Community Structure of Macrobiota and Environmental Parameters in Shallow Water Hydrothermal Vents off Kueishan Island, Taiwan

Hydrothermal vents represent a unique habitat in the marine ecosystem characterized with high water temperature and toxic acidic chemistry. Vents are distributed at depths ranging from a few meters to several thousand meters. The biological communities of shallow-water vents have, however, been insufficiently studied in most biogeographic areas. We attempted to characterize the macrofauna and macroflora community inhabiting the shallow-water vents off Kueishan Island, Taiwan, to identify the main abiotic factors shaping the community structure and the species distribution. We determined that positively buoyant vent fluid exhibits a more pronounced negative impact to species on the surface water than on the bottom layer. Species richness increased with horizontal distance from the vent, and continuing for a distance of 2000 m, indicating that the vent fluid may exert a negative impact over several kilometers. The community structure off Kueishan Island displayed numerous transitions along the horizontal gradient, which were broadly congruent with changes in environmental conditions. Combination of variation in Ca2+, Cl-, temperature, pH and depth were revealed to show the strongest correlation with the change in benthic community structure, suggesting multiple factors of vent fluid were influencing the associated fauna. Only the vent crabs of Kueishan Island may have an obligated relationship with vents and inhabit the vent mouths because other fauna found nearby are opportunistic taxa that are more tolerant to acidic and toxic environments.

热液喷口（Hydrothermal vents）是海洋生态系统中一类独特的生境，其特征为水体温度极高、化学环境呈酸性且富含有毒物质。喷口的分布深度范围从数米至数千米不等。然而，在多数生物地理区域中，浅水热液喷口的生物群落尚未得到充分研究。本研究旨在表征中国台湾龟山岛附近浅水热液喷口栖息的大型动物群与大型植物群群落，以明确塑造该群落结构及物种分布的主要非生物因子。研究发现，具有正浮力的喷口流体对表层水体物种的负面影响较底层水体更为显著。物种丰富度随与喷口的水平距离增加而升高，且这一趋势延续至2000米距离处，表明喷口流体可能在数千米范围内产生负面影响。龟山岛附近的群落结构沿水平梯度呈现多次转变，这与环境条件的变化大体一致。分析显示，钙离子（Ca²+）、氯离子（Cl-）、温度、pH值与水深的综合变化，与底栖群落结构的变化相关性最强，表明喷口流体的多重因子对伴生动物群落产生了影响。仅龟山岛的喷口蟹类可能与热液喷口存在专性依存关系，并栖息于喷口口部；而附近发现的其他物种均为机会主义类群，对酸性有毒环境具有更高的耐受性。