Short-Term Nitrogen and Phosphorus Release during the Disturbance of Surface Sediments: A Case Study in an Urbanised Estuarine System (Gold Coast Broadwater, Australia)

Abstract

Understanding the effects of sediment disturbances on nutrient loadings is important for the management of estuarine settings. This study investigated the initial influence of sediment disturbance on water column nutrient concentrations in a shallow estuarine setting within the Gold Coast Broadwater, using a laboratory-based approach. Undisturbed sediment cores (200 mm Ø × 330 mm length, plexiglass) were incubated before and after being subjected to a disturbance event, to investigate the effect on the immediate and subsequent short-term water column nutrient concentrations. Sediment NH 4 + bio and PO 4 3− bio concentrations ranged from 150 to 478 and 1.50 to 8.56 nmol g −1 dry wt, respectively. Water column NH 4 + concentrations underwent the greatest increase (>1000% or approx. 14 times greater) immediately following disturbance, with mean effluxes increasing by >300%. Thereafter, water column NH 4 + concentrations and efflux rates declined to near initial pre-disturbance concentrations. Water column NH 4 + concentrations accounted for 0.58%-5.50% of the depth-integrated sediment NH 4 + bio concentration, indicating mobilization of the sediment bound exchangeable NH 4 + . The observed changes in PO 4 3− concentrations and fluxes were much lower in comparison to those observed for N-species. Following disturbance, increases in the water column PO 4 3− concentration accounted for 7.16%-8.22% depth-integrated sediment bioavailable PO 4 3− at +1 and +2 hours, and 5.65% at +7 hours, respectively. These results provide important insight into the potential implications of disturbance events, such as vessel activities and dredging operations, within the case study region, providing information for potential management options and relevant water quality concerns.

Dynamics of Phosphorus Content in the Water‐Sediment Interface of Wetlands in a Mid‐Temperature Steppe

“…In this study, a slight disturbance during sampling periods may have contributed to an increasing phosphorus release rate in August, and with the increase of settling time, the WTP content in the wetland pipe appears to decline, to a certain degree, in September (Figures 2 and 3). This variation tendency is consistent with existing research conclusions (Dunn et al, 2017).…”

Assessing the Seasonal Changes on Physicochemical Parameters and Major Nutrient Levels in Water and Sediments from Sulal River, Bureti Sub County, Kericho County, Kenya

“…The mean value of PO 3 -P was significantly (t=-3.776, p< 0.004) higher during wet season than dry. According to Kroiss, et al [21] and Dunn et al [22], there isn't a lot of ortho-phosphate in water during dry season because it is incorporated into sediments and aquatic plants during wet season. Continuous accumulation of soil sediment in the bottom of the river will then make phosphorus to settle too deep to be reintroduced to the water surface.…”

Boating- and Shipping-Related Environmental Impacts and Example Management Measures: A Review

“…Factors influencing the anthropogenic resuspension from vessels includes size and speed of vessel, hull design, engine size, seabed sediment grain-sizes, degree of seabed cohesiveness, water depth, and under-keel clearance. The erosion and resuspension of bottom sediments have direct and indirect effects on system condition and function including increased suspended solids and correspondingly decreased light availability, changes in benthic community structure, potential smothering of biota, remobilization of toxicants and nutrients, and alterations to nutrient cycling processes and sediment transport [91,[96][97][98].…”