Monitoring Auckland's intertidal zones

NIWA has been designing and analysing long-term monitoring programmes for the Auckland Regional Council (ARC) to check whether the ecology of some of the region’s harbours is changing.

It can be difficult to measure the impact of human-induced changes on the animals which live in the sandflats, mudflats, rock, beaches, and other terrain between the high and low tide marks. The creatures are generally small, hidden, and tend to cluster together in small patches. We must take all this into account if we are to sample them adequately.

When we see changes in the abundance of species, we establish whether the changes are likely to be natural or not and determine the most likely cause.

Manukau Harbour, for example, has been monitored since 1987. The communities found on its extensive intertidal sandflats are rich and varied. Many species have pronounced cycles in abundance – from season to season, and even over longer time periods of 3–7 years. These cycles can differ from location to location. Despite this, we are able to document with a high degree of certainty that the sandflat communities are stable and no major changes have occurred over more than 25 years now.