A fine plankton net is dragged across Lake Taharoa, one of the Kai Iwi Lakes, to collect microplastics samples as part of a ground-breaking international study. Photo / NRC
A fine plankton net is dragged across Lake Taharoa, one of the Kai Iwi Lakes, to collect microplastics samples as part of a ground-breaking international study. Photo / NRC
Two Northland dune lakes are part of a ground-breaking international study measuring the presence of microplastics in lakes.
Microplastics — tiny pieces of plastic waste, often invisible to the naked eye — are created when plastic bottles, bags, wrapping and other items break down. They also come from car tyres, synthetic clothing and fishing nets and are washed into waterways by rain and water runoff.
Microplastics in the marine environment are known to harm animals, birds and kaimoana, but no one has ever measured how prevalent they are in New Zealand's freshwater lakes.
The results of the study will guide attempts to protect waterways from the emerging pollutant.
The Northland Regional Council (NRC) and the National Institute of Water and Atmospheric Research (Niwa) are taking part in Galactic, a two-year global study of microplastic levels in lakes.
The project involves gathering water from the surfaces of 54 lakes in 22 countries. Universities in Canada, Italy and the UK are analysing the samples, a complex process that comes at no cost to NRC.
Filter-feeding native species such as kākahi (freshwater mussels) could be affected by microplastics. Photo / NRC
In September, NRC staff took samples from two of Northland's most precious dune lakes, the 198ha Lake Taharoa (in Kaipara's Kai Iwi Lakes) and 56ha Lake Ngatu (northwest of Awanui in the Far North).
That entailed using a boat to drag a fine plankton net across each lake's surface, then rinsing the net with pure water to collect the microplastics samples.
The project is strongly supported by Ngāi Takoto (Lake Ngatu) and the Taharoa Domain Governance Committee.
Niwa asked the NRC to participate because the organisations already work together to monitor plastic in coastal areas and litter in Whangārei's Hātea River.
NRC freshwater scientist Manas Chakraborty said Northland's dune lakes supported native fish, invertebrates and kākahi (freshwater mussels) and were very sensitive to pollution.
"No one knows how microplastics affect freshwater animals, because this hasn't been studied in-depth before. But several of them are filter feeders, meaning they filter water to get food, so microplastics can easily accumulate in their systems," he said.
''Being part of this world-first study will give us valuable information, such as to what extent microplastics are accumulated in the system, what types of plastic there are, where they come from, and how long they stay in the freshwater system. It enables us to establish a valuable baseline for future studies."
NRC deputy chairman Justin Blaikie it wasn't known how much microplastic pollution the environment could deal with and how it could be treated.
''This research will build our knowledge of the issue so we can be prepared and put measures in place to manage future problems. We are very fortunate to get Te Taitokerau involved in this exceptional, first-of-its-kind international project.''
