Simon Maude / Things
Lake Pupuke was one of the lakes in Auckland that was rated ‘poor’.
More than two-thirds of Auckland’s lakes tested by scientists are below the bottom line for biodiversity and native vegetation, a new report shows.
The National Institute for Water and Atmospheric Research (NIWA) has assessed the ecological status of 15 natural lakes in the Auckland region.
While there were some positives, the report showed that native vegetation and biodiversity in most lakes was low – an indicator of poor water quality.
It comes after a report on Auckland’s rivers, for the year 2020, showed that the majority had high E coli levels.
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In the most recent report for Auckland Council, Niwa used the Lake Submerged Plant Index to give each lake an overall health rating. It took into account native conditions (biodiversity and native vegetation) and the impact of invasive species.
Of the 15 lakes, six were not vegetated and were not scored.
Of the remaining nine, two were healthy, two moderate and five poor.
Pupuke, Pehiakura, Kawaupaku, Okaihau and Kuwakatai were the lakes that got the score ‘poor’.
Most lakes did well when tested for invasive effects, but performed poorly under native conditions — where 69% fell below the national bottom line.
Delivered
Native vegetation provides habitat, food and oxygen in lakes.
More than half of the lakes were in stable condition, but Auckland Council scientist Dr Jane Groom said improvements were needed.
Some lakes were degraded and in poor ecological health, she said.
Submerged vegetation created a habitat for fish, provided a food source and added oxygen to the water, Groom said.
The work was in a pilot phase to see how best to combat the problem, she said.
water care
The Waikato River and the location where Auckland draws water into its pipeline
The public could do their part by checking to make sure they didn’t bring invasive weeds onto the lakes on themselves, their equipment or boats, she said.
Compared to the rest of the country, Auckland had no lakes in the ‘excellent’ category, fewer in the ‘high’ and ‘moderate’ category and more in the ‘poor’ category.
However, the comparison was somewhat skewed, Groom said — there were regions with lakes in alpine environments that were far from human pressure, while Auckland’s were mainly lowlands and surrounded by a rural environment.
The tests were conducted between December 2021 and April 2022.