Keys to a hidden marine world

A screen shot of the home page of the Antarctic Marine Protists taxonomic key website. Users can click on the images to launch keys to the relevant taxonomic group. Many of the images were taken in the Australian Antarctic Division’s electron microscopy laboratory. Others are credited and referenced accordingly.
A screen shot of the home page of the Antarctic Marine Protists taxonomic key website. Users can click on the images to launch keys to the relevant taxonomic group. Many of the images were taken in the Australian Antarctic Division’s electron microscopy laboratory. Others are credited and referenced accordingly. (Photo: AAD)
Dinophysis ovum; one of 82 species of dinoflagellates described in the key. Dinoflagellates have two whip-like ‘flagella’ which allow them to move in a whirling motion. The cells are large enough that they can be identified by light microscopy, but scanning electron microscopy may be needed to resolve some features.This silicoflagellate is one of the most spectacular and readily identified organisms in the Southern Ocean. As the name suggests their structure is made primarily of silicon.This cell is from the Cryptophyte group and was collected in the waters off Davis station, Antarctica. Cryptophytes are single celled animals (protozoa) with whip-like ‘flagella’.  A scanning electron micrograph of a coccolithophorid (marine alga) Calcidiscus leptoporous. Coccolithophorids differ from other phytoplankton in having an external covering of scales made of the mineral calcite – a major component of sea shells.

An online tool, capturing the intricate structures of hundreds of microscopic Antarctic marine plants and animals, is helping scientists identify these important organisms.

They are works of art on a microscopic scale – perfectly formed, single-celled Antarctic marine plants and animals. Some look like dimpled water jugs, others like cricket balls, roughly woven baskets, or six-pointed stars.

These cells (which together are called ‘protists’) range in size from one micron (one thousandth of a millimetre) to four millimetres in length. But their small size belies their importance. Protists sit at the base of the marine food web and their vast numbers support the wealth of life for which Antarctica is renowned. They also alter concentrations of gases in the atmosphere that affect global climate, and are responsible for much of the oxygen we breathe.

Now, highly detailed images of more than 600 of these microscopic plants and animals feature in a collection of interactive ‘taxonomic’ (identification) keys, developed by Australian Antarctic Division scientists Dr Fiona Scott and Dr Imojen Pearce. The keys fill a gap in modern protist identification and have already attracted both national and international interest.

The online Antarctic Marine Protists keys allow Antarctic biologists to classify protists within 12 taxonomic groups. Classifying such organisms is vital if we are to detect the effects of environmental change on their distribution and abundance, and to predict the possible future for life in Antarctic waters.  Any climate-induced change in their composition, abundance and activity in the Southern Ocean is likely to have far-reaching consequences for marine food webs, wildlife conservation and fisheries productivity, and will feed back to affect rates of climate change.

As the numbers of scientists with the knowledge to identify organisms using their physical features are in decline, these new interactive keys make the specialist knowledge and skills required to identify Antarctic marine protists available to all.

The information and images used in the keys are mainly sourced from the book Antarctic Marine Protists, published jointly by the Australian Antarctic Division and the Australian Biological Resources Study in 2005. The book synthesises decades of research in the Antarctic and subantarctic regions by Australian and international scientists, and describes and illustrates the diagnostic features of each protist recorded.

These diagnostic features drive the interactive keys, by allowing biologists to select multiple features of a cell, based on what they can see in their own sample. The keys contain over 2000 electron micrographs, light micrographs and line drawings, which record the intricate details of each organism. Biologists can either match their specimen to an image in the keys, or work through a checklist of features, such as the presence or absence of physical structures, and cell size and shape. This offers a faster and more powerful method than using traditional paper-based dichotomous keys or pictorial guides.

The sheer diversity of marine protists means the identity of some organisms remains unknown to science. To accommodate this, the keys include two groups containing images of cells of ‘unknown’ or ‘uncertain’ classification, with an invitation for users to contribute data and images to address these knowledge gaps.

Each organism in the keys is linked to a fact sheet that details its distribution, where it was first recorded and by whom, its physical attributes, and references. There is even scope to include genetic information about each species in the future. The keys also include recent new discoveries, taxonomic revisions and many updated images not contained in the book. Importantly, the keys can operate from a CD or flash-drive, so that they can be used offline, onboard ships or in Antarctica.

Fiona Scott and Andrew Davidson
Science Branch, Australian Antarctic Division