The Hauraki Gulf faces contamination from many sources - urbanisation, historical mining, agriculture, stormwater runoff, marinas and wastewater. Contaminants bind to sediments on the seabed, affecting marine life and ecosystems. The primary concerns are heavy metals copper and zinc, with lead and mercury also present. For Māori, the impacts on the mauri (life force) of coastal areas and the safety of kai moana are of particular concern.

Contamination can be dramatic and localised, as with major spills, but much of the damage comes from countless small sources across catchments that combine to affect broad areas of harbours and estuaries. Environmental scientists are struggling to keep pace with an ever-growing list of emerging contaminants.

Recent Protection - A Turning Point

The Hauraki Gulf / Tīkapa Moana Marine Protection Act (October 2025) aims to reverse decades of ecological decline, creating 12 High Protection Areas, 5 Seafloor Protection Areas and extending 2 Marine Reserves.

The Act also recognises mana whenua as Kaitiaki (guardians), supporting authorised customary fishing, iwi-led restoration projects such as rebuilding mussel beds and managing kina barrens, and the placement of rāhui (temporary closures) to protect struggling shellfish beds.