Allan Pentecost, Honorary Research Fellow and course tutor at FBA Windermere, recently investigated a historic sample brought to life when several large wooden crates of bottles were relocated to avoid risk of flooding. The bottles, numbering around 180, contain historic water samples from the Percy Sladen Trust Expedition to Lake Titicaca undertaken in 1937. Allan describes their provenance and what he found inside.
History of the samples
They were sent to H. Carey Gilson who led the expedition and coordinated the subsequent research, and who later became director of the FBA. The results were published in a series of papers in the Transactions of the Linnean Society in 1939-1940.
According to Dr Jack Talling, formerly at the FBA, the samples of water were to be passed on for analysis by the Government Chemist but somehow they have remained unopened at the FBA. Some idea of the logistics and preparation of the expedition can be gained by listing the resulting publications:
Gilson provided a detailed description of the lake in the introduction followed by the meteorology (Gilson and Paul F. Holmes, both University of Cambridge); the geology (H.P. Moon, University of Southampton); the tardigrades (E. Marcus, University of Sao Paulo); rotifers (P. de Beauchamp, Universty of Strasbourg); oligochaetes (L. Cernositov, Natural History Museum); coleoptera (H.E. Hinton, Natural History Museum); crustacea (J.P. Harding, Natural History Museum); macrophytes and algae (T.G. Tutin, University of Manchester) and amphibia (H.W. Parker, Natural History Museum).
The diatoms were sent to Mr R. Ross at the Natural History Museum who was then a young diatomist, but there is no evidence of a report. Such a comprehensive study by young and enthusiastic researchers is remarkable for the time – it was a period of austerity with the looming prospect of another world war.
Where do the samples tell us?
The bottles are of thick soda-glass sealed by rubber-ringed porcelain stoppers, firmly bound to the top with wire. None appear to have been opened and for the most part the bottles remain almost full of water (c. 500 ml), suggesting minimal evaporation.
No preservative seems to have been added to the samples. The labels remain intact giving a coded location on the lake, the depth taken, assumed to be in feet, and the date. Samples were taken from about 30 localities on the lake down to 60 feet but it is not possible to determine their positions on the lake. The report makes no reference to the samples, presumably because the analyses were never undertaken.
The writer, curious to examine the contents for traces of freshwater algae, opened a bottle for microscopic examination.
Diatoms were evident in the traces of sediment, and surprisingly, one coccoid green alga could still be identified as Coelastrum microporum. After almost 80 years of storage, the samples would no longer be fit for nutrient and minor element analyses, but major elements such as sodium and sulphate would probably yield useful results.
The Lake Titicaca waters are weakly saline and two further bottles from station H71 taken on 14 September 1937 yielded 3.8 ppt solids at the surface and 3.5 ppt at a depth of 60 feet. These values are rather higher than the published records.
Since the Percy Sladen Expedition, there have been several detailed surveys of the lake. The phytoplankton is described by Carey et al. (1987) who noted the occurrence of Coelastrum microporum. The general limnology, including water chemistry is described in a large collection of papers edited by Dejoux & Iltis (1992). The lake is now showing signs of eutrophication.
It is unfortunate that the samples held by the FBA were never analysed in the light of this later work, but understandable in the circumstances. The samples still contain potentially useful information and it is to be hoped that the key to the collecting sites will be uncovered in the FBA’s unpublished collections. The remaining salinities could be determined and the diatoms identified and enumerated and the original collection, transport and storage of the bottles could come to fruition and add to our knowledge.
Thanks to Jack Talling F.R.S., for providing information about the origin of the bottles.
Carney, H.J., Richerson, P.J. & Eloranta, P. (1987). Lake Titicaca (Peru/Bolivia phytoplankton. Species composition and structural comparison with other tropical and temperate lakes. Arch. Hydrobiol. 110: 365–385.
Dejoux, C. & Iltis, A. (1992). Lake Titicaca. A Synthesis of Limnological Knowledge. Monographiae Biologicae 68. Kluwer, Dordrecht.
Gilson, H. C. (1939–40). The Percy Sladen Trust Expedition to Lake Titicaca in 1937. Parts 1 and 2. Trans. Linn. Soc. London, 1. pp. 1–215.
Allan Pentecost, FBA Honorary Research Fellow and Course Tutor