Water movements, sediment transport and deposition, Western Port, Victoria

Harris, John E.; Hinwood, Jonathan Barry; Marsden, M.A.H.; Sternberg, Richard W.

doi:10.1016/0025-3227(79)90010-0

Cited by 21 publications

(18 citation statements)

References 11 publications

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“…The study showed that all the sites are accreting, with the highest accretion occurring at Rhyll and Pioneer Bay. This is in keeping with previous studies which show that these areas are important depositional areas within Westernport Bay (Harris et al, 1979). These results are also in line with some horizontal measurements of growth of the shoreline within the bay with sites such as Tooradin and Hastings showing 0.5 and 0.3 m growth since 1988 (Bishop-Taylor et al, 2021a,b).…”

Section: Small Scale Stochasticitysupporting

confidence: 91%

“…Sediment transport within the bay and to the sites is then governed by the net clockwise circulation of water. Areas near Pioneer Bay and Rhyll sites are considered important depositional areas for mud (Harris et al, 1979). Differences in sedimentation between Rhyll and other sites could be partially linked to the difference in site hydrodynamics; where other sites are fringed by mangroves and sediment is delivered via wave action across the front margin of the mangrove.…”

Section: Large Scale Ordermentioning

confidence: 99%

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Short-Term Sedimentation Dynamics of Temperate Mangroves in Western Port Bay, Victoria

Sayers

Reef

2022

Front. Mar. Sci.

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The promotion of sedimentation by mangrove ecosystems with adequate sediment supply has been well documented. However, predicting the amount of accretion or erosion at a specific point, is difficult due to the inherent stochasticity of sediment movement and deposition. Forcings which have been thought to influence short-term sedimentation rates, such as the amount of suspended matter in the incoming water, the wave regime at the site, elevation above sea level, distance from the low tide mark, and vegetation density, were investigated using large arrays of erosion pins at five sites around Western Port, Victoria over the course of one and a half years. We analyzed large scale/short-term and small-scale/longer-term vertical displacement within and between sites, and quantified small-scale intra-site variability. Results show, that while all study sites within Western Port were accreting sediment, they were not doing so at the same rate, and both intra-site and inter-site variability is high. Short-term large-scale or site wide analysis shows that total suspended matter and significant wave height (SWH) did not significantly affect vertical displacement rates. Surprisingly, neither distance from water nor vegetation density significantly affected vertical displacement or explain the spatial distribution of accretion and erosion within the sites. The coefficient of variation at each pin shows that there is high temporal variability in vertical displacement at each location, with individual pins alternating between erosion and accretion over time. Our study finds that while large scale (1 km2) patterns of sedimentation are temporally consistent, small scale patterns (< 100 m2) are difficult to predict. This small-scale stochasticity therefore compounds management of mangrove ecosystems, especially as it relates to predicting the response to sea level rise. Thus, investment in small scale management of vegetation density, or microtopography, is perhaps not required for overall shoreline stability with sea level rise and blue carbon accumulation, making ecosystem restoration more feasible where resources are limited. However, at larger, forest-wide, spatial scales a higher level of predictability exists such as the overall response of the coastal tract to prevalent wave energy and sediment supply.

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Section: Small Scale Stochasticitysupporting

confidence: 91%

Section: Large Scale Ordermentioning

confidence: 99%

Short-Term Sedimentation Dynamics of Temperate Mangroves in Western Port Bay, Victoria

Sayers

Reef

2022

Front. Mar. Sci.

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“…All three sites were located along the eastern margin of Western Port. The site at Corinella was selected due to its proximity to appreciable sediment inputs (Harris et al ) and higher nutrient concentrations relative to the other study sites. Coronet Bay was chosen because of its high areal seagrass extent and its greater distance from human activities than the other sites.…”

Section: Methodsmentioning

confidence: 99%

The balance between nitrogen fixation and denitrification on vegetated and non‐vegetated intertidal sediments

