Research aims to quantify New Zealand’s Blue Carbon capacity of kelp seaweeds

A research project co-led by Blue Carbon Services and NIWA will aim to provide New Zealand’s first national estimate of natural kelp-carbon sequestration in the marine environment.

Kelp beds are at the centre of a Smart Idea study to determine a national estimate on kelp-carbon sequestration.

A research project co-led by Blue Carbon Services and NIWA will aim to provide New Zealand’s first national estimate of natural kelp-carbon sequestration in the marine environment.

Carbon sequestration is the process of capturing and storing atmospheric carbon dioxide.

Blue Carbon is the term for carbon captured by the world's ocean and coastal ecosystems. 

Kelp forests absorb carbon from the atmosphere via photosynthesis. As kelp matures, it releases organic material which sinks to the bottom of the ocean where it is stored, unlikely to be disturbed for thousands of years.

Researching this natural process presents an opportunity to mitigate climate change.

The Quantifying Kelp Blue Carbon project will aim to improve our understanding of the overall role of deep-sea kelp in offsetting New Zealand’s carbon emissions.

The project was awarded $1.15m from MBIE Endeavour “Smart Ideas” fund to conduct research from 2022-24.

Its findings could provide incentives to develop near and offshore kelp aquaculture, and to conserve and grow existing macroalgae beds to contribute to the country’s zero carbon emission objectives.

Kelp beds are the dominant primary producers in the coastal zone, with average drawdown of around 28 tonnes of carbon dioxide per hectare, per year.

In the case of the New Zealand native Giant Kelp, this is about 52 tonnes of carbon dioxide per hectare, per year, more than double that of pine trees.

High-level estimates suggest about 11% of the carbon drawdown by kelp could be sequestered for thousands of years in deep marine sediments.

The figure maybe higher for Aotearoa New Zealand because of our connections to deep water via submarine canyons that extend close into the coast.

“We propose to test this hypothesis,” the project’s science leader, NIWA Marine Geologist/Biogeochemist Dr Scott Nodder said.

“New Zealand has rich kelp beds and adjacent deep submarine canyons provide a unique situation where locally produced kelp biomass can be exported from the coast to the deep sea,” Dr Nodder said.

NIWA’s Dr Scott Nodder, Wellington, is the science leader for the three-year study.

About the study

The pioneering study will draw upon NIWA and Blue Carbon Services substantial expertise and research infrastructure.

Researchers are planning to conduct experimental work at NIWA’s Marine Environmental Manipulation Facility at Greta Point in Te Whanganui a Tara, Wellington.

Field research is likely to be conducted in Wellington Harbour, along Wellington’s south coast, followed by sampling in Te Tau Ihu - Marlborough Sounds, Te Moana o Raukawakawa - Cook Strait, and off Kaikoura.

NIWA would like to focus the research on the northern tip of Te Waipounamu South Island and central Aotearoa New Zealand for field sampling because of the wide distribution of natural kelp beds, which are likely to export carbon into the deep Hikurangi Trough via the Cook Strait and Kaikōura submarine canyons.

Researchers will measure kelp-carbon in the water column and marine sediments. It will be a multi-disciplinary approach to quantify how much of the country’s kelp biomass is contributing to blue carbon sequestration in the deep-sea.

It includes chemical biomarker analyses (fatty and amino acids) and quantitative environmental-DNA (eDNA) estimates using metabarcoding, droplet digital Polymerase Chain Reaction (ddPCR) methods, stable isotope analysis, combined with data on sediment transport, deposition and accumulation rates.

Mari Deinhart collects macroalgae samples from Moa Point in Wellington.

Radiocarbon and lead isotope dating of marine sediments will determine kelp-carbon accumulation rates and the longevity of kelp carbon sequestration. It is expected that this carbon sequestration is likely to be in the timescales of hundreds to thousands of years.

Data on the distribution of kelp beds, their productivity rates, ocean currents and seabed topography will allow an estimate of the overall transport to and the natural sequestration rate of kelp-carbon in sediments surrounding Aotearoa New Zealand.

Mari Deinhart has joined the project as a PhD student through Te Herenga Waka Victoria University of Wellington. She will focus on novel degradation experiments and field sampling. This will be the first step in a larger research project that aims to create a national inventory of the country’s blue carbon kelp-sequestration potential.

The overall project results could support the country’s move towards net zero emissions by providing data required to include kelp-sequestered carbon into national carbon budgets and potentially for inclusion in carbon markets.

It could also incentivise protection of natural kelp beds and the development of kelp aquaculture, not only for its nutritional, pharmaceutical, mussel co-culture, agricultural, energy and bioremediation opportunities, but also for natural and artificial biological carbon capture and storage.

PhD student Mari Deinhart will conduct degradation experiments and field sampling for the study.

Project Team

Rob Hickson from Blue Carbon Services Limited is responsible for quantitative and economic analysis, team co-ordination and project management. He has managed international research projects for the Asian Development Bank and World Bank. He is managing another Smart Ideas funded project “Carbon Sequestration and Mussel Productivity in Integrated Multi-Trophic Aquaculture”.

Dr Scott Nodder has led nationally significant research programmes on marine productivity and planktonic ecosystem structure and function, focussing his research on the fate of primary production and carbon cycling in the deep-sea.

Marine Biologist Dr Roberta D’Archino specialises in macroalgal ecology and biodiversity. She recently led a major MPI-funded project investigating the use of macroalgae as ecological indicators.

Molecular biologists Dr Jaret Bilewitch and Dr Judy Sutherland have extensive expertise in the development and application of species-specific eDNA and ddPCR assays for organism detection and quantification.

Marine ecologist Dr Daniel Leduc has experience researching seabed ecosystem processes in shallow and deep-sea environments. He leads NIWA’s Protecting Marine Biodiversity programme.

Mari Deinhart and Scott Nodder collecting samples on Wellington's south coast. Other field research areas include Wellington Harbour, Te Tau Ihu - Marlborough Sounds, Te Moana o Raukawakawa - Cook Strait and off Kaikōura.


What is Blue Carbon?

Blue Carbon is the term for carbon captured by the world's ocean and coastal ecosystems. Oceans provide a natural way of reducing the impact of greenhouse gases on our atmosphere, through the capture and sequestration (or storage) of this carbon.

What is a Blue Economy?

A blue economy is made up of marine activities that generate economic value and contribute positively to social, cultural and ecological well-being. Aquaculture, seaweed farming, offshore renewable energy, low carbon marine transport, tourism and biotechnology are all potential examples.

What is eDNA?

Environmental DNA, or eDNA, refers to the tiny traces of genetic material left behind as living things pass through water or soil. From kereru to kowhai, and the leaves in the wind, all living things shed genetic information into their local environment.

What is a ddPCR?

Droplet digital PCR (ddPCR) has emerged in the past decade. It represents one of the most sensitive, precise, and accurate methods for amplifying and quantifying sequences of different nucleic acids (DNA, RNA, and cDNA).