Fisheries and Oceans Canada, Institute of Ocean Sciences, Sidney, British Columbia, Canada.
Fisheries and Oceans Canada, Pacific Biological Station, Nanaimo, British Columbia, Canada.
PLoS One. 2021 May 14;16(5):e0249818. doi: 10.1371/journal.pone.0249818. eCollection 2021.
Euphausiids are a keystone species in coastal food webs due to their high lipid content and seasonally high biomass. Understanding the habitat and environmental drivers that lead to areas of high biomass, or 'hotspots', and their seasonal persistence, will support the identification of important foraging regions for mid- and upper- trophic level predators. We quantify the distribution of hotspots of the two dominant species of euphausiid in the north-east Pacific Ocean: Euphausia pacifica and Thysanoessa spinifera, as well as euphausiid larvae (mixed species). The Canadian coast encompasses the northern California Current Ecosystem and the transition zone to the Alaska current, and is a highly productive region for fisheries, marine mammals, and seabirds. We used spatiotemporal modelling to predict the distribution of these three euphausiid groups in relation to geomorphic and environmental variables during the important spring-summer months (April through September) when euphausiid biomass is highest. We quantified the area, intensity, and persistence of biomass hotspots across months according to specific oceanographic ecosections developed for marine spatial planning purposes. Persistent hotspots of both adult species were predicted to occur along the 200 m depth contour of the continental slope; however, differences were predicted on the shallower Dixon shelf, which was a key area for T. spinifera, and within the Juan de Fuca Eddy system where E. pacifica hotspots occurred. The continental slope along the west coast of Vancouver Island was the only persistent hotspot region common between both adult species and euphausiid larvae. Larval distribution was more correlated with T. spinifera than E. pacifica biomass. Hotspots of adults were more persistent across months than hotspots of euphausiid larvae, which were seasonally patchy. The persistence of biomass hotspots of forage species through periods of low overall biomass could maintain trophic connectivity through perturbation events and increase ecosystem resilience to climate change.
磷虾是沿海食物网中的关键物种，因为它们的脂肪含量高，生物量季节性高。了解导致高生物量区域或“热点”及其季节性持续存在的栖息地和环境驱动因素，将支持确定中上层捕食者重要觅食区域。我们量化了东北太平洋两种优势磷虾物种（太平洋磷虾和磷虾）以及磷虾幼虫（混合物种）的热点分布。加拿大海岸涵盖了加利福尼亚当前生态系统的北部和阿拉斯加当前的过渡区，是渔业、海洋哺乳动物和海鸟的高度多产地区。我们使用时空建模来预测这三种磷虾群体在与地理形态和环境变量相关的分布，这些变量在生物量最高的重要春夏月份（四月至九月）。我们根据海洋空间规划目的开发的特定海洋生态分区，根据月份量化了生物量热点的面积、强度和持续时间。预测两种成年物种的持久热点将沿着大陆坡 200 米深度轮廓线出现；然而，在迪克森浅滩（T. spinifera 的关键区域）和胡安·德富卡涡系统（E. pacifica 热点出现的地方）预测到了不同的差异。温哥华岛西海岸的大陆坡是唯一的持久热点区域，同时也是两种成年物种和磷虾幼虫共有的区域。幼虫的分布与 T. spinifera 的相关性高于与 E. pacifica 生物量的相关性。与磷虾幼虫的热点相比，成年个体的热点在整个月份的持续时间更长，而磷虾幼虫的热点则季节性地分散。在总生物量较低的时期，饲料物种生物量热点的持续存在可以通过扰动事件维持营养连接，并提高生态系统对气候变化的恢复力。