2016

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Rates of denitrification (isotope pairing) and nitrogen fixation (acetylene reduction) were simultaneously measured in three temperate, intertidal Zostera muelleri meadows and adjacent non‐vegetated tidal flats within Western Port, Australia. Net daily nitrogen fluxes ranged from −276 (net denitrification) to 520 μmol N/m2 d (net nitrogen fixation), and were generally positive, with only two instances of net negative fluxes. The highest fluxes were observed at the sites with the lowest water column nitrate concentrations. No significant differences in net nitrogen fluxes were found between vegetated and non‐vegetated sediments (p = 0.213). Nitrogen fixation was generally the dominant process occurring, which was stimulated in the presence of vegetation except at the most marine‐influenced site, where nitrogen fixation in non‐vegetated sediments was higher. Nitrogen fixation rates in non‐vegetated sediments were highly correlated to cyanobacterial cell counts (although no mats were present). Rates were ∼65 μmol N/m2 d at 0 cell counts, suggesting a basal rate driven within the sediment. Additional slurry experiments confirmed significant rates of nitrogen fixation within the sediment, which were stimulated by sucrose and terminated by nitrate (p < 0.05), strongly suggesting sulfate‐reducing bacteria contributed to nitrogen fixation. At the bay‐wide scale, nitrogen fixation was estimated to contribute ∼430 t N/yr compared to ∼650 t N/yr from catchment and atmospheric inputs and 230 t N/yr lost through denitrification. Sensitivity analysis confirmed that while the loss of seagrass would affect the magnitude of the bay‐wide flux of nitrogen on these tidal flats, nitrogen fixation remains the dominant process.

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“…The Western Port BBRs occur in seafloor depressions at the terminus of sub-channels. Harris et al (1979) noted that due to the proximity of the Rhyll Segment to the Eastern Entrance of to bay, currents in this area do not display the directional symmetry that is typical of other sites but rather are generally counterclockwise circulation pattern. During our surveys, underwater and surface observations were that tidal currents in the BBR areas are lower than those in the neighbouring main channels and there is significant eddying.…”

Section: Ecophysical Controlsmentioning

confidence: 93%

“…The bryozoan biogenic reef (BBR) area is situated in the Eastern Arm of Western Port (WP), VIC, Australia, in an area termed the "Rhyll Segment" (Harris et al, 1979;Jenkins et al, 2013) between French Island, Corinella and Rhyll (Figure 1). Potential reef areas were initially identified based on the seabed textures in a 2009 bay-wide multibeam bathymetry product (2.5 m horizontal resolution) generated by the Port of Hastings Development Authority.…”

Section: Study Area and Ground-truthingmentioning

confidence: 99%

Extent and Characteristics of a Newly Discovered Unique Bryozoan Biogenic Reef Complex

Dutka

Fejer²,

Williams³

et al. 2022

Front. Mar. Sci.

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Using multibeam echosounding (R2Sonic, Austin, Texas) combined with underwater observation and imagery surveys, this study sought to estimate the size and describe the typology of newly discovered biogenic bryozoan reefs in Western Port (VIC, Australia). The bryozoan species forming the biogenic structure are Triphyllozoon moniliferum, T. munitum (both fenestrate forms and dominant on the reef) and Celleporaria (non-fenestrate form and sub-dominant). The bryozoan biogenic reefs occupy a total area of 1.74 km2. Their distribution appears to be geomorphically and depth-controlled, which might limit their maximum possible extent. The Western Port bryozoan reefs are unique and globally significant because they: (1) occur in shallow water (typically 5–10 m), (2) are dominated by delicate fenestrate colonies of T. moniliferum and T. munitum, (3) have two distinct morphologies (linear and patch-like), (4) form continuous rows of reef interspersed with fine sediment, and (5) the size and vertical relief (up to approximately 1.5 m) are among the largest recorded in the world. In Western Port, these bryozoan reefs are habitat-forming and may represent sites of enhanced biodiversity, which is currently being investigated in another separate study and are likely important habitat utilised by commercially and recreationally fished species. The bryozoan biogenic reefs are a previously unrecognised feature of conservation significance in this Ramsar site. The reefs are potentially vulnerable to physical damage from recreational fishing practices, sediment smothering and scouring, algal encroachment and hydrological alteration. Recommendations for monitoring and potential management of this unique biotope are made.

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Water movements, sediment transport and deposition, Western Port, Victoria

Cited by 21 publications

References 11 publications

Short-Term Sedimentation Dynamics of Temperate Mangroves in Western Port Bay, Victoria

Short-Term Sedimentation Dynamics of Temperate Mangroves in Western Port Bay, Victoria

The balance between nitrogen fixation and denitrification on vegetated and non‐vegetated intertidal sediments

Extent and Characteristics of a Newly Discovered Unique Bryozoan Biogenic Reef Complex

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