Photosynthesis and respiration of seagrasses are mainly controlled by water temperature. In this study, the photosynthetic physiology and respiratory changes of the Asian surfgrass Phyllospadix japonicus, which is mainly distributed on the eastern and southern coasts of Korea, were investigated in response to changing water temperature (5, 10, 15, 20, 25, and 30°C) by conducting mesocosm experiments. Photosynthetic parameters (maximum photosynthetic rate, Pmax; compensation irradiance, Ic; and saturation irradiance, Ik) and respiration rate of surfgrass increased with rising water temperature, whereas photosynthetic efficiency (α) was fairly constant among the water temperature conditions. The Pmax and Ik dramatically decreased under the highest water temperature condition (30°C), whereas the Ic and respiration rate increased continuously with the increasing water temperature. Ratios of maximum photosynthetic rates to respiration rates (Pmax : R ) were highest at 5°C and declined markedly at higher temperatures with the lowest ratio at 30°C. The minimum requirement of Hsat (the daily period of irradiancesaturated photosynthesis) of P. japonicus was 2.5 hours at 5°C and 10.6 hours at 30°C for the positive carbon balance. Because longer Hsat was required for the positive carbon balance of P. japonicus under the increased water temperature, the rising water temperature should have negatively affected the growth, distribution, and survival of P. japonicus on the coast of Korea. Since the temperature in the temperate coastal waters is rising gradually due to global warming, the results of this study could provide insights into surfgrass responses to future severe sea warming and light attenuation.

본 연구는 우리나라의 대표적인 잘피 2종인 거머리말과 게바다말의 빛, 염분과 수온 조건에 따른 발아율을 조사하였다. 빛의 유무는 거머리말의 발아에는 영향을 주지 않았으나, 게바다말은 유광조건에서 발아율이 유의하게 높았다. 거머리말과 게바다말은 각각 0 psu와 15 psu에서 발아율이 가장 높았고, 두 종 모두 염분이 증가할수록 발아율이 급격히 낮아졌다. 최적 수온조건은 거머리말과 게바다말이 각각 5􀆆C와 15􀆆C로 나타났으며, 25℃에서는 현저히 낮았다. 이러한 거머리말과 게바다말의 최적 발아율의 차이는 두 종의 서식환경의 차이에서 기인하는 것으로 추측된다. 지금까지 우리나라 연안에 분포하는 잘피 종자의 발아에 대한 자료가 전무하므로, 이 결과는 잘피서식지 보전에도 중요한 정보를 제공할 것이다.