Sea lettuce or ulva is a common seaweed that can be found in high and low intertidal zones in most parts of the world. While some people like to dry it and use it as a flavourful addition in their recipes, a team of researchers in New Zealand has a somewhat different idea. AgriSea, a seaweed innovation company based in Paeroa on the North Island, is currently working with the University of Waikato on a land-based sea lettuce growing trial at Kopu marine precinct. The cooperation hopes to help restore New Zealand’s waterways.

Damien O’Connor, New Zealand’s minister of agriculture said the trial is a nationwide first and seeks to address an important environmental issue by using the seaweed to soak up nutrients that freshwater plants are currently unable to absorb: “Currently the loss of nutrients not absorbed by plants enters the soil and drains into groundwater that leads straight to our waterways. This promotes algal blooms which reduces oxygen levels, which then threatens animals such as eels, freshwater mussels, freshwater crayfish, and whitebait. This bioremediation project is using Kiwi ingenuity to see if the seaweed can act as a sponge, soaking up excess nitrogen, phosphorus and helping clean our waterways.”

Three ponds totalling 60 square metres that draw water from the Waihou estuary will grow the locally present green seaweed species ulva for 12 months in the hope of providing data from real-world ambient conditions. “Sea lettuce will be cultivated and scaled up at the University of Waikato’s aquaculture facility. Researchers will use DNA barcoding to confirm its genetic identity. Species selection will be based on growth performance for bioremediation in conditions mimicking the Waihou river estuarine water,” says O’Connor and continues: “If successful, this will be an environmentally-friendly way to improve water quality, create jobs in the science sector, revitalise our waterways and improve our on-land farming systems.”