Multiple angle acoustic classification of zooplankton

Single Particle Differentiation through 2D Optical Fiber Trapping and Back-Scattered Signal Statistical Analysis: An Exploratory Approach

Recent trends on microbiology point out the urge to develop optical micro-tools with multifunctionalities such as simultaneous manipulation and sensing. Considering that miniaturization has been recognized as one of the most important paradigms of emerging sensing biotechnologies, optical fiber tools, including Optical Fiber Tweezers (OFTs), are suitable candidates for developing multifunctional small sensors for Medicine and Biology. OFTs are flexible and versatile optotools based on fibers with one extremity patterned to form a micro-lens. These are able to focus laser beams and exert forces onto microparticles strong enough (piconewtons) to trap and manipulate them. In this paper, through an exploratory analysis of a 45 features set, including time and frequency-domain parameters of the back-scattered signal of particles trapped by a polymeric lens, we created a novel single feature able to differentiate synthetic particles (PMMA and Polystyrene) from living yeasts cells. This single statistical feature can be useful for the development of label-free hybrid optical fiber sensors with applications in infectious diseases detection or cells sorting. It can also contribute, by revealing the most significant information that can be extracted from the scattered signal, to the development of a simpler method for particles characterization (in terms of composition, heterogeneity degree) than existent technologies.

Ecological Insights from Pelagic Habitats Acquired Using Active Acoustic Techniques

Marine pelagic ecosystems present fascinating opportunities for ecological investigation but pose important methodological challenges for sampling. Active acoustic techniques involve producing sound and receiving signals from organisms and other water column sources, offering the benefit of high spatial and temporal resolution and, via integration into different platforms, the ability to make measurements spanning a range of spatial and temporal scales. As a consequence, a variety of questions concerning the ecology of pelagic systems lend themselves to active acoustics, ranging from organism-level investigations and physiological responses to the environment to ecosystem-level studies and climate. As technologies and data analysis methods have matured, the use of acoustics in ecological studies has grown rapidly. We explore the continued role of active acoustics in addressing questions concerning life in the ocean, highlight creative applications to key ecological themes ranging from physiology and behavior to biogeography and climate, and discuss emerging avenues where acoustics can help determine how pelagic ecosystems function.

Estimating fish orientation from broadband, limited-angle, multiview, acoustic reflections

This article demonstrates that multiview, broadband (635-935 kHz), nearly monostatic, acoustic reflections recorded from lateral views of juvenile fish can be used to infer animal orientation. Calibrated acoustic data were recorded from live fish in a laboratory, while orientation was measured simultaneously via optical images. Using eight animals, two-dimensional data sets of target strength as a function of frequency and orientation were obtained. Fish length, lateral thickness, and dorsoventral thickness ranged from 24 to 48 mm, 3 to 7 mm and 10 to 20 mm, respectively. Preliminary estimates of orientation were computed from the direction of the gradient of the local autocorrelation function in the target strength image. These local estimates were then median-filtered over the full system bandwidth (but still limited-angle) to improve accuracy. Angular estimates were then corrected for systematic bias via a simple, one-dimensional model that approximated the animals' reflection by that of a bar target. Taken over all orientations, the average absolute error in orientation estimation is 5.6° to 17°, dependent on the data set. Results indicate, for most sets of views, reasonable estimates of lateral orientation can be obtained from broadband, multiview data over a set of limited angular reflections.

Classification of live, untethered zooplankton from observations of multiple-angle acoustic scatter

A broadband, multiple-angle acoustic array was used to classify millimeter to centimeter sized live zooplankton in a laboratory tank. Reflections in the frequency range from 1.5 to 2.5 MHz were recorded from untethered 1-4 mm calanoid copepods and 8-12 mm mysids over an angular range of 0 degrees -47 degrees . A synchronized, coregistered video system recorded animal location and orientation. To highlight differences between animals, a frequency correlation matrix was computed from the observed wide-band power spectra of the scattered sound. Significant differences in the slopes and shapes of the eigenvalue spectra of this matrix were found for mysids versus copepods. These results support the idea that broadband, multiple-angle scatter can be used to classify organisms of different sizes and shapes.