## 1 Introduction  
It has long been recognized that inherent light-scattering properties of natural waters are of crucial importance and have strong potential for wide-ranging applications in aquatic sciences, including oceanography. These properties are essential inputs to the radiative transfer models used to compute the ambient light fields in natural water bodies [1; 2; 3; 4]. The variability in the light scattering properties of seawater is driven primarily by the concentration of suspended particles, particle size distribution, and composition through particle refractive index, internal structure, and shape. Hence, scattering measurements carry potentially useful information about characteristics of natural particle assemblages. For example, the scattering and backscattering coefficients of suspended particles have been shown to provide useful proxies of mass concentration of total suspended particulate matter (SPM), particulate inorganic carbon (PIC), and particulate organic carbon (POC) in the ocean [5; 6; 7]. Multi-angle light scattering measurements provide a means to estimate the particle size distribution [8; 9; 10; 11], including the submicrometer size range [12; 13; 14]. The angular pattern of light scattering can also contain useful information about the composition of particulate assemblages, including the bulk refractive index of particles [15; 16; 17; 18; 19]. In addition, measurements of the scattering matrix that provide information about polarization effects of light scattering [15; 20; 21; 22; 23] have the potential for identifying and discriminating different types of particles, such as phytoplankton species or minerals, which are present in complex natural assemblages [24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34]. Despite the potential usefulness of information provided by light scattering measurements, the complexity and variability in composition of natural particulate assemblages impose significant challenges in achieving an understanding of bulk light-scattering properties of seawater in terms of detailed compositional characteristics of particulate matter [35]. The volume scattering function, \(\beta_{p}(\psi,\lambda)\), and the degree of linear polarization, \(DoLP_{p}(\psi,\lambda)\) of light scattered by marine particles are of primary interest in this study. Here, \(\psi\) denotes the scattering angle, \(\lambda\) the light wavelength in vacuum, and the subscript \(p\) indicates that the quantity is associated with particles. When the subscript \(p\) is omitted, the quantity describes the scattering by the entire suspension with additive contributions from both water molecules and suspended particles. The volume scattering function, \(\beta(\psi,\lambda)\) [in units of m\({}^{-1}\) sr\({}^{-1}\)], is one of the fundamental inherent optical properties (IOPs) of seawater, which describes the scattered intensity as a function of scattering angle per unit incident irradiance per unit volume of small sample of water [2]. Several light-scattering related IOPs can be derived from \(\beta(\psi,\lambda)\). For example, integrating \(\beta(\psi,\lambda)\) over all scattering directions gives the total spectral scattering coefficient, \(b(\lambda)\) [m\({}^{-1}\)]. In this integration, it is commonly assumed that light scattering by an assemblage of randomly-oriented scatterers (molecules and particles) in natural waters is azimuthally symmetric about the incident direction of light beam. When \(\beta(\psi,\lambda)\) is normalized by \(b(\lambda)\), the resulting scattering phase function \(\widetilde{\beta}(\psi,\lambda)\) [sr\({}^{-1}\)] provides a useful indicator of the angular shape of the volume scattering function. In optical remote sensing applications based on measurements with above-water sensors (e.g., from satellites or aircraft), the spectral backscattering coefficient, \(b_{b}(\lambda)\) [m\({}^{-1}\)], is particularly useful. This coefficient can be obtained by integrating \(\beta(\psi,\ \lambda)\) over the range of backward scattering angles [2].