Optical Properties of Marine Particulates in Coastal Waters

Coastal waters host a complex assemblage of suspended particles—ranging from mineral sediments and detrital matter to phytoplankton and organic aggregates—whose interactions with sunlight govern underwater light fields and influence biogeochemical cycles. The inherent optical properties of these particles, notably their absorption, scattering and backscattering coefficients, along with beam attenuation, depend on particle composition, size, shape, aggregation state and orientation. Spectral variations in these properties underpin ocean-colour remote sensing algorithms used to estimate chlorophyll, suspended sediment and dissolved organic matter. In situ measurement techniques and laboratory characterisations reveal how seasonal blooms, riverine inputs and resuspension events modulate optical signatures. Improved understanding of particle optics in coastal zones informs water-quality monitoring, sediment transport models, assessments of primary productivity and the calibration of satellite sensors in dynamic nearshore environments.

Research from Nature Portfolio

Recent studies have applied a novel complex amplitude sensor to characterise size-resolved suspended particulate matter (SPM) in the western North Pacific. By measuring the complex forward-scattering amplitude of individual particles (0.2–5 µm), researchers classified major particle types—such as diatom fragments, organic carbonaceous material, mineral dust, iron oxides and black carbon—based on amplitude signatures and electron-microscopy validation. Depth profiles revealed peaks in SPM dominated by diatom fragments and organic matter closely associated with elevated turbidity and chlorophyll a. This work demonstrates the advantages and limitations of using high-resolution scattering measurements to resolve both concentration and composition of SPM in coastal and shelf waters, offering a pathway toward improved in situ monitoring of particulate optics and biogeochemical fluxes.

Optical Properties of Marine Particulates in Coastal Waters publication trend

The graph below shows the total number of articles in optical properties of marine particulates in coastal waters across all publications each year (not limited to Nature Index journals).

Technical terms

Particulate Backscattering Coefficient (bbp): Fraction of light scattered backward by suspended particles per unit pathlength.

Particle Size Distribution (PSD): Statistical description of particle concentration as a function of size.

Complex Amplitude Sensor (CAS): Instrument that measures the complex forward-scattering amplitude of individual suspended particles.

Beam Attenuation Coefficient (c): Rate of light loss due to combined absorption and scattering by particles.

Volume Scattering Function (βp): Angular distribution of light scattered by particles at a given angle.

References

1. Analysis of oceanic suspended particulate matter in the western North Pacific using the complex amplitude sensor. Scientific Reports (2024).
2. Particle Size Distribution Slope Changes along the Yellow River Delta Observed from Sentinel 3A/B OLCI Images. Remote Sensing (2024).
3. Improved correction methods for field measurements of particulate light backscattering in turbid waters. Optics Express (2016).
4. Assessing the effects of particle size and composition on light scattering through measurements of size‐fractionated seawater samples. Limnology and Oceanography (2019).