Divers and snorkelers are privileged to experience the beauty and bounty of life in Wellington’s coastal seaweed forests. To raise awareness about the importance of, and threats to, local marine ecosystems, Wellington Underwater Club started a seaweed monitoring project through the global Project Baseline group.
The temperate waters around the Te Whanga-nui-a-Tara / Wellington coastline sustain highly diverse and productive marine ecosystems. Large brown kelp species dominate the rocky reefs along the coastlines and provide shelter, habitat and food and act as natural shore protection. Giant kelp (Macrocystis pyrifera) is particularly visible with fronds reaching up from the seafloor and floating along on the surface. It can grow a staggering 60 cm a day under ideal conditions.
Giant kelp is less likely to occur in areas where water temperatures exceed 18-19°C, and the inner bays of Te Whanga-nui-a-Tara / Wellington Harbour have already been noted as the very limit of growth.
Seaweed forests face a range of threats besides increasing water temperatures – sedimentation, sand inundation, coastal development, and pollution, including the impact of weed killers.
Overgrazing by exploding numbers of kina due to the lack of natural kina predators through overfishing can turn thriving seaweed forests into barren rock within a few years.
The group wanted to know how summer water temperatures affected the growth and abundance of giant kelp at Kau Bay. This bay, off the Miramar Peninsula, is one of the common dive sites in Te Whanga-nui-a-Tara / Wellington Harbour.
Over five years, they snorkeled around the giant kelp bed in May/June and Nov/Dec, using a GPS device to plot the surface area. They also used temperature monitoring data from the regional council. This indicated a warm summer or a cooler summer.
The project was designed to create awareness about the importance of seaweed as highly productive coastal ecosystem. It also aims to build understanding of threats to seaweeds and potential solutions for restoring a thriving coastal ecosystem.
Project Baseline Wellington is looking for volunteers. Regular snorkeler, freediver, scuba diver or underwater photographer in Wellington? Email Wellington Underwater Club.
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Project reports are publicly available on the Project Baseline Database.