## 3 Results and Discussion
### Measured Light Scattering Properties of Natural Particulate Assemblages
Note that sample C also has the lowest \(\beta_{p}^{LISST}(45^{\circ})/\beta_{p}^{LISST}(135^{\circ})\) ratio of 12, which indicates a higher degree of symmetry in the angular pattern of scattering about 90\({}^{\circ}\), which is consistent with the relatively high value of \(\widetilde{b}_{bp}^{LISST}\) for this sample. In addition, sample C has the lowest \(DoLp_{p,max}^{LISST}\) of 0.58. Figure 11: Measurements of \(\beta_{p}^{LISST}\) and \(DoLp_{p}^{LISST}\) obtained with the LISST-VSF on natural seawater samples from the San Diego region representing **(a,b)** subsurface offshore waters, **(c,d)** SIO Pier, and **(e,f)** San Diego River Estuary. Solid lines represent median values while dotted lines indicate the 10 th and 90 th percentiles obtained from a series of measurements on each sample. Insets in **(a,c,d)** display greater detail on the near-forward scattering range. For comparison, Table 3 also includes the values for the selected optical parameters estimated from measurements reported by Petzold [38] for clear ocean waters (off Bahamas), coastal waters (San Diego coastal region), and turbid waters (San Diego Harbor). These measurements span a generally similar range of scattering angles as the LISST-VSF (10-180\({}^{\circ}\) in 5\({}^{\circ}\) increments), but are based on a spectrally broader incident beam (75 nm full width half maximum) centered at 514 nm. The estimates of particulate volume scattering function \(\beta_{p}\) from Petzold's measurements were obtained by subtracting pure seawater contribution \(\beta_{w}\) from the measured total \(\beta\). The \(\beta_{w}\) value was calculated assuming a water temperature of 15 \({}^{\circ}\)C and salinity of 33 PSU [77]. Although Petzold's data include measurements made in clearer waters compared with our samples, the range of values for the dimensionless parameters associated with the shape of angular scattering pattern, \(\widetilde{b}_{pp}^{LISST}\) and \(\beta_{p}^{LISST}(45^{\circ})/\beta_{p}^{LISST}(135^{\circ})\), is very similar. Specifically, our data for the offshore sample A are similar to Petzold's data from clear waters, sample B from the SIO Pier aligns with Petzold's data from coastal San Diego waters, and sample C from San Diego River Estuary with Petzold's data from the San Diego Harbor. We note that the dotted lines in Figure 11 reflect some variations in \(\beta_{p}^{LISST}(\psi)\) and \(DoLP_{p}^{LISST}(\psi)\) between the individual measurements within a given set of measurements for each sample. For example, on the basis of the collection of 200 to 400 measurements for each of the two linear polarization states of the incident beam and the scattered light, the coefficient of variation at \(\psi\) = 90\({}^{\circ}\) was 14%, 8%, and 13% for \(\beta_{p}^{LISST}\) and 20%, 13%, and 15% for \(DoLP_{p}^{LISST}\) for samples A, B, and C, respectively. These variations between the individual measurements that have been taken in rapid succession do not necessarily reflect the measurement precision, as they can also be associated with actual variations in the sample, for example the fluctuations in the presence of relatively rare large particles within the interrogated sample volume. Another important point is that the small negative values of \(DoLP_{p}^{LISST}\) observed for some individual measurements at forward scattering angles \(<\)30\({}^{\circ}\) (see the 10 th percentile dotted lines in Figure 11b,d,f) are not necessarily an indication of measurement uncertainty because the negative values, especially in this angular range, are physically possible for certain types of particles [30; 54; 56; 58]. Figure 12 depicts scatter plots of the relationships between the dimensionless optical parameters, \(\widetilde{b}_{pp}^{LISST}\) and \(DoLP_{p,max}^{LISST}\), and the dimensionless particulate compositional properties, POC/SPM and Chla/SPM, for all 17 samples examined in this study. The overall range of POC/SPM in our dataset is 0.04 to 0.6.