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Sediment contained low and ecologically insignificant levels of trace metal contaminants, total organic carbon and nutrients; however, despite these chemical indicators of trophic state suggesting good ecological health, the sediment profile at all sites showed visible signs of moderate enrichment. A three to four fold increase in mud in the upper Pāuatahanui site and the upper Onepoto site was measured. The most notable shift over time has been a gradual decline in diversity and abundance of sediment-dwelling macrofauna species at all sites except that adjacent to Porirua City, with a total of 96 species recorded from the Harbour in 2020. These declines appear in part attributable to increased sediment mud content, and have been accompanied by the loss of several species intolerant of mud.

Reference: Forrest BM, Stevens LM, Rabel H. 2020. Fine Scale Intertidal Monitoring of Te Awarua-o-Porirua Harbour. Salt Ecology Report 044, prepared for Greater Wellington Regional Council, August 2020. 33p.

Author/s: Barrie Forrest, Leigh Stevens and Hayden Rabel. Salt Ecology