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Cyanobacterial monitoring results

The Bay of Plenty Regional Council monitors the Rotorua Te Arawa Lakes for algal blooms. There are currently health warnings for Lake Rotoehu and Lake Okaro.

We monitor thirteen sites for cyanobacteria, spread across four lakes : Lake Rotorua, Lake Rotoiti, Lake Rotoehu, and Lake Ōkaro (and Lake Tarawera if required). These sites have been selected because they have been known to bloom in the past and the area is regularly used by the public for recreational activities.  

Sites are given an alert level status based on the amount of bacteria found. These results help Toi Te Ora to make a decision on whether a health warning should be put in place.

Key

Alert Level

Biovolume (mm3/L)

Green

<0.5

Amber

0.5 - 9.99

Red

>10

 

 

 

LOCATION

11/01/2018

07/01/2018

28/12/2017

21/12/2017

Kaituna

Trout Pool

0.0036

0.000

0.0131

0.0004

Okaro

Boat Ramp

8.7230

3.5590

7.2265

39.1498

Rotoehu

Kennedy Bay

0.7610

0.0349

0.5539

0.1516

 

Otautu

0.5570

0.0034

0.6315

1.1963

Rotoiti

Okawa Bay

0.5905

0.1188

0.0590

0.0143

 

Okere Arm

0.0047

0.0000

0.0189

0.0106

 

Otaramarae

0.0000

0.0006

0.0231

0.0174

 

Hinehopu

0.0002

0.0000

0.0105

0.0333

 

Te Weta

0.0067

0.0027

0.0175

0.0175

Rotorua

Hamurana

0.0010

0.0006

0.0576

0.0890

 

Holdens Bay

0.0012

0.0163

0.3546

0.0081

 

Ngongotaha

0.0000

0.0015

0.0008

0.0026

 

Ohau Channel

0.0027

 

0.0000

0.0035

 

0.0057

 

 

 

 

 

 

 

 

Lake Rotoehu

These results show that both Otautu and Kennedy Bay in Lake Rotoehu have increased from the green ‘surveillance’ level into the amber ‘alert’ level.  Microcystis sp. appears to be the most common species at both sites.  

 

Lake Ōkaro

Lake Ōkaro remains in the amber ‘alert’ level.  The main toxic species found in Lake Ōkaro was Dolichospermum (Anabaena) cf. circinale.

 

Lake Rotoiti

Okawa Bay in Lake Rotoiti has increased into the amber ‘alert’ level in this sample. The dominant toxic species found in Okawa bay was Anabaena Dolichospermum (Anabaena) cf. planctonicum.

 

Lake Rotorua & Kaituna 

All of the sample sites in Lake Rotorua and Kaituna (trout pool) remain in the green ‘surveillance’ level.

 

Visual observations summary:

Samples were collected on a fine day with clear visual signs of suspended particulate matter in Lake Rotoehu (both sites). There were minor signs of particulate matter in Lake Ōkaro and Okawa Bay (of Lake Rotoiti). 

 

For earlier results please email info@rotorualakes.co.nz