Reproductive strategy of the intertidal seagrass Zostera japonica under different levels of disturbance and tidal inundation

• Published in: Estuarine, coastal and shelf science Vol. 197; pp. 185 - 193
• Main Authors: Suonan, Zhaxi, Kim, Seung Hyeon, Qin, Le-Zheng, Lee, Kun-Seop
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.10.2017
• Subjects: 128°35′E; 34°47′N; Clam harvesting; Intertidal zone; Koje Island; Korea; Reproductive strategy; Seagrass; South coast; Zostera japonica; Intertidal zone; Reproductive strategy; 128°35′E; Zostera japonica; Koje Island; South coast; 34°47′N; Seagrass; Clam harvesting; Korea
• ISSN: 0272-7714; 1096-0015
• DOI: 10.1016/j.ecss.2017.08.031

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. [Display omitted] •The impacts of clam harvesting and intertidal stresses on the reproductive strategy of Zostera japonica were investigated.•Zostera japonica populations displayed higher levels of sexual reproduction when disturbed by clamming activity.•Stresses associated with inundation enhanced the sexual reproduction of Z. japonica in the lower intertidal zone.•Enhanced sexual reproduction will improve resilience and persistence of Z. japonica populations under stressful conditions.