Seasonal Changes in the Abundance of Ulva Mats on a Rocky Intertidal Zone of the Southern Coast of Korea

Algae > Volume 16(3); 2001 > Article

Algae 2001;16(3): 337-341.

Tae Seob Choi, Jeong Ha Kim, Kwang Young Kim

ABSTRACT

Seasonal dynamics in surface percent cover and dry weight biomass were determined for Ulva mats (mainly Ulva pertusa Kjellman) on the rocky intertidal zone of the southern coast of Korea.
Method
including monitoring of permanent intact quadrats using photography and a modified point-contact quadrat technique, and harvesting adjacent quadrats, were employed to sample Ulva mats at approximately every two weeks intervals for fifteen months. Surface percent cover of Ulva mats showed relatively constant during the study period, excluding the summer months when surface cover decreased to 13%. After the summer, there was a gradual increase and subsequent recovery of Ulva mats during the cold months. Biomass of Ulva mats showed a clear seasonal trend during the study period. Maximum biomass was recorded in May (ca. 720 g dry weight?m-2), which corresponded to a maximum surface percent cover (ca. 95-100%). The biomass decreased to ca. 17 g dry weight?m-2 in August. During the rest of the year the biomass of Ulva mats remained between ca. 20 and ca.182 g dry weight?m-2. These field observations indicate that Ulva mats exhibit a monomodal pattern of seasonal growth with peak biomass occurring in spring. Water temperature was identified as the environmental variable contributing most significantly to the seasonal variation in abundance of Ulva mats. Abundance of Ulva was also correlated with rainfall events. In summer daylight exposure resulted in a considerable loss of plant biomass through desiccation.

Key words: dry weight biomass, monomodal pattern, rainfall, surface percent cover, temperature, Ulva mats