Reproductive strategy of the intertidal seagrass <i>Zostera japonica</i> under different levels of disturbance and tidal inundation

Suonan, Zhaxi,Kim, Seung Hyeon,Qin, Le-Zheng,Lee, Kun-Seop Academic Press in association with the Estuarine a 2017 Estuarine, coastal and shelf science Vol.197 No.-

<P>Zostera japonica populations along the coastline of the northwestern Pacific Ocean are declining, mainly due to anthropogenic and natural disturbances. Although reproductive strategy is an important factor in achieving population persistence, changes in the reproductive strategy of Z. japonica under anthropogenic disturbances and tidal stresses are largely unknown. Thus, the duration and frequency of flowering, reproductive effort, potential seed production, and seed density in sediments were measured at three study stations (undisturbed upper, undisturbed lower, and disturbed stations), which were classified based on the levels of inundation stress and clamming activity, in monospecific meadows of Z. japonica on the southern coast of Korea. The flowering duration was approximately six months in the disturbed station, with disturbance due to clam harvesting, whereas the duration was about five months in the undisturbed lower station, and only three months in the undisturbed upper station. The maximum flowering frequency was 25.5% in the disturbed station, which was approximately 4- and 2-fold higher than in the undisturbed upper (6.1%) and lower (12.3%) stations, respectively. A similar trend in reproductive effort was also found among the three study stations. Potential seed production was 7850, 6220, and 1560 seeds m(-2) in the disturbed, undisturbed lower, and undisturbed upper stations, respectively. The annual maximum seed density in sediments was also higher in the disturbed and undisturbed lower stations than in the undisturbed upper station, but the densities were relatively low (ranging from 71 to 254 seeds m-2) at all three study stations. It was found that the allocation to sexual reproduction was highest in the disturbed station, followed by the undisturbed, lower station, and lowest in the undisturbed upper station, suggesting that sexual reproduction in Z. japonica tends to be enhanced under disturbed and inundated environmental conditions for population persistence. (C) 2017 Elsevier Ltd. All rights reserved.</P>

Heavy metal accumulation and phytoremediation potential by transplants of the seagrass <i>Zostera marina</i> in the polluted bay systems

Lee, Garam,Suonan, Zhaxi,Kim, Seung Hyeon,Hwang, Dong-Woon,Lee, Kun-Seop Elsevier 2019 Marine pollution bulletin Vol.149 No.-

<P><B>Abstract</B></P> <P>Although seagrasses can incorporate heavy metals from the marine environment, few studies have been conducted on heavy metal uptake and phytoremediation potential by seagrass transplants in the heavy metal contaminated sediments. <I>Zostera marina</I> shoots were transplanted in two polluted bay systems on Korean coasts to evaluate the heavy metal contaminations in sediments and the possibility of using <I>Z</I>. <I>marina</I> transplants as a bioindicator and phytoremediation agent. The major concentrated metals in sediments were As, Cu, Fe, and Pb in Jaran Bay, and Cd, Co, Zn, and Hg in Onsan Bay. The Co, Zn, Pb, and Hg concentrations in <I>Z</I>. <I>marina</I> tissues reflected the sediment heavy metal concentrations, and thus the tissue heavy metal concentrations may be used as bio-indicators of the metal contaminations. Since <I>Z</I>. <I>marina</I> transplants accumulated a great amount of heavy metals in their tissues, they may have the phytoremediation potential for the heavy metal contaminated sediments.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Heavy metal concentrations in <I>Zostera marina</I> tissues reflected the sediment heavy metal concentrations. </LI> <LI> Heavy metal content of eelgrass transplant can be used as a bio-indicator of heavy metal contamination in coastal sediments. </LI> <LI> <I>Zostera marina</I> transplants had the phytoremediation potential for heavy metal contaminated coastal sediments. </LI> </UL> </P>

Factors influencing the variability of blue carbon stocks in seagrass meadows on the coasts of the Korean peninsula

Seung Hyeon Kim,Zhaxi Suonan,Hyegwang Kim,Hwi-June Song,Kun-Seop Lee 한국해양환경·에너지학회 2021 한국해양환경공학회 학술대회논문집 Vol.2021 No.5

Since seagrass meadows rank among the Earth’s most productive aquatic ecosystems, they can sequester and store large amounts of organic carbon (C_org), which is termed as “Blue Carbon”. Thus, seagrass habitats that serve as carbon sinks could play a key role in mitigation and adaptation of climate change. Globally, there is considerable interest in quantifying the capacity of blue carbon storage in seagrass meadows, but the information on blue carbon stock and factors affecting its variability are still lacking. In the present study, we assessed the C_org stocks in 9 seagrass meadows on the coasts of Korea. Biological and environmental parameters in seagrass meadows were also measured to determine which factors could affect the variability of blue carbon stocks by the partial least square (PLS) regression analysis. C_org stocks in living seagrass biomass ranged from 0.39 to 1.98 Mg C ha^-1, which accounted for only 0.67-3.33% of total C_org stocks in seagrass meadows, whereas those in sediments extrapolating to top 1 m ranged from 49.10 to 124.83 Mg C ha^-1. According to our results of PLS model, 3 sediment characteristics such as dry bulk density and water and mud contents explained over 62% of the variation in sediment C_org contents of seagrass meadows in Korean coastal waters. This study will provide invaluable information with respect to the variability of blue carbon sink and storage capacity associated with biotic and abiotic factors in seagrass meadows.

Estimation of the potential blue carbon ecosystem services of the seagrass Zostera marina on the southern coast of Korea

Seung Hyeon Kim(김승현),Suonan Zhaxi,Le-Zheng Qin,Kun-Seop Lee(이근섭) 한국해양환경·에너지학회 2020 한국해양환경공학회 학술대회논문집 Vol.2020 No.7

수온 상승에 따른 게바다말의 광합성 및 호흡률 변화

김혜광,김종협,김승현,suonan zhaxi,이근섭 한국환경생물학회 2022 환경생물 : 환경생물학회지 Vol.40 No.3

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 irradiance saturated 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. 우리나라 동해와 남해 연안에 주로 분포하는 게바다말의 수온 상승에 따른 탄소수지 변화를 예측하기 위하여 5°C에서 30°C까지의 수온에서 5°C 간격으로 광합성과 호흡률을 측정하였다. 광합성 매개변수 중 광합성 효율 (α)을 제외한 최대광합성률 (Pmax)과 보상광도 (Ic), 포화광도(Ik)가 수온이 상승함에 따라 증가하였으며, 호흡률 (R) 또한 수온 상승에 따라 증가하였다. 가장 높은 수온 (30°C)에서 Pmax와 Ik는 급격히 감소하였으나, 반면에 Ic와 호흡률은 지속적으로 증가하였다. Pmax : R ratio는 가장 높은 수온(30°C)에서 최소값을, 가장 낮은 수온 (5°C)에서 최대값을 보였다. 이러한 결과를 토대로 게바다말이 양의 탄소수지를 유지하기 위해 필요한 일일 포화광도 시간 (Hsat)을 계산한 결과, 5°C에서는 2.50시간 이상, 30°C에서는 10.61시간 이상이 요구되어, 수온이 상승할수록 더 많은 시간의 포화광도 (Hsat)가 요구되는 것으로 나타났다. 따라서 수온이 꾸준히 상승되어 여름철 고수온이 장기간 지속되면 우리 연안 게바다말 생육지의 분포에 부정적인 영향을 미칠 것으로 판단되었다.