The red seaweed of Otago Harbour

We join Marine Science PhD student Namrata Chand on her Autumn field work collecting seaweed samples to learn more about this 'underdog of the ocean'.

Namrata Chand began diving in the coral reefs and warm crystal-clear waters around her native Fiji. Diving to sample seaweed in Otago Harbour for her PhD is quite a different experience.

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'I describe it as refreshing' she says, 'My first dive in Dunedin was in nine-degree water'.

Namrata, or Nam, is studying a type of endemic (found only in New Zealand) red seaweed called Adamsiella chauvinii. Instead of attaching to rock like kelp, this seaweed species can grow on the soft sediment habitat found in Otago Harbour. It is thought to play important roles for this ecosystem including taking up nutrients from the water and providing habitat for a range of other seaweed species and marine creatures.

For her research, Nam wants to understand where this red seaweed grows in the harbour and in what quantities, which nutrient, light and temperature conditions it likes, and what other seaweed species grow with it.

To do this, she has been sampling seaweed at sites in three different areas of the harbour. The samples are taken back to the University of Otago's Portobello Marine Laboratory where Namrata sorts them into different species and weighs them to get the biomass of each type.

Alongside this, over the last two years, Nam has been gathering data on the light and temperature conditions in each area, as well as water samples to do seasonal nutrient analysis.

In the footsteps of female phycologists, Nancy Adams (after whom the species is named), and her co-supervisor Professor Wendy Nelson, Nam has also begun pressing some of the seaweed samples she has collected. This has helped her to get up close and personal with the different species, aiding her identification skills. But it will also be part of her PhD legacy - Nam will deposit her pressed seaweed collection into the University of Otago herbarium for future students to be able to view and use.

In this episode, Claire Concannon joins Nam on her Autumn seaweed sampling trip to learn more about this 'underdog of the ocean', and the art of seaweed pressing.

To learn more

Scientists elsewhere in Aotearoa are growing macroalgae for research purposes and to explore potential uses of native seaweed and freshwater macroalgae. Listen to this episode about the Facility for Aquaculture Research or Macroalgae in Tauranga Moana…

Go to this episode on rnz.co.nz for more details