Robert Hickson1, Scott D. Nodder2, Roberta D’Archino2, Judith E. Sutherland2, Jaret P. Bilewitch2, Joe Zuccarello3, Daniel Leduc2, Mari Deinhart2,3,
1 Blue Carbon Services Limited, 77 Mataikona Rd, Castlepoint, Masterton 5889 New Zealand.
2 National Institute of Water and Atmospheric Research (NIWA) Ltd, Private Bag 14-901, Kilbirnie, Wellington 6021, New Zealand
3 School of Biological Sciences, Victoria University of Wellington, Wellington New Zealand.
Even with Paris carbon emission-reduction commitments the world faces an average 3.5°C temperature rise (Steer & Reid, 2018). The promotion of kelp-derived blue-carbon sequestration is emerging as an exciting opportunity to mitigate climate change. Kelp beds are the dominant primary producers in the coastal zone, with global production of 28.3 tonnes CO2eq ha-1yr–1. High-level estimates suggest approximately 11% of carbon fixed by kelp is sequestered near-permanently (100s-1000s of years) in deep (>1,000m) marine sediments (Krause-Jensen & Duarte, 2016). We are testing this hypothesis with direct data measurement on the Aotearoa New Zealand continental margin, where rich kelp beds and adjacent deep submarine canyons allow export of kelp biomass to the deep sea. We are quantifying the accumulation of kelp-derived carbon in offshore water columns and sediments using a range of techniques including; bulk and compound-specific stable isotopes, eDNA and droplet digital PCR as well as radiometric dating (14C and 210Pb). We will utilise a range of endemic NZ kelp species (e.g., Macrocystis pyrifera, Ecklonia radiata, Lessonia variegata, Marginariella boryana, M. urvilliana, Durvillaea spp.), focussing on the central Te Tau Ihu Marlborough Sounds and Te Moana-o-Raukawa Cook Strait region. By determining carbon concentrations, age and biological sources in kelp-degradation experiments, sediment cores and filtered water samples, we will establish relationships between coastal kelp-biomass and the quantity and longevity of kelp-derived carbon sequestration. We will interface this information with macroalgae distribution and regional hydrodynamic models to determine high potential sites for kelp-carbon sequestration and perhaps allow blue-carbon inclusion in future markets.