Joint research project between Calypso Science and the Mediterranean Institute of Oceanography, in collaboration with the University of Auckland

Attracting(blue) and repulsive (red) LCS within the Hauraki Gulf. See the animated version at the end of the article.

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Calypso Science is pleased to participate in a joint research project with the Mediterranean Institute of Oceanography, in collaboration with the University of Auckland. The research project focuses on the fine-scale physical characterization of the seascape and its impacts on spatial distribution and connectivity of marine populations, with a comparative approach on two different but highly-valued marine environments : the Hauraki Gulf Marine Park in New Zealand and the Port-Cros National Park in the Mediterranean Sea.

The seascape concept provides a useful framework to study and interpret how the physical structures and processes in the ocean define regions with distinct characteristics that can shape ecological patterns in the marine environment.

Seascapes are characterised  by several factors which are outlined below:

• Oceanographic processes: The ocean comprises distinct regions characterised by varying physical properties including current flows, temperature, salinity, wave exposure etc.. that create a mosaic of different environments from open waters to coastal zones. The seascape framework examines how these oceanic patches interact and evolve across multiple temporal scales, from daily to annual cycles and longer.

• Boundary Interactions: Seascape characterization examines boundaries between oceanic regions, such as coastal-open ocean interfaces and areas of contrasting hydrodynamic flows, where significant exchanges of energy and biological activity occur through processes like currents, eddies, and tides. These dynamic processes create distinct fronts and convergence/divergence zones that influence the transport of nutrients, larvae, and plankton, ultimately shaping the distribution and composition of marine communities.

• Underwater Habitat: Underwater offshore topography (like continental shelves, canyons) along with coastal features (like reefs, beaches, cliffs, mangrove ) define the underlying seascape structure. These features provide various habitats compatible with different marine species.

• Human Activities: Fishing, coastal development, pollution, aquaculture, tourism, can affect the natural seascape by modifying habitat, increasing pollution, or bringing in invasive species.

 Calypso Science 's role in the research project includes three main components:

• High-resolution modelling. We provide high-resolution hydrodynamic models of the Hauraki Gulf and Port-Cros regions which provide the foundation for the ocean physical assessment of the seascape (see example  in Figure 1).

• Particle tracking modelling. We will develop tools to derive marine connectivity metrics, such as connectivity matrices, residence time, flushing rates. These metrics allow interrogating the hydrodynamic model for the likelihood of connection between different regions within the seascape, including different natural areas (e.g. due to flows, habitats), as well as areas of human activities (fishing, aquaculture, wastewater discharge etc…) and protected areas.

• Lagrangian Coherent Structures (LCS). We will characterise LCS regime within the Hauraki Gulf and Port-Cros areas, such as flow convergence/divergence fronts and transport barriers, and evaluate its influence in shaping the marine connectivity within the studied seascapes (see Figure 2). More information on LCS can be found in our white paper.

These metrics will be used to inform how the fine-scale ocean circulation and frontal structures control the retention and transport of target marine species, for example identification of source and sinks areas for larvae, and how they are modulated over time. For this study, the target species will be the iconic Tāmure/Snapper (Chrysophrys Auratus) which is a fish of significant economic, cultural and ecological importance in New Zealand and particularly in the Hauraki Gulf.

The tools developed to derive marine connectivity metrics and characterise the coastal and ocean frontal structures have a broad range of applications including improved design and management of marine protected areas, assessment of biosecurity threats, impact assessment and optimization of aquaculture operations, guidance for Search and Rescue (SAR) operations.

The project team includes French M.Sc. student Emma Bruder working under supervision of Vincent Rossi from the Mediterranean institute of Oceanography, Simon Weppe and Remy Zyngfogel from Calypso Science, and Giovanni Coco and Alice Della Penna from the University of Auckland.

Please contact us if you would like to learn more about the project.

Figure 1. Currents within the Hauraki Gulf from a high-resolution SCHISM domain with spatial resolution ranging from 20 m to 1600m. The polygons show the existing (red) and proposed (white) marine protected areas, and existing fish farms (yellow). A similar domain will be implemented for the Port-Cros study site.

Figure 2. Attracting(blue) and repulsive (red) LCS within the Hauraki Gulf. Repulsive structures tend to mark separation lines along which particles are repelled to each other. On the contrary, attracting structures show lines of accumulation, along which particles tend to be collected, without transfer of mass. Regions in which the attracting and repulsive LCS are aligned are subject to high shear transport whereas the intersection between the two locates transport barriers.