Seasonal growth and reproductive dynamics of <i>Chondrus ocellatus</i> in relation to shore height in the <scp>Korean</scp> intertidal zone

SUMMARY We examined the seasonal growth and reproduction of the carrageenophyte Chondrus ocellatus in Hakampo, Korea (July 2014–April 2015), to understand its adaptation to environmental variability across the intertidal zone. Three hypotheses were tested: (1) growth is greater at the lower shore with reduced stress; (2) gametophytes dominate at the upper shore; and (3) the gametophytes: sporophytes (G:T) ratio varies with season and shore height. Biomass and frond weight were significantly higher at the lower shore than at the upper shore, with clear seasonal variation. Maximum biomass (1695.82 ± 492.84 g wet wt. m −2 , mean ± SE) occurred in July, and maximum mean frond weight (797.27 ± 67.97 mg) in October. In contrast, frond density did not differ significantly between seasons or shore heights. Gametophytes predominated at the upper shore, whereas tetrasporophytes were more abundant at the lower shore. Seasonal reproductive patterns were consistent, with tetrasporic and cystocarpic fronds peaking in October and reaching their lowest abundance in April. Tetrasporic fronds remained more abundant than cystocarpic fronds throughout the study period. The G:T ratio varied significantly with both season and shore height, ranging from 0.05 to 2.45. These findings indicate that intertidal environmental stress strongly affects the abundance and reproductive dynamics of Chondrus ocellatus , which shows a primary growth period from July to October and reproductive peaks in October and January.