 15, 20 and 23 m off Touji, Shimoda, Shizuoka Prefecture, Japan. The combined biomass of E. cava and E. bicyclis was 0.13-1.50 kg d.w./square m, maximal at 0-2.5 m depth and minimal at 23 m depth. Density of E. cava gradually increased with the depth from 20 ind./square m at 2.5 m depth to 49 ind./square m at 20 m depth. Conversely, the density of E. bicyclis decreased with the depth from 31 ind./square m at O m to 4 ind./square m at 2.5 m depth. E. cava and E. bicyclis co-occurred at 2.5 m depth. The mean values of stipe length and diameter of E. cava were minimal at 23 m depth (17.2 cm and 11.0 mm, respectively) and maximal at 2.5 m depth (91.5 cm and 23.2 mm, respectively). The mean values of primary blade length of E. cava ranged 22.0-29.1 cm irrespective of the depths. The mean values of stipe length, stipe diameter and arm length of E. bicyclis were 45.3 cm, 27.1 mm and 6.8 cm, respectively. Other seaweeds surrounding or within the marine forest were also surveyed at each depth. A total of 68 species were identified: 8 Chlorophyta, 26 Phaeophyta, and 34 Rhodophyta. The number of species was greater at >= 15 m depth.

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