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）陆架深水区的典型特征为：春夏季会发生大量植物碎屑（phytodetritus）沉积，而冬季几乎无营养物质能够抵达海底。目前，学界对底栖大型生物（benthic megafauna）响应这种高度波动的食物供给的机制仍不甚明晰。为表征植物碎屑的沉积过程与大型底栖群落的响应特征，我们于安弗斯岛西侧的WAP陆架中部约590米水深处部署了一台海底定时延时相机（seafloor time-lapse camera），布设时长共计15个月。1999年12月9日（南极冬季）至2001年3月20日（夏季）期间，我们以12或24小时的间隔近乎连续地拍摄海底照片，并针对植物碎屑沉积情况与大型底栖生物动态开展分析。海底影像显示，绿色植物碎屑的输入具有显著的季节性特征，沉积碎屑颗粒的覆盖度存在较大的年际与季节差异。以表层沉积物为食的楯手海参类（elasipod holothurians）——普氏原海参（Protelpidia murrayi）与维氏佩海参（Peniagone vignoni）——全年占据底上大型生物群落的优势地位，二者通常占总丰度的80%以上，总密度最高可达2.4个/平方米。楯手海参类的丰度在夏季显著高于冬季。在夏季植物碎屑输入量较高的时段，普氏原海参的粪便铸型（faecal casts）产生速率更高，表明种群水平的摄食活动有所增强。2000年3月至6月期间，粪便铸型的留存时间最长，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，普氏原海参种群会通过提高摄食速率，响应沉积物表层有机质含量和/或易降解性的提升。假设该物种仅以沉积物表层毫米级的有机质为食，我们估算得出，在植物碎屑高输入时段，普氏原海参种群仅需约287天即可扰动1平方米的沉积物表层。我们认为，普氏原海参是WAP陆架深水区有机碳循环的关键物种，其可调控沉积下来的易降解植物碎屑向更广范围的陆架底栖群落的可利用性。