Karati Kusum Komal, Vineetha G, Madhu N V, Anil P, Dayana M, Shihab B K, Muhsin A I, Riyas C, Raveendran T V
National Institute of Oceanography-CSIR, Dr. Salim Ali Road, Kochi, India.
Central Marine Fisheries Research Institute, Kochi, India.
Environ Monit Assess. 2017 Nov 29;189(12):653. doi: 10.1007/s10661-017-6369-5.
El Niño, an interannual climate event characterized by elevated oceanic temperature, is a prime threat for coral reef ecosystems worldwide, owing to their thermal threshold sensitivity. Phytoplankton plays a crucial role in the sustenance of reef trophodynamics. The cell size of the phytoplankton forms the "master morphological trait" with implications for growth, resource acquisition, and adaptability to nutrients. In the context of a strong El Niño prediction for 2015-2016, the present study was undertaken to evaluate the variations in the size-structured phytoplankton of Kavaratti reef waters, a major coral atoll along the southeast coast of India. The present study witnessed a remarkable change in the physicochemical environment of the reef water and massive coral bleaching with the progression of El Niño 2015-2016 from its peak to waning phase. The fluctuations observed in sea surface temperature, pH, and nutrient concentration of the reef water with the El Niño progression resulted in a remarkable shift in phytoplankton size structure, abundance, and community composition of the reef waters. Though low nutrient concentration of the waning phase resulted in lower phytoplankton biomass and abundance, the diazotroph Trichodesmium erythraeum predominated the reef waters, owing to its capability of the atmospheric nitrogen fixation and dissolved organic phosphate utilization.
厄尔尼诺现象是一种以海洋温度升高为特征的年际气候事件，由于其对热阈值的敏感性，它对全球珊瑚礁生态系统构成了主要威胁。浮游植物在珊瑚礁营养动力学的维持中起着至关重要的作用。浮游植物的细胞大小形成了“主要形态特征”，对生长、资源获取以及对营养物质的适应性具有影响。在对2015 - 2016年强厄尔尼诺现象的预测背景下，本研究旨在评估印度东南沿海主要珊瑚环礁卡瓦拉蒂礁水域中大小结构各异的浮游植物的变化情况。随着2015 - 2016年厄尔尼诺现象从高峰期到衰退期的发展，本研究见证了礁水理化环境的显著变化以及大规模的珊瑚白化现象。随着厄尔尼诺现象的发展，礁水的海面温度、pH值和营养物质浓度出现波动，导致礁水浮游植物的大小结构、丰度和群落组成发生了显著变化。尽管衰退期的低营养浓度导致浮游植物生物量和丰度较低，但由于其具有大气固氮和利用溶解有机磷的能力，固氮蓝藻红海束毛藻在礁水中占主导地位。
