A crab swarm at an ecological hotspot: patchiness and population density from AUV observations at a coastal, tropical seamount.
A crab swarm at an ecological hotspot: patchiness and population density from AUV observations at a coastal, tropical seamount.
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作者：
Pineda J;Cho W;Starczak V;Govindarajan AF;Guzman HM;Girdhar Y;Holleman RC;Churchill J;Singh H;Ralston DK
汉尼拔浅滩是巴拿马附近东热带太平洋沿海的一座海山和生态热点，一次对汉尼拔浅滩的研究航行探索了导致海山生物量增加的分区、生物多样性和生态过程。在这里，我们使用海底视频和自主水下航行器（AUV）照片描述了底栖异壁红蟹种群的空间结构。高密度聚集体和红蟹群与底部上方 4-10 m 的致密浑浊层相关。高密度聚集仅限于海山西北侧 355-385 m 水深，尽管螃蟹也以较低密度出现在较浅水域（~280 m）和海山的其他位置。螃蟹聚集发生在低氧水中，氧气含量为0.04毫升/升。对汉尼拔红蟹和 2015 年美国加利福尼亚州圣地亚哥海滩大规模搁浅事件中采样的远洋红蟹进行条形码分析表明，巴拿马蟹和加利福尼亚蟹可能是同一个物种，即 Pleuroncodes planipes，这些发现代表了该物种南端的延伸。沿1.6公里样带测量发现，存在3个高密度聚集体，最高密度达78只/平方米，呈斑片状分布。螃蟹密度在该斑块的中部达到峰值，其密度结构类似于群居昆虫的密度结构。
A research cruise to Hannibal Bank, a seamount and an ecological hotspot in the coastal eastern tropical Pacific Ocean off Panama, explored the zonation, biodiversity, and the ecological processes that contribute to the seamount’s elevated biomass. Here we describe the spatial structure of a benthic anomuran red crab population, using submarine video and autonomous underwater vehicle (AUV) photographs. High density aggregations and a swarm of red crabs were associated with a dense turbid layer 4–10 m above the bottom. The high density aggregations were constrained to 355–385 m water depth over the Northwest flank of the seamount, although the crabs also occurred at lower densities in shallower waters (∼280 m) and in another location of the seamount. The crab aggregations occurred in hypoxic water, with oxygen levels of 0.04 ml/l. Barcoding of Hannibal red crabs, and pelagic red crabs sampled in a mass stranding event in 2015 at a beach in San Diego, California, USA, revealed that the Panamanian and the Californian crabs are likely the same species, Pleuroncodes planipes, and these findings represent an extension of the southern endrange of this species. Measurements along a 1.6 km transect revealed three high density aggregations, with the highest density up to 78 crabs/m2, and that the crabs were patchily distributed. Crab density peaked in the middle of the patch, a density structure similar to that of swarming insects.