Marine ecosystems around the world have been impacted by degradation and loss of biodiversity as a result of human impacts and climate change. The monitoring and management of ecologically significant areas is vital in understanding the effects of habitat degradation on marine ecosystems. Traditional monitoring methods are often expensive, time consuming, labour intensive and invasive. Soundscapes offer a unique opportunity for monitoring habitats in a way that is cost effective, minimally invasive and efficient. The aim of this study was to use passive acoustic monitoring to create a baseline data set using ambient sound data to investigate the spatial and temporal changes in ambient sound pressure levels, and to identify biotic, abiotic and anthropogenic sound sources which make up the marine soundscapes at the Motiti Island and Ōtaiti/Astrolabe Reef. Five diverse and ecologically significant sites in the Motiti Protection Area – at Ōtaiti/Astrolabe Reef and Motiti Island, in the Bay of Plenty, New Zealand were selected and monitored over the course of a year. This provided a wide variety of data to show the diel, lunar and seasonal patterns and trends in acoustic biological activity in order to represent the ecosystems accurately. The results showed that all sites showed strong diel patterns, with a sound pressure level increase of ~6-10dB during daylight hours compared to dark hours, and evident peaks during dawn and dusk hours as a result of biological choruses composed largely of sea urchins. There were also strong seasonal trends among the five sites, with Summer having the overall highest sound pressure level compared to Spring, Autumn and Winter, this also had an effect on the peaks in dusk choruses, which were also found to be highest during Summer. Lunar phases were also found to have an impact on the sound pressure levels of all five sites, with increased sound pressure levels during the new moon, compared to sound pressure levels during the full moon. This study created a baseline data set for a culturally, ecologically, and economically valuable area. Passive acoustic monitoring was found to be an incredibly useful tool in understand the ecosystems health and biological condition, and offers an alternative to traditional monitoring which is an effective, minimally invasive, and less labour intensive way of monitoring marine ecosystems.