In Situ Measurements of the Acoustic Properties of Antarctic Krill

南极磷虾是南极海洋生态系统的关键物种，也是需要接受国际评估和管理的物种。已使用各种技术来估计其生物量和/或生物量，包括生物学和声学估计。然而，这两种方法估计的总丰度/生物量并不一致，两者都存在相当大的误差。这一建议的目的是提供一种新的方法，可以用来减少由声学测量引起的估计误差。众所周知，声学技术在研究浮游动物的时空分布方面远比传统的网、泵和拖网调查技术有效得多。然而，准确地解释声散射数据需要可靠的活体动物材料声学特性(声速和密度对比)的知识。这些材料特性取决于海洋参数的时空分布：温度和压力，以及动物的身体结构。对于类流体的弱散射海洋动物，如磷虾，声速的微小变化会导致测量的体积散射强度发生很大变化，缺乏预测和/或现场测量声学性质变化的能力，极大地影响和限制了我们准确解释声学数据和获得可靠的丰度和/或生物量估计的能力。这项建议旨在通过现场测量南极磷虾的材料特性及其时空变异性来解决这一问题。这些测量对南极地区的丰度和/或生物量估计至关重要。为了提供材料声学特性的现场测量，我们建议在南极地区进行的巡航中使用伍兹霍尔海洋研究所开发的浮游动物声学特性(APOP)。APOP系统能够在现场测量海洋生物的声速和密度对比度。通过这项拟议的研究，我们希望获得南极磷虾就地物质性质的时间和空间变化。通过将南极磷虾的现场物质特性与声学和生物调查数据结合起来，预计将大大增强对南极磷虾丰度和/或生物量估计的信心。

0125629ChuAntarctic krill is a key species of the Antarctic marine ecosystem and it is a species that is subject tointernational assessment and management. A variety of techniques have been used to estimate theirabundance and/or biomass including biological and acoustical estimations. However, the totalabundance/biomass estimated from the two approaches do not agree and both are subject to considerableerrors. The purpose of this proposal is to provide a new approach that can be used to reduce the estimatederrors resulting from the acoustic measurements.It is well known that the acoustic technique is far more efficient than the conventional survey techniquesinvolving nets, pumps and trawls in studying the temporal and spatial distributions of zooplankton.However, the accurate interpretations of acoustic scattering data require reliable knowledge of the materialacoustic properties (sound speed and density contrasts) of live animals. These material properties dependon the spatial and temporal distributions of the oceanographic parameters: temperature and pressure, aswell as the animals body structure. For fluid-like weakly scattering marine animals, such as krill, smallvariations in the sound speed can result in substantial variations in the measured volume scattering strength.The lack of the ability in predicting and/or measuring the variations of the acoustic properties in situ greatly affects and limits our ability to accurately interpret the acoustic data and to obtain reliable abundance and/or biomass estimates. This proposal is intended to address this issue by in situ measurement of the material properties of Antarctic krill and their spatial and temporal variability. These measurements are crucial to the abundance and/or biomass estimates in the Antarctic region. To provide in situ measurements of material acoustic properties, we propose to use the Acoustic Properties Of zooPlankton (APOP), developed at the Woods Hole Oceanographic Institution, in a cruise conducted in the Antarctic region. The APOP system is able to measure the sound speed and density contrasts of marine organisms in situ. From this proposed research, we expect to obtain a temporal and spatial variation of in situ material properties of Antarctic krill. By incorporating in situ material properties of Antarctic krill with acoustic and biological survey data, the confidence in estimates of the abundance and/or biomass of Antarctic krill is expected to be strengthened greatly.