New Zealand’s coastline rich in ‘tasty’ red alga
Science Centres: Aquatic Biodiversity and Biosecurity
The microscopic conchocelis phase of a Porphyra species.
The outgoing tide has flattened this oily-looking Porphyra blade.
What do karengo (a Maori taonga), nori (the wrapping around Japanese sushi), and laverbread (a Welsh delicacy) have in common? The answer is the red alga Porphyra. Different species of this red alga grow in the intertidal zone all around the world from the Arctic and Antarctica through to the tropics. Porphyra is highly prized for its flavour and as a healthy food that is rich in protein and vitamins.
For many years it was believed that New Zealand had only one species of Porphyra; however, a NIWA biodiversity research programme, which extends to the Chathams and the subantarctic islands, shows there are many more species. New Zealand appears to be home to the greatest number of Porphyra species in the world. We can currently recognise 35 species, and more are discovered each year. Some of the species are widespread and occur throughout the North and South Islands, whereas others have very restricted distributions.
There are three important parts to the research programme – collections, culture, and molecular biology. We need to make seasonal collections around the coast to learn how the different species vary over time and location. In some areas the Porphyra populations are very seasonal, with big crops present on the rocks for only one to two months, and few or no crops at other times of the year. In other places you can find species of Porphyra almost all year round. Different species vary greatly in their texture, colour, size, shape, geography, and seasonal growth patterns. For example, some species are found mainly in winter and spring, while others are more likely found in autumn. It is important to gather as much information as possible about what species are growing where, and when, so we can build up a profile of each species.
We also need to study Porphyra in the laboratory; for example, growing it in culture and observing its blades and reproductive structures. It is not straightforward to study Porphyra because it has two stages in its life history: the conspicuous blade that grows on rocks is the form we collect from beaches around New Zealand, but there is also a microscopic fuzz stage, or conchocelis, which burrows into shells and rocks. You cannot see conchocelis when you go to the beach, but this phase is lurking in the shoreline, and, when the seasonal conditions are right (e.g., the right temperature and amount of light) the conchocelis phase produces spores that will develop again into blades. The ‘right’ conditions for one species may be subtly different from the ‘right’ conditions for another. Understanding these triggers helps us to determine what drives the differences in geography and seasonal growth patterns. NIWA holds a ‘seedbank’ of conchocelis from more than 100 strains of Porphyra from around New Zealand.
The third critical part of the research programme is to get a unique DNA profile for each species. Some Porphyra species that are not closely related to one another can look very similar, which is confusing when you are trying to understand which species grow where. But we also have the opposite problem where a single species takes on a whole range of different shapes and colours, depending on the growth conditions it has been subject to and the age of the thallus. Analysing the DNA is a dependable and rapid way of determining which sample belongs to which species. This helps build up a picture of each species, including its variability, what it could be confused with, and its seasonality and distribution. DNA profiles also help when comparing species and understanding their relationships. This information is used to build a kind of whakapapa of the species, so we can learn how Porphyra in New Zealand relate to Porphyra in other parts of the world.
Untangling the rich diversity of species, and understanding where and when these many species grow, will provide useful information for communities wanting to protect and sustainably manage their local resources.