Impact of an extreme flood event on optical and biogeochemical properties in a subtropical coastal periurban embayment (Eastern Australia)

Abstract

Major floods impacted the city of Brisbane, eastern Australia, in January 2011, delivering large amounts of dissolved and particulate materials and nutrients into the adjacent coastal embayment, Moreton Bay. The resulting spatially resolved changes in biogeochemical and optical properties in Moreton Bay were examined 1, 2, 6, 19, and 49 weeks after the main freshwater discharge. One week postflood, total suspended matter (TSM) and chlorophyll a (TChla) concentrations varied over 1 order of magnitude throughout Moreton Bay, the particle scattering coefficient at 555 nm varied by a factor of 20, and the total absorption coefficient and colored dissolved organic matter (CDOM) absorption coefficient at 440 nm varied by a factor of 5. The largest changes in biogeochemical and optical properties observed during our study were from 1 to 2 weeks after the floods: near the Brisbane River mouth, TSM decreased by a factor of 3, CDOM by a factor of 2, while TChla increased by a factor of 3. Within a year, optical and biogeochemical properties recovered to levels similar to nonflood conditions. The strong changes in the characteristics of the particulate and dissolved material following the flood event and subsequent biological and photochemical processes led to a large spatial and temporal variability in the relative contribution of different constituents to the total absorption coefficient at 440 nm, the particle single scattering albedo, and the specific inherent optical properties. This work has significant implications for the accuracy of standard ocean color remote sensing algorithms in coastal waters during flood events.

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

“…Overall, the relative standard deviation between all triplicates was 8% (N = 57), varying the least for the DH dry season samples (2%) and the most for the VDG dry and wet season samples (13%). Laboratoryestimated particulate inorganic (PIM) and organic (POM) matter fractions of TSS were only available for the 2012 wet season samples and were extracted as described in Oubelkheir et al (2014).…”

“…The tidal range in their study region was comparable (∼3 m) to that observed during our study of the VDG. Oubelkheir et al (2014) also emphasized the role of short-term processes, such as wind stress and tides, as key drivers of the dissolved and particulate material in the shallow and dynamic subtropical environment of Moreton Bay (SE Queensland). In our study, the sampling strategy was primarily to ensure our stations had a large spatial distribution rather than to sample the small-scale temporal variability due to the tides, thus the tidal phase was not taken into account.…”

Phytoplankton absorption predicts patterns in primary productivity in Australian coastal shelf waters

“…Samples collected from V3 and PHNRS were analysed using a fibre optic UV/VIS spectrometer (Ocean Optics, Florida, USA) as in Robinson et al (2014). Samples collected from V1, V2 and V4 were measured using a dual beam scanning spectrophotometer equipped with an integrating sphere (GBC 916 UV/VIS; Oubelkheir et al, 2014). Absorption (a(λ)) at wavelengths between and 700 nm (m -1 ) was calculated using equation 14of Tassan and Ferrari (1995).…”

“…The satellite phytoplankton absorption coefficient was derived from the Generalised IOP DC model which has demonstrated a high percentage (> 80 %) of valid retrievals of a PHY in waters of all trophic levels and across all seasons (Werdell et al, 2013). Although the GIOP DC was applied to optically complex waters (Cherukuru et al, 2016;Oubelkheir et al, 2014) and without local atmospheric correction, the GIOP-DC uncertainty product for a PHY (443) indicates generally low uncertainty across the 2003-2015 time-series of a PHY (443) retrievals at Port Hacking and Yongala NRS. Within the 589 weeks of a PHY (443) observations at Port…”

Characterisation of extreme events waves in marine ecosystems: the case of Mediterranean Sea

“…We focused our investigation to the open-sea domain, i.e. we neglected the areas which are more directly affected by bottom and riverine dynamics (e.g., Oubelkheir et al, 2014).…”