Stressor footprints and dynamics
We investigated how coastal waters and oceans mix and transport materials that can stress marine ecosystems.
Project leader: Craig Stevens, NIWA/University of Auckland
Duration: April 2016 – June 2019
We investigated the connection between open ocean processes and the movement of stressors, such as contaminants, nutrients or sediment. The information we collected tells us about the potential ‘footprint’ of a stressor in Aotearoa New Zealand waters.
Our research investigated how stressors from land use or coastal ecosystems connect with the wider marine environment. We were particularly interested in how the coastal areas of Tasman and Golden Bays connect with the open ocean of Cook Strait.
We used cutting-edge technology – including ocean gliders, drifters and met-ocean buoys – to measure biological and physical properties, and track movement and dilution of water between coastal bays and oceans. A NIWA ocean glider has now made over a dozen missions through the focal region to measure stratification, layers of varying temperature and salinity in the ocean. This field data is integral to the development of predictive numerical models of stressor dispersal.
We also used drifters to gather information about the provenance and fate of materials, such as suspended sediment and bacteria or macroalgal larvae in Tasman and Golden Bays. For one experiment, we released four long-distance drifters. Their satellite positions over two months show that parcels of water that started out 30 kilometres apart ended up many hundreds of kilometres apart.
A better understanding of how biophysical factors can influence or alter these processes, and how these systems interlink is critical for ecosystem-based management.
- O’Callaghan JM & Steven CL (2015) Transient river flow into a fjord and its control of plume energy partitioning. Journal of Geophysical Research, 120(5), 3444-3461 DOI: 10.1002/2015JC010721
- O’Callaghan J et al (2019) Developing an integrated ocean observing system for New Zealand. Frontiers in Marine Science. https://doi.org/10.3389/fmars.2019.00143
- Stevens CL (2018). Turbulent length scales in a fast-flowing, weakly stratified, strait: Cook Strait, New Zealand Ocean Science 14: 801-812 DOI: 10.5194/os-2017-30
- Stevens C & Noll B (2019) Coastal seas around New Zealand are heading into a marine heatwave, again. The Conversation.
- Stevens CL, O’Callaghan JM, Chiswell SM & Hadfield MG (2019) Physical oceanography of New Zealand/Aotearoa shelf seas – a review. New Zealand Journal of Marine and Freshwater Research, DOI: 10.1080/00288330.2019.1588746
- Stevens C & Plew D (2019) Perspective: Bridging the Separation Between Studies of the Biophysics of Natural and Built Marine Canopies. Frontiers in Marine Science, Marine Ecosystem Ecology, DOI: 10.3389/fmars.2019.00217
- Zeldis JR & Swaney DP (2018). Balance of catchment and offshore nutrient loading and biogeochemical response in four New Zealand coastal systems: Implications for resource Management. Estuaries and Coasts 41(8) 2240-2259 DOI: 10.1007/s12237-018-0432-5
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Last week (3–5 March), schoolchildren from across New Zealand travelled with LEARNZ and the Sustainable Seas Challenge to discover what's threatening mussels/kuku or kūtai, a taonga species, in Ōhiwa Harbour, and how science and mātauranga Māori are being combined by local kaitiaki to understand – and address – the problem.