## 3 Results and Discussion
### Measured Light Scattering Properties of Natural Particulate Assemblages  
Figure 11 depicts the corrected measured volume scattering function, \(\beta_{p}^{LISST}(\psi)\), and the degree of linear polarization, \(\textit{DoLP}_{p}^{LISST}(\psi)\), for three contrasting natural assemblages of particles. The selected parameters describing the particulate and optical properties of these samples are provided in Table 3. Sample A was obtained \(\sim\)8 km offshore from the subsurface chlorophyll-\(a\) maximum at a depth of 18 m, sample B was collected just beneath the sea surface at SIO Pier during a calm sunny summer day, and sample C was collected \(\sim\)2 km inland at the San Diego River Estuary during low tide. The SPM range covers about one order of magnitude from 0.36 g m\({}^{-3}\) for sample A to 3.18 g m\({}^{-3}\) for sample C, which is reflected in significant range of the particulate scattering coefficient, \(\beta_{p}^{LISST}\), from 0.36 m\({}^{-1}\) to 2.23 m\({}^{-1}\). Chla was also lowest for sample A (0.75 mg m\({}^{-3}\)) but highest for sample B (2.5 mg m\({}^{-3}\)). Thus, whereas the offshore sample A represents a particle concentration that is within the range of observations in relatively clear open ocean waters, sample C is representative of more turbid coastal or nearshore waters [5,7]. Samples A and B have similarly high values of the ratio POC/SPM (0.43 and 0.47, respectively) and relatively high values of Chla/SPM (2.1 \(\times\) 10\({}^{-3}\) and 2.2 \(\times\) 10\({}^{-3}\), respectively), indicating organic-dominated particulate assemblages with significant contribution of phytoplankton. In contrast, sample C has much lower values of POC/SPM (0.14) and Chla/SPM (3.8 \(\times\) 10\({}^{-4}\)), indicating inorganic-dominated particulate assemblage and relatively small role of phytoplankton, despite significant chlorophyll-\(a\) concentration (1.21 mg m\({}^{-3}\)). These differences in particle properties between the three samples are responsible for the differences in the magnitude and angular shape of \(\beta_{p}^{LISST}(\psi)\) and \(\textit{DoLP}_{p}^{LISST}(\psi)\) presented in Figure 11 and the optical parameters listed in Table 3. These optical parameters include the particulate backscattering ratio, \(\widetilde{b}_{pp}^{LISST}\), the ratio of \(\beta_{p}^{LISST}(45^{\circ})\) to \(\beta_{p}^{LISST}(135^{\circ})\), and the maximum value of \(\textit{DoLP}_{p}^{LISST}(\psi)\) denoted as \(\textit{DoLP}_{p,max}^{LISST}\). This maximum value occurs at a scattering angle \(\psi_{max}\) which is also provided in Table 3. The offshore sample A has an intermediate value of \(\widetilde{b}_{pp}^{LISST}\) and the highest \(\textit{DoLP}_{p,max}^{LISST}\) of about 0.77 associated with the smallest \(\psi_{max}\) of 92\({}^{\circ}\). Sample B from the SIO Pier has the lowest \(\widetilde{b}_{pp}^{LISST}\) of 0.008 among the three samples, suggesting a relatively steep slope of particle size distribution, relatively low bulk particle refractive index, or both [17]. This sample also shows the least steep near-forward scattering pattern (Figure 11c), which suggests a higher proportion of small particles relative to larger  
Figure 10: Similar to Figure 7, but for \(\textit{DoLP}_{p}\). All data are obtained with the Roving Eyeball sensor, and the residuals between \(\textit{DoLP}_{p}^{LISST}\) and \(\textit{DoLP}_{p}^{REF}\) in (**b**) are expressed as absolute differences. particles compared with the two other samples. Finally, the most turbid and least organic sample, sample C, exhibits an enhanced proportion of backscattering with the highest \(\widetilde{b}_{bp}^{LISST}\) of 0.027. While this result may suggest a relatively high bulk particle refractive index [17] consistent with the lowest POC/SPM ratio among the three samples, the additional influence of particle size distribution cannot be ruled out. Sample C shows steep near-forward scattering pattern (Figure 11c), which is typically indicative of an increased proportion of large particles relative to small particles.