Diatoms are siliceous phytoplankton that play a major role in global carbon fixation, as well as forming the basis of most marine food webs. In the Southern Ocean, diatoms are responsible for significant volumes of carbon export and sequestration in the deep sea. Diatoms are unicellular and microscopic, thus diatom taxonomy has naturally progressed as imaging and molecular technologies have developed. Despite recent advancements, some aspects of diatom taxonomy remain unclear. The genus Shionodiscus was separated from Thalassiosira in 2006, and possesses, as a group, internal extensions of the marginal strutted processes as well as a labiate process on the valve face, usually distant from the margin. The features distinguishing Shionodiscus from Thalassiosira, and Shionodiscus spp. from each other, are difficult to examine under light microscopy, and most taxonomists will group similar Shionodiscus species together when encountered, rather than discriminating species. As a result, the full extent of Shionodiscus diversity is rarely examined in individual studies. In this study, sediment trap material captured in the Australian sector of the Subantarctic Zone was examined using both light and scanning electron microscopy, and compared to known measurements on Shionodiscus species and varieties. This study had two aims; to catalogue for the first time the diversity of Shionodiscus spp. within the Australian sector, and to create a formalized set of criteria for grouping Shionodiscus species, when only light microscopy analysis is possible. By documenting Shionodiscus diversity in the Australian sector and establishing a standard identification protocol, researchers will be better able to determine the ecological significance of the genus in diatom assemblages.
- Southern Ocean
- sediment traps