Algal Blooms Start

Hawke’s Bay Regional Council has had an alert that a severe algal bloom is in Lake Tūtira at present.

HBRC’s environment science team have assessed data from the monitored buoy on the lake which is showing high ‘phycocyanin’ levels, indicative of a high level of cyanobacteria, or blue–green, algae which is a potentially toxic species.

HBRC has advised the Guthrie Smith outdoor education centre against taking school groups boating or kayaking on the lake. HBRC will be sampling the lake water to confirm the algal bloom.

With warmer temperatures and summer almost here, algal blooms can occur in streams, rivers and lakes around the region. Algae are naturally found in waterways, but under favourable conditions they can grow to large numbers, causing them to ‘bloom’. Algal blooms in rivers occur more frequently when the flows are low in warm and dry weather. Algal blooms in lakes can also be stimulated by the input of additional nutrients following heavy rain.

In rivers, blooms may form mats. In the river these mats are often a shiny black colour, but when they wash up on river margins, they may be bleached pale by the sun. These dried mats can still be a risk. In lakes, algal blooms may change the colour of lake water to red or bright green. . Toxins may still be present in a lake after the colour from a bloom has returned to normal.

During periods of low river flow, HBRC monitors sites known to be prone to cyanobacterial growth. When cyanobacteria exceeds guideline levels, HBRC and the Hawke’s Bay DHB Population Health Service issue warnings to the public. Permanent signage is also used to warn the public at locations, such as Lake Tutira where there have been frequent algal blooms in recent years.

Blue-green algae - cyanobacteria - are species that, when they bloom, can produce toxins which can be harmful to people and animals. Toxic algal blooms can result in adverse health effects for people, including skin rashes where people have been in direct contact with the algae.

Dogs that scavenge along rivers are particularly susceptible to getting ill after contact with cyanobacteria. Dog owners are advised to keep dogs under control by rivers and lakes, and to take containers of clean water for dogs to drink.

People showing signs of illness following a visit to a river or lake potentially affected by algal blooms should consult a doctor. A vet should be consulted if any animals appear unwell.

18 April 2016

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