A Bay of Plenty estuary was the focus of a week-long investigation to see how climate change and heat waves might impact marine species.
New Zealand's estuaries host a range of shellfish and invertebrate animals, which experience extreme temperature fluctuations as the tides sweep in and out.
Over seven days, marine ecologists used open-top chambers, which look like mini-greenhouses, to warm the air and sediment within them.
The estuary is near Pukehina, and there are two sites with 20 chambers, but the sites are quite different. One is muddy and degraded, and the other is on a sandy surface and appears much healthier.
NIWA ecologist Emily Douglas said understanding how warming affects or stresses marine species would help manage them in the future.
"We don't really understand the role of the shallow estuary ecosystems in the carbon cycle, so we don't actually know whether they're absorbing or emitting greenhouse gases."
The team expected the heat stress to increase the metabolism of the sediments, which would, in turn, increase carbon dioxide and methane emissions because processes occur more quickly as temperatures increase.
Ngāti Whakahemo, Ngāti Whakaue ki Maketū, Ngāti Mākino, Ngāti Pikiao, and Tapuika were also concerned about the estuary, and NIWA's research would be used alongside iwi.
Drew Lohrer, NIWA Strategy Manager, said the estuary's health has decreased over the decades.
"There's been something like 70% loss of sea grass over the last 70 years.
"[Iwi] realise that some of the land use has affected the estuary, and they're increasingly concerned with climate change and the loss of kaimoana."
Those working at the estuary said extreme sea temperatures and marine heatwaves were a "prime risk" to the ecosystems, particularly in shallow water, and there was a gap in knowledge that it was trying to fill.
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