Geological and hydrothermal controls on the distribution of megafauna in Ashes Vent Field, Juan de Fuca Ridge
Geological and hydrothermal controls on the distribution of megafauna in Ashes Vent Field, Juan de Fuca Ridge
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胡安德富卡山脊灰烬通风场巨型动物分布的地质和热液控制
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发表时间：
1990
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通讯作者：
Anne Arquit
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作者：
Anne Arquit
建立了一个计算机化数据库，以帮助解释1985-1986年期间使用双鱼座四号潜水器和拖曳照相机系统拍摄的灰烬喷口区（位于胡安·德富卡海岭中轴火山山顶破火山口西南壁沿着）的7662张照片中记录的生物和地质观测结果。火山灰喷口区高温喷口位置与火山灰喷口位置之间的过渡区（即，地狱，326°C;地狱，301°C;和Virgin Mound，298°C），并在沉积物类型和生物组合方面对Axial火山顶破火山口的环境条件进行了空间分带。在热液喷口区划分出三个一般的生态区：（1）中央热液喷口区（高温喷口100 m范围内），以喷口相关生物为主（vestimentiferan管蠕虫，蛤，细菌垫）和沉降（高温、羽流衍生和低温、原地沉积）;（2）远端通气区（距离任何高温喷口100-725米），特点是广泛的氧化铁、硅酸铁和二氧化硅烟囱和沉积物（绿脱石组合材料），以及大多数非喷口动物的最大密度;和（3）非喷口影响区（725-1300米），由非喷口生物相对于区域（即，破火山口范围）的值和最大Bathydorus sp.海绵密度。vestimentiferan管蠕虫的分布仅限于90米的已知高温通风（中央通风区）;海葵只观察到30和40米之间的热喷口。蛤和微生物席也集中在中央喷口区，但在距离热喷口1 250米处零星出现，与热液绿脱石有关，绿脱石可能是从低于60摄氏度的喷口流体就地沉淀下来的;因此，巨型动物的分布是海底不明确的、往往是扩散的低温热液活动的有用指标。无孔棘皮动物的最大密度（即，海参、海星、海胆）与远端排气区有关。非喷口环境特有的巨型动物的分布对当地地质（特别是底质的性质）和热液活动的影响（如食物供应增加或热液沉积）都很敏感。虽然在非喷口影响区没有明显的活动喷口证据，但照片数据表明，生活在这一区域的巨型动物的类型和数量受到靠近低温和高温热液源的重大影响，这些热液源支持微生物的生产，并产生热液沉积物，这些沉积物可能被平流输送到周边环境。对摄影数据的统计解释表明，喷口对海底巨型动物的影响程度有一个外部界限（即，1985-1986年，在火山灰喷口区活动的热液系统中，Bathydorus sp.海绵）位于约1000-1300米处。在单一喷口区的规模上，热液活动显然使中央和远端喷口区内的底栖非喷口生物的分布不像非喷口环境中常见的那样零散。
A computerized data base was constructed to aid in the interpretation of biological and geological observations recorded from 7662 photographs taken of Ashes vent field (located along the SW wall of the summit caldera of Axial Volcano, Juan de Fuca Ridge) during 1985–1986 using the Pisces IV submersible and a towed camera system. The transition region between the locus of high-temperature vents in Ashes vent field (i.e., Inferno, 326°C; Hell, 301°C; and Virgin Mound, 298°C) and more typical environmental conditions for the summit caldera of Axial Volcano as a whole is zoned spatially with respect to sediment type and organism assemblage. Three general ecological zones are identified within the vent field: (1) the central vent zone (within 100 m of a high-temperature vent), dominated by vent-associated organisms (vestimentiferan tube worms, clams, bacterial mats) and sedimentation (high-temperature, plume-derived and low-temperature, in situ deposits); (2) the distal vent zone (100–725 m from any high-temperature vent), characterized by extensive fields of iron oxide, iron silicate and silica chimneys and sediment (nontronite assemblage material), as well as maximum densities of most nonvent fauna; and (3) the nonvent impact zone (725–1300 m), indicated by elevated densities of nonvent organisms relative to regional (i.e., caldera-wide) values and maximum Bathydorus sp. sponge densities. The distribution of vestimentiferan tube worms is limited to within 90 m of known high-temperature venting (central vent zone); and anemones were observed only between 30 and 40 m from hot vents. Clams and microbial mats are concentrated in the central vent zone, as well, but occur sporadically up to 1250 m from the hot vents in association with hydrothermal nontronite that is probably precipitating in situ from <60°C vent fluid; thus megafaunal distributions are a useful indicator of poorly defined, often diffuse low-temperature hydrothermal activity on the seafloor. Maximum densities of nonvent echinoderms (i.e., holothurians, sea stars, urchins) are associated with the distal venting zone. Distributions of megafauna not endemic to the vent environment are sensitive to both local geology (particularly the nature of the substrate) and effects of hydrothermal activity such as enhanced food availability or hydrothermal sedimentation. Although evidence for active venting is not apparent in the nonvent impact zone, photographic data suggest that the type and number of megafauna living in this region are significantly influenced by proximity to low- and high-temperature hydrothermal sources that support enhanced microbial production and produce sediment of hydrothermal origin, which may be advected to the peripheral environment. Statistical interpretation of photographic data suggests an outer limit to the extent of vent influence on benthic megafauna (i.e., Bathydorus sp. sponges) of about 1000–1300 m for the hydrothermal system active at Ashes vent field in 1985–1986. On the scale of a single vent field, hydrothermal activity apparently results in a less patchy distribution of benthic, nonvent organisms within the central and distal vent zones than is common in the nonvent environment.