June 19, 2011

A day in the desmid field

To see the world in a grain of sand,
And heaven in a wild flower,
Hold infinity in the palm of your hand,
And eternity in an hour.

Auguries of Innocence - by William Blake (1757-1827)

Huis ter Heide estate lies between the villages of De Moer and Loon op Zand in the Province of Brabant, northwest of Tilburg City in the Netherlands. It's an attractive nature reserve with ponds, lakes, moorland, agricultural fields and forests. Huis ter Heide was therefore the location of the fieldtrip of June 8th 2011 for the Dutch Desmid working group. We started sampling the northern boundaries of Lake Leikeven. The landscape of Leikeven is characterized by low growing vegetation on acidic soils.

My colleague Wim and I are sampling the first
location at the Northern side of Leikeven.
Photograph: Ruud Janissen/Aquon

Lake Leikeven was originally a landscape of peat and extensive bogs. At some locations, the peat layer was several metres thick. Peat was very useful as fuel and was therefore excavated between 1200 and 1600. After the peat was excavated and exploited, a new landscape was formed: Leikeven became a moorland lake, just like Plakkeven, also a part of Huis ter Heide estate. The water of the lakes was very pure, resulting in the ultimate survival of very rare and almost extinct species of animals and plants, like water lobelia.

As a result of the severe soil and microclimate characteristics, moorland habitat often leads to the appearance of endemic species. It's possible that we would find species of desmids that are new to us, or variations on existing species. A habitat to treasure so close to my home.

South of Leikeven

After the peat excavation during the Middle Ages, the people of Brabant decided to use the land for agricultural purposes. They were not all that lucky: part of the Southern fields were troublesome due to drainage problems. The South transformed to wet heathlands, while forests for wood production were submitted to the landscape. Meanwhile, intensive farming lead to other complications.

Manures were washed away into the lakes, creating a thick layer of silt on the bottom of the lakes. Pollution became a real threat to the rare species existing at Huis ter Heide nature reserve. Interventions were therefore necessary to reverse the damage and to create new opportunities for rare species. The nature organization Natuurmonumenten worked for more than 18 years on Plan Lobelia, to restore Huis ter Heide to a more natural state.

Lobelia dortmanna (Water Lobelia) is a
rarely seen aquatic plant. I didn't
take my macrolens with me,
so I had to do with a landscape picture

Since then, the water quality of lakes like Leikeven has been greatly improved by interventions like excavating, clearing and cleaning. The result is that more desmids get a real chance for survival: after restoring the lakes, desmids tend to recover in a spectacular way. Besides, spores of desmids are able to overcome dehydration and general deterioration of water quality, to some extent. They also get help from animals: waterbirds and insects transport spores to better locations for germination.

And even plants like the very rare water lobelia, which once flourished abundantly, are back at Huis ter Heide nature reserve. Sundew and marsh gentian germinate in the nutrient-rich soil.

We did see that sundew were in abundance around Lake Leikeven during the fieldtrip. Equipped with rubber boots, sample tubes and a plankton net, we took various samples of Leikeven at different locations to discover the richness of the site. We got some instructions from other members of the Desmid working group how to extract the best of water plants like bladderworts for quality samples, possibly containing desmids.

We saw various species of green grasshoppers, small
brown toads and tiny lizards. This photograph was taken
a while ago in Tilburg (not at Huis ter Heide).

The weather forecast predicted rain and clouds, while the sun would peep through the cloudcover now and again. We were very lucky to have warmth and sunshine almost throughout the day. The warmth and wetness of the moorland made animals come to life. Animal life showed tiny toads, green grasshoppers, blue coloured damselflies and small lizards. A colony of great black-backed gulls rested on the small plates of mud close to the pathway to Leikeven, The Spinderpad. The gulls are particularly attracted to the Spinder, a landfill close to the nature reserve.

We continued our fieldtrip to Plakkeven and Bodemven. You can find the locations on the small map of the nine sampling locations on the estate of Huis ter Heide.

Sampling locations at Huis ter Heide nature reserve.
Map by: Marien van Westen

Data collection by: Marien van Westen

When we sampled Plakkeven, we were spotted by walkers. They thought to see birds! Instead, they saw a group of people standing in the water in rubber boots, bending over to squeeze water plants and algae. Frogs surrounded us with their loud calls and tiny lizards crept at our feet, while algae drab crept down our fingers into the sample tubes.

Sampling tubes with algae, water and mud

The last visit was to Bodemven, a lake of no expectation due to the low pH of 3.7 - desmids flourish at best with a pH between 5 and 7. We did see a kind of film on the water surface and there was an unpleasant stench, revealing the presence of sulfur bacteria. Sulfur bacteria produce a slime and can promote the growth of other bacteria, such as iron bacteria. Bacterial slime may be white, grey, black, or reddish brown if associated with iron bacteria. The bacterial slime gives off a smell of rotten eggs, clearly not a stench you would want to smell for a long time!

Eventually, after a drink at a terrace in the village De Moer we went home with lots of sample tubes. These samples may show us 'the world in a grain of sand', the secrets of the shallow.

And finally...
THE FIRST RESULTS of a day in the desmid field:

Micrasterias papelifera - after defining the species,
expert AMT Joosten told me that this one at Leikeven
is more stretched than usual. It may be a new
variation on the species.

From left to right: Staurodesmus convergens,
Cosmarium reniforme var. reniforme,
Euastrum ansatum var. ansatum

Literature and resources

Coesel PFM & Meesters KJ (2007) Desmids (Desmidiaceae) in the Netherlands http://www.desmids.nl/

Coesel PFM & Meesters KJ (2007) Desmids of the Lowlands - Mesotaeniaceae and Desmidiaceae of the European Lowlands, KNNV Publishing Zeist

Joosten AMT (2011) Cursus Fytoplankton, at Gemeenschappelijk Waterschaps Laboratorium Boxtel

Natuurmonumenten (2011) Huis ter Heide http://www.natuurmonumenten.nl/huis-ter-heide 

Roefs F (2002) Sierwieren, de pareltjes van onze Brabantse vennen, Brabants Landschap, Uitgave van de Stichting Het Noordbrabants Landschap, zomer 2002 41-44

Van Westen M (2011) Desmids of Drenthe http://desmids.science4all.nl/

All microscopic photographs were taken with Nikon Inverted Microscope Eclipse Ti-U (100w), Nikon DS-Fi1 camera, NIS Elements BR 3.22.00 at 600x (1x or 1.5x) magnification, oil. Mastered in Photoshop Elements 8. Photographs: Marta Demarteau/GWL