Kina cull brings sealife back to Taranaki wharf
Beneath Wellington's waterfront a submarine renaissance is blooming, with maritime ecology returning to the shoreline and the vision of a "blue belt" for the capital coming to life.
In late 2011 diver Steve Journee - owner of The Dive Guys scuba company - hatched a plan with the Wellington Waterfront group to try to recover marine life under Taranaki wharf.
"The next stage of the restoration project is to install informative signs and a periscope or two, at various points of interest, to tell and show off the beauty of what is down there," Mr Journee says.
A glass-bottomed walkway has also been mooted to complement strategically placed periscopes.
Ultimately Mr Journee would love to see a "blue belt" of thriving marine ecosystems linking the harbour with the Taputeranga Marine Reserve on the south coast.
The mission is to educate Wellingtonians about the harbour's rich biodiversity while highlighting the perils of polluting the stormwater system that drains into the harbour.
"If the public look into the water and see a hive of activity, I like to think they'll be far less inclined to allow litter and pollutants to wash into the harbour from stormwater drains," he says.
Dog faeces, oil, heavy metals, paint, detergents, fertilisers and all manner of rubbish end up in the harbour carried by these largely unseen portals.
As settlers built the city, streams were gradually piped to improve sanitation - and so houses, roads and other infrastructure could be built on top.
"These piped streams are part of the city's stormwater network," Wellington City Council Our Living City adviser Nicci Wood says. "Collectively, we all need to look after the quality of this water as it flows untreated through our streams and into the harbour. If we don't have the blue belt, the green belt's going to go pretty quickly."
The Taranaki wharf restoration team first had to establish why there were no weeds growing there when all around there were sponges and sea squirts and masses of other sea life.
They tested the water to see if the nutrient levels could support plant life while test plants were put in and monitored for kina action. The sea urchins swarmed the plants, which were devoured in a matter of days.
"As the water samples came back with good levels of nutrients, kina were the clear reason for there being no plants."
The samples also showed an imbalance in the ecosystem; there were too many kina with no clear threats to it. As more plants were introduced into the area and became established Mr Journee devised an organic method of dealing with the burgeoning kina.
They were moved to patches of undaria, an invasive weed, at a rate of about 100 per dive. When that number had dropped to about 20 per dive, 11-armed star fish, a kina predator, were transported from rocks and piles under the wharf and placed around the weeds in a "defensive" formation to chase the kina away.
"With less kina in the immediate area the weeds are doing well and other natural harbour weeds and algae are also coming back," he says. "Also the weeds are now being used by juvenile fish and pipefish as safe swimming zones, which is also bringing the short-tailed sting rays closer in to feed, thus creating a balance in the eco system which was the plan in the first place."
The Dominion Post