Data from: Seasonal dynamics of megafauna on the deep West Antarctic Peninsula shelf in response to variable phytodetrital influx

The deep West Antarctic Peninsula (WAP) shelf is characterized by intense deposition of phytodetritus during spring/summer months, while very little food material reaches the seafloor during winter. The response of the shelf benthic megafauna to this highly variable food supply is still poorly understood. In order to characterize the deposition of phytodetritus and the megabenthic community response, we deployed a seafloor time-lapse camera at approximately 590 m depth on the mid WAP shelf west of Anvers Island for 15 months. Seafloor photographs were taken at intervals of 12 or 24 h nearly continuously from 9 December 1999 (austral winter) to 20 March 2001 (summer) and analysed for phytodetritus deposition and megafaunal dynamics. Seafloor images indicated a marked seasonal arrival of greenish phytodetritus, with large interannual and seasonal variability in the coverage of depositing phytodetrital particles. The surface-deposit-feeding elasipod holothurians Protelpidia murrayi and Peniagone vignoni dominated the epibenthic megafauna throughout the year, frequently constituting more than 80% of the megafaunal abundance, attaining total densities of up to 2.4 individuals m−2. Elasipod abundances were significantly higher in summer than winter. During summer periods of high phytodetrital flux, Pr. murrayi produced faecal casts at higher rates, indicating intensified population-level feeding activity. In March–June 2000, faecal casts lasted longest, suggesting lower horizontal bioturbation activity during autumn–winter. Our data indicate that the Pr. murrayi population increases its feeding rates in response to increasing amounts and/or lability of organic matter on the sediment surface. Assuming that this species feeds on the top millimetre of the sediment, we estimate that, during periods of high phytodetrital flux, the Pr. murrayi population reworks one square metre of sediment surface in approximately 287 days. We suggest that Pr. murrayi is an important species for organic-carbon recycling on the deep WAP shelf, controlling the availability of deposited labile phytodetritus to the broader shelf benthic community.

西南极半岛（West Antarctic Peninsula, WAP）深水陆架，在春夏季以浮游植物碎屑（phytodetritus）的强烈沉积为特征，而冬季几乎鲜有食物物质抵达海底。目前学界对该陆架底栖大型动物群（benthic megafauna）应对这种高度波动的食物供给的响应机制仍知之甚少。
为阐明浮游植物碎屑的沉积过程与大型底栖群落的响应特征，我们于昂韦尔岛以西的WAP陆架中部约590米水深处布设了一台海底延时相机，部署时长共计15个月。该相机于1999年12月9日（南极冬季）至2001年3月20日（南极夏季）期间，以12或24小时的间隔近乎连续地拍摄海底照片，并针对浮游植物碎屑沉积与大型底栖动物动态开展分析。
海底影像显示，绿色浮游植物碎屑的沉降具有显著的季节节律，且沉积碎屑的覆盖度存在较大的年际与季节变异。全年以表层沉积食性平足目海参（elasipod holothurians）*Protelpidia murrayi*与*Peniagone vignoni*为底上大型动物群（epibenthic megafauna）的优势类群，其丰度通常占大型底栖动物总丰度的80%以上，最大总密度可达2.4个·m⁻²。平足海参的丰度在夏季显著高于冬季。在浮游植物碎屑输入量较高的夏季时段，*Pr. murrayi*产生粪粒的速率更高，表明种群水平的摄食活动增强。
2000年3月至6月期间，粪粒的留存时长最长，这暗示秋冬季节的水平生物扰动（bioturbation）活动较弱。我们的数据表明，*Pr. murrayi*种群会通过提高摄食速率，响应沉积物表层有机质（organic matter）数量和/或易降解性的提升。假设该物种仅以沉积物最上层的毫米级表层为食，我们估算得出，在浮游植物碎屑高输入时段，*Pr. murrayi*种群重新扰动1平方米沉积物表层大约需要287天。
我们认为，*Pr. murrayi*是WAP深水陆架有机碳循环（organic-carbon recycling）的关键物种，其可通过调控沉积的易降解浮游植物碎屑的可获得性，进而影响整个陆架底栖群落的资源供给。