Beds of New Zealand seagrass (Zostera muelleri) provide important habitat for coastal species such as small fish, seahorses, and shellfish. Much of New Zealand’s seagrass habitat has been lost or degraded, mainly as a result of sedimentation. NIWA is leading a small-scale seagrass transplantation trial in Whangarei Harbour, with promising early results.
Before the early 1960s, seagrass beds covered an estimated 14 square kilometres of the outer Whangarei Harbour. They have since almost disappeared, with only small pockets remaining on the southern shores of the harbour. Northland Regional Council is taking steps to reduce harbour contamination and is working with NIWA and the Whangarei harbour kaitiaki roopu on restoring seagrass beds.
Because the New Zealand seagrass grows mostly by clonal spread, and so is limited in its ability to colonise distant sites, it needs a helping hand to return to its former extent. NIWA has transplanted 18 square metres of seagrass from a remnant pocket at One Tree Point to the Takahiwai sandflats, once the site of extensive seagrass meadows.
Both the donor and transplant sites have been monitored since April 2008. The extracted plots recovered fully within nine months and transplanted seagrass has thrived and spread from the mid-tide transplant zone. It has so far spread over an area of 2400 square metres, at least half of which is a direct result of transplantation.