Glider based real-time monitoring of marine mammals in the Arctic, 2016

Shipboard observations of marine mammal distribution and habitat are expensive and logistically challenging to collect in Arctic waters. Port facilities are minimal and access to appropriate vessels for spending extended periods of time at sea is extremely limited. Autonomous platforms like gliders provide the capability to collect both oceanographic and passive acoustic data for far longer periods of time (weeks to months) and at significantly reduced costs than traditional shipboard or aerial surveys. We have developed a system to record, detect, classify, and remotely report Arctic and sub-Arctic marine mammal calls in real time from Slocum ocean gliders based on the digital acoustic monitoring (DMON) instrument and the low-frequency detection and classification system (LFDCS). The system has been used several times in the northwest Atlantic Ocean and was successfully demonstrated for Arctic research during two pilot studies in the Chukchi Sea during September 2013 and 2014. Deployments to date have been short (1-3 weeks), but the capability exists for much longer missions. Our objective is to conduct an 8-10 week survey of the northeastern Chukchi Sea using a G2 Slocum glider to (1) examine the distribution, occurrence, and habitat of marine mammals using in-situ passive acoustic and oceanographic data collected by the glider, and (2) demonstrate the near real-time detection and reporting capability of the system. We hypothesize that some Arctic species associate with a front separating Bering Sea water and Alaska Coastal Current water to take advantage of aggregations of either pelagic or benthic prey. We further hypothesize that marine mammal community composition will change predictably with the strong spatial variability in oceanographic properties found in this region. We anticipate that these predictions will improve efforts to (1) mitigate impacts on marine mammals by human activities and (2) forecast changes in species distributions caused by climate change.

在北极海域开展船基海洋哺乳动物分布与栖息地观测，不仅成本高昂，且受后勤保障限制，实施难度极大。该区域港口设施匮乏，可供长期海上作业的合格船舶资源亦极度有限。相较于传统船基或航空调查，海洋滑翔机（glider）这类自主观测平台可在数周至数月的更长周期内同步采集海洋水文与被动声学数据，且成本显著降低。我们基于数字声学监测（digital acoustic monitoring, DMON）仪器与低频检测分类系统（low-frequency detection and classification system, LFDCS），研发了一套可从Slocum海洋滑翔机上实时记录、检测、分类并远程上报北极及亚北极海域海洋哺乳动物鸣叫声的系统。该系统已在西北大西洋完成多次部署，并于2013年9月和2014年9月在楚科奇海开展的两项先导研究中，成功完成北极相关研究的演示验证。截至目前，该系统的单次部署时长较短（1至3周），但技术上支持更长周期的作业任务。本研究旨在利用G2型Slocum海洋滑翔机，在楚科奇海东北部开展为期8至10周的调查，以达成两个目标：(1) 通过滑翔机采集的原位被动声学与海洋水文数据，解析海洋哺乳动物的分布、出现规律与栖息地特征；(2) 验证本系统的近实时检测与上报能力。我们提出如下假说：部分北极海洋哺乳动物会栖息在分隔白令海水域与阿拉斯加沿岸流水域的锋面区域，以利用集群的浮游或底栖猎物资源。我们进一步假设，该区域海洋哺乳动物的群落组成会随海洋水文属性的显著空间异质性呈现可预测的变化规律。我们预期，上述研究预测将有助于优化两项工作：(1) 减轻人类活动对海洋哺乳动物的负面影响；(2) 预测气候变化引发的物种分布变化。