고수온 장기지속이 거머리말의 생장과 생육밀도에 미치는 영향

Abstract

Seagrasses are highly productive marine flowering plants that provide various ecosystem services in coastal and estuarine areas. However, significant declines in seagrass habitats have been reported worldwide. Rapid reductions in growth and biomass of temperate seagrasses have been observed during high water temperatures period in summer. Mass die-offs of seagrasses were occasionally observed after high water temperature periods in temperate regions. Thus, water temperature rise and a prolonged summer period due to global climate change should be considered an unfavorable environmental condition that can induce the significant decline of temperate seagrasses. To examine the effects of the prolonged high water temperature periods on the Z. marina growth, Z. marina growth was monitored under manipulated light and temperature conditions in a controlled environmental room. I hypothesized that seasonal growth pattern of Z. marina can be modified by the manipulation of high water temperature periods and underwater irradiance levels. Cores of eelgrass plants collected from the monotypic Z.marina bed in Koje Bay were cultured under two water temperature (20°C and 27°C) and light (150 and 400 μmol photon m-2s-1) conditions for 6 – 8 weeks. Eelgrass shoot density, biomass and leaf productivities exhibited significant difference in the two temperature treatments. Eelgrass shoot density and growth significantly decreased by the prolonged high water temperature period, and increased by the shortened high water temperature period. Shoot density and leaf productivity increased by 70.9% and 15.1%, respectively as a result of the shortened high water temperature period, but decreased by 51.2% and 62.3%, respectively, due to the prolonged high water temperature period. Shoot density and leaf productivity increased under high light treatment in the optimal temperature (20°C) condition. However, light treatments did not significantly affect shoot density and productivity in the high temperature (27°C) condition. Zostera marina leaf tissues exhibited various symptoms of heat stress such as blacken leaf tissues and meristem degradation by the high water temperature treatment. The results of this study will provide valuable information for better understanding of the effects of water temperatures rise due to global warming on temperate seagrasses ecosystems.