Date and Time: Thursday 29th April, 12:30-1:30pm
PART ONE: Using satellite-derived optical properties to extract the true coastal water colour in Tauranga Harbour (Zhanchao Shao)
In order to monitor estuarine health, a wide range of monitoring strategies are applied, including in situ water sampling, sediment bed level monitoring, observations of sediment properties, etc. However, these traditional ground-based surveys are expensive and labour-intensive. Therefore, remote sensing imagery like Sentinel-2 or Landsat-8 is widely used to monitor large-scale regions due to their high temporal and spatial resolutions. However, for the Case II water, the water surface reflectance is easily affected by the water bottom substrate reflectance. This may result in the greater errors in true water colour detection when the water depth gets shallower.
The proposed paper aims to detect true water colour from Sentinel-2 imagery for Tauranga Harbour and relate the water colour to other ecological factors. Here we develop and test a new methodology to extract the dominant wavelength of water from Sentinel-2 while removing the errors from the seabed and seagrass reflectance in shallow water and intertidal regions. The new methodology is based on estimating water bottom reflectance at the subtidal regions and the regression between seabed particle sizes and their reflectance. Our results show the high feasibility of this methodology to be used in large-scale true water colour extraction in the coastal regions. The extracted true water colour of Tauranga Harbour reflects the seasonal fluctuations and strong correlations with chlorophyll-a, suspended sediments and oloured metal ions. Future work will be directed to applying this methodology to all the coastal water in New Zealand and interpreting the colour dynamics in terms of ecological changes.
PART TWO: Sediment-effects on seagrass Zostera muelleri in New Zealand (Inigo Zabarte)
New Zealand’s seagrass meadows have declined substantially in the last 50 years, notably in estuaries affected by human activities. This is also a trend that is evident globally. The sole New Zealand species, Zostera muelleri, has a national threat status of “at risk – declining”. Globally, different factors are implicated in causing the decline of seagrass ecosystems. In New Zealand, fine sediment is considered to be the most pervasive stressor of estuarine environments and the most likely cause of seagrass decline in these systems. To increase our understanding of this threat-response issue, our research aims to determine acute and chronic fine sediment-effect thresholds for Zostera muelleri in terms of light attenuation, smothering and biogeochemical alteration of substrate. The research was based primarily in Pāuatahanui Inlet, North Island, New Zealand, where approximately 40% of seagrass meadows have been lost since the 1980s, primarily from the upper estuary. Both field surveys and experiments were used to explore the research aims. Previous investigations in the harbour have suggested that alteration to substrate biogeochemistry and/or smothering of plants is probably responsible for seagrass loss rather than sediment effects on the water column light climate. Thus, our research addressed the complex and multi-faceted effects of fine sediment inputs on the seagrass growing environment.
Kei te rangatira, tēnā koutou. The Local Organising Committee, under the auspices of the New Zealand Coastal Society, Engineers Australia’s National Committee on Coastal and Ocean Engineering, and PIANC Australia and New Zealand, invite you to attend Australasian Coasts & Ports 2021; an amalgamation of the 29th New Zealand Coastal Society Conference; the 25th Australasian Coastal & Ocean Engineering Conference; and the 18th Australasian Port and Harbour Conference.
The Australasian Coasts & Ports Conference series is the pre-eminent forum in the Australasian region for professionals to meet and discuss issues extending across all disciplines related to coasts and ports. Our Conference theme “Te oranga takutai – Adapt and Thrive” recognises the dynamic coastal environment that we live in and the need for coastal communities to be resilient and adaptable to thrive. Ōtautahi Christchurch and the wider Canterbury region are outstanding examples of this, with major seismic events having caused rapid and significant changes to the coastal environment and substantial damage to public and private assets and infrastructure. These events provide an ideal laboratory to examine the ongoing physical and built environment adjustments, and the possibilities for building stronger, more resilient and vibrant communities.
Australasian Coasts & Ports 2021 will bring together engineers, scientists and planners; academics, practitioners and those in the construction industry to focus on the present and future challenges of adapting coastal communities to thrive in dynamic coastal environments. Opportunities will be provided, in particular, to focus on challenges and solutions for port resilience, impacts and responses to catastrophic events, as well as to explore how local and indigenous values can be effectively represented in coastal management.
Australasian Coasts & Ports 2021 will feature engaging keynote speakers, incorporate numerous concurrent streams for technical presentations, trade exhibition, half-day field trips and the opportunity to network with colleagues in a vibrant social programme.