Microscopic lungs of the earth
18 May 2005
Protists, the phytoplankton (single celled plants) and protozoa (single celled animals), account for over 90 percent of the biomass of all living organisms in the ocean. Protists are arguably the most important organisms in the oceans. They are the base of the food web on which essentially all other marine life depends. In addition they play a major role in the global carbon cycle taking up about 50% of the carbon dioxide produced by living things, including humans, and produce about 50% of the oxygen we breathe. Some species produce chemicals, which when ventilated to the atmosphere, promote the formation of clouds.
Protists are tiny – you need a light microscope to see them and most often an electron microscope to positively identify them. They range in size from less than a micrometre (one thousandth of a millimetre) to over a millimetre. However what they lack in size they make up for not only in abundance, with concentrations reaching millions of cells per millilitre of seawater, but also in species diversity. Just as species of macroscopic organisms differ in size, life-style, and food value to predators so too do different species of protists. If we are to understand the way in which most of the fundamental marine processes work, it is essential to know what protistan species are involved.
The literature on Antarctic marine protists is widely scattered in journals and specialised texts. Until now there has been no single resource that draws this information together to enable non-specialists to identify and readily access the literature on these fundamentally important organisms.
The recently published book, Antarctic Marine Protists edited by Fiona Scott and Harvey Marchant describes and illustrates over 550 species from south of the Antarctic Polar Front. A bibliography of more than 1000 entries and a glossary will make this an indispensable resource for marine biologists.
The idea for a guide book to Antarctic marine protists grew out of necessity. In the early 1980s the Australian Antarctic Division participated in the BIOMASS (Biological Investigation of Marine Antarctic Systems and Stocks) program. This highly successful international campaign took a comprehensive look at the oceanography, and the distribution and abundance of protists, zooplankton, fish and seabirds of the Southern Ocean. The principal focus of BIOMASS was an investigation of krill stocks, their food and predators. At the time of these cruises there were no comprehensive guides to the protists or zooplankton of the Southern Ocean to aid in the identification of samples. To facilitate protist identification, articles from the widely scattered literature were assembled along with a growing collection of AAD light and electron micrographs. From this work, new species were described and the basis of a working field guide to the phytoplankton was developed. In the mid 1980s funds were attracted to employ specialists to formalise the work, but it was quickly realised that the scope of the guide had to be expanded to include several groups of protozoa as well as the phytoplankton.
The resultant text, Antarctic Marine Protists, was published jointly by the Australian Biological Resources Study (ABRS) and the Australian Antarctic Division, and provides descriptions, illustrations and a comprehensive bibliography of these unique organisms. For the first time anyone wanting to identify protists from the surface waters of the Antarctic Ocean can go to a single source of information.