Yellow-eyed penguins / hoiho live in the sea and on land and therefore come into contact with a range of pollutants which cross both habitats. Typically, penguins are most vulnerable to pollution in the ocean as this is where they feed and likely to ingest or come into direct contact with pollutants.
Toxins or pollutants released on land make their way to the coast via storm drains, sewage outfall pipes or as run off from land into our rivers. Pollution is likely to be an issue for penguins living close to larger settlements (e.g. Dunedin).
Oil spills can have devastating localised effects particularly for small penguin populations. Oil affects penguins in two ways either through ingestion which may lower hormones and suppress breeding or poison them; or through the oiling of feathers. Oil reduces the waterproofing and insulation of the feathers, making the birds lose buoyancy and either drown or leaving them vulnerable to cold.
Algal blooms (a fast growing dense population of algae) can result from an increase in nutrients (e.g. from outfalls, storm water), and a combination of favourable environmental conditions. Less than 2% of these blooms can release toxins. Toxic algal blooms were a suspect in the unexplained mass mortality events of adult hoiho in 1989-90 and 2012-13, although there was no direct evidence.
Ingestion and entanglement in marine debris, is a major issue for many seabirds, although it has not yet been observed in hoiho. Plastic is a growing problem as it does not biodegrade quickly and forms more than 70% of the litter on New Zealand’s beaches. Plastic also contains toxins which can accumulate in the food web.