Using inherent optical properties to investigate biogeochemical dynamics in a tropical macrotidal coastal system

Abstract

[1] The variability in the inherent optical properties along an estuary-coast-ocean continuum in tropical Australia has been studied. The study area, the Fitzroy Estuary and Keppel Bay system, is a shallow coastal environment (depth < 30 m) with highly turbid waters in the estuary and blue oceanic waters in the bay and subject to macrotides. Biogeochemical and inherent optical properties (IOPs) were sampled in the near-surface layer spatially and across the tidal phase during the dry season. These determinations included continuous measurements of spectral absorption, scattering and backscattering coefficients, together with discrete measurements of spectral absorption coefficients of phytoplankton, nonalgal particles and colored dissolved organic matter, and concentrations of phytoplankton pigments and suspended matter. Because of a large variability in the characteristics of the water components on short spatial and temporal scales, we observe a large variability in the associated optical properties. From the estuary to the bay, particle scattering and dissolved absorption decreased by 2 orders of magnitude, and nonalgal particle absorption decreased by 3 orders of magnitude. We also observed a strong variability in particle single scattering albedo and backscattering efficiency (by a factor of 6) and in specific IOPs (IOPs normalized by the relevant constituent concentration) such as suspended matter-specific particle scattering and chlorophyll-specific phytoplankton absorption. Superimposed on this strong spatial variability is the effect of the semidiurnal tide, which affects the spatial distribution of all measured properties. These results emphasize the need for spatially and temporally adjusted algorithms for remote sensing in complex coastal systems.

Intercomparison of shallow water bathymetry, hydro‐optics, and benthos mapping techniques in Australian and Caribbean coastal environments

“…The values of the SIOP parameters for this study are similar to those reported previously for Moreton Bay and other Australian coastal waters (Brando and Dekker 2003;Oubelkheir et al 2006;Qin et al 2007;Blondeau-Patissier et al 2009). …”

“…In-situ absorption, attenuation, backscattering, reflectance, and vertical attenuation were measured at 20 locations in the bay using ac-9, Hydroscat-and TRIOS-Ramses instruments Brando et al 2009), and water samples were collected for measuring in vivo absorption of CDOM, chlorophyll and NAP, as well as the NAP and chlorophyll concentrations. All measurements were carried out following (Brando et al 2009;Oubelkheir et al 2006;Phinn et al 2006).…”

Bio-Optical Properties of Two Neigboring Coastal Regions of Tropical Northern Australia: The Van Diemen Gulf and Darwin Harbour

“…Previous studies on subtropical estuarine systems of the South East Australian coast have shown the pronounced effect of shorttimescale variability in dissolved and particulate matter (particle size, composition) due to the spring-neap tidal cycle (Oubelkheir et al, 2006), stressing the need to take into account the tidal phase in the sampling strategy. Shi et al (2011) demonstrated that the magnitude of the spring-neap tidal cycle on the variations of satellite-derived K d (490) and TSS was comparable to the seasonal FIGURE 11 | Photo-acclimation and photo-adaptation processes in the NMR.…”

Optimization of a Semi-Analytical Algorithm for Multi-Temporal Water Quality Monitoring in Inland Waters with Wide Natural Variability

“…CDOM absorption was determined by measuring the absorbance of water samples filtered through 0.2 µm nylon filters and converting to absorption coefficients as in Clementson et al [50] and Oubelkheir et al [8]: …”