Steiner S C C, Macfarlane K J, Price L M, Willette D A
Institute for Tropical Marine Ecology Inc. (ITME), P.O. Box 944, Roseau, Commonwealth of Dominica.
Rev Biol Trop. 2010 Oct;58 Suppl 3:89-98.
Seagrass beds are the largest organism-built marine habitat in Dominica, yet have only been surveyed since 2007. Standardized examinations along a depth gradient between 0 and 24 m, focusing on magnoliophyte species composition and benthic cover of shoots at 17 seagrass bed sites, were carried out between September 10 and December 7, 2008. The Cymodoceaceae Syringodium filiforme (Kuetzing 1860) and Halodule wrightii (Ascherson 1868), as well as the Hydrocharitaceae Halophila decipiens (Ostenfeld 1902), H. stipulacea (Fosskal & Ascherson 1867) and Thalassia testudinum (Banks ex König 1805) displayed distinct regional and horizontal distribution patterns. Syringodium filiforme is the island's dominant seagrass along the western and northern coasts, occurring at depths between 2 and 18 m and with a mean benthic cover ranging from 0.9-10% along the West coast. Along the North coast it grew between 0.2 and 1 m depth with a mean maximum benthic cover of 48.9%. Halodule wrightii grew along the North and West coasts, in depths between 1 and 14m in areas of recent and chronic disturbances. Its delicate morphology and sparse benthic cover (< 0.1%) did not constitute seagrass beds. Halophila decipiens grew along the deep, shallow and lateral margins of west coast S. filiforme beds and monospecifically in depths between 3 and 24m. Halophila stipulacea, an invasive species, was widespread along 45km of the West coast and was found in depths between 5 and 24m. Both Halophila species formed extensive beds at depths beyond the survey limit of 24m thus playing a potentially important role in the resettlement of shallow areas after storms. H. decipiens and H. stipulacea are currently the second and third most common seagrasses on the island respectively, despite their absence along the North coast. T. testudinum was confined to North coast's sheltered reef flats at depths Im or less with mean a benthic cover ranging from 2 to 76%. It grew monospecifically in the most turbulent and in the calmest locations, yet intermixed with S. filiforme in areas of moderate turbulence. Strong surge along the West coast (October 15-16, 2008), associated with Hurricane Omar, caused uprooting and burial of seagrass beds in varying degrees, in particular along the shallow margins between 2 and 10m depth. This event also demonstrated the dynamic nature of Dominica's shallow seagrass bed margins and the resistance level of individual beds to storm disturbances.
海草床是多米尼克最大的生物构建海洋栖息地，但自2007年以来才开始进行调查。2008年9月10日至12月7日，在17个海草床地点进行了标准化检查，检查范围为0至24米的深度梯度，重点关注显花植物物种组成和海草茎的底栖覆盖率。丝粉藻科的丝状针叶藻（库岑，1860年）和莱氏二药藻（阿舍尔森，1868年），以及水鳖科的隐匿喜盐草（奥斯坦费尔德，1902年）、具茎喜盐草（福斯卡尔和阿舍尔森，1867年）和泰来草（班克斯 ex 柯尼希，1805年）呈现出明显的区域和水平分布模式。丝状针叶藻是该岛西部和北部海岸的优势海草，生长在2至18米的深度，西海岸的平均底栖覆盖率为0.9 - 10%。在北海岸，它生长在0.2至1米的深度，平均最大底栖覆盖率为48.9%。莱氏二药藻生长在北部和西部海岸，在近期和长期受到干扰的区域，生长深度为1至14米。其纤细的形态和稀疏的底栖覆盖率（< 0.1%）并未形成海草床。隐匿喜盐草生长在西海岸丝状针叶藻床的深、浅边缘和侧面，也单生在3至24米的深度。具茎喜盐草是一种入侵物种，在西海岸45公里的区域广泛分布，生长深度为5至24米。这两种喜盐草在24米的调查深度极限之外形成了广泛的草床，因此在风暴后浅水区的重新定居中可能发挥重要作用。尽管北海岸没有，但隐匿喜盐草和具茎喜盐草目前分别是该岛第二和第三常见的海草。泰来草局限于北海岸受庇护的礁坪，生长深度在1米或以下，平均底栖覆盖率为2至76%。它在最动荡和最平静的地点单生，但在中等动荡的区域与丝状针叶藻混生。2008年10月15日至16日，与奥马尔飓风相关的强烈涌浪导致西海岸不同程度的海草床被连根拔起和掩埋，特别是在2至10米深度的浅边缘区域。这一事件也证明了多米尼克浅海草床边缘的动态性质以及各个草床对风暴干扰的抵抗水平。
