Glandart Lake - Ecology of a Hilltop Lake

The water in Glandart Lake is slightly acidic at pH 6 to 6.5 near the surface, nearer 5.5 at the bottom of the lake. Being on a hilltop at around 1000 feet elevation there is a restricted biota, and limited organic inflow to the lake. It is clean, but nutrient poor (oligotrophic), the water being fed principally by ground water from the water table. The banks are steep, with no shelving, either being sheer rock, or overhanging vegetative mat, with water depths of over 50 cm at the shoreline.

For interactive maps and physical characteristics of the Glandart Lake site, see here.

Three dimensional rotatable and zoomable models (topo-models) of Glandart Lake have been constructed to illustrate the difference between the surveying strategy on the digital surface , or terrain, models that result. These can be found

on this page for the elevation model based on a 25 m survey grid(opens in a new tab), and on this page for the elevation model based on a 25 cm survey grid(opens in a new tab).

The magnification text in the individual images details the objective only. Multiply by 10 (the magnification of the eyepiece) to get the full magnification. All measurements, where they occur, are in microns - thousandths of a mm, millionths of a metre.

The alga Paludicola turfosa

The main alga found in Glandart Lough is beautifully branching whorled alga called 'Paludicola turfosa', a member of the family of red algae (Rhodophyta).

About 3% (c. 180 species) of red algae (Rhodophyta) are freshwater, the majority being marine. The freshwater species are mostly found in light poor and nutrient poor waters, which is a complete contrast to the marine conditions. They are important inhabitants of river systems and widely distributed globally, but three species are principally pond and lake dwellers, and one of these is Batrachospermum turfosum - or Paludicola turfosa as it is now known.


Paludicola turfosa from Glandart Lake (x200)

The high level of adaptability displayed by Paludicola turfosa has made this alga the subject of quite a few studies.

Paludicola turfosa occurs mostly in higher altitude microhabitats in dark-coloured, nutrient-poor (oligotrophic to ultra-oligotrophic) water, high in humic acids, possibly containing unfavourable organic and inorganic compounds. The alga grows attached to stones, lake banks, or pieces of wood.

This alga produces transparent filaments that make it very slimy to the touch and act as a protective casing, but also contain enzymes that enable the uptake of phosphates from organic molecules, which would be problematical when Iron 3 compounds are present; which they are in these low nutrient acidic waters.

Paludicola turfosa showing slime

Paludicola turfosa from Glandart Lake (x200) - note the barely visible filaments of transparent slime.

Because of the size (generally small) and altitude (generally high) of Paludicola's habitats the alga is subject to quite high fluctuations of temperature, solar radiations, and light levels. From dim, to very bright and intense, high in UV radiation, and from freezing, to over 30°C.

Experiments have shown that this alga is able to adjust to all these changes in light intensity and temperature - it can be described as 'euryoecious'.

This is partly to be expected in that marine algae may well adapt to changes in water depth and temperature within limits, but the much greater variability of the freshwater small lentic environment has caused this adaptation in Paludicola turfosa.

Of particular interest is the possibility that this algal species may be displaying adaptations acquired during periods of extreme climate change at the end of the ice age about 15,000 years ago, and through the Nahanagan (Younger Dryas) stadial, a climatic downturn that saw the return of very cold conditions for 1200 years ending about 11,700 years ago.


  • Aigner S. et al. 2017. The freshwater red alga Batrachospermum turfosum (Florideophyceae) can acclimate to a wide range of light and temperature conditions. Phycologia. 52(2): 238–249
  • Wehr J.D. et al. 2015. Freshwater Algae of North America Ecology and Classification. Elsevier.

Testate Amoebae

A group of protozoans that have been called variously, Rhizopods, Thecamoebians, Arcellaceans. These are single celled amoebae that construct tests, or shells, within which they shelter. Testate amoebae occur in mosses - particularly sphagnum and other bog mosses that are permanently wet - and in lakes and bogs. The shape, size and materials that the test is made of help in identifying the species. The tests remain after the organism has died, providing a useful indicator within lakebed and bog sediments of the environmental conditions at the time - principally water quality, temperature, acidity, and nutrient status.

A good website with lots of information about amoebae generally, and many excellent images, is Ferry Siemensma's "Microworld - world of amoeboid organisms".

Paludicola turfosa showing slime

Centropyxis aculeata a testate amoeba test from Glandart Lake (x200).

This is just one of a very large assortmemnt of testate amoebae tests lying on the bed of the lake in various states of preservation or disintegration.

Testate Amoeba film 1

A live testate amoeba, yet to be identified, in action. Mag x200. This film has been speeded up to double.


  • An Atlas of Freshwater Testate Amoebae by C. G. Ogden & R. H. Hedley, 1980.
  • The Identification of Testate Amoebae (Protozoa: Rhizopoda) in Peats by Charman, Hendon and Woodland. 2000


5 sided suctorian

A ? suctorian ?, with five sides, from Glandart Lake (x200). Tentatively identified as a suctorian becuase of its similarity with that below.

7 sided suctorian

A suctorian, with seven sides, from Glandart Lake. x200. Note the (dangerous) fine filaments coming from the apices.


<i>Surirella</i> sp., a large raphid epipelic diatom from the bed of Glandart Lake.

Surirella sp., a large raphid epipelic diatom from the bed of Glandart Lake. x200.

<i>Surirella</i> sp., a large raphid epipelic diatom from the bed of Glandart Lake.

A side view of Surirella sp., from the bed of Glandart Lake, showing the interesting three dimensional shape. x200.

<i>Tabellaria flocculosa</i>.

Tabellaria flocculosa, a small planktonic diatom from amongst the Paludicola of Glandart Lake. These usually occur in chains, zig zag chains. x1000.

<i>Tabellaria flocculosa</i> chain.

Tabellaria flocculosa in a zig zag chain. x200.

<i>Frustulia saxonica</i>.

Frustulia saxonica live diatom from amongst the Paludicola. x1000. Measurements in microns (thousandths of a mm).

<i>Frustulia saxonica</i> in mucus tube.

Frustulia saxonica live diatom from amongst the Paludicola. Several individuals within a mucus tube.

<i>Eunotia exigua</i>.

Eunotia exigua live diatom from amongst the Paludicola. x1000. This species of diatom makes a very obvious use of the Paludicola as an anchorage and possibly also protection from grazers, in amongst the mucus filaments.

<i>Eunotia tetraodon</i>.

Eunotia tetraodon both halves of this diatom, or maybe two individuals. This photo was taken using phase contrast microscopy, to show better definition.

Cyclotella sp., a small 'centric' (circular or cylindrical) diatom from amoungst the <i>Paludicola</i>.

Cyclotella sp., a small 'centric' (circular or cylindrical) planktonic diatom from amongst the Paludicola. x1000.

Other protists

Sample film 2

A protist, yet to be identified. Mag x200.