In January we transferred the Botany Palynology (pollen and spore) Collection to a new location within the micropalaeontology collections. The  collection includes 32,500 glass microscope slides and 155 files of images of pollen and spores from named living plants from worldwide locations. So why should we be interested in moving this collection to the Palaeontology Department?

This collection is already being used by Earth Science staff studying the contents of fossil hyena dung, evidence of early human agricultural activity and changes in the landscape over approximately the last 2.5 million years as a result of climate change. The collection also has potential for supporting forensic studies to help solve crime.

Dr Tom Hill taking great pride in wheeling a trolley of pollen and spore slide cabinets past the giant Sequoia in the main hall of the museum. For health and safety reasons we were only able to move the collection before the Museum opened to the public.

In one of my first blog posts - what is micropalaeontology? - I mentioned that there is not always a clear distinction between fossil and extant (living) collections and this is very much the case here. This is an important collection for palynologists looking to reconstruct environments over the the Quaternary Period which covers approximately the last 2.5 million years as many of the plant species present today are represented in the Quaternary fossil record.

Pollen and spore grains have an outer wall of an extremely resistant material known as sporopollenin so are widespread in both fossil and recent terrestrial and near shore sediments. Most are smaller than 50 microns so relatively small samples can produce thousands of pollen grains of species diagnostic of particular climatic conditions.

Some of Tom's Holocene core from Somerset, showing a lighter estuarine layer between freshwater peats.

Dr Tom Hill of the Earth Sciences Department at the Museum is analysing pollen from sediments from Somerset that cover the Holocene Epoch (i.e. the last 11,500 years).  He collected them using a sedimentary corer, which is essentially a larger version of an apple corer that is inserted into the ground to extract deposits preserved beneath our feet. He said, 'by taking sediment samples at regular intervals throughout the sediment sequence, you are able to develop ‘snapshots’ of what the landscape looked like every few hundred years.'

Tom doing fieldwork with a sediment corer in a 'real field' at Shapwick Heath Nature Reserve.

The landscape changed in response to climate and human activity: an abundance of tree pollen suggests that woodlands dominated the landscape while shrubs, herbs and grasses infer an open grassland setting. 'Shifts from woodlands to grasslands are often indicators of human activity in the form of deforestation; the earliest cereal pollen found in these deposits is an indicator of the onset of agriculture during the Holocene' according to Tom.

Hordeum secalinum - barley, BM10490. Cereal crop pollen grains like these are much larger than average (>40 microns), are typically round with a single opening (pore) and indicate periods of cultivation during prehistory. Photo Tom Hill.

Artemisia - mugwort, BM8975_1. This species/genus thrives on bare ground with immature soil and is often found in sediments accumulated during cold periods such as late glacial episodes in the Earth's history. Photo Tom Hill.

Mark Lewis of the Ancient Human Occupation of Britain (AHOB) Project has been using the distribution of pollen from sediments and hyena coprolites (fossil dung), to reconstruct Quaternary environments. Coprolite pollen is useful in situations where sedimentary pollen is absent, for example in caves, where evidence of early humans is sometimes found. Pollen grains can occasionally be reworked from older sediments so analysis of coprolites alongside sediments associated with early human finds can be a useful test to see if the pollen has been preserved in situ.

Mark worked on pollen assemblages from Happisburgh, where the earliest evidence of human activity in Britain has been uncovered from c.850,000 year old sediments (for details of their publication in Nature see my previous post on what microfossils tell us about the early humans in Britain). These pollen assemblages showed the climatic setting of the finds and led to breakthroughs in the understanding of early human behaviour, adaptation and survival.

Both Mark and Tom are actively using this collection for their research by checking identifications of plant species represented by pollen in their samples. Catalogues, including 8 volumes published by the Northwest European Pollen Flora Project, provide 2-dimensional reference images of pollen but there is no substitute for examining museum reference collections like this one under a microscope. 'The collection provides the user the opportunity to look at numerous examples of an individual species present on a single slide, and review that species in multiple orientations' said Mark Lewis.

Micropalaeontologists/palynologists Steve Stukins and Tom Hill examining the Northwest European part of the pollen and spore collection in its new home in the Palaeontology Building of the Earth Science Department.

The Northwest European part of this collection is particularly well ordered thanks to Dr Peter Stafford, Palynologist at the Museum until his death in 2009 who was a major contributor to the collection and publication of the Northwest European Pollen Flora volumes. He worked with many palynologists including Mark Lewis and Prof Steve Blackmoor, former Keeper of the Botany Department. As a result it is now possible to locate examples of the pollen and spores of a named Northwest European plant with ease.

Tom in the old Botany tower examining some of the 155 folders of scanning electron microscope images of pollen and spores prior to their transfer to the Palaeontology Building.

