PATTERNS OF RECRUITMENT AND DISTRIBUTION OF ULVA AND ENTEROMORPHA POPULATIONS IN A KOREAN INTERTIDAL SHORE

Abstract

Patterns of recruitment and abundance of Ulva pertusa and Enteromorpha linza in the three locations on the south coast of Korea where green tide frequently occurred were investigated with respect to the substrate profile, temporal and spatial variations, and their persistence. Artificial substrates (10 to 20 cm) were made of a mixture of a piece of granite rock and cement on ceramic tiles. These setting plates, representing different surface texture, were placed horizontally and vertically along the rocky shoreline, and replaced every 1 to 2 months. Both populations showed highly seasonal blooms, with peaks in October, 1998 to February, 1999 and another slight peak was observed in the fall of 1999 only for Ulva. However, the winter peak of 1998 did not appeared in the following year, indicating that a significant year‐to‐year variation existed. Regarding their settlement onto artificial plates with different roughness, Ulva preferred to settle on the rough surface both in the upper and lower intertidal zone; however, this pattern only appeared in the upper zone for Enteromorpha. Vertical distribution of the two populations was well separated; Enteromorpha was more abundant in the upper zone and Ulva in the lower zone. Their seasonal blooms were concomitant with ammonia levels, but occurrence was not well correlated with nitrate and phosphate. The ability of the populations to persist, once blooms occurred, was also distinct; Ulva persisted ca. twice as long as Enteromorpha, having a greater impact in the presence of green tide in this geographical area.