National estuary experiment gets off the (muddy) ground

Field work has begun for a national study assessing the potential risks and consequences of nutrient and sediment runoff on marine ecosystems.

Evidence from around the world shows that subtle but cumulative effects can suddenly and profoundly alter the way marine ecosystems function, and their ability to cope with changing conditions. These sudden changes are called ‘tipping points’, and they are almost always negative – for example a loss in a valuable resource such as fish or ecosystem services such as water purification.

Our tipping points experiment is assessing the potential for rapid changes in marine ecosystems, identifying what activities are likely to cause such changes, and identifying what parts of the ecosystem are likely to be most affected. This knowledge will help New Zealand’s coastal management.

The researchers are setting up the first field sites, in Manukau. Next on the list are sites in Leigh, Coromandel, Whangarei and Otago.

First national experiment

“This research is particularly exciting because it’s the first marine experiment focusing on estuaries and harbours across the whole country,” says Prof Simon Thrush, project leader and Director of the Institute of Marine Science at the University of Auckland.

“We’re studying the two most influential factors affecting our coasts: nutrient and sediment runoff. We’ve selected sites with varying levels of sedimentation and burying slow release fertiliser at each site to mimic increasing levels of terrestrial nutrients entering the estuary or harbour. Over the next 1–2 years we’re monitoring the effect on the numbers of worms and shellfish and how the sediments get rid of these excess nutrients.”

Worms and shellfish affect estuary health because they influence the ability of microbes to process nutrients.

There are more than 20 sites in estuaries and harbours from Northland to Southland, including Whangarei, Whangateau, Mahurangi, Manukau, Raglan, Whitianga, Tauranga, Delaware Inlet, Nelson Haven, Banks Peninsula, Waimea Inlet, Blueskin Bay, and Jacobs River.

The project involves researchers from NIWA and the universities of Auckland, Waikato, Canterbury and Otago.

Related pages

• Tipping points hosts interdisciplinary workshop (news)
• Coastal tipping points talk at EDS conference (news)

• Project proposal

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