While Poole had seen the council through "a period of rapid growth and expensive growth" it was time for a new direction with a focus on "core services and cost efficiencies".
He thanked Poole for his service over the past five years.
Poole has been asked to stay on to help with the transition after what was a seven-month recruitment process.
The council's decision was not linked to the fallout from the Bella Vista saga, Brownless said.
"I don't think it did play a role because we are still waiting to find out what happened at Bella Vista."
The council was waiting to hear the results of an independent investigation into the issues by former High Court judge Paul Heath.
In a council-released statement, Poole said that while he was disappointed, he was also "proud of what we have been able to do".
"We have faced some challenging times, as you do when you're growing. However, I believe council is now focused on the right things, is more effective, and is on the way to becoming an internationally competitive city."
The Bay of Plenty Times has approached Poole for further comment.
Who is Marty Grenfell?
Before being appointed to lead Whakatāne's council in 2011, Grenfell was a senior manager at Upper Hutt City Council and Hutt City Council, and had 20 years' experience with NZ Police.
Grenfell said while he was excited by the challenge ahead, it would be tough leaving behind friends and colleagues and the Whakātane area.
"Whakatāne has become home and will always remain a special place for our family. Professionally, I have relished the opportunities my role has given me and I'm grateful for the faith and support provided by elected members, staff and the community.
"Tauranga is only an hour away, so I intend to maintain the enduring relationships I have formed with so many people in the Whakatāne District."
Whakatāne District Council Mayor Tony Bonne announced the news this morning "with tremendous sadness".
"But at the same time, we always knew Marty would be moving on to bigger things at some stage and this move is a wonderful opportunity for him".
Tauranga City Council chief executive Garry Poole pictured during a press conference about the Bella Vista evacuation. Photo/file
Poole "disappointed"
Poole said while he was disappointed to not have been reappointed, "I am very proud of what we have been able to do".
"We have faced some challenging times, as you do when you're growing. However, I believe council is now focused on the right things, is more effective, and that Tauranga is on the way to becoming an internationally competitive city.
"For me, some of the standout highlights from the last five years include the new university, which is changing the downtown skyline as we speak; improved relationships with key partners, particularly tangata whenua; and collaborative projects that are changing the face of Tauranga, such as the Marine Precinct, Bay Oval lights, Paradox Street Art Festival, tidal steps, High Performance Sports Centre and the return of 60 Chapel St to Ngāi Tamarāwaho."
Poole was appointed in April 2013, after 15 years as chief executive at Wellington City Council.
