Can corals adapt to climate change?

DR DAVID AGUIRRE - Institute of Natural and Mathematical Sciences, College of Sciences

It is a well-kept secret that New Zealand has its own coral reefs, located in a part of our territory that many may not know belongs to us. Our northernmost outpost, the remote and uninhabited Kermadec Islands, has some of the southernmost coral reefs in the world, in conditions of temperature and light that are almost at the lower limit in which corals can survive.

‘Corals there are really just hanging on by their fingernails,’ explains evolutionary ecologist Dr David Aguirre of Massey’s Institute of Natural and Mathematical Sciences. ‘However, as our oceans warm and tropical regions become less hospitable for coral growth, it is theorised that corals will expand their range further towards the poles, meaning that the Kermadecs could become a more coral-dominated ecosystem.’

Corals are particularly important organisms because they are ‘ecosystem engineers’ — that is, they house many other organisms and have a disproportionately large effect on ecosystems. They are the foundation of coral-reef ecosystems as we know them, and without them, those ecosystems would be structured completely differently. But corals are struggling in the face of climate change, with warmer conditions causing mass-bleaching events in many regions of the world. One of the important questions is, can they adapt?

Over the last three years, Dr Aguirre has taken part in scientific expeditions on board the RV Braveheart and NIWA’s Tangaroa to learn more about the region’s coral species. In 2017, he explored some of the most isolated rocks in the Pacific Ocean — Ongo Teleki/Minerva Reefs — located between the Kermadecs and Tonga, which are one of the potential stepping stones for corals and coral-reef species colonising the Kermadec Islands. The trip involved generating a biodiversity inventory for the islands and collecting genetic samples of coral-reef species in this area to investigate their genetic relationship to populations at the Kermadecs.

‘We know very little about the Kermadec Islands, and there are a lot of discoveries that could be made there,’ Dr Aguirre says. ‘It’s the northernmost range extent for a lot of temperate species, and the southern extremes for a lot of coral-reef species — it’s one of the few places in the world where these types of organisms interact. Every time we go, we find new species, and learn more about how these ecosystems are structured.’

In another project, Dr Aguirre and his colleagues at Massey — Dr Matthew Pawley, Dr Libby Liggins, Ms Margaret Kawharu and Dr Alastair Clement — as well as Dr Barbara Bollard-Breen at Auckland University of Technology, are using innovative methods and local knowledge to learn more about the toheroa population in Kaipara, an area where the large molluscs used to be plentiful. Local iwi, Ngāti Whātua o Kaipara, have noticed a dramatic decline in toheroa numbers, which used to support all the hapū in and around the south Kaipara area. However, carrying out a systematic survey of toheroa populations is difficult.

‘The problem with studying toheroa is that they tend to occur in dense patches spread over huge open sandy beaches that appear almost featureless,’ Dr Aguirre says. ‘To survey them accurately, you have to dig up incredible amounts of sand. This is logistically problematic and damaging to the environment. We wanted to see if we could come up with some clever ways of sampling toheroa that would be more feasible, and that did not cause any environmental damage.’

The team’s solution was threefold: to use ground-penetrating radar to help locate toheroa; to look for traces of toheroa DNA in the sand; and to use drones to search for the telltale marks toheroa leave on the beach. ‘The project was partly designed to generate some excitement around the innovative use of different technologies,’ Dr Aguirre says. ‘It’s fun to think about, and has the potential to be financially rewarding given you don’t have to spend so much time digging holes in the sand, which means surveys could be conducted more regularly, giving better information trajectories of those populations.’

In this project, Dr Aguirre and his colleagues worked with local kaitiaki to develop the protocols they would use to carry out systematic surveys of an area. ‘We had a couple of sessions with local high school kids and kaitiaki from Ngāti Whātua o Kaipara, running through how you would generate an estimate of the size of the toheroa population in the area, and the survey techniques that are typically used. We had really good engagement from the hapū members and the kaitiaki, and we have learned so much as well. That melding of Western science and mātauranga Māori changed how we designed the surveys, probably more so than we might have expected going into the project. Despite how clever we think we are as scientists, the traditional knowledge that accumulates though centuries of observation is irreplaceable.’

Project details

Award Massey University Early Career Researcher Medal
Date 2017

Project Linking genes, phenotypes and communities: Uncovering heritable variation in community structure
Dates 2014–present
Funder The Marsden Fund

Project Rapuhia te mea ngaro — Seek the things being lost: Incorporating traditional ecological knowledge in assessments of toheroa abundance
Dates 2016–present
Funder Unlocking Curious Minds, Ministry of Business, Innovation and Employment