95bFM Wellington's sewage discharge & marine impacts
8 May, 2026
Interview by Pranuja Tahal, adapted by Chloe Porter
Untreated sewage has been flowing into coastal waters after severe flooding in Wellington, leading to concerns about what this could mean for marine ecosystems. Experts say the impacts could extend beyond immediate pollution, affecting habitats and species over time.
Dr. Christopher Cornwall, Senior Lecturer in Marine Biology at Victoria University of Wellington, spoke with 95bFM’s The Wire to discuss the environmental risks following the recent flooding in Wellington.
He explains that both short and long sewage outfalls are currently discharging untreated waste directly onto, or very close to, rocky reef ecosystems. Pumping this sewage out is “degrading kelp forest systems” as untreated waste “increases anthropogenic nitrogen, also micro algae that we do not want in the system.”
Cornwall notes that harm to kelp forests shift the balance in the ecosystem, with multiple other species dependent on kelp for their food and habitat. The untreated sewage suffocates these organisms. “Think about invertebrates, if we smother their gills, they can't breathe. Think about the seaweed, we smother the seaweed, they can no longer photosynthesise.”
Cornwall explains how Land and Water Aotearoa (LAWA) have picked up an increase of ‘human-derived bacteria’ on their recent readings through changes in the microbiome of organisms. This change in microbiome ”has negative impacts and can constrict growth and cause stress for these marine organisms.”
Currently, nitrogen microplastics and other contaminants are not being filtered out, so all these foreign waste items are flowing straight into the sea. Microplastics can “go into organisms like sponges, filter feeders”, which starts to “alter their physiology, release compounds, basically excessively stress them out.”
There are further risks for the public as this pollution affects food sources and local fisheries. Cornwalls warns that he “certainly wouldn't be eating any of the kai species, and wouldn’t think to for a long time after this is fixed.” Creatures like filter feeders specifically would have impacts on human health, as these animals essentially eat the sewage.
The flooding has exposed gaps in infrastructure and the system's ability to deal with extreme weather events. Cornwall suggests creating targeted “reef-by-reef scale” management systems, as well as “greater monitoring of these types of events across Aotearoa.”
He also emphasises the role of public accountability, urging people to “vote for policies that enact better management of our marine systems.”
