CoastClim expedition to New Zealand highlights importance of coastal management for the climate
Marine researchers from Stockholm University and the University of Helsinki have temporarily changed their site of research; from the Baltic Sea to New Zealand. Using their unique set of instrumentation, they are spending three weeks exploring patterns in greenhouse gas emissions along the coastline. The preliminary results agree with the findings from the Baltic Sea that stressed and degraded coastal ecosystems become net emitters of greenhouse gases, and highlights the importance of proper management of coastal areas.
Within the research platform CoastClim, researchers at Stockholm University and the University of Helsinki have spent the past three years investigating the links between coastal biodiversity and greenhouse gas dynamics in the Baltic Sea. The objective has been to quantify the role of healthy or degraded coastal habitats in the life cycles of greenhouse gases such as carbon dioxide and methane, and the links to climate change.
Now they have adopted a global perspective on the issue, and a group of CoastClim researchers are currently in New Zealand for a three-week sampling campaign.
"The New Zealand coastline is very different from the Baltic Sea and therefore gives us an idea of the generality of our findings", explains Christoph Humborg, scientific leader of Stockholm University Baltic Sea Centre and CoastClim.
Precise measurement techniques
Christoph Humborg and his colleague at Stockholm University; Julika Zinke, have been conducting online measurements of greenhouse gases (including carbon dioxide, methane and nitrous oxide) along New Zealand’s coastal waters, particularly around the Auckland region, using the WEGAS system.
The system was developed at Stockholm University to enable collection of precise data on greenhouse gas emissions in water and air simultaneously, and has now been installed on the research vessel from the Institute of Marine Science, Auckland University.
Meanwhile, researchers from the University of Helsinki, including Alf Norkko, Nicolas Geilfus, and Anna Villnäs, have been using a similar setup on a smaller boat. This is allowing the team to study both open waters and more shallow systems, such as mangroves, mudflats, and the upper reaches of estuaries, simultaneously.
"We are investigating estuaries, lagoons, mussel farms, and water bodies close to a catchment with intense agriculture and livestock production", explains Christoph Humborg. "Even in these ultraoligotrophic systems — areas that in contrast to the Baltic Sea do not suffer from hypoxia or dead zones — we observe significant emissions of carbon dioxide and methane from the sediment in the upper reaches of the harbours and lagoon."
Elevated emissions measured
Although results are yet preliminary, methane concentrations were found to be elevated around the mussel farms, whereas concentrations of carbon dioxide were elevated throughout all systems, especially in the muddy sandflats that have increased in New Zealand, possibly due to deforestation.
"Importantly, the data highlights a very important finding – as we stress and degrade these coastal ecosystems, they transform into net emitters of greenhouse gases”, says Christoph Humborg, continuing:
"Therefore the message is to manage these ecosystems in a proper integrative fashion. It is not only about identifying the best places to store carbon but also places to optimise management to reduce cumulative effects and seafloor disturbance, and consequently release of greenhouse gases."
Closing the loop of New Zealand research
The researchers at the Institute of Marie Science, Auckland University have for a number of years been studying how different stressors (e.g., sediment run-off from land, nutrients from livestock production and microplastics) affect the way that nitrogen, carbon and oxygen are processed in coastal sediments.
These processes have important implications for the release of greenhouse gases, but until now the New Zealand scientist have not been able to test some connections and close the loop on some of their ideas. This is the reason why Professor Simon Thrush, a global leader in soft-sediment ecology, invited the CoastClim researchers with their unique skills and instrumentation to the country.
"This allows us to explore patterns in greenhouse gas emissions from the seafloor in ways that would not otherwise be impossible", he says.
"The joint effort between CoastClim and the Institute of Marie Science in New Zealand acknowledges that the interrelationships between the climate and biodiversity crises and transition to a nature-positive blue economy are key perspectives to move forward. Importantly, if we try and manage one ignorant of the other, we risk failure."
Text: Lisa Bergqvist
Further reading
CoastClim's web page coastclim.org
Methane bubbles dominate emissions in brackish stratified waters
Deciphering coastal climate impact: Sandviken Bay exploration
Last updated: January 31, 2025
Source: Baltic Sea Centre