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Back to University as well

So I took the plunge and returned to UCC realising that there was no way I was going to channel my interests sufficiently well to produce something meaningful from my studies of palaeoecology and palaeoenvironment in West Cork, without some management, some tuition, and some focussing.

I'll cut to the chase - the first couple of months has seen me focussing on testate amoebae in the modern environment - to get a grip on identifying them - and then latterly in the core samples.

The initial identification exercises gave me an opportunity to go and collect some surface samples from lakes and bogs I (and you, if you have read other blog entries) know well. They are great places.

Glandart Lake, Driminidy Lake, and Three Lakes middle lake.

I have to say here, that some of these places can be pretty dangerous. These lowland lakes (even though Loch Agower is at 320m ) have plenty of plant growth around the edge which often turns out to be a floating mat. Extreme caution is needed. Sinking through the floating mat would be akin to a quicksand - extremely difficult to get out of, and ultimately deadly. One does not take ANY risks.

The reason for examining the sediment for testate amoebae is that the different taxa have been found to be quite specific as to the wetness of their habitat. So by identifying the different taxa of testate amoebae that are present, and then looking at - and performing some statistical analysis on the figures - it is possible to ascertain the 'depth to water table' (DWT) that they represent. And we can then build up a picture as to how the DWT changed over time, and postulate why that might have changed. And the reason may be increased or decreased rainfall, episodic flooding or drying, changes in drainage patterns, changes in the catchment area from which the bog or lake water comes, and so on.

But most of these studies have been undertaken at bogs, and, more specifically, ombrotrophic bogs; that is, sphagnum moss dominated raised bogs, which are supplied by water from rainfall only, have low levels of nutrition, and generally have a low acidity of pH 5 or 4 or 3. Some studies have been undertaken on lake sediment, but they represent a different picture. The testate amoebae that occur in lakes are more indicative of the trophic level of the lake, that is, what sort of nutrition level is there. And an added complication is that the tests (shells) of the testate amoebae once the organism dies, are deposited and sink to the bottom, but then, depending on water circulation currents, they may get swept together in a congregation on the bed of the lake. This may include tests from those that lived on plants on the edge of the lake, those that lived in the depths (profundal), or on the shallow beach like (littoral) habitats. All mixed up. Which gives us a bit of sorting out to do, but overall this can all be dealt with by numerical and statistical analysis of the numbers of different taxa.

I have run into a different problem at Three Lakes.

The 'bog' surrounding the lakes at Three Lakes is mineratrophic, that is, they get their water supply from the ground water as well as from rainfall, so the plants and mosses growing there have the input of minerals.

Not many studies of testate amoebae have been undertaken in mineratrophic mires, which means that the taxa I can expect to find might not fit in too well with the data obtained by studies of either bogs or lakes.

But there is an added complication. Studies generally indicate a lessening in number of tests further down the core (deeper into the sediment and therefore the older the sediment). Is the change in number because there were fewer living there, or because the environment has changed, or because the tests do not survive the time spent in the sediment, or the pressure of several metres of sediment on top of them? There have been experiments to ascertain how the different types of tests survive different conditions. And there have been statistical explorations into how a reduction in different types of tests will affect the final determination of DWT. The experimenting with conditions came up with a certain number of conclusions, but overall it seems that the problem is how to mimic in an experiment, the gradual burial over hundreds or thousands of years, and the possible changes in environment as that happened. The statistical explorations concluded that changed numbers of tests do have a certain effect, but generally not a dramatic one.

But what happens when we look at the sediment down core and don't find any testate amoebae tests? What then?

This is what I am finding at the moment, and although this is going to impact the project quite seriously, it is a fact of nature and presents a challenge. We need to find out why.

Where have all the tests gone?