Coralline algae are classified in the red algae (Rhodophyta) phylum and are found in three orders (Corallinales, Hapalidialaes and Sporolithales). Coralline algal species can be found in a broad range of marine habitats across the globe, from the tropics to polar regions, from the intertidal zone to the euphotic zone and from rocky shores to tropical reefs and seagrass meadows.

Coralline algae are slow growing and provide habitat, protection and food for many different fish and invertebrate species. They also provide favourable conditions for the settlement of some marine invertebrates such as pāua, corals and kina.

Coralline algae contain calcium carbonate in their cell walls. The algae can be geniculate or non-geniculate. Geniculate corallines have upright branches that consist of alternating calcified and non-calcified segments, forming turfs on substrates. Non-geniculate corallines are completely calcified and form pink crusts over surfaces. These are commonly known as ‘crustose’ coralline algae. Non-geniculate coralline algae can also be found unattached to substrate (free floating) in a growth form known as a rhodolith or maerl.

New Zealand’s Subantarctic Islands coralline species

Little is known about the diversity and taxonomy of coralline species around New Zealand’s Subantarctic Islands. In 2016, the Sir Peter Blake Trust Young Blake Expedition, under the supervision of Dr Rebecca McLeod, a marine ecologist, collected coralline algae samples at a range of representative habitats in the intertidal zone around the east coast inlets of the Auckland Islands. Student voyagers were responsible for collecting the samples, recording data – observations, counts and measurements – and then preserving the material so it could be analysed in a lab back on the mainland.

Back in the lab

Brenton Twist, a University of Auckland PhD student working under the guidance of Wendy Nelson at NIWA, analysed both the genetic and anatomical features of the coralline algae that had been collected. DNA was extracted from the samples, and using the PCR technique, one specific gene was sequenced and compared against the existing dataset of internationally and locally recorded DNA sequences. This comparison indicates whether a new species has been discovered. These analyses will also help to improve the knowledge on diversity and distribution of coralline algae in southern New Zealand.

The collection of baseline data is vital work, not only for the possibility of discovering new species but because the Subantarctic is vulnerable to the impacts of climate change. Monitoring ecological communities such as coralline algae contributes to our understanding of the impacts of climate change.

Coralline algae play an especially important role as an indicator of global climate change since the calcium carbonate in their cell walls will dissolve more easily as the ocean becomes more acidic.

The baseline data collected and subsequent measurements can be used to determine the rate and scale of change and the effect that ocean acidification is having.

Nature of science

Scientific knowledge may change with the discovery of new techniques and new information. Scientists commonly debate new information and arrive at new understandings, and as a result, the classification of organisms can change. For example, recent developments in DNA technologies have resulted in the reclassification of some species.

Activity idea

In the activity Develop a classification system, students work in small groups and come up with their own classification system for a number of marine organisms.

In the activity Exploring genetic variation, students gain an understanding of the importance of genetic diversity within a population.

Bryozoans

This article is about tiny marine animals called bryozoans. Like the coralline algae, bryozoans may help indicate the impact of ocean acidification on the marine ecosystem.

Acknowledgement

This article’s main contributor was Cherie Fenemor from Freyberg High School, who joined the Young Blake Expedition to the Subantarctic as the Sir Peter Blake Trust Educator in February 2016.

In memory of Sir Peter Blake, the Sir Peter Blake Trust was established. This Trust supports a wide range of programmes that encourage environmental awareness and action, and leadership development. Sir Peter was one of New Zealand’s best known sailors and explorers.

    Published 23 September 2016