Wakame (Undaria pinnatifida), has been regarded as a noxious invasive seaweed in countries other than those where it’s native. Its believed undaria was introduced to foreign waters through the ballast water of cargo ships from Asia, as the spores (gametophytes) contained in the water can survive long-distance journies.
In New Zealand, Undaria (or wakame) was declared as an unwanted organism in 2000 under the Biosecurity Act 1993. It was first discovered in Wellington Harbour in 1987 and probably arrived as hull fouling on shipping or fishing vessels from Asia. Wakame is now found around much of New Zealand, from Stewart Island to as far north as Karikari Peninsula. Even though it is an invasive seaweed, in 2012 the government allowed for the farming of wakame in Wellington, Marlborough and Banks Peninsula.
Undaria spreads in two ways: naturally, through the millions of microscopic spores released by each fertile organism, and through human activities, most commonly via the hull of shipping vessels or marine farming equipment. It is a highly successful and fertile species, which makes it a serious invader. However, its impacts are not well understood and can vary depending on the location.
Wakame the ‘foe’
The downside of undaria is that it is invasive and can change the structure of ecosystems, especially in areas where native seaweeds are absent. By forming a dense canopy, it shades the sub-canopy, and can impact the growth of slower-growing native seaweed species. For instance, in New Zealand the native coralline algae which are important for paua (edible marine snail) settlement were partially displaced by wakame, resulting in decreased paua quantities.
Moreover, this invasive seaweed can affect not only the biodiversity of flora, but also the fauna communities which are based on these phytogroups. Wakame can grow on reefs which offer refuges for fish, and gradually lead to habitat loss of fishes that dwell on the reefs. Studies carried out in the Nuevo Gulf showed that the removal of wakame from invaded sites resulted in an increase in the biodiversity at those locations.
NIMPIS, 2002 states that Undaria pinnatifida has the potential to become a problem for marine farms because it increases labour and harvesting costs, due to fish cages, oyster racks, scallop bags and mussel ropes becoming covered. This growth can also restrict water circulation through cages.
Wakame the ‘friend’
On the flip side, Pacific Harvest is proud to offer a clean, ethically harvested wild wakame, which is densely nutritious and beneficial for health. The responsible harvesting and appropriate drying of wakame, and subsequent use of it as an amazingly beneficial kitchen pantry staple, means we rid our oceans of a ‘pest’, reduce costs of eradication and contribute to a circular economy.