The remainder of the 32,500 glass slide collection is currently housed in old metal drawers that do not conform to current storage standards and will need to be transferred into a cabinet next to the Northwest European collection. A start has been made by volunteers and students to rehouse the slides in special conservation grade sleeves but there is much work remaining to be done.

While I am very glad that this collection has been moved to our department, it would take me the rest of my career to carry out this task alongside the other collections management responsibilities that I have. As a result Tom Hill will shortly be advertising a couple of volunteer opportunities to help re-arrange the remaining part of this important collection.

Slides of pollen from cannabis plants housed in special conservation sleeves in the Northwest European Collection.

Finding slides from cannabis plants jogged my memory to mention that while we anticipate that Quaternary palynologists will be the main users of the collection, there are applications for this collection beyond Palaeontology. Pollen grains present in mud on shoes or in tyre treads have been used to link suspects to crime scenes. This collection has potential to act as a reference for forensic palynologists as well as those looking to study the Quaternary.

Finally a big thank you to Tom Hill, Steve Stukins and Jo Wilbraham for help with transferring this important collection from Life to Earth Sciences and to Mark Lewis for providing details of the history of the collection and his research. The collection is available to - and will hopefully continue to be used by - both Life and Earth Scientists.

The answer to this question is the straightforward part of this post: palaeontology is the study of fossils and micropalaeontolgy is the study of microfossils. Alas, that’s the easy bit done… what then, are microfossils?

I’ll assume that we all know what a fossil is (if not, I recommend starting here) so a microfossil must be a small fossil, right? Actually, this is a harder question to answer than you might think so here are some thoughts on how large a microfossil is, how old they are and how we manage them at the Museum.

Size

There is no agreed size below which a fossil stops being a large fossil and starts becoming a microfossil. Some people arbitrarily say that if you need to use a microscope to view a fossil then you are looking at a microfossil. However, some fossils we consider microfossils measure more than a couple of centimetres in diameter. The rocks that were used to construct the pyramids in Egypt contain microfossils that can be as large as a ten pence piece!

Photo of Egyptian pyramid courtesy of Bobbie Molloy.

This size delimiting definition also gets slightly difficult to use when you are studying the microscopic parts of a larger organism, for example the fossilised scales of a fish or a minute example of something that is usually larger like a gastropod (e.g. a snail). Most people studying these topics would consider themselves microvertebrate workers or gastropod workers and not micropalaeontologists. However, many micropalaeontologists, like me also study microscopic remains of larger organisms like fish that they find during laboratory preparations for other microscopic remains.

Biological classification

Some people try to restrict micropalaeontology to particular biological groups that are commonly considered microfossils. This can also be open to personal opinion, for example, palynologists study microscopic organic remains like spores, pollen and oceanic plankton – all microscopic in size – but some of them would consider themselves palynologists rather than micropalaeontologists. The Micropalaeontological Society defines its specialist groups to reflect biological classifications of organisms commonly accepted as microfossil groups.

Age

As with size, there is no agreed age beyond which something stops being recently dead and becomes a fossil. With specimens in this narrow window of age (ie 0-10,000 years old) it is virtually impossible to tell how old a microfossil specimen is without carrying out some sort of destructive chemical analysis on it.

Our collections

At the Museum, we mainly follow the Micropalaeontological Society's definition of a microfossil and in the Palaeontology Department we have collections of Foraminifera, Ostracoda, conodonts, Radiolaria, nannofossils and various palynological groups such as the dinoflagellates and spores. In future posts I will introduce each of these microfossil groups as I highlight projects that are currently happening here at the Museum.

My job is to manage all of these collections which number over 750,000 objects. It would be impossible to count the exact number of specimens because some slides and residues contain hundreds of thousands of specimens.

The lack of clarity over what age makes a microfossil causes problems sometimes with deciding where to store specimens in the Museum collections. In the Palaeontology Department we have all the extant (modern) Foraminifera as well as the fossil specimens, so no problem there. However, ostracods are split between our department and the Zoology Department, with us holding the fossils and Zoology the recent (extant) forms. In practise it is very difficult to draw the line between fossil and recent and we certainly have some ostracods that could be in the Zoology Department and probably vice versa.

The majority of the microfossil collections are Foraminifera, which are unicellular animals with a foramen (i.e. an opening, sometimes multiple) that form small shells of calcium carbonate, silica or organic materials. Examples of Foraminifera are shown below, where the field of view of the slide from the Heron-Allen Collection is about 2cm.

The Heron-Allen Collection

I mentioned that some micropalaeontologists like me also work on microscopic fragments of fish (microvertebrates). At the Museum these are kept with the fish collections so they do not come under my ‘jurisdiction’. However, I still study them and some of my most important discoveries have been on this subject as you will find out in the next post to the blog.