Abstract
A national observing network has been operating over the past 4 years to inform the scientific and economic challenges of ocean acidification (OA) facing New Zealand. The New Zealand Ocean Acidification Observing Network (NZOA-ON) consists of 12 sites across varied coastal ecosystems. These ecosystems range from oligotrophic ocean-dominated systems to eutrophic river-dominated systems, with sites that are pristine or affected by agriculture and urbanisation. Fortnightly measurements of total alkalinity and dissolved inorganic carbon provide the baseline of carbonate chemistry in these varied ecosystems and will facilitate detection of future changes, as well as providing a present-day baseline. The National Institute of Water and Atmospheric Research and the University of Otago have developed a 'grass-roots' sampling program, providing training and equipment that enable sampling partners to collect field samples for analyses at a central laboratory. NZOA-ON leverages existing infrastructure and partnerships to maximise data captured for understanding the drivers of chemical changes associated with OA and ecological responses. NZOA-ON coordinates with and contributes to global initiatives to understand and mitigate the broader impacts of OA. A description of NZOA-ON is presented with preliminary analyses and comparison of data from different sites after the first 4 years of the network.