Kappaphycus alvarezii, a red seaweed cultured in tropical waters for extraction of carrageenan, is widely considered a bioinvader of coral reefs. In India, this seaweed is cultivated in Palk Bay, South India by the coastal community amidst the concern of its invasion in the sub-tidal reef regions of adjoining Gulf of Mannar Marine National Park (GoMMNP). The current study was undertaken to assess the extent of coral reefs in Pak Bay and Gulf of Mannar (GoM) affected by this red alga and evaluate the possible causes for its spread in GoM including the long-term commercial seaweed cultivation in Palk Bay. The study was carried out in Palk Bay and 19 emergent and two submerged Islands of GoM. Landsat 7 Enhanced Thematic Mapper Plus (ETM+) satellite images were used to map the spatial cover of the alga over the reef. The reef zones with K. alvarezii were mapped using GIS. The study showed that K. alvarezii has not spread over the coral reefs in Palk Bay, a region where the cultivation is underway for over ten years. Nevertheless, the algae had spread in some of the islands in Gulf of Mannar region viz., Shingle (1.1 ha; 2.12% of reef area), Krusadai (0.572 ha; 0.35% of reef area) and Mulli Islands (0.00025 ha; 0.00022% of reef area). The temporal change in the extent of live corals (between 2002 and 2014) in Palk Bay and GoM corroborated a possible phase shift i.e., from a coral dominated reef to an algal dominated reef, with Halimeda spp., Caulerpa spp. and Ulva reticulata being the dominant macro-algae. Based on a critical analysis of the sources of fragments for the spread of the alga in GoM and the factors that aid in their dispersion, we conclude that K. alvarezii farming activities in Palk Bay are not the primary source for the broken fragments, responsible for the spread of the alga in GoM. However, considering the potential risks of unintended transfer of farmed algae into the sensitive ecosystems, the study calls for evolving codes for cultivation of seaweeds so as to leave least ecological footprints over the coastal ecologically sensitive ecosystems like coral reefs.

Kappaphycus alvarezii，一种在热带水域养殖以提取角叉菜胶的红海藻，被广泛认为是珊瑚礁的生物入侵者。在印度，这种海藻是由沿海社区在印度南部的帕克湾（Palk Bay）种植的，人们担心它会入侵毗邻马纳尔湾国家海洋公园（GoMMNP）的潮下珊瑚礁地区。当前的研究是为了评估受该红藻影响的白湾和马纳那湾（GoM）的珊瑚礁范围，并评估其在GoM中传播的可能原因，包括在Palk Bay进行长期商业性海藻养殖。这项研究是在帕克湾，19个紧急事件和两个GoM淹没岛屿中进行的。Landsat 7增强型专题制图仪增强版（ETM +）卫星图像用于在珊瑚礁上绘制藻类的空间覆盖图。珊瑚礁带K. alvarezii是使用GIS绘制的。这项研究表明，阿尔瓦雷克斯氏菌尚未扩散到帕克湾（Palk Bay）的珊瑚礁上。帕克湾（Palk Bay）的种植已有十多年的历史了。尽管如此，藻类仍在Mannar海湾地区的一些岛屿中扩散，即碎裂（1.1公顷;礁石面积的2.12％），Krusadai（0.572公顷;礁石面积的0.35％）和穆利群岛（0.00025公顷; 0.00022）礁石面积的百分比）。Palk Bay和GoM中活珊瑚范围的时间变化（2002年至2014年之间）证实了可能的相移，即从Halimeda物种，Caulerpa物种从珊瑚为主的礁石到藻类为主的礁石。和网Ul是占主导地位的大型藻类。根据对藻类在GoM中传播的碎片来源的关键分析以及有助于藻类扩散的因素的分析，我们得出结论，在Palk湾中的K. alvarezii养殖活动不是破碎碎片的主要来源，而是藻类在GoM中的传播。但是，考虑到养殖藻类意外转移到敏感生态系统中的潜在风险，该研究呼吁制定不断发展的海藻守则，以便在沿海生态敏感生态系统（如珊瑚礁）上留下最少的生态足迹。