Beam attenuation (m^-1) calibrated to particle concentration overlain by the density structure of the water column.

Transmissometers are effective in monitoring and measuring diel cycles in the particle load.

Optical instrumentation can provide crucial data for biogeochemical studies. In the open ocean, the particle field is dominated by phytoplankton and biologically derived particles such as empty tests and plant material.
 
With a well designed sampling scheme, optical instruments can capture the variability in biological systems driven by physical forcing functions such as the light field and vertical mixing. In the Equatorial Pacific, beam attenuation profiles taken with a 660 nm transmissometer showed diel cycles in the particle load in the photic zone. The daily change in the total particle load for three days during which profiles were taken every three hours can be represented by a sine curve. Taking the peak-to-trough difference and dividing by the trough value yields a dimensionless growth rate (mu) that can be compared to traditional methods of estimating phytoplankton productivity, such as labled CO₂ uptake and physiological modeling.
 
 The beam attenuation coefficient in the red wavelengths can be well correlated with the both the total particle load and the particulate organic carbon concentration. The transmissometer data set can then be used to calculate integrated production and test models of production. Spectral attenuation and absorption instruments (ac-9 and ac-s) expand the available data sets by constraining the dissolved organic carbon pool, the particle size spectra and the particle composition.

Diel and time series studies of growth and loss using integrated and multiple-depth data sets in the upper water column of the Equatorial Pacific.

Near-bottom particle concentrations represent both a substrate and a stress to benthic communities, which will respond to the source and magnitude of particle concentrations in the benthic nepheloid layer. Optical instrumentation can bring a unique data set to benthic studies, allowing the researcher to compare the variability in concentration and sources of particles in the benthic nepheloid layer to the underlying community.
 
Repeated profiling at the same sites can constrain the variability of the nepheloid layer and give important clues to the differences between similarly located sites. In this study on the Mississippi-Alabama margin, hard bottom communities were significantly different even though productivity in the overlying water column was similar. Differences in depth, current dynamics and relationships to local hydraulic features resulted in differences in the nepheloid layer average concentration and variability which was reflected in the community structures at each site.