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.
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
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.
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.
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.
References:
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.
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.
Reference:
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
