Manikandan Balakrishnan, Ravindran Jeyaraman, Vidya Pottekkatt Jayabalan, Shrinivasu Selvaraju, Manimurali Rajagopal, Paramasivam Kaliyaperumal
CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India.
Marine Biology Regional Centre, Zoological Survey of India, Chennai, 600028, India.
Environ Sci Pollut Res Int. 2017 May;24(15):13614-13625. doi: 10.1007/s11356-017-8772-4. Epub 2017 Apr 9.
Coral reefs are degraded by the synergistic action of climate and anthropogenic stressors. Coral cover in the Palk Bay reef at the northern Indian Ocean largely declined in the past decade due to frequent bleaching events, tsunami and increased fishing activities. In this study, we carried out a comparative assessment to assess the differences in the recovery and resilience of three spatially distant reefs viz. Vedhalai, Mandapam and Pamban along Palk Bay affected by moderate, severe and low fishing pressure respectively. The assessment was based on the juvenile coral recruitment pattern and its survivability combined with availability of hard substratum, live coral cover and herbivore reef fish stock. The Vedhalai reef has the highest coral cover (14.6 ± 6.3%), and ≥90% of the live corals in Vedhalai and Mandapam were affected by turf algal overgrowth. The density of herbivore reef fish was low in Vedhalai and Mandapam reefs compared to the Pamban reef with relatively few grazing species. The juvenile coral diversity and density were high in the Pamban reef and low in Vedhalai and Mandapam reefs despite high hard substratum cover. In total, 22 species of juvenile corals of 10 genera were recorded in Palk Bay. Comparison of the species diversity of juvenile corals with adult ones suggested that the Pamban reef is connected with other distant reefs whereas Vedhalai and Mandapam reefs were self-seeded. There was no statistically significant difference in the survivability of juvenile corals between the study sites, and in total, ≥90% of the juvenile corals survived the high sedimentation stress triggered by the northeast monsoon and bleaching stress that occurred recurrently. Our results indicated that the human activities indirectly affected the juvenile coral recruitment by degrading the live coral cover and contributed to the spatial variation in the recovery and resilience of the Palk Bay reef. Low species diversity of the juvenile corals will increase the vulnerability of the Palk Bay reef to species-specific endemic threats.
珊瑚礁因气候和人为压力源的协同作用而退化。由于频繁的白化事件、海啸和捕鱼活动增加,印度洋北部保克湾珊瑚礁的珊瑚覆盖率在过去十年中大幅下降。在本研究中,我们进行了一项比较评估,以评估受中等、严重和低捕鱼压力影响的保克湾沿岸三个空间距离较远的珊瑚礁,即韦德哈莱、曼达帕姆和潘班的恢复能力和恢复力差异。该评估基于幼体珊瑚的补充模式及其生存能力,同时结合硬底质的可用性、活珊瑚覆盖率和食草性礁鱼种群数量。韦德哈莱珊瑚礁的珊瑚覆盖率最高(14.6±6.3%),韦德哈莱和曼达帕姆90%以上的活珊瑚受到草皮藻过度生长的影响。与潘班珊瑚礁相比,韦德哈莱和曼达帕姆珊瑚礁的食草性礁鱼密度较低,且放牧物种相对较少。尽管硬底质覆盖率较高,但潘班珊瑚礁的幼体珊瑚多样性和密度较高,而韦德哈莱和曼达帕姆珊瑚礁的则较低。在保克湾共记录到10属22种幼体珊瑚。幼体珊瑚与成体珊瑚的物种多样性比较表明,潘班珊瑚礁与其他遥远的珊瑚礁相连,而韦德哈莱和曼达帕姆珊瑚礁是自我繁殖的。研究地点之间幼体珊瑚的生存能力没有统计学上的显著差异,总体而言,≥90%的幼体珊瑚在东北季风引发的高沉积压力和反复发生的白化压力下存活下来。我们的结果表明,人类活动通过破坏活珊瑚覆盖率间接影响幼体珊瑚的补充,并导致了保克湾珊瑚礁恢复能力和恢复力的空间差异。幼体珊瑚的低物种多样性将增加保克湾珊瑚礁对特定物种特有威胁的脆弱性。