One area of research where diatoms are used is in the field of paleolimnology. Paleolimnology, or the study of old lakes, is an area that is especially useful when assessing problems that have arisen. For example, the acid status of a water body, and the effect of changing pH on the species that inhabit the area.
Diatoms are useful as a bioindicator species for a number of reasons, previously discussed here. The main feature of diatoms that makes them useful for examining the past is their silica cell wall, or frustule. This cell wall does not decompose easily, and so can be found extremely well preserved in sediments of almost every water body. This allows for the diatom species to be identified, even when only the fossilised remains are present.
The Soil & Water Conservation Society of Metro Halifax website has an excellent page with a great deal of information about paleolimnology (linked in references), including many applications and interesting findings. The ‘methodology’ section was of particular interest to me, as it stated that diatoms, and in particular their frustules, are the main biological indicator used in paleolimnology. For more information about frustules, see my previous post on the subject: link.
In order to assess how conditions have changed, a good knowledge of previous conditions is necessary; paleolimnology provides information about the water body’s historic condition. Analogue matching uses historic records of the types of diatoms found in the lake sediments, and compares it with the types of diatoms found in current sediments. Slices of sediment are taken and analysed to identify the layers of the different ecological periods in the water body’s history. Modern lakes that have diatom species most similar to those found in the records, are assumed to be displaying similar conditions. This can provide a useful view as to how the environment used to look. (Simpson et al. 2005)
In conclusion, diatoms are a vital tool for examining the history of our water bodies, and a method that will continue to be relevant and useful as monitoring the environment comes increasingly into focus.
SIMPSON, G., SHILLAND, E., WINTERBOTTOM, J. and KEAY, J. (2005). Defining reference conditions for acidified waters using a modern analogue approach. Environmental Pollution, 137(1), pp.119-133.
Soil & Water Conservation Society of Metro Halifax: http://lakes.chebucto.org/PALEO/paleo.html