Rotorua Lakes Report Out
Rotorua Lakes Report
For immediate release: 15 May 2008
The health of Lake Okaro is improving and blue green algae levels are down, according to the latest report on Rotorua lakes water quality.
However boaties, fisherman and other lake users should still check and clean their equipment, as new weeds have been found in previously clean lakes.
The Rotorua Lakes Water Quality Report is produced annually by Environment Bay of Plenty. It analyses 12 lakes Okaro, Rotorua, Rotoehu, Rotoiti, Rotomahana, Rerewhakaaitu, Okareka, Tikitapu, Okataina, Tarawera, Rotoma and Rotokakahi.
Environment Bay of Plenty Scientist Matt Bloxham, one of the authors of the report, said overall the outlook was positive.
“The 2007 report was business as usual and there was both good and bad news in terms of lake quality. Algal blooms, or cyanobacteria blooms, were down on previous seasons. However we did find some new invasive weed in a couple of the lakes which is of concern,” said Mr Bloxham
The good news is that Lake Okaro’s water quality showed definite improvement and this was the third continuous season of good results for the lake. The positive outcome is a result of remediation works including the introduction of a wetland by farmer Shane Birchall and the use of treatment products to absorb phosphorous and nitrogen.
There were also improvements in the level of blue green algae in the worst affected lakes with only two public health warnings issued by the officer of medical health over the period from Spring to late autumn 2007. In previous years around four warnings per season had been issued.
Environment Bay of Plenty scientists were disappointed to find invasive weeds called hornwort and egeria in Lake Rotomahana. New weed was also found in Lake Okataina but it was just one plant which was eradicated immediately.
People using the lakes are reminded to check and clean their equipment every time they move between lakes to prevent the spread of aquatic weeds.
“The water quality of the lakes is something the whole community can work together to improve. I would therefore urge all boaties, fishermen and other users to pause before they leave one lake for another and check their equipment thoroughly for weed,” said Mr Bloxham.
Boaties are advised to look under the boat trailer, check the anchor and run their hands along the trailer to check for the smallest pieces of weed. It only takes a piece of weed the size of a fingernail to cause a problem in a pristine lake.
All the lakes were monitored in terms of their ecological health and Trophic Level Index, which takes into account the total nitrogen, total phosphorus, clarity and chlorophyll a in a lake. Nitrogen and phosphorus are essential plant nutrients. In large quantities they can encourage the growth of nuisance aquatic plants such as algal blooms.
Nine lakes exceeded the Trophic Level Index targets set by Environment Bay of Plenty. When a lake reaches this trigger level, Environment Bay of Plenty staff work with local communities to examine the causes and an action plan is drawn up, which addresses potential sources of contamination.
Lakes Okareka and Okaro have action plans while the plans for the other lakes are at a draft stage.