Horo was appointed full-time rowing manager for Otago and Southland five years ago, but the role was scaled down when funding was reduced two years ago.
"I have taken on extra responsibilities in my role with the Academy of Sport," Horo told the Otago Daily Times yesterday.
"I cannot effectively manage both roles and can't do justice to rowing."
Horo helped to lift rowing's profile in Otago.
Successful rowing coach Sergio Salis acknowledged Horo's contribution.
"Dean's involvement will be missed," Salis said.
"His objective and non-partisan approach has been of great value tothe sport in Otago.
"His work in fundraising has been excellent and has taken a great load off the volunteer members of the Otago Rowing Association."
The ORA has confirmed it will look for a replacement for Horo.
Horo is a performance adviser and programme co-ordinator for the pre-carding programme role at the Academy of Sport.
There are 13 promising athletes across a range of sports in the programme's first-year intake.
Horo will also assist with the motorsport academy run by former New Zealand cricketer Martyn Croy.
After growing up in Southland, Horo was an intermediate school teacher in Invercargill before spending time overseas.
On returning to New Zealand he worked for the Academy of Sport in Auckland and for Sport North Harbour before returning to the South five years ago.